BIOLOGY O610 SYLLABUS 2023-25 NOTES
MWASHITA
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Characteristics And Classification Of Living Organisms
Cells And Organisation Of The Organism
Movements In And Out Of Cells
Biological Molecules
Enzymes
Plant Nutrition
Human Nutrition
Transport In Plants
Transport In Animals
Diseases and Immunity
Gas Exchange
Respiration
Excretion In Humans
Coordination And Response
Drugs
Reproduction
Inheritance
Variation And Selection
Organisms And Their Environment
Biotechnology And Genetic Modification
Human Influences On Ecosystems
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BIOLOGY 0610
1. Characteristics Of Living Organs And Classification
Every organism has certain traits that it needs to be demonstrating in
order for it to be classified as “living”. The characteristics are listed below: Movement – An action by an organism or part of an organism causing a change of position
or place
Respiration – The chemical reactions in cells that break down nutrient molecules and
release energy for metabolism.
Sensitivity – The ability to detect or sense stimuli in the internal or external environment
and make appropriate responses. Internal environment (blood sugar concentration, CO2
concentration) and external environment (detecting light, heat from the sun, coldness of the
weather)
A Venus flytrap leaf shows:
-sensitivity when a fly lands on it,
-movement when it closes,
-nutrition when it secretes enzymes to digest the fly
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BIOLOGY 0610
Growth – Permanent increase in size and dry mass by an increase in cell number or cell size
or both.
Pufferfish below can increase their body sizes when faced with a threat, that’s not growth,
their body sizes return to normal.
Reproduction – The processes that make more of the same kind of organism. Bacteria
reproduces by binary fission, Ferns and fungi by spores, plants by asexual and sexual means
and mammals by sexual means e.g. humans
Excretion – Removal from organisms of the waste products of metabolism (chemical
reactions in cells including respiration), toxic materials, and substances in excess of
requirements. Metabolic wastes include CO2, Urea, excess salts and water.
-Expulsion of fecal matter through the anus is not excretion, it is called egestion
-Secretion is the release of useful substances from glands e.g. mucus, tears and saliva.
Sweating is both an excretion and secretion
Nutrition -Taking in of materials for energy, growth and development; plants require light,
carbon dioxide, water and ions; animals need organic compounds and ions and usually need
water
-plants manufacture their own food through photosynthesis
-animals depend on plants directly (these are herbivores or primary consumers) or indirectly
(feeding on primary consumers e.g., carnivores) or can feed on both plants and other
animals (these are called omnivores.
Concept and use of classification system
Organisms can be put into groups by features that they share. Classification systems aim to
therefore classify groups of organisms in a systemic way, in order to reflect their
evolutionary relationships. Animals sharing a recent ancestor are grouped together.
Mammals share a recent common ancestor –apes, chimpanzees, baboons, monkeys and
humans share a very close common ancestor
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BIOLOGY 0610
Criteria used in classification
1. Morphology and anatomy—certain organisms “look” similar and share similar features,
they are classified under the same umbrella.
2. DNA—can be used to accurately classify organisms by analysing their DNA (rather than
look at appearance alone).
-DNA makes genes and genes code for proteins.
-One gene –one protein
-the DNA in genes is in form of a sequence of bases
-each set of three bases code for one amino acid and since these bases are in
a sequence, the amino acids coded are joined together to form chains of
proteins
-mutations produce changes in the sequences of bases in DNA
-mutations coffering an advantage will be passed on and more mutation continue
to occur
-the resulting generations become more and more different from their ancestors
-the DNA becomes more different and there will be no breeding-thus a new
species formed.
-base sequences of different species are analysed and compared to establish
whether species are closely related or share a recent common or a distant common
ancestor.
-identical DNA base sequences mean the organisms belong to the same species
and vice versa.
-smaller difference-they only stopped breeding recently -they share a recent
ancestor
-huge differences suggest a long period of mutations-they share a distant ancestor
-DNA base sequences are now used to classify animals into species, genera, families etc.
-related organisms have a similar sequence of bases in their genes and hence similar
sequences of amino acids in their proteins.
-these organisms can be placed in one group, these organisms usually share a
close ancestor
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BIOLOGY 0610
Kingdoms of Organisms
-animals on earth fall in one of the 5Kingdoms below: • Animal (Lion, Goat, Zebra, Whale, Fish, Butterfly, Birds)
• Plant
(Tree, Grass)
• Fungus
(Yeast, Bread mold, Mushroom)
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• Prokaryote
(Bacteria)
• Protoctista
(Amoeba, Euglena, Protozoa, Paramecium, Chlamydomonas)
The features of the kingdoms:
KINGDOMS
FEATURES
1. Plant
• Multicellular
• Body not compacted-roots and leaves spread
• Growth limited to tips of roots and stems
• Carry out photosynthesis
• Cells have chloroplasts, cellulose cell wall + large
central vacuole
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BIOLOGY 0610
2. Animal
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Multicellular
Compact bodies
Growth is in the whole body
Do not photosynthesise.
Cells have no cell wall, no chloroplasts, no
centralvacuole
Have a nervous system
Unicellular and multicellular
Have a nucleus compared to prokaryotes
Some have chloroplasts
Some photosynthesis
4. Prokaryote
(Bacteria)
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Unicellular
Microscopic (few micrometers long)
Cell walls
No nucleus
Loop of DNA
Some have an extra loop of DNA – a plasmid
No organelles like mitochondria or chloroplasts
5. Fungus
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3. Protoctista
Some unicellular and some multicellular
Nucleus
Cell wall made of chitin
No cellulose
No photosynthesis
Made up of a mycelium with branching hyphae for
feeding
• They are saprotroph
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Viruses
These cannot fit in the above 5kingdoms
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They are not cells
Made up of a protein coat surrounding a genetic material (DNA or RNA)
The DNA and RNA have few genes to code for proteins for the coat
They can only reproduce when they combine with the host’s DNA.
They are parasitic, they take over the host cell instructing it to make new viral
particles
• Viruses are not living organisms, they are genetic materials
The Binomial System
-naming organisms using two names, the genus name and the species name.
-different names can be used to name one organism and this can create confusion.
-names for a Donkey: - donki, bhemhe, dhongi, buro
-names given to a Person: - motho, munhu, persona, umuntu, muntu,
-names of a Mongoose in Kalahari Desert: - meerkat, suricate, sun angel
-the binomial system gives scientific names to animals and plants to get rid of
confusion.
The scientific name is two worded, hence “bi” and “nomios ” means name
-the first word is the genus name, which is always begins with an uppercase letter
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-the second word is the trivial name or species name, which is written with a lower
case
e.g. a person is called Homo sapiens
Homo = genus name
sapiens = species name
Common Name
1. Meerkat
2. Baobab
3. Cholera bacterium
4. Malaria parasite
5. Cat
6. Lion
7.Dog
Scientific name
Suricata suricatta
Adansonia digitata
Vibrio cholerae
Plasmodium falciparum
Felis catus
Panthera leo
Canis familiaris
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Vertebrates
-organisms with a vertebral column or backbone
-internal skeleton with bones or cartilage
-belong to phylum vertebrates
-opposite of vertebrates is invertebrates (e.g., Arthropods)
Main groups of vertebrates
Fish
Amphibians
Reptiles
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Birds/Aves
Mammals
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Features of vertebrates:
VERTEBRATES
FISH
FEATURES
• Streamlined bodies-for
swimming
• Lateral line- detecting pressure
and vibrations
• Gills- for gas exchange
• Fins –for movements
• Body covered in scales
e.g. bream, herring, tuna, shark
AMPHIBIANS
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Damp smooth skin
External fertilization
Jelly like eggs
Tadpoles use gills
Breed in water
Adults frogs breath using lungs
on land and skin in water
• Experience metamorphosis- a
major change in the shape as
they become adults
e.g. frogs, toads, salamanders,
newts
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REPTILES
• Dry scaly skin-reduce water
loss
• Internal fertilization
• Lay leathery and waterproof
eggs
• Have lungs
e.g. snakes, lizards, turtles,
tortoises
BIRDS/AVES
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Feathers
Beak
Hard shelled eggs
Front limbs modified as
wings
• Internal fertilization
• Warm
blooded(homeothermic)
e.g. hawks, ducks, owls, wood
packer, parrots,
MAMMALS
• Hair/fur on their bodies
• Have sweat glands
• Internal development inside a
womb
• Feed young ones with
milk(suckling)
• Different types of teeth
• Live birth
• Have a diaphragm
e.g. leopards, bats, dolphins, bears,
whales
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Arthropodes
-animals with no back bone/vertebral column
-have a waterproof exoskeleton
- Segmented bodies
- Jointed limbs/appendices
- Exoskeleton made of chitin, limestone and calcium
The 4 classes of arthropods
a. Insects
b. Arachnids
c. Crustaceans
d. Myriapods
Features of arthropods:
INSECTS
FEATURES
• 3pairs of legs
• Body with 3parts-head,
thoraxand abdomen
• Breath through tubes called
tracheae
• 1pair of antennae
• 1 pair of compound eyes
• 1-2pairs of wings
• E.g. housefly, wasp,
dragonfly
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Features of arthropods cont…
ARACHNIDS
• 4pairs of legs
• No antennae
• Body divided into
cephalothorax and abdomen
• Several pairs of simple
eyes
• Poisonous claws(chelicera)
• E.g. spider, mite, scorpion
CRUSTACEANS
• 5 or more pairs of legs
• Cephalothorax and
abdomen
• 2 pairs of antennae
• 1 pair of compound
eyes
• Calcified exoskeleton
(calcareous exoskeleton)
• E.g. crab, woodlouse,
lobster
MYRIAPODS
• 10 or more pairs of legs
-1pair per segmentcentipede
-2pairs per segmentmillipede
• Long segmented body
• 1 pair of antennae
• Simple eyes
• E.g. millipede
(chongololo);centipede
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Classification Of Plants
-plants are in the kingdom: Plants
they possess: -chloroplasts which make a green pigment called chlorophyll,
- cellulose cell walls
-large permanent sap vacuole
-they photosynthesis
Plants are classified into:
Flowering Plants and Non-flowering Plants
Non-flowering plants
-they do not produce flowers
e.g. ferns and mosses
Ferns
-have roots, stems and leaves
-the leaves are called fronds
-reproduce by spores
-no flowers
Flowering Plants
-most familiar to us
-some are tiny and others are huge
-have roots, stems and leaves
-reproduce sexually using flowers and seeds
-seeds are produced inside the ovary
-seeds are developed/matured ovules
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Two groups of flowering plants
a. Monocotyledonous plants
b. Dicotyledonous plants
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Comparing Monocotyledons and Dicotyledons
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Size Of Specimens
In the lab, a microscope is a useful apparatus. We can’t exam the cells of a human
tissue with our naked eyes. The microscope is to magnify our specimen so that it
appears bigger for us to be able to actually see.
Basic equations regarding magnification, the image size (of the specimen) and the
actual size (of specimen). Please memorize the following equation:
Image size = Actual x Magnification
In an exam, 2 out of the 3 components in the equation are given. You
need to find the missing one. Just apply the formulas.
Cells are so small that we cannot use mm to measure them. We use
micrometers andnanometers
1mm = 1000micrometers(um)
1um = 0.001mm (a um is 1000x smaller than a mm)
1um = 1000nanometers(nm)
1nm = 0.001um (a nm is 1000x smaller than a um)
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Magnification
-magnification is how many times an image is made bigger than the actual object.
Example:Mpho was asked to draw an egg whose original length was 50mm and his drawing
measured 120mm. Calculate the magnification of the egg on his drawing.
1. Write down the formula
Magnification = size/length of drawing/image
Actual size/length
2. Make substitutions in the formula
Magnification = 120mm
50mm
3. Cancel out the units. Magnification has no units (mm/cm)
4. Round off your answer to 1d.p.
5. Next to your answer, before or after the answer, place a times sign (x)
Magnification = 120mm
50mm
= 120
50
= x2.4 or 2.4x
Biological Drawings
-a biological drawing is a plan drawing of a biological specimen, which can
be a wholefruit, section through a fruit, a seed or section through a seed, an
organ or section through an organ or even a plant cell or animal cell.
-a plan drawing does not show very fine details, but only the major/prominent
regions of the spacemen
Expectations
• Use a sharp HB pencil
• Use a clean eraser
• Draw clear, smooth, continuous lines. Lines should not be woolly or too
thick or vary in thickness along its length
• Do not shade
• Use label lines not arrows when labelling
• Drawing should be ½ or greater than half the space given
• Drawing should resemble the specimen/original object
• Drawing should only reveal the major regions/major details of the specimen
• The wall of a section through an organ e.g. a fruit or root and the cell wall of
a plant cell should be represented by double lines
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Keys
-a key is used to identify an organism basing on the features the organism has.
-a key begins with the more general features and finalizes with the more
specific features that suite a given organism
-a key leads you through two contrasting features at each stage, until you get to
name the organism.
Dichotomous key
-a type of key which always have two contrasting features/descriptions of
which you have to choose one at a time at each stage.
A dichotomous key is a tool that allows the user to determine the identity of items in
the natural world, such as trees, wildflowers, mammals, reptiles, rocks, and fish.
Keys consist of a series of choices that lead the user to the correct name of a given
item.
The dichotomous key below the picture is used to classify the organisms below
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Constructing a key.
Take the shapes below to be animals. Create a key as shown below to identify
the animals. Use letters to name the animals.
1. Animal with 3 sides ...................................................................................... B
Animal with more than 3 sides ............................................................. go to 2
2. Animal with 4 sides .............................................................................. go to 3
Animal with 6 sides ....................................................................................... A
3. Animal with 4 equal sides .............................................................................. D
Animal with 4 different sides................................................................ go to 4
4. Animal with 2 of the sides equal .................................................................... C
Animal with all side different ......................................................................... E
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Use the key to identify the insect below
1. Wings present .............................................. Go to 2
Wings absent ...............................................Go to 3
2. One pair of wings visible ..................................... A
Two pairs of wings visible ....................................B
3. Three pairs of legs ................................................. C
Two pairs of legs ...................................................D
Since this insect has wins, and has two pairs visible, the answer is B!
2. Organisation of the organism
-Eukaryotes – cells with nucleus Prokaryotes –no nucleus)
-cells are microscopic, cannot be seen by a naked eye
-plants and animals are multicellular- they have millions of cells.
-other organisms like bacteria and yeast are unicellular- made up of only one cell
Microscopes are used to see or observe tiny cells. There are two types of microscopes
a). The Light Microscope -it has a smaller magnification and smaller ability to make
details of specimen being observed. It is cheaper than the electron microscope. It uses
natural light or artificial light.
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b). The Electron Microscope -it has a very high magnification and a higher
ability to make details of specimens
-it is very expensive
-requires experts to manipulate it
-it uses electrons as a source of radiation
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Animal And Plant Cells Under A Light Microscope
Animal Cell
Plant Cell
SIMILARITIES
They all have cytoplasm, nucleus, cell membrane, mitochondria,
ribosomes
DIFFERENCES
No cell cellulose cell
wall
No large central sap
vacuole
No chloroplasts
Cellulose cell wall present
Irregular shape
Regular shape
Large central sap vacuole
present
Chloroplasts present
Animal And Plant Cells Under An Electron Microscope
-the electron microscope is more powerful in terms of magnification and resolution.
-it therefore shows more details of cells than the light microscope
Animal Cell
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Plant cell
More organelles are clearly visible when observed under an electron microscope
Structures & Functions of cell
structures Cell membrane: surrounds the cell
-it is partially / selectively permeable- it allows some substances to pass and prevent
others
Cell Wall: made of cellulose, it is permeable, it protects the cell, it gives cells
support and shape. It prevents bursting when plant cells absorb water by osmosis
Cytoplasm: a jelly like-fluid which bathes cell structures, it is where chemical
reactions take place
Vacuole: -fluid filled space with its own surrounding membrane. Contains cell sap in
plants and is permanent but temporary in animals and called vesicles
Nucleus: where genetic material is stored in structures called chromosomes, it
controls activities of the cell
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Mitochondria:
it has a double membrane; the inner membrane is folded to increase its surface area
for respiration. It is where aerobic respiration takes place.
Rough Endoplasmic Reticulum:
-it has ribosomes scattered on its surface, that’s why it is called “rough”, it is made
up of flattened sac-like membranes
-it makes proteins and transport them
Chloroplasts:
-has a double membrane, it produces a pigment called chlorophyll.
-chloroplast absorbs sunlight energy, it is the site for photosynthesis
-it stores starch
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Ribosomes – only seen with an electron microscope. Cells make proteins at
ribosomes.
Bacterial Cells (Prokaryotic cells - cells with no nucleus)
Features
-cell wall made of peptidoglycan, not cellulose, cell wall provides support
-cell membrane to control entrance and exit of substances
-no mitochondria or chloroplasts
-ribosomes present
-no nucleus,
-presence of a circular DNA (bacterial chromosome) in the cytoplasm
-some bacteria have plasmids- smaller circular DNA molecules
Levels Of Organisation
Cell - Tissue – Organ - Organ system
Cell
-some organisms are just a single cell e.g. bacteria
-some cells are
specialised
Specialised Cells
-both plants and animals have specialised cells
-specialised cell is a cell with a specific structure and is adapted for a specific
function
Specialised cells in
Animals
Red blood cell
Muscle cell
Nerve cell
Egg cell
Sperm cell
Ciliated cell
Specialised cells
in plants
Palisade
cell Xylem
cell
Phloem
cell Root
hair cell
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Red blood cell
-the cell has a biconcave disc shape- to increase surface area for absorption of oxygen
-it has no nucleus- to contain as much haemoglobin as possible
-it has haemoglobin – to combine with oxygen form oxyhaemoglobin during it
transportation
-it is tiny and flexible – to squeeze through narrow blood vessels
Muscle cell
-it is long and contractile- it can contract and relax to cause movements in animals
Nerve cell
-long and capable of conducting electrical impulses
Sperm cell
-has an acrosome containing enzymes to digest through the jelly coat of the
egg to allow fertilisation to take place
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Egg cell
-it is10x bigger than the sperm cell
-it stores food
-it has a jelly coat which transforms to a fertilisation membrane which is
impenetrable to other sperms cells after fertilisation
Ciliated cell
-the cell has hair-like structures called cilia which move back and forth sweeping
mucus containing trapped dust to the back of the mouth in the bronchi and trachea
-these cells are also present in the oviduct- to move the eggs
Palisade cell
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-have a lot of chloroplasts- these take part in photosynthesis
-large central sap vacuole- to push chloroplasts to the edges to maximise the
absorption of sunlight energy during photosynthesis
-it is where most of photosynthesis take place
Xylem Cell
-cell is dead- it does not contain protoplast
-it is hollow, it joins with other cells to form long tubes
-it transports water and mineral salts
Phloem Cell
-cell is living, it has a thin film of moisture – to reduce resistance to flow of
substances
-it does not have a nucleus
-it has perforated ends where it joins with the next cells called the sieve – end plates
-it is also called the sieve element/tube
-its activities are controlled by a companion cell which lies adjacent to it
-it transports sucrose and amino acids
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Root hair cell
-has a long extension (root hair) to increase surface area for absorption of water and
mineral ions
-has a large vacuole to maximise absorption of water by osmosis
-though is a plant cell, it does not have chloroplasts
Tissues
-a tissue is a group of similar cells which work together to achieve one shared
function
Examples of tissues: Blood- it has cells and fluids aimed at transporting substances and for defense
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Muscle tissue- for movements e.g. biceps, quadriceps etc. The heart is made up
of the cardiac muscle/tissue
Nerve tissue- for transmission of nerve impulses and coordination. It includes the
brain and spinal cord cells and neurones
Ciliated tissue- to wipe or sweep out mucus in the trachea and movement of the egg
in the oviduct
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Palisade tissue or palisade mesophyll tissue
-makes a layer just below the upper epidermis in the leaf(see diagram below)
-it is the site for photosynthesis
-other tissues in the leaf are spongy mesophyll, upper and lower epidermis
Phloem Tissue
-all the cells related with the carrying of nutrients (sucrose and amino acids) in
plants- this includes the packing cells supporting the sieve tubes
Xylem Tissue
-all cells supporting the xylem tubes including the xylem vessels themselves
Organ
-a group of tissues, working together to perform specific functions
-the heart pumps blood – it is made up of muscles, blood tissue, etc
-the kidney filters blood, cleaning it and get rid of metabolic wastes
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-the liver breaks down toxic substances including drugs and excess amino acids,
it also releases and distribute heat energy in the body, it stores carbohydrates in
form of glycogen
-plant organs include the leaf, the flower, the root, the stem
Organ Systems
-group of organs with related functions, working together to perform body functions
-examples include the digestive system, gas exchange system, excretory system,
reproductive system
Digestive system
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Gas Exchange System
Organism
-systems of organs group together to sustain life in an organism
-examples of organisms
• Goat
• Hyena
• Human being
• Grass
• Tree
• Bacteria
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Relationship between cells, tissues and organs
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3.Movements In And Out Of Cells
Three ways by which molecules of substances can move in and out of cells
-Diffusion
-Osmosis
-Active Transport
Diffusion
-is the movement of particles or molecules of a substance from a region of their higher
concentration to a region of their lower concentration down a concentration gradient until
they are evenly distributed.
-concentration gradient is an imaginary “slope” from high to low concentration.
-diffusion happens in solids, liquids and gases
# Particles of a solid do not move freely, they vibrate in one position
# Particles of a liquid move more freely, but remain attached to each other.
# Particles of a gas move freely and independently of each other
-particles move by kinetic energy in diffusion.
*Dipping a piece of chalk in a red dye will see the piece of chalk turning red—it means the
dye particles move by diffusion into the solid chalk
*Putting a crystal of potassium permanganate in a beaker of water. The water turns purple
as the particles of the crystal spread evenly by diffusion
*A strong perfume spreads by diffusion from where it is highly concentrated say from a
teacher standing on the door way. The boy or girl at one end of the room will then smell it
as its particles spread randomly across the room.
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Factors affecting the rate of diffusion
Surface area: - the greater the surface area the higher the rate of diffusion. Leaves provide
a larger surface area for diffusion of gases through the stomata, the air sacs in the lungs
provide a large surface area for gas exchange in animals. Unicellular organisms e.g.
bacteria have a larger surface area to volume ration, so diffusion is an efficient method of
transport in and out of them
Temperature: - as temperature increases particles gain heat energy and therefore start to
vibrate and move about faster, their kinetic energy increases as temperature(heat) increases.
Lower temperature reduces the kinetic energy of particles this reduces the diffusion rate.
Distance to be moved by particles: - the smaller the distance or the thinner the
membrane, the higher the rate of diffusion. Thicker membranes reduce the speed at which
substances can cross by diffusion. Cell membranes are very thin and particles move across
faster
Size of particles: - the smaller the particles the faster the rate of diffusion and vice versa.
Gas particles move faster than liquid and solid particles
Concentration of substance molecules: - the higher the concentration of particles of a
substance the greater the rate of diffusion
Diffusion in real life
-Gas exchange in lungs (oxygen from air sacs into the blood stream and CO2 from blood
into the air sac; gas exchange through the stomata in leaves (CO2 in and O2 out); absorption
of nutrients in the small intestines; exchange of substances between blood and cells in
animals; movement of solutes through the cytoplasm.
Osmosis:
-it is the net movement of water molecules from a region of high-water potential to a region
of low water potential through a partially/selectively permeable membrane.
-it is a form of diffusion that involves water molecules only and a selectively/partially
permeable
membrane.
-water potential is the tendency of water molecules to leave a system/ a solution, distilled
water or a dilute solution has a high-water potential
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The diagram shows how water molecules can move from one system to another
Descriptions
-Water moves from A to B and its level in A decreases
-Sugar particles will not pass to A, level of solution in B increases
Explanations
-Water molecules are tiny enough to pass through the pores of the partially permeable
membrane by osmosis
-Solution A has a higher water potential than solution B
-Sugar particles are too big to cross the partially permeable membrane
Solutions
-a solution is a mixture of a solute and a solvent
-a solute is a substance that dissolves in a solvent, e.g. sugar, salt
-a solvent is a substance/liquid that dissolves a solute, e.g. water, ethanol
*sugar solution = sugar + water
*salt solution = salt + water
Types of solutions
-named according to how dilute or concentrated the solutions are
Dilute solution: - it has more water molecules than solutes. It is also called a weak solution
Concentrated solution: -it has more particles of a solute than water. It is also called a
strong solution
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Behaviour of plant and animal cells in different solutions.
CELL
Red blood
cell
Palisade cell
WEAK
/DILUTED
SOLUTION
-absorbs water by osmosis
-cell enlarges/expands
-cell bursts because it does not
have a cell wall
-absorbs water by osmosis
-turgor pressure builds from inside
-cell enlarges/expands
-turgor pressure builds from inside
the vacuole
-cell becomes turgid/firm
-cell does not burst because it
has a cellulose cell wall
STRONG/CONCENTRA
TED SOLUTION
-cell loses water by osmosis
-cell shrinks and becomes
smaller
-loses water by osmosis
-loses turgor pressure
-cell becomes small
-cell becomes plasmolysed
and flaccid
-wilting is a sign of
plasmolysis in plants
-gaps between cytoplasm and cell
wall is occupied by the external
solution
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Behaviour of plant tissues in a dilute and concentrated solution
-strips of freshly cut potato can be used.
-make sure the strips are from one type of potato, of the same length, mass and freshness
-freshly cut potatoes are firm and rigid
-Place 5 potato strip in a petri dish containing distilled water and 5 in a petri dish containing
a strong sugar/salt solution for the same length of time at the same temperature
-Remove the strips from the solutions and blot them with paper towels
-feel the strips
NB: Strips from the distilled water feel more rigid, harder and firmer – the strips absorbed
water by osmosis
Strips from a strong sugar/salt solution feel soft/slimy and weak: - the strips lost water by
osmosis
If masses or lengths were recorded, strips in dilute solution would gain more mass or
length while those in a strong solution lose mass or shorten to show that they would have
lost water by osmosis
Osmosis in living organisms
Allows plants to absorb water by their root hair cells. Water molecules move from a region
of high-water potential(soil) to a region of low water potential (root hair cell) by osmosis
Water molecules move from cell to cell in a plant or in animals by osmosis .Water is
absorbed into the blood stream from the digestive system by osmosis .Water moves by
osmosis in to plant stems and leaves to provide support.
Importance of water
-dissolves food in the alimentary canal facilitating digestion
-combines with urea and salts to form urine
-make body fluids- saliva, tears, mucus, blood
-it is a transport medium – substances are transported in solution made of water.
34
Osmosis and Diffusion
-these two processes are passive- they do not use energy from respiration
-they use the kinetic energy of the moving particles
-particles move from a region of their high concentration to a region of their low
concentration
-osmosis is a special type of diffusion
Active Transport /Uptake
- the movement of molecules of a substance from a region of lower concentration to a
region of higher concentration against a concentration gradient using energy from
respiration. The energy used is in form of ATP (Adenosine Tri-phosphate)
-there are special proteins across the membrane which take part in active transport
-these proteins are called carrier proteins –
-carrier proteins are capable of changing their structures and their orientation- thus they can
at one time face outside the membrane accepting molecules outside the cell and then
change and face inwards inside the cell, moving molecules of substances into the cell
Importance of active transport in life
Plants absorb mineral ions like nitrates, magnesium ions etc. from the soil by active
transport
Glucose is reabsorbed in the kidneys by active transport
Sucrose is transported in phloem vessels by active transport
Active transport takes place in transmission of nerve impulses
Active transport uses energy from respiration unlike diffusion and osmosis
-active transport happens in living cells only, while osmosis and diffusion can also happen
in non-living things
35
Experiments on Diffusion and Osmosis
1. A glass tube is prepared as follows:
-Same sized pieces of red litmus papers are place from one end of the glass tube to the
other end at uniform intervals.
-A cotton wool is soaked in ammonia (a base)
-The cotton wool is plugged at the mouth of the glass tube and time is recorded for each of
the 10 red litmus papers to turn blue in colour. See the apparatus below.
Description:
-particles of ammonia diffuse from a region of high concentration (cotton wool) along the
length of the tube-this is evidenced by the damp red litmus papers turning blue.
-The higher the concentration of ammonia, the faster the red litmus papers turn blue and
vice versa.
2.An apparatus is set as shown below. The visking tubing/dialysis tube is a partially
/selectively permeable artificial membrane.
After just a few seconds of suspending the visking tubing containing starch, into the test
tube containing Iodine solution, the following observations are made:
-Starch solution turns blue black
36
Explanation:
-Iodine particles are smaller enough and they therefore pass through the pores of the
partially permeable visking tubing.
-Iodine solution remains yellow – brown in the test tube
Explanation:
starch particles are too large to pass through the pores of the visking tubing.
3.An apparatus was set up as shown below.
The visking tubing is filled with a sucrose solution and a capillary tube connected to it. The
level of the solution is marked in the capillary tube as shown in the diagram. The tube is
held upright in a beaker of distilled water and left for 30mins. Describe and explain
observations after 30mins.
Description:
-the level of solution rise in the capillary tube.
-water enters the visking tubing.
-level of water drops in the beaker.
Explanation:
-water enters by osmosis
-sucrose molecules are too large to pass into the beaker
37
4.A crystal of Iodine is placed in a beaker of distilled water. Within a few minutes the
water turns yellow – brown
Explanation:
-particles spread by diffusion
Alternatively set up three beakers and subject them to 0°C and 30°C and the third at 60°C
and compare the rate of diffusion between the three beakers.
Description:
-diffusion happens fastest at 60°C
Explanation:
-particles gain more kinetic energy and therefore move very fast and distribute themselves
evenly in the solution.
5. Set up 100cm3 of 5 different solutions (distilled water0.0mol/dm3, 0.1mol/dm3,0.
2mol/dm3, 0.3mol/dm3 and 0.4mol/dm3)
-Use a Cork borer to make the thinnest cylinders of potato of 40mm lengths
-Place 10 potato cylinders in each solution for two hours.
-Describe and explain your observations after 2hrs.
Distilled water:
Potato cylinders increase in length and they become very rigid. The cylinders absorb water
by osmosis, the cells expand and gain turgor pressure.
0.1moldm3:
Cylinders get slightly firmer and have a slight increase in length. The solution has a greater
water potential than the potatoes. Water moves into cylinders by osmosis.
0.2moldm3:
Potatoes did not change in size or firmness. The water potentials of the cylinders and
solution were the same.
0.3moldm3:
Cylinders reduced in length.
Cylinders lost water by osmosis.
Cell getting plasmolysed- cells become flaccid. Cylinders become soft and floppy
38
0.4moldm3:
Cylinders become shorter than the ones in 0.3moldm3.
They are also more softy and floppy
6.An egg is the largest animal cell which has a shell acting like a cell wall, though it does
not allow substances to pass. The shell is made up of calcium salts deposited in it.
Take two eggs and put them in HCL (Hydrochloric acid) for several hours. The acid
dissolves the egg shells and leaves the eggs soft, covered or surrounded by the cell
membrane only. This is called deshelling.
-feel the eggs and record your observations
-record their masses
-check also their sizes (make sure they are the same size or you will need to calculate
percentage change in mass after the experiment
-put one of the eggs in distilled water and another r in a strong salt solution as shown
below:
39
Descriptions
Distilled water
The egg enlarged or increased in size.
Pressure increases inside it
Salty water
The egg reduced in size and it shrunk.
Explanations
Distilled water
-The egg absorbed water by osmosis,
-water moved from its region of higher water potential (beaker) to its region of lower water
potential (inside the egg), through the partially permeable membrane of the egg.
Salty water
-the egg lost water by osmosis
-water moved from the egg, its region of higher water potential to the salty solution, a
region of it lower water potential.
40
4. Biological Molecules
These are any of the numerous substances that are produced by cells and living organisms.
They have a wide range of sizes and structures and perform a vast array of functions.
Types of biological molecules
-carbohydrates,
-proteins
-lipids,
-nucleic acids (DNA and RNA)
Subunits
-these are simple or smallest molecules/monomers that make up biological molecules
-biological molecules are giant molecules(macromolecules) made when monomers or
subunits join by condensation
-condensation is a process where molecules join together releasing water.
-below is a table showing the biological molecules and their subunits.
Biological
Subunit
molecule
Carbohydrate
Glucose
Proteins
Amino acids
Fatty acids
Fats/Lipids
and Glycerol
Nucleic Acids
nucleotides
(DNA)
41
Carbohydrates
starch is a storage carbohydrate found in leaves, fruits and roots
-glucose molecules join to form starch soon after photosynthesis
-starch is an ideal storage carbohydrate for it is unreactive and insoluble in water.
-glucose is reactive and soluble so cells would absorb water and this can interfere with
chemical processes in cells
glycogen is a storage carbohydrate in animals in the liver and muscles
-it is also unreactive and insoluble
-both starch and glycogen are easy to break down to provide glucose molecules needed
for respiration. The two are also compact allowing them to pack inside cells
cellulose is a structural carbohydrate making cell walls and the woody part of plants, it
gives mechanical support in plants, it is insoluble in water
-starch, glycogen and cellulose are polysaccharides (‘poly’ means many, ‘saccharides
mean sugars)-many sugars joined by condensation.
sugars – these include monosaccharides and disaccharides
-‘mono’ means one , ‘saccharide’ means sugar
Monosaccharide is a single molecule of a sugar e.g. Glucose
-glucose has a molecular formula C6H12O6 - this means it is made up of 6 carbon
atoms, 12 hydrogen atoms and 6 oxygen atoms.
-the formula shows the number of each atom in a molecule of a substance
Formula for glucose
-the structure shows the positions of the atoms
Properties of a monosaccharide/sugar
-it is sweet
-soluble in water
-reacts with other substances
-very small molecule
42
Disaccharides
-‘di’ means two
- a disaccharide is a sugar made up of two monosaccharides joined by condensation
-examples of disaccharides: i-maltose-malt sugar (in germinating seeds) or produced during digestion of starch iilactose – a milk sugar
iii-sucrose – a sugar transported in phloem vessels in plants
Properties of disaccharides
-sweet
-soluble in water
Proteins
-the subunit for a protein is an amino acid
structure of an amino acid
-the amino acids join by condensation to make proteins
-different amino acids join to form a protein molecule or polypeptide
-each shape represents a different amino acid
-only 20 different amino acids exist, but many different proteins are found in both
plants and animals.
-the different arrangements of amino acids produce many different proteins.
-some proteins are soluble in water e.g. haemoglobin
-others are insoluble e.g. keratin in hairs and nails, collagen in bones
43
-protein chains can curl up producing a three-dimensional shape – this allows proteins
to carry out different functions. Enzymes and antibodies rely on their shapes to carry
out their functions. different shapes
Fats
-also known as lipids
-made up of glycerol and fatty acids
-liquid fats at room temperature are called oils.
-fats are insoluble in water
Deoxyribonucleic Acid (DNA)
-the subunits are nucleotides
Structure of a nucleotide
-has a deoxyribose sugar
-a phosphate group
-a nitrogenous base/organic base (A, T, G or C)
-the nucleotides join together by condensation to form the strand of DNA
The structure of DNA
-made up of two strands of polynucleotides- it is a double stranded molecule
-the two strands are anti-parallel
-the two strands form a double helix
44
-made up of the bases (A, T, G and C)
-A pairs with T, G pairs with C
-the pairs of bases are complementary to each other – this is called complementary base
pairing
-the sugar phosphate backbones are like the upright members of a ladder and the paired
bases are like the cross members of a ladder
45
-the molecule of DNA forms a double helix as shown below-the nucleotide chains wind
around each other
-the sequence of bases in DNA forms a code needed for the production of specific
proteins in cells
-the sequence determines that you are a human not a dog, sloth or a donkey
-DNA determines your features and characteristics
Biological molecules, Elements and Functions
Biological Molecule
Carbohydrates
-sugars (mono and
disaccharides)
-polysaccharides (starch,
glycogen, cellulose)
Proteins
Common
elements
Carbon C
Hydrogen H
Oxygen O
Carbon C
Hydrogen H
Oxygen O
Nitrogen N
Sulfur S (in
some proteins)
46
Functions
-make cell membranes
-provide energy during
respiration(glucose)
-used as storage
material (starch in
plants and glycogen in
animals)
-make cell walls
(cellulose)
-glucose converted to
fats, starch, cellulose
-make hormones,
enzymes, antibodies,
-make blood proteins
-make cell membranes
-make body structures
hairs and nails(keratin),
bones, ligaments and
tendons(collagen)
Fats/ Lipids
Carbon C
Hydrogen H
Oxygen O
Phosphorus P (in
some fats
DNA
Nitrogen N
Phosphate P
Carbon C
Hydrogen H
Oxygen O
-make cell membranes
-provides energy (twice as
much energy provided by
carbohydrates of the same
mass)
-insulation in temperature
regulation
-makes blabber in whales for
buoyance
-protects delicate organs
-make genes
-genes carry genetic
information
-genes determine the type of
proteins produced in your
cells
-our features and
characteristics are due to the
genes present in our cells
Food Tests
-they are done to identify the nutrients present in a given food type
-allow dietitian to prepare special diets for people with special dietary needs
1
2
Food
Starch
Name of test
Iodine Test
-iodine
solution(brown) is
used
Procedure
-add drops of iodine
solution to a food sample
e.g. slice of bread
Reducing
sugar (a
sugar
reduces the
Benedict’s
solution)
-Benedict’s
Test
-Benedict’s
solution (blue
colour)
-put 2cm3 of a food sample
in a test tube.
-Add 2cm3 of Benedict’s
solution to the same test
tube
-Heat the test tube in a
water bath for 2-3mins
*safety precaution: eye protection, avoid
spilling hot water, put
off source of heat after
the activity
47
Observations
-the food sample turns
blue/black in colour to
show a positive result
-if starch is absent the
food sample turn
brown, the colour of
iodine solution
-the solution turns
green, yellow or brick
red if reducing sugars
are present.
-remains blue if
absent Green= low
sugar Yellow=
medium
Brick red=high
quantity
3
Proteins
4
Fats
5
Vitamin
C
Biuret Test
One can use: -Biuret solution
(blue colour)
-put 2cm3 of a food sample
in a test tube.
-add 2cm3 of Biuret
solution to the sample
-Biuret
Reagents: *Potassium
hydroxide (KOH)
and *Copper
(II) sulfate
(Cu2SO4)
Ethanol
Test/Emulsion
Test
-ethanol is
used
-add 2cm3 of KOH to the
test tube containing a
food sample.
-shake
-add Copper (II) sulfate
drop by drop up to 3 drops
only
-put 2cm3 of a food sample
in a test tube
-add the same volume of
ethanol to the test tube.
-shake vigorously
NB:- Ethanol dissolves
any fat in the solution
-add distilled water to the
test tube
-put 2cm3 DCPIP in a
test tube
-add drop by drop of the
food sample to the same
test tube
DCPIP Test
-DCPIP(blue) is
used
- purple/lilac/mauve/vi
olet colour shows
presence of proteins
-blue colour shows
absence
- purple/lilac/mauve/vi
olet colour shows
presence of proteins
-blue colour shows
absence
-a cloudy or white
emulsion is formed in
the test tube, this shows
presence of fats
-a clear colour
shows absence of
fats
-the DCPIP turns
clear if vitamin C is
present
NB:- it takes very few
drops to clear DCPIP if
vit C is high in the food
sample and vice versa.
Water
-it is one of the very important biological molecules in life
-it is made up of hydrogen and oxygen in the ratio of 2:1
-Water is a useful molecule due to its properties
Properties of water and Uses of water
1. Water as a solvent – substances dissolve in water, chemical reactions take
place in solutions made of water
2. Water as a reagent – it takes part in chemical reactions e.g. photosynthesis
3. Water as a transport medium – it forms blood which transports nutrients around
the body, urea is transported to the kidneys and later excreted through the
kidneys
48
5. Enzymes
-an enzyme is a biological catalyst that speeds up chemical reactions without it being
altered by the reaction
-a catalyst is a substance that speeds up chemical reactions without it being changes
by the reaction. It can be biological (meaning produced by living organisms) or
artificial (man-made e.g. chemicals)
Properties of enzymes
a)
b)
c)
d)
e)
They are proteins in nature- all enzymes are made of proteins
They are specific – each enzyme acts on a specific substance called a substrate
They are not changed by a reaction/they can be used again and again
They speed up chemical reactions
They have active sites – the part of an enzyme where the substrate binds,
leading to its break down or leading to substrates to join
f) Enzymes work best at a given temperature
g) Enzymes work best at a given pH level
How an enzyme works
-the enzyme has an active site
-the substrate fits perfectly into the active site forming an enzyme - substrate complex.
-the union of the enzyme and substrate brings about mechanical stress in the substrate
-the substrate breaks forming products e.g. A and B in the diagram below
-the enzyme becomes free again
49
-maltose can also be broken down into simple molecules of glucose
- the actions above show that enzymes can take part in break down reactions- the
substrate is split into two simple products
-enzymes also take part in building up reactions – the substrates are joined
together to form a more complex product
-the enzyme action shown above shows us that: •
•
•
Enzymes are specific (one enzyme-one substrate
Enzymes take part in both build up and break down reactions
Enzymes can be used again and again
The Lock and Key Hypothesis/Theory
-this theory states that the enzyme is the Lock and the substrate is the Key
-the substrate gets/fits into the enzyme’s active site, the way a key fit into a key hole of
a locker
-the keyhole is the active site in an enzyme, the lock
-in this theory the active site has a shape complementary to the shape of the substrate
-this theory is quite rigid, for it suggests that both the enzyme and substrate
are solids/ are not flexible.
50
Effects of Temperature on enzyme-controlled reactions
-enzymes work best at a given temperature
-enzymes in humans work best at 370CDescriptions
if temperatures are too low, activity is low.
-as temperature increases activity increases and will be at its optimum at the
optimum temperature (400C in the graph below)
-further increase beyond the optimum temperature activity slows down until the
reaction stops
Explanations
-at low temperature enzymes are inactivated-they have very little kinetic energy so
both enzyme and substrate particles vibrate slow
-increasing heat energy increases kinetic energy and chances of collision increase
between the substrate and the enzyme molecules. Enzyme – substrate complexes
are created and reactions take place at the active sites
-above the optimum temperature, the vibrations due to too much heat energy break
down protein molecules causing them to denature
51
-to denature is when an enzyme molecule is deformed and therefore loses the shape of
its active site. The enzyme then fails to combine with its substrate, no enzyme –
complexes are formed and therefore no reaction will take place.
Effects of pH on the activities of enzymes
-enzymes work best at a given pH
-different enzymes (pepsin, amylase, lipase, trypsin etc, work best at different pH
levels
Descriptions
-too low and too high pH slow down and even stop enzyme activities
-increasing pH and lowering pH back to its optimum pH, for any enzyme
increases the enzyme’s activity
52
Explanations
-too low and too high pH denature enzymes, the protein molecule breaks down
or deforms due to changes in pH. The active site deforms also and enzyme substrate complexes are not formed
There are different types of enzymes
-enzymes are named and grouped according to substrates they digest or reactions they
catalyse.
-their names often have “ase” at the end
Substrate
Group Name of
enzymes
Examples of
enzymes
Carbohydrate
digested
Carbohydrate
Carbohydrases
Salivary
amylase
Pancreatic
Amylase
Maltase
Lactase
Sucrase
Starch
Starch
Maltose
Lactose
sucrose
Protein
Proteases
Pepsin
Trypsin
Peptidase
Protein
Protein
polypeptides
Lipid/ Fat
Lipases
Pancreatic
lipase
Lipid/Fat
Another enzyme is catalase, this breaks down hydrogen peroxide produced in cells
during metabolism. Hydrogen peroxide is toxic so it must be broken down to oxygen
and water
53
6. Plant Nutrition
-plants are the only organisms that can make their own food
-animals depend on plants directly (eating grass, fruits, roots and leaves including
maize meal and rice) or indirectly (feeding on animal products meat, milk, cheese, of
which the animals depended directly on plants)
-Nutrition is a way of feeding
-Plants make their food through a process called Photosynthesis
-the process of photosynthesis takes place mainly in the leaves
External structure of a leaf: -
Internal structure of a leaf
Parts and functions
1. Cuticle: - a waxy-like substance which prevents water loss by evaporation.
2. Upper epidermis: - cells are closely packed together, cells are transparent to allow
light to pass, cells also secrete cuticle
54
3. Palisade Mesophyll layer: -it is a site for photosynthesis cells, it contains a lot
of chloroplasts, chloroplasts contain chlorophyll, chlorophyll is a green substance
whichabsorbs sunlight, sunlight energy is converted to chemical energy in sugars
duringphotosynthesis
4. Spongy mesophyll layer:- cells are irregular in shape, so they leave air spaces,
air spaces allow circulation of gases, carbon dioxide, water vapour, and oxygen
5. Vascular bundle:- made up of the xylem and phloem vessels, xylem vessels
transport water and mineral ions; phloem vessels transport sugars (sucrose) and
amino acids
6. Stamata:- are pores mainly on the underside of a leaf, which allow exchange of
gases ,carbon dioxide in from the atmosphere and oxygen out from the leaf; each
stoma is made up of two guard cells(stomata when more than 1 stoma)
7. Lower epidermis:- some of its cells are modified to make guard cells which make
Stomata; its function is to protect the leaf.
Photosynthesis
-it is a process whereby plants manufacture their own food(sugars) using inorganic
substances (water and carbon dioxide) in the presence of sunlight and chlorophyll,
giving out oxygen as a by-product.
Word equation for photosynthesis
sunlight
Carbon dioxide + Water---------------> glucose + Oxygen
chlorophyll
Chemical/Symbol equation
6CO 2 + 6H 2O —> C 6 H 12 O6 + 6O 2
Raw materials for photosynthesis
1. Water
2. Carbon dioxide
Products of photosynthesis
• Sugars(glucose)
• Oxygen
55
47
Factors necessary for photosynthesis to take place
•
•
•
•
Sunlight
Chlorophyll
Carbon dioxide
Water
Events involved during Photosynthesis
56
A. To investigate whether CO2 is necessary for photosynthesis
i.
ii.
iii.
iv.
The two plants, X and Y are destached, starch is removed by putting them in
darkness for 48hrs
Soda lime / sodium hydroxide/potassium hydroxide in set up Y absorbs carbon
dioxide and sodium hydrogen carbonate in set up X releases carbon dioxide
Expose the two plant to sunlight for several hours
The one leaf from each plant, for starch
Observations & Explanations
-leaf from plant X turns blue-black –this shows presence of starch, CO2 was present
-leaf from plant Y takes the colour of iodine solution(brown) –this shows absence of
starch, no carbon dioxide was present, no photosynthesis
B. To investigate whether chlorophyll is necessary for photosynthesis
-use variegated leaves, leaves with one part green and the other yellow or white
-the green part contains chlorophyll and the yellow/white part has no chlorophyll
57
i.
ii.
iii.
Destarch the plant
Expose the plant to sunlight for several hours
Test one of the variegated leaves for starch
Observations & Explanations
-the yellow/white part turns brown –no starch present, did not photosynthesise,
chlorophyll absent
-the green part turns blue-black –starch present, managed to photosynthesise,
chlorophyll absorbed sunlight.
C. To investigate whether sunlight is important for photosynthesis
i.
ii.
iii.
iv.
Destarch a potted plant
Cover one leaf with aluminium foil as in the diagram
Leave the plant in sunlight for several hours
Test the leaf for starch
Observations & Explanations
-the covered part turns brown –no starch present, did not photosynthesise as sunlight
was blocked
-uncovered part turns blue-black –starch present, the part absorbed sunlight and
photosynthesised
58
How to test for starch in a leaf
1. Boil the leaf in water –to break open cell walls
2. Boil the leaf in alcohol (ethanol) –to remove chlorophyll. Chlorophyll interferes
with colour changes when iodine solution is added.
-the leaf loses its green colour and it becomes hard and brittle
3. Soak the leaf in water –to soften it
4. Spread the leaf on a white tile –a white tile makes observations clear
5. Add drops of iodine –to test for the presence of starch. If starch is present the leaf
turns blue-black (positive test) and if absent, the leaf turns brown (negative test)
The uses of products of photosynthesis
Glucose (sugar)
• used by the plant during respiration to release energy
• converted to starch and stored in the leaves, roots and seeds
• converted to cellulose and make the structural part of the plant
• converted to fats, to amino acids to make proteins
• converted to sucrose so that it can be translocated in the phloem vessels
• making nectar to attract insects for pollination
• making chlorophyll
Oxygen
• used during respiration
• expelled through the stomata to the atmosphere
59
Factors affecting rate of photosynthesis
-a factor which when in short supply reduces or stops a reaction is called a limiting
factor
-as the factor increases rate of reaction increases, until the amount of the factor present
stop to be a limiting factor. At this point other factors start to limit the process
-in photosynthesis limiting factors are sunlight intensity, carbon dioxide concentration
and temperature
a) sunlight intensity
-the graph shows that at low light intensities, the rate of photosynthesis is low. Rate
increases as light intensity increases up to a point where light intensity ceases to be a
limiting factor, other factors start to limit photosynthesis
-at this point a further increase in intensity will not increase the rate of
photosynthesis
-the graph levels off as rate becomes constant
To show that rate of photosynthesis changes with light intensity
-set up the apparatus as above
60
-the pond weed used is Elodea, it readily releases oxygen bubbles as it
photosynthesises in water
-moving the lamp nearer to the Elodea in the beaker, causes a higher production of
oxygen bubbles as light intensity increases
-pushing the lamp away, reduces the light intensity and hence less bubbles are
produced as rate of photosynthesis decreases.
-the thermometer is there to check the level of water temperature
To test for the gas (oxygen)
-bring a glowing splint to the mouth of the test tube
-the splint relights/rekindles/bursts into flames
b) carbon dioxide concentration
-at low CO2 concentration, the rate of photosynthesis is low
-as the concentration increases, rate of photosynthesis increases up to a point where
the graph levels off as rate remains constant, other factors start to limit
photosynthesis
c) temperature
-as temperature increases rate of photosynthesis increases up to a point where rate is
highest.
-A further increase slows down the reaction as high temperature starts to denature
enzymes
61
Mineral requirements
Plants need mineral ions to make other essential molecules such as proteins and
chlorophyll.
Two mineral ions are magnesium and nitrate ions
These mineral ions are absorbed by the root hair cells from the soil by active
transport.
Magnesium ions are needed to make chlorophyll inside chloroplasts
-chlorophyll is a pigment in plants that absorbs sunlight energy which is need
during photosynthesis.
-shortage of magnesium leads to chlorosis (yellowing of leaves)
Nitrate ions are need to make amino acids which in turn make proteins
-plants falling short of nitrate ions experience stunted growth
7. Human Nutrition
-humans cannot make their own food like plants
-humans rely directly on plants for food (they eat grains and fruits) or indirectly
(theyfeed on other animals that feed on plants, they eat animal products)
-humans need a balanced diet
Balanced diet:- this is a meal or diet containing all nutrients in the right quantities and
proportions.
Components of a balanced diet, their sources and functions in the human body
Component
Source
Function(s)
Carbohydrates
Rice, Maize,
Potatoes, Cassava,
Pastas,
Milk, Eggs, Beans,
Meat, Mushroom,
Fish
-provide energy
-make cell membranes
Proteins
Fats/Lipids
-growth
-repair of tissues
-replacement of tissues
-make enzymes,
hormones, antibodies
-provide twice the energy
provided by carbohydrates
Sunflower, Maize,
Meat, Fish
62
Deficiency
Disease /
Condition
Marasmus
Kwashiorkor
Component
E.g.
Sources
Calcium
Milk, Eggs,
Cheese
Iron
Red meat,
egg yolk,
spinach
Mineral salts
Vitamins
Fibre/Roughage
Water
Functions
Deficiency Diseases
/ Condition
-to make bones
and teeth
-blood clotting
-rickets
-brittle bones and
teeth
-poor blood clotting
-formation of
-anaemia (shortage red
haemoglobin/formation blood cellsleading and
of redblood cells
shortage of oxygen to
cells, and therefore less
energy released
-scurvy: pains in joints and
- make collagen
C
Citrus
muscles, bleedingof gums
in
the
skin,
fruits,
Common in people who
-proper tissue
Lettice,
lack fresh vegetables
repair andhealing
and fruits
of wounds
D
-rickets: poor bones
Butter, egg yolk, -help in
absorption
of
and teeth
madein the skin
calcium
development, bones
in sunlight
are soft and
-bone and teeth
deformed producing
formation
bow legs
-Constipation
Fruits, Rice, vegetables, bread
-make the bulk of
faecal matter
facilitating
peristalsis
-prevents
constipation
-70% of cells is
Fruits, drinking water
-dehydration
water
-transport
medium
-medium for
chemical
reactions
-make body
fluids(semen,tears,
sweat, urine)
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Dietary needs
-dietary needs depends on the following
• Age
• Sex
• Activity of the individual/Occupation
Age
-young children need more carbohydrates for energy since they are more activity
-they need more proteins for body building and repair of broken tissues
-they need more iron for blood formation
-more calcium and vitamin D for bones and teeth formation
Sex
-young boys need more energy giving foods than girls for they are more active
-girls need more iron for blood formation since they lose blood during menstruation
-man need more food compared to females
Activity Of The Individual/Occupation
-builders and farm labourers need more carbohydrates for energy- their jobs demand
moreenergy
-builders require more proteins for muscle building
-pregnant women need more proteins for the growth of the fetus, they also need more
calciumand vitamins D for bone and teeth formation in the fetus, they also need more
iron for blood formation in the fetus.
The processes associated with the digestive system
1. Ingestion
-taking in of food through the mouth
2. Digestion
-break down of insoluble complex food substances to simple soluble substances
which canbe absorbed
3. Absorption
-the process whereby digested food substances pass into the blood stream
4. Assimilation
-passing of food (nutrients) into the cells and its use in the cells
5. Egestion
-removal of undigested food substances as fecal matter through the anus
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Two types of digestion in the human digestive system
a. Mechanical digestion is the break down of large food particles to smaller particles.
This increasesthe surface area of food to facilitate the action of enzymes. The teeth,
bile and muscles of the stomach take part in mechanical/physical digestion
b. Chemical digestion is the breakdown of large complex insoluble food
molecules to simplesoluble molecules by enzymes
The human teeth
-there are 4 types of teeth
The action of each tooth is part of mechanical digestion
a. incisors -they are at the front part of the mouth, they are for cutting/biting food,
chisel shaped teeth, 8 in total
b. canines -on the sides, they are conical/pointed, they grab or tear flesh,4 in total.
c. premolars -before the molars and towards the back of the mouth, they grind or
chew food, they have cusps and a wide with two roots, 8 in total.
d. molars -at the back of the mouth, wider and larger than premolars, they grind or
chew the food, have cusps and three roots
Importance of chewing food
- breaks down food into smaller particles, this increases the surface area of food,
facilitating action of enzymes
- mixes food with saliva allowing salivary amylase to act on starch
- makes swallowing easy
Tooth decay
-bacteria breakdown food remains anaerobically, releasing lactic acid
-lactic acid dissolves enamel and dentine making a hole into the tooth
-bacteria get into the pulp cavity, releasing toxins which cause pain and the ultimate
break down of the tooth.
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The structure of a molar tooth
Crown - the white part of a tooth-that which protrudes from the gums
Neck - the part in of a tooth in contact with the gums
Root - the part fixed into the jaw bone, by a substance called cement
A section through a molar tooth reveals the following parts
1. Enamel – the hardest part of a tooth which is wear resistant, making teeth ideal for
chewing, biting and tearing flesh
2. Dentine – softer layer than the enamel, hard bone material, has blood vessels
3. Pulp cavity – has nerve endings and blood vessels, makes a tooth sensitive
-blood vessels distribute nutrients and oxygen to the tooth
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The Alimentary Canal & Associated Organs
Parts of the alimentary canal, associated organs and their functions
A. Mouth
-ingestion takes place here-we take in food through the mouth
-two types of digestion take place in the mouth-mechanical/physical digestion and
chemical digestion
-Mechanical digestion is carried out by the teeth and tongue
-mechanical/physical digestion is whereby large food substances are broken down to
smallerpieces
-there are teeth in the mouth for biting/cutting and chewing food- this is
mechanicaldigestion
-the tongue presses and mixes food with saliva and in the process the food is broken down
tosmaller pieces
-chemical digestion-this is whereby complex insoluble food substances are broken down
byenzymes(chemicals) to simple soluble substances
-salivary glands secrete an enzyme called salivary amylase
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-salivary amylase breaks down starch to maltose
-the food is rolled into a bolus and is passed to the Oesophagus
B. Oesophagus
-passing of food to the oesophagus is called swallowing
-food moves down the oesophagus by peristalsis
-peristalsis is the voluntary contractions and relaxations of the gut muscles causing
smoothmovement of the food along the gut.
-there are no enzymes produced in the oesophagus, but digestion continues, of starch
fromthe mouth by the salivary amylase
C. Stomach
-a bag like structure which receive and store food
-the stomach secretes the gastric juice
-gastric juice contains hydrochloric acid(HCL) and an enzyme called protease
HCL
-kills bacteria coming in with food from the mouth
-create acid condition in the mouth which is needed by the protease
Protease- takes part in chemical digestion
-break down proteins to amino acids
Stomach muscles- squeeze food to break down mechanically/physically
-the food from the stomach is acidic and is in a semi liquid state called chime
D. Liver &Pancreas
-these two organs are not part of the alimentary canal
-they are associated organs
Liver- make and secrete bile
-bile is a yellow - green fluid which contain bile salts.
-bile salts take part in mechanical/physical digestion.
-the salts emulsify fats- that’s break fats to smaller droplets increasing surface area for
digestion by lipase
-the liver does not secrete enzymes
Pancreas – secrete three enzymes – pancreatic amylase, lipase and trypsin
-the pancreas and the liver secrete their contents in to ducts e.g. the bile duct and the
pancreaticduct which carry the contents to the duodenum
E. Small intestines
-the small intestines receive acidic chime from the stomach
-the small intestines are made up of the duodenum and the ileum
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Duodenum
-receives contents from the ducts-bile and pancreatic ducts
-bile salts emulsify fats
-bile also neutralise acids from the stomach
-pancreatic amylase, lipase and trypsin carry out chemical digestion in the duodenum
• Pancreatic amylase – digest starch to maltose
• Trypsin-a protease which digest proteins to amino acids.
• Lipase – digest fats/lipids to fatty acids and glycerol
Ileum
-digestion ends in the ileum
-more proteins are broken down to amino acids by protease
-absorption of final products of digestion takes place in the ileum
Food
Starch
Proteins
Fats/lipids
Final product
Glucose
Amino acids
Fatty acids and glycerol
Absorption
-the ileum is adapted for absorption
• It is long and folded to increase surface area for absorption
• They have villi to crease surface area for absorption- villi are finger-like-structures
in theinner lining of the ileum
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The structure of a villus
-lacteals absorb fatty acids and glycerol
-thin surface layer-one cell thick- reduces the diffusion distance
-capillaries maintain a steep diffusion gradient between blood and the ileummakingdiffusion of nutrients efficient
-the absorbed food is taken to the liver through the hepatic portal vein
Processes involved in absorption
a. Diffusion
b. Active transport
F. Large intestines
-allow formation of faeces
-there is absorption of water by osmosis
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G. Rectum
-stores faeces temporarily
H. Anus
-allow faeces to move out
8. Transport In Plants
-plants are complex and multicellular, diffusion stops to be an effective way of
transportingsubstances
-substances in plants are moved from point of production(source) to point of storage or
use(sink)
-amino acids and sucrose are moved from leaves while mineral ions and water are moved
from thesoil
-The transport system is made up of the root hair cells; xylem; phloem and stomata
Root hair cells
-has a long extension to increase surface area for absorption of water and mineral ions
-water is absorbed by osmosis
-mineral ions are absorbed by active transport
Xylem and Phloem
-xylem are dead cells, which are joined end to end forming hollow tubes
-these tubes have lignified walls to prevent collapsing-xylem provides support to plants
-xylem tubes run from the roots to the leaves
-they transport water and mineral ions up the plant from the roots
-xylem carry water and minerals in one direction
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-phloem cells are living and are joined end to end
-end walls (sieve plates) are found between joined cells-they have perforations to
allow flowof substances
-phloem transport sucrose and amino acids- these are organic molecules
-transport in phloem is in either ways- up or down
Structure of a plant
-the plant has the following as the major parts
• Roots; Stem; Leaves;
• Some may produce flowers and others do not produce flowers
72
Positions of the xylem and phloem in the root; stem and leaves
73
How water is absorbed from the soil until they reach the xylem
-there is a high-water potential in the soil than in the root hair cells
-water moves by osmosis into the root hair cells
-turgor pressure builds up in the root hair cells, this increases the water potential in root
hair cellcompared to the next cortex cells adjacent to them-thus the cortex cells will have
a low water potential
-water moves across the cortex cells down their water potential gradient until it reaches
thexylem vessels
-water enters the xylem vessels through the pits by diffusion
-mineral salts dissolve in water, they pass through the root hair cells by active
uptake/transport
-mineral ions move together with water across the cortex cells until they reach the xylem
vessels
How water travel from the xylem to the leaves and out through the stomata during
transpiration
-the mineral salts reaching the xylem vessels lower the water potential in the xylem
-water enters the xylem by diffusion increasing its pressure (hydrostatic pressure) and its
waterpotential
-water starts to move upwards the xylem vessels
-cohesion forces make water molecules to attract each other and pull each other up
-water molecules stick to the walls of the xylem due to adhesion forces
-continuous loss of water by transpiration creates a water potential gradient between
the leavesand the roots. This effect is the transpiration pull.
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-water getting to the leaves is used during photosynthesis and to make cells turgid for
mechanical support
-more water is drawn from the soil
Transpiration
-transpiration is the evaporation of water vapour from the surfaces of the mesophyll cells
and itsdiffusion through the stomata.
-transpiration happens in the leaf
-transpiration cools the plant
-“transpiration pull” or “tension pull” causes a continuous up take of water from the
groundthrough the roots and up to the leaves and out through the stomata
-a water potential gradient is created from the roots up to the leaves causing cohesive
watermolecules to stream continuously up the plant
Factors affecting transpiration
A. Humidity
-humidity is the amount of water vapour in the atmosphere.
-the higher the amount of water vapour/humidity the lower the rate of transpiration
-the concentration of water vapour inside the leaf will be equal to or below that of
theatmosphere so diffusion will be very minimal
-if the atmosphere is dry the rate of transpiration will be higher as more water
vapourdiffuses from the leaf to the atmosphere
B. Temperature
-temperature is a measure of how hot or cold it is
-increasing heat energy increases the temperature- water molecules gain kinetic energy
and they evaporate at a higher rate and diffuse out of the leaf
-transpiration increases
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-transpiration is lower when temperature is low because the water molecules inside the
leaf will not have energy to evaporate and diffuse
C. Wind speed
-stomata releases water vapour
-the air around the leaf becomes saturated with water vapour
-on a windy day(day with high wind speed), the air is blown away
-transpiration rate increases as a water potential difference is maintained between the
leaf and the atmosphere.
-the lower the wind speed the lower the rate of transpiration
-water molecules accumulate around the stomatal pores and reduce the water potential
gradient between the leaf and the atmosphere.
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Investigation into movement of water through a plant
-If the leaves are to be cut the coloured dyes (blue and red) would be located in the xylem
vessels
Investigations on transpiration
1. Set up the apparatus as shown below
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-the set-up is exposed to the sun for several hours
Observations
-in the control experiment, no drops are formed in the glass jar
Reason: the plastic cover blocked the water from evaporating from the pot
-in the test experiment, liquid drops form in the glass jar
-the liquid drains into the container and mix with anhydrous coppersulfate(white)
turning it blue
-the liquid that turns anhydrous copper sulfate blue is water
-this shows that water is released during transpiration
-the plant loses water through the stomata
2. Set up the apparatus as shown below
-support 4 leaves A, B, C and D using a string and stands as shown above
-treat the leaves as follows
Leaf A: smear petroleum jelly (Vaseline) on both sides
Leaf B: smear on the lower side/surface
Leaf C: smear on the upper surface
Leaf D: do not smear it
-leave the set up on a window seal for several days
Observations and Explanations
Leaf A: remains fresh and green
-the leaf will not lose water by transpiration, the Vaseline block the
stomata
Leaf B: looks fresh more than leaves C and D, but not as fresh as leaf A
-there will be no loss of water through the stamata, the Vaseline blocksthe
stomata on the lower surface. Stomata are mainly on the lower lower
surface of the leaf. The leaf loses some water by evaporation
from the upper surface.
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Leaf C: the leaf dries up as it loses most water through the stomata which areopen at
the lower surface
Leaf D: the leaf will dry completely more than the rest
-the leaf loses water by transpiration through the stomata on the lower
lower surface and by evaporation on the upper surface
Measuring rate of transpiration
-a potometer is used
How it works
-a leafy twig is fixed to the apparatus as shown above
-the apparatus has a ruler or scale fixed to a capillary tube which is immersed inwater
-an air bubble is moved an initial position e.g. zero
-the apparatus is exposed to the sun and a stop watch is started
-as the leafy twig loses water by transpiration, it absorbs more water from the
beaker. The bubble moves towards the left
-After a desired time ,1hr,2hrs or 3hrs, the final distance moved by the air bubbleis
read/recorded
Rate of transpiration will be = distance moved by air bubble
Time taken
Example if the air bubble moves 50mm in 2hrs
The rate of transpiration = 50mm
= 0.4mm/min
120mins
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Translocation
-translocation is the transport of sucrose and amino acids from the point of manufacture
or source (leaves) to point of utilisation (any part of the plant) or storage (roots, seeds
fruits and the leaves themselves)
-sucrose is used to reform glucose needed for respiration
-amino acids are used during protein synthesis and growth
At one time a certain part of a plant acts as a source and at another, as a sink,
e.g. in potato plants
When a new potato plant grows from a tuber, the tuber supplies all the nutrients
and water needed by the new shoot- it acts as the source. The food
moves
upwards to the developing leaves, which act as sink.
When the new plant is well established, the food reserves in the tuber gets finished.
The new plant starts to photosynthesise, thus making its food in theleaves(leaves
become the source). The food moves down wards in the phloem vessels to be stored in
new tubers(now the sink)
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9. Transport In Animals
There are two type of circulation in animals
1. Single circulation
2. Double circulation
-the circulations have:
a. pump (the heart)
b. tubes/blood vessels
c. blood
Single Circulation (Fish)
-the heart has two chambers -an atrium and a ventricle
-the heart(atrium) receives deoxygenated blood from the body through the vena cava
-the atrium contracts forcing blood into the ventricle which pumps blood into the aorta.
- blood passes through the gills where it loses carbon dioxide and gain oxygen.
-the oxygenated blood travels to the body together with nutrients.
- oxygen and nutrients are used in the body in metabolic reactions
-Example respiration, which releases carbon dioxide. The blood becomes deoxygenated
and is carried back to the heart.
NB: Blood passes through the heart once to complete a circuit around the body, hence
single circulation
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Double circulation
-humans have a double circulatory system
-the circulatory system is a system of tube (blood vessels), a pump(heart) and valves to
ensure one -way flow of blood
-the circulatory system is a double circulation -this means blood passes twice though the
heart before it makes a complete circuit around the body
-the double circulation of blood involves two circulations
1. pulmonary circulation
2. systemic circulation
Pulmonary Circulation
-deoxygenated blood (blood with more CO2) travels from the heart to the lungs in blood
vessel A (pulmonary artery),
-blood loses CO2 and gains O2 in the lungs and becomes oxygenated blood
-oxygenated blood travels from the lungs to the heart in blood vessel A (pulmonary vein)
-blood in the pulmonary circulation has lower pressure, there is less resistance to flow of
blood in the lungs
-this circulation ensures the body gets rid of carbon dioxide and gains oxygen
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Systemic Circulation
-oxygenated blood (blood rich in oxygen) travels to the rest of the body in arteries, the
biggest artery C is the aorta.
-nutrients, water and oxygen are carried to the body in blood vessel A
-body tissues and cells use the nutrients, water and oxygen in different processes e.g.
respiration
-respiration releases energy and carbon dioxide
-carbon dioxide gets into the blood making it deoxygenated and this carbon dioxide must
be removed from the body
-deoxygenated blood travels to the heart in veins, and the biggest vein(D) is the vena cava
-blood in the systemic circulation has a higher pressure, to overcome resistance to flow of
blood in arteries around the body
-this circulation allows nutrients, water and oxygen to get to body tissues and cells and
guarantee the removal of carbon dioxide and other wastes like urea from tissues and cells.
Main components of the circulatory system
a. the heart (acts as a pump)
b. blood vessels (tubes carrying blood)
c. blood(medium for transport of dissolved substances)
The Heart
83
-made up of the cardiac muscle
-has 4 chambers and two sides- right and left sides
-each side has an atrium and a ventricle
-we have the right and left atrium and right and left ventricle
-another name for atrium is auricle Valves in the heart
Atrioventricular valves – these are found between the atria and the ventricles
Bicuspid valve is an atrioventricular valve between the left atrium and the left ventricle
Tricuspid valve is an atrioventricular valve between the right atrium and the right
ventricle
Semi-lunar valves – these are valves found in the heart where the aorta and the pulmonary
artery leave the heart
NB:- valves prevent back flow of blow, this ensures one way flow of blood.
-the right and left side of the heart are separated by the septum (still cardiac muscle)
Blood vessels connected to the heart
(to be written)
How the heart works
-the right atrium receives deoxygenated blood from the body through the vena cava
-right atrium fills up with blood and contracts forcing blood through the tricuspid valve
into the right ventricle
-this ventricle fills up and contract forcing blood into the pulmonary artery, which takes
the blood to the lungs
-when the right ventricle contracts the tricuspid valves close to prevent back flow into the
right atrium
-oxygenated blood is carried to the heart by the pulmonary veins from the lungs
-blood enters the left atrium, which fills up and contract
-blood is forced into the left ventricle through the bicuspid valve
-the left ventricle fills up and contract, forcing the blood into the aorta through the semi
lunar valves
-the bicuspid valve closes when the left ventricle contracts, to prevent back flow of blood
into the left atrium
After contraction of ventricles, pressure in them decreases and blood in the pulmonary
artery and aorta tend to flow back. The semi-lunar valves close to prevent back flow of
blood to the ventricles
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Important facts
Both atria fill up and contract at the same time
Both ventricles fill up and contract at the same time
Why is the left side of the heart (the left ventricle) thicker than the right side?
Left side
-the left ventricle needs to generate enough pressure to force blood to the rest of the body
-to overcome the resistance to flow of blood in arteries.
Right side
-it only pumps blood to lungs which are near
-lungs offer less resistance to blood flow
General blood circulation
-smaller arteries branch from the aorta (main artery) to supply different organs
1. the hepatic artery supplies the liver;
2. the renal arteries supply the kidneys
-smaller veins from the body organs carrying deoxygenated blood join to form the vena
cava
1. the hepatic vein from the liver
2. the renal veins from the kidneys
-pulmonary artery carries blood to the lungs from the heart
-pulmonary veins carry blood from the lungs to the heart
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-the coronary arteries supply blood containing oxygen, water and nutrients to the heart
tissue
Monitoring activity of the heart
-can be monitored by:1. Electrocardiogram (ECG)
2. Pulse rate
3. Listening to sounds of closing valves (use of a stethoscope)
A.ECG
-electrodes are connected to the body
-the electrodes are connected to a monitor which converts the electrical signals to a
graphical presentation on the screen as shown below
-a normal single heart beat has parts PQRST where
(i). P represent atrial contraction (systole)
(ii). QRS represent ventricular contraction (systole)
(iii). T represent relaxation of the heart(diastole)
-PQRST takes 0.8 seconds so a single heart beat takes 0.8s
B. Pulse rate and physical activity
-pulse is a wave of contraction of the heart transmitted along the walls of the arteries
-pulse is felt where an artery is passing near or over the surface of a bone e.g. the temple,
wrist, neck, elbow etc
-Pulse rate is how many times the heart beats in a minute, it is also referred to as
the heart rate
-the average pulse rate/heart rate is 72beats/minute
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-the pulse rate increases with a vigorous physical activity, can get up to 90+ beats per
minute. Why?
-to allow more O2 and nutrients to move fast to working muscles
-to allow fast removal of CO2 and lactic acid from muscles
-too high or too low pulse rate at rest means a poor state of health of the heart
To calculate pulse rate
1. Locate the pulse
2. Count the pulse for 15secs and multiply by 4 to find the pulse rate in mins
D. Listening to sounds of the heart
-the normal sounds of the heart are “lub” and “dub”
-lub closing of the atrio-ventricular valves and dub closing of the semi –lunar valves
-the stethoscope is place on the chest or at the back. The surgeon listens to the sounds of
the heart and any unusual sounds is a cause for investigation
Coronary Heart Diseases (CHD)
-it is when a major artery is blocked due to atheroma and clotting blood
-atheroma are fat deposits in the lining of arteries of the heart
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-the atheroma may increase in size and extension reducing the diameter of arteries and
reduce their elasticity (hardening them)- this result in high blood pressure
-atheroma are not smooth, some red blood cells puncture when they rub past and
fibrinogen turns into fibrin form a thrombus -a clot which then blocks the artery.
-blocking an artery may result in a heart attack.
-a heart attack due to a blockage of a major artery may result in a heart failure
-the heart stops working and death may occur
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Risk factors for CHD
1. Genetic predisposition – it runs in families
2. Diet with too much fats
3. Smoking – increase fat deposition
-there is evidence that more smokers die of CHD than non - smokers
-there is a positive co-relation between death due to CHD and smoking
4.
5.
6.
7.
Stress – increased blood pressure increases fat deposition
Age (old age) – heart loses tone and effective pumping
Gender - more men are affected than women
Lack of exercises- fats accumulate, heart becomes weak
Control measures for CHD
(i). Exercise regularly
(ii). Eat a balanced diet
(iii). Live a stress-free life
(iv). Stop smoking and drinking alcohol
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BLOOD VESSELS
-there are 3 blood vessels
1.Arteries
2.Veins
3.Capillaries
ARTERIES
1. have a thick muscular and elastic wall – to overcome the pressure and force of the
pulsating blood from the heart
-elastic fibres allow the arteries to expand and recoil
2. narrow lumen- to maintain the pressure of blood
3. has internal folds – to allow for expansion or distension during blood flow
4. no valves
-arteries carry blood away from the heart
-arteries carry oxygenated blood, except the pulmonary artery which carries deoxygenated
blood from the heart to the lungs
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Veins
1. have thin less muscular and less elastic walls- blood is under low pressure
2. wider lumen – to accommodate as much blood as possible as it returns to the heart
3. have valves – to prevent back flow of blood as blood flows under low pressure
-veins are situated between muscles. Muscles help blood movement as they contract and
relax
-veins carry blood towards the heart
-veins carry deoxygenated blood, except the pulmonary veins which carry oxygenated
blood to the heart from the lungs
Capillaries
1. a capillary wall is one cell thick – this reduces the diffusion gradient of substances from
blood to the surround tissue fluid.
2. walls have pores – to allow easy exchange of substances
3. have a very narrow lumen – blood moves slowly allowing efficient diffusion of
substances
-capillaries allow exchange of substances between the blood and the surrounding tissue
cells
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-capillaries connect arteries to veins
Capillary Bed
-arteries divide into smaller arteries called arterioles
-arterioles further divide to form capillaries
-capillaries penetrate between cells of tissues and allow exchange of substances between
blood and cells by diffusion, active transport and osmosis (water only)
-capillaries join up to form venules and venioles form veins
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Blood
Blood is the fluid that flows in the blood vessels.
Components of blood, structure and functions
Component
Structure
Red blood
cells
White blood
cells
Lymphocytes
make
antibodies
Phagocytes engulf
and destroy
pathogens ( this is
called
phagocytosis)
Help in blood
clotting
Platelets
Plasma
Function
Transport oxygen
mainly Transport
small amounts of
carbon dioxide
Water, containing many
substances in solution
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Transport
substances in
solution (nutrients,
CO2, urea,
hormones,
proteins,
antibodies)
Transport heat
Phagocytosis
-the white blood cells detect pathogens among tissue cells or in tissue fluid
-a phagocyte approaches the pathogen e.g. bacteria
-it produces cytoplasmic extensions to surround and engulf the bacteria
-the engulfed bacteria are then killed and digested
Blood Clotting
A cut in the skin exposes blood to the air
Platelets are activated to release enzymes which convert a blood protein fibrinogen to
fibrin
Fibrin makes a mesh across the wound, trapping red blood cells
The trapped red blood cells form a clot.
A blood clot stops further loss of blood and prevent entrance of pathogens
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The role of blood in transport
i. Transport oxygen as oxyhaemoglobin in red blood cells
ii. Transport of carbon dioxide, dissolved in the plasma as hydrogencarbonate ions, HCO3Some carbon dioxide is transported in red blood cells combined with haemoglobin
(carboxyhaemoglobin)
iii. Transport of food materials – digested food is transported to the liver by the hepatic
portal vein. The form dissolves in the plasma
iv. Transport of urea – urea is made in the liver as excess amino acids are deaminated. It
dissolves in the plasma and is carried to the kidneys for excretion
v. Transport of hormones – these dissolve in the plasma and are transported around the
body
vi. Transport of heat – the blood distribute heat around the body maintaining body
temperature
vii. Transport of plasma proteins – these proteins are dissolved in the plasma. Fibrinogen is
an example of a blood protein which is important for blood clotting
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10.
Diseases And Immunity
A disease is an illness or disorder of the body or mind that leads to poorhealth.
-diseases are classified into:
• infectious(transmissible/communicable) diseases
-these are caused by pathogens
-the pathogens are passed from one organism to another e.g. from oneperson to
another person or from an animal/insect to other animals or people.
-a pathogen is a microorganism that causes diseases e.g. bacteria, fungi,viruses,
Protoctista
Example of pathogens and the infectious diseases they cause
Type of pathogen
Specific name
Disease caused
Bacterium
Vibrio cholerae
Cholera
Mycobacterium
tuberculosis
Tuberculosis
Fungus
Tinea
Athlete’s foot
Protoctista / protozoa
Plasmodium
falciparum
Malaria
Virus
HIV
Aids
Corona
Covid 19
• non-infectious(non-transmissible/non-communicable) diseases
-not passed on from one organism to the other
-no pathogens are involved
-these include cancer (lung cancer), degenerative diseases (arthritis), diabetes,
inherited disorders (sickle cell anaemia), CHDs (coronary heart diseases), COPDs
(chronic obstructive pulmonary diseases-bronchitis andemphysema)
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A host is an organism that harbours another organism usually a parasite.
-the parasite then passes the pathogen to the organism
A vector is a carrier of a disease-causing organism e.g. a mosquito, itcarries
the pathogen for malaria
A parasite is an organism that relies on another for shelter and nutrients.
-it benefits at the expense of the host
How pathogens are spread
-pathogens are spread by one of the methods below
a. Direct contact
-through body fluids like blood,
semen, e.g. STIs like HIV/AIDS
-sharing clothes, shoes and towels
b. Indirect contact
-through droplet infection/air borne when
sneezing, coughing (infuenza, TB, Covid
19),
-through contaminated water and
food(cholera),
-through vectors (malaria)
Immunity – the resistance of the body to infections/protection of thebody
against infections
-the system is made up of the bone marrow, thymus, white blood cells and the antibodies
-the immunity system involves some body defenses to protect the body
Body Defenses
-prevent entrance of pathogens into the body or to a part of the body where they
can breed.
Types
• Mechanical/physical barriers- first line of defense
• Chemical barriers – second line
• Cells – last line
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Mechanical/Physical barriers
-structures of the body that stop pathogens from invading the body.
Examples
i.
ii.
iii.
Nostrils- hairs trap dust that might be carrying pathogens
Skin – the dead layer of cells (made up of a protein called keratin) on the skin
surface prevents entrance of bacteria.
Formation of a blood clot also prevent entrance of pathogens on a cut skin.
Chemical barriers
a. mucus -secreted by internal body linings e.g. the respiratory tract-the
trachea, bronchi and bronchioles, it traps pathogens, which are swept out by
thecilia.
b. hydrochloric acid (HCL) –secreted by the stomach lining, it kills bacteria
coming in with food
Cells
-white blood cells are the last line of defense
-phagocytes detect and engulf bacteria, protozoa, fungi and digest them- a process
called phagocytosis
-lymphocytes produce chemicals called antibodies
-antibodies are chemicals that kill pathogens and also neutralise toxins/venom
-antibodies are specific (one antibody one antigen)
Note: - each pathogen carries a specific antigen
-some antibodies lock on to antigens and cause direct destruction of pathogens
-some mark pathogen facilitating phagocytosis- they act as markers
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-production of antibodies is enhanced by vaccines
- a vaccine is preparation which when injected in one’s body it triggers production
of antibodies by the lymphocytes.
Other practices which minimise spread of pathogens
a.
b.
c.
d.
Food hygiene
Personal hygiene
Sewage treatment
Proper waste disposal
Food hygiene
1. Keep your own bacteria and viruses from food
-wash hands before handling food
-avoid putting your fingers in your mouth
-keep hair away from food
-wear clear uniforms and hats at a food outlet.
-never cough or sneeze over food
2. Keep animals away from food
-animals such as rats carry dangerous bacteria
-flies carry bacteria from rubbish, faeces and dead animals
-cover food securely
3. Do not keep food at room temp for a long time
-room temperatures favour growth of bacteria
-refrigerators slow down growth of bacteria
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How temperature affects bacteria
4. Keep raw meat from other foods
-raw meat often contain bacteria (cooking meat kills these bacteria)
5. Keep fruits going bad from fresh ones
6. Wash fruits and vegetables to be eaten raw such as for salads
Personal hygiene
-keep your body clean
-it reduces growth and spread of bacteria
-dirty, oils and salts on the skin create a breeding ground for bacteria
-wash your body with soap and shampoo
-brush your teeth regularly
Waste disposal
-waste (plastics, papers, leftover foods e.tc) should be collected and put at
a protected landfill site
-rats, dogs and houseflies visit these landfill sites for food
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-bacteria breed very well in these areas
-chemicals seep from these landfills and pollute the water in streams and rivers
-proper management is expected on landfills and licensed operators are engaged to
check for dangerous substances in the wastes
-humus can be obtained and returned to land for agriculture after decay
-methane gas usually build up in landfills which can cause fire explosions
-methane can be tapped out using pipes and can be used as a fuel
-landfills can finally be covered and trees and grasses are grown
Sewage treatment
-sewage is a combination of urine, faeces, waste waters from washing basins,
factories and run off from road surfaces which collect in drains leading to a sewage
treatment plant.
-materials in sewage include: - urine, faeces, toilet paper, detergents, oil and
many other chemicals
-raw sewage spread pathogens like bacteria which can cause cholera, typhoid,
dysentery e.tc.
-raw sewage can also cause eutrophication in water bodies like lakes and dams
-at a sewage treatment plant organic substances are broken down and
-harmful bacteria are destroyed.
-water recovered from a sewage treatment plant is free of pathogens andraw
sewage
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a. Antibodies
-thousands of lymphocytes in our bodies produce different types of
antibodies
-antibodies have specific shapes which are complementary to the shapesof the
antigens they destroy
-antibody A cannot attack antigen B and vice versa
-antigens are found on surfaces of the cells of pathogens
-antibodies start of a series of reaction which produce enzymes to digestthe
pathogens or may alert phagocytes
-lymphocytes only produce antibodies when necessary
-first the lymphocytes are activated and then divide repeatedly to for aclone
-some clones become plasma cells—these produce antibodies and some become
memory cells –these remain in the blood and provide long termimmunity.
-During activation, cloning and production of antibodies- is the periodwhen one
gets ill/sick, the time you start to feel better is the time enough antibodies would
have been produced and would have destroyed the pathogens
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How lymphocytes respond to antigens
-a response of the lymphocytes to pathogens is called the immuneresponse
b. Memory cells
-after cloning some cells remain in the blood and act as memory cells
-these cells remain in the blood long after the disease is healed so that when the
pathogen invades the body again it is recognized and destroyedbefore the pathogen
cause any harm-thus the memory cells will clone again and produce more
antibodies
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Vaccination
-vaccines are given mainly to children to protect them from diseases e.g.
Tuberculosis, Polio, Tetanus, Whooping cough e.tc
-adults can also be vaccinated e.g., against flue (H1N1 against bird fluin2011
and Covid 19)
-a vaccine is a weakened or dead pathogen (virus or bacteria) whichwhen
introduced into the body can trigger an immune response.
The process of vaccination
•
•
•
•
•
a harmless pathogen(vaccine) is injected or administered into one ‘sbody
the vaccine carries antigens
antigens trigger an immune response by lymphocytes
lymphocytes produce antibodies and memory cells
memory cells provide long term protection- if the harmful bacteria get into
the body it is destroyed before it can cause harm to the body
Note:- we do not get TB or Polio because we were vaccinated when wewere
children.
Controlling Diseases By Vaccination
Vaccines are used in immunization programs in different countries
-babies are immunised against killer diseases: 1. Tuberculosis -BCG is the vaccine
2. Polio
3. Measles
4. Tetanus
5. Whooping cough
6. Diphtheria
-Small pox is a fatal disease caused by a virus, transmitted by direct contact.
-leave recovered patients with scars or blind
-1956- WHO campaign to eradicate smallpox, many people were vaccinated worldwide.
-1977-last case recorded in Somalia 1977.
-1980 WHO declared eradication of smallpox
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-Poliomyelitis, another viral disease on the list to be eradicated, it infects children,
leaving then with paralysis, efforts to vaccinate all the children is facing resistance. Polio
is now rare in most parts of the world.
-Measles is another viral disease, spread by airborne droplets
-causes skin rush, fever, blindness and brain damage
Herd immunity – it is whereby a large population say of children are vaccinated at one
goal
-this leaves fewer places for the pathogens to breed or multiply.
-herd immunity is common with measles and other viral diseases- this protects both the
vaccinated and the unvaccinated.
Cholera
-a serious transmissible disease
- a disease caused by a bacterium (Vibrio cholerae) which is transmitted in contaminated
water, food and surfaces
-the cholera bacterium lives and breeds in small intestines, produces a toxin that causes
secretion of chloride ions into the small intestine, causing osmotic movement of water
into the gut. Water potential of the gut is lowered, water moves into intestines from the
surrounding blood vessels by osmosis, causing severe diarrhoea (rice water), dehydration
and loss of ions from the blood.
-cholera can cause death within 24hrs if not treated
-cholera is more of a disease due to poor hygiene.
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-it spread fast in refugee camps and squatter camps
-it can also spread after disasters like earth quakes when sewer pipes break e.g. in Haiti 2010
or when floods occur
Covid -19
-detected Dec 2019, in Wu-Hang China
- caused by a new virus- SARS-CoV-2(Severe Acute Respiratory Syndrome Coronavirus 2)
-Coronaviruses are spherical with protein spikes on their surfaces
-the protein spikes help the viruses to stick to human cells
-some coronaviruses cause colds and flu.
-Covid-19 is more severe and can kill.
Facts about Covid-19
1. Spreads easily from one person to another
-by droplet infection- through sneezing, coughing, talking
-can be taken by hands from surfaces-tables, handles or taps and passed to the mouth or
nose
2. Passed on by asymptotic people
3. Can be mild in some people and severe in others-causing severe damage to the lungs
leading to death
4. A lot of information has been collected by scientists about the pandemic and trends have
been used to dictate the trajectory of the disease
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5. During the very first occurrences, there were a lot of lock downs people were banned from
moving about and wearing of masks has been mandatory in most countries, washing hands
with soapy water has been mandatory too, including sanitising and sneezing or coughing
in the flexed elbow
6. Today day restrictions are easing and movements across borders has since resumed.
Malaria is a disease caused by a protozoa called Plasmodium falciparum.
-a serious disease in the tropics, claiming lives of many people.
-WHO is fighting to discover the malaria vaccine
11.
Gas Exchange in humans
The system is responsible for the process of gas exchange, carbon dioxide gets out and
oxygen gets in the body.
The gas exchange system
a. Nasal passage
-have hairs to trap dust
-secrete mucus to trap bacteria and dust
-secrete mucus to warm and moisten the air
b. Larynx (voice box)
-allows air to pass into the trachea; has vocal cords
c. Trachea
-has cartilage to prevent collapsing; cartilage is C shaped
-mucus glands in goblet cells secrete mucus
-mucus warm and moisten air
-mucus trap dust and bacteria
-cilia wipe out mucus and trapped bacteria and dust
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d. Bronchi
-trachea divides into two bronchi
-each lung is connected to one of the bronchi
-mucus trap dust and bacteria
-cilia sweep out trapped dust and bacteria in mucus
e. Bronchioles
-each bronchus divides to form numerous tubes called bronchioles inside
eachlung
f. Alveoli/air sacs
-each bronchiole ends in tiny structures called air sacs or alveoli
-gas exchange takes place in alveoli
g. Rib cage
-made up of ribs and muscles
-its volume and pressure increase and decrease when breaching
h. Diaphragm
-a muscle which take part in breathing.
Features of a gas exchange surface
• Alveoli/air sacs have a large surface area for easy diffusion of gases
• Have thin walls - only one cell thick- to reduce the diffusion distance
• Rich network of capillaries-to maintain a diffusion gradient
• Air sacs are well ventilated and has a film of moisture
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Structure of the alveolus/air sac
-there is a higher concentration of oxygen in theair sacs than in the blood. Oxygen diffuses in
the blood stream down its concentration gradient.
-there is a higher conc. of carbon dioxide in the blood than in the air sacs. CO2 diffuses from
theblood into the air sacs down its concentration gradient.
-it is called double diffusion because CO2 andO2 diffuse at the same time
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Breathing; - taking in and out of air
-air which is taken into the lungs is called inspired air
-air which is taken out of the lungs is called expired air
Inspired Air
Oxygen 21%
Carbon dioxide 0.04%
Moisture: Varies
Temperature: varies
Expired Air
Oxygen 16%
Carbon dioxide 4%
Saturated with moisture
Body temperature
The mechanism of breathing involves inspiration and expiration
INSPIRATION
EXPIRATION
1. External intercostal muscles
Internal intercostal muscles relax,
contract, raising the rib cage
lowering the ribcage down and inwards
up and outwards
2. The diaphragm contracts and
Relaxes and attain a dome shape
it flattens
3. The volume of the ribcage
Volume decreases
increases
4. Pressure in the thorax
Pressure increases above that of the
decreases below atmospheric
atmosphere
pressure
5. Atmospheric pressure forces
Air is forced out of lungs
air into the lungs
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To investigate the difference in composition of inspired air and expired air
Test for carbon dioxide
-put lime water in a test tube
-use a stroll to blow in expired air into the lime water
Observe colour change
-limewater has a clear colour
-it changes to milk white when carbon dioxide is present
Effect of exercises on depth and rate of breathing
During a physical activity your breathing rate and depth change.
Explanations
-during an exercise, more energy is required so more oxygen must be taken in through the
lungs
-more carbon dioxide must be removed from the lungs
NB: - heart rate also increases to ensure more blood is pumped to and from respiring
tissues.
But oxygen needs cannot be met always yet energy is needed.
-anaerobic respiration takes place creating an oxygen debt -thus you get borrowed
energywithout paying with the currency- oxygen
-after a vigorous activity you need to pay back the debt- you breathe deeply to supply
moreoxygen to break down the lactic acid which would have accumulated in the body.
-the brain has a direct control over rate of breathing, it detects low pH in blood due to
risingcarbon dioxide and lactic acid
-the brain sends impulses to the diaphragm and intercostal muscles and trigger
contractions andrelaxations increasing breathing rate.
12. Respiration
-a process whereby food(glucose) is burnt or broken down in cells to release carbon
dioxide,water and energy
Uses of energy in the body
1.
2.
3.
4.
5.
6.
Contraction of muscles for movements
Making protein molecules
Cell division-for growth and repair
Active transport across cell membranes
Transmission of nerve impulses
Maintaining body temperature
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-Energy is derived from the food we eat
-digestion takes place and products of digestion are absorbed in the blood stream
-blood transport nutrients to all the cells
-glucose is the main nutrient providing energy
-respiration unlocks the glucose and release energy in it-this requires enzymes.
Two types of respiration
➢ Aerobic respiration
➢ Anaerobic respiration
Aerobic Respiration
-happens in the presence of oxygen
-Enzymes combine oxygen with glucose in a series of steps
-aerobic respiration is the release of a relative large amount of energy by break down of
foodsubstances in the presence of oxygen
-carbon dioxide is released
-no alcohol or lactic acid made
Word equation
Glucose +Oxygen →Carbon dioxide +Water
Chemical equation
C6H12O6 + 6O2 → 6CO2 + 6H2O
-most of the steps in aerobic respiration takes place inside mitochondria
Anaerobic respiration
-happens in the absence of oxygen
-it is the release of a relatively small amount of energy from food in the absence of oxygen
-energy can still be released from glucose without oxygen
-its not an efficient way of releasing energy from glucose, but it can still supply energy
neededduring critical moments.
-less energy is released compared to aerobic respiration.
-it happens for a short time
-‘an’ means without
-alcohol is produced in yeast and plants
-lactic acid is produced in muscles
-carbon dioxide is produced by yeast and plants not by animals
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Anaerobic respiration in plants and yeast
-the reaction produces Alcohol and Carbon dioxide and little energy.
Word equation
Glucose →Alcohol + Carbon dioxide
Chemical equation
C6H12O6→2C2H5OH+2CO2
Anaerobic Respiration in muscles
-the reaction releases lactic acid instead of alcohol and there is no production of carbon
dioxide.
Word equation Glucose →Lactic acid
Chemical equation C6H12O6→2C3H6O3
-lactic acid causes fatigue and cramps, it is the substance which
accumulatein muscles during a vigorous activity making us to feel
tired
-a person having a vigorous activity in which anaerobic respiration
occurswill have an oxygen debt
-oxygen debt means one continue to have energy yet he/she is not
havingoxygen being pumped to the working muscles
-oxygen debt is repaid by continuous deep breathing long after the exercise
-the extra oxygen taken is used in the liver to break down lactic
acid tocarbon dioxide and water
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To show the uptake of Oxygen during aerobic respiration
Set up the apparatus as shown below
1. Let this apparatus be for set up A
2. Set, set up B with no seeds
3. Record the initial positions of the small drop in each set up
4. Continue to record the positions of the small drop at regular intervals e.g. every 2minutes
Observations
-the small drop in set up A changes position, it keeps moving to the left towards the seeds.
-remain stationary in set up B
Explanations
-in A, the seeds are using oxygen in respiration and release carbon dioxide which is
absorbedby the soda lime, this creates low pressure which causes the drop to move in that
direction
-in B, there are no respiring seeds
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Investigating production of carbon dioxide by anaerobic respiration
Set up anapparatus as show below: -
1.
2.
3.
4.
Put a glucose and yeast suspension in a boiling tube
Put a layer of oil in the same boiling tube to create anaerobic condition
Seal the boiling tube with a cork connected to a delivery tube
Dip the end of the delivery tube in a test tube containing lime water
5. Leave for some minutes
6. Observations
-bubbles of a gas are produced in the test tube containing lime water
-lime water turns cloudy or milky
Explanations
-the gas is carbon dioxide; it turns clear lime water milky/cloudy
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13. Excretion in humans
-Excretion is a process whereby metabolicwaste substances are expelled from the body.
-Metabolism is a combination of all processand reactions happening in the cells.
-the reactions release useful products together with harmful products, calledmetabolic waste
products
EXCRETORY METABOLIC
ORGAN
Lung
Kidney
Skin
WASTE
Carbon
dioxide,water
Urea, salts, water
Salts, traces of
urea,
Bile pigments
Liver
Nitrogenous waste
How urea is made/produced
-formed from excess proteins and aminoacids
-animals cannot store amino acids, so excess is broken down in the liver to formurea, by a process
called deamination
-deamination happens in the liver
-the liver receives food through the hepaticportal vein
-the liver distributes all the needed amino acids and other nutrients to the whole body
-excess amino acids are split by enzymesinto carbohydrates and the nitrogen containing part.
-the carbohydrate is used by the body for energy or converted to glycogen and storedin the
liver and muscle cells.
-the nitrogen containing part is converted to ammonia and immediately converted to urea
-ammonia is immediately converted to ureabecause it is more toxic than urea.
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-urea should not stay long in the body cells for it becomes toxic, it is taken to the kidneyin
blood plasma for excretion.
-some urea is lost in sweat.
Functions of the liver
1. Convert excess amino acids to urea andcarbohydrates
2. Synthesises plasma proteins, e.g.fibrinogen
3. Stores carbohydrates in form of apolysaccharide- glycogen
4. Makes bile
5. Stores vitamins- A, B, D, E and K
6. Break down old red blood cells to makebile pigments and store the iron
7. Break down harmful substances-drugs(e.g. Alcohol) and spend hormones
8. Store potassium
9. Make cholesterol needed to make cellmembranes
10. Control amount of glucose in blood usinghormones like insulin and glucagon
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The human urinary system
The system is made up of the following organs: 1. Kidneys- a pair at back of the abdomen
-they make urine-renal artery supplies the kidney withoxygenated blood
-renal veins take away deoxygenatedblood away from kidneys
2. Ureters- a pair, one from each kidney
-carry urine to the urinary bladder
3. Urinary bladder – it stores urinetemporarily.
-the sphincter muscles close and open thebladder
4. Urethra – leads the urine out of thebladder
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The structure of a kidney
-the kidney is bean shaped
-a section through it show four major parts:
1. Cortex which has a darker brown colour- it is the site of ultra-filtration
2. Medulla which is lighter in colour- it is the part containing many collecting ducts and parts of
the nephron descend in it - there is reabsorption of water to make the urine concentrated or no
Reabsorption to make the urine dilute
3.Pelvis where collecting duct converge to make the ureter
4.Ureter carries urine to the urinary bladder
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The nephron and urine formation
-nephron or kidney tubule is the basicfunctional unit of a kidney.
-urine formation takes place in the nephron
Structure of a nephron
a. Glomerulus – a mass of tangled bloodcapillaries, where filtration of blood takes place.
Capillaries have poles to allow filtering of substances
b. Nephron – makes an extension from the cortex into the medulla and up again into the cortex
c. Collecting duct- leads the urine to the pelvis
NB:-The renal artery divides to form numerous tiny arteries called arterioles
-each arteriole gets to a particular nephron in therenal capsule
-arterioles form a tangle of capillaries calledthe Glomerulus
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-arteriole getting into the renal capsule is wider than the blood vessel leaving the
Glomerulus
-more blood gets into the Glomerulus compared to that leaving, this create great blood
pressure which forces nearly every substance -glucose, amino acids, salts, water, sugars
and urea, to filter into the renal capsule, except large molecules like blood proteins and
blood cells- this is filtration
-the filtrate travels along inside of the renal tubule where reabsorption of water,
glucose, salts e.tc takes place, leaving excesswater, excess salts and urea to form the
urine.
-over 99% of the water is reabsorbed
-urine is collected by collecting ducts towards the pelvis where the collecting ductsjoin
to form the ureters.
NB:- urine formation is all about filtration
and reabsorption
-filtration is mainly by diffusion
-reabsorption is by osmosis(water), diffusion (amino acids) and active transport
(glucose and mineral salts/ions)
-99% of water entering tubules is reabsorbed
-kidneys filter 170dm3 of water daily
-1.5dm3 of urine is produced in a day
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Factors affecting the volume and concentration of urine
1. Volume of water taken in – a greater vol result in more dilute urine
-lower vol result in less & concentrated urine
2. Physical exercises –vigorous activities cause sweating, less urine produced, but
concentrated
3. Temperatures of the day –cold days -more dilute urine produced and vice versa
-Concentrated urine has a dark yellowish brown/golden colour
-Dilute urine is lighter
14. Coordination And Response
Co-ordination is the way all the organs and systems of the body are made to
workefficiently together under the control of the nervous and hormonal
systems.
Response – reaction of the body to a stimulus guided by the nervous and hormonal
systems
Systems taking part in coordination and response
A. The nervous system
B. The hormonal system
Nervous control in humans
-made up of: • Central nervous system (CNS) -brain and spinal cord
• Peripheral nervous system (PNS) - nerves (bundles of neurons) and ganglions
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A nerve is a bundle of fibre made up of neurons (nerve cells) running from sense organs
tothe CNS
117
Types of nerve cells(neurones)
a. Motor neurone
b. Sensory neurone
c. Relay neurone
a. Motor neurone – has a cell body at one end
-has a long axon
-impulses travel away from cell body
Function
-transmit nerve impulses from the CNS to the effectors (muscles or glands)
b. Sensory neurone – has a cell body along its length
-has a long dendron
-has a short axon
Function
-transmit nerve impulses from the sense organ to the CNS
c. Relay/Connector/Intermediate neurone
-has a cell body and many branching dendrites
-found inside the CNS
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Function
-join sensory neurones to motor neurones, allowing transfer of nerve impulses
betweenthem.
Myelin: - is a layer of fat and proteins which insulate neurones
-myelin speeds up transmission of nerve impulses up to 100m/sec in
myelinated nerve fibre.
-non-myelinated nerve cells can carry up to 5m/sec only
Reflex Action and Reflex Arc
•
•
•
•
•
•
•
•
•
•
Reflex action
A reflex action is a rapid response to stimulus without involving the brain.
This action prevents injury to the body
Most reflex actions are coordinated by the spinal
cordExamples of reflex actions
Withdrawal reflex (e.g. removing a hand from a hot/pricky object)
Cry of a newly born
Blinking
Sneezing
Vomiting
Pupil reflex
Knee jerk reflex
Reflex arc
-a reflex arc is a pathway taken by an impulse from the time a stimulus is detected to a
timea response is given
Components of a reflex arc
i.
ii.
iii.
iv.
v.
Receptor (specialised cells inside sense organs e.g. skin, eye, ear, nose)
Sensory neurone,
Central Nervous System (brain/spinal cord),
Motor neurone
Effector (muscle/gland)
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The diagram shows a knee jerk reflex and its reflex arc.
120
117
The diagram shows a withdrawal reflex and its reflex arc.
Synapse - a miniature gap between two neurones, it allows communication between the
two neurones
-information passes through a synapse in form of a chemical called a neurotransmitter
substance.
121
Structure of a synapse
How a synapse work
-a nerve impulse arrives at a synaptic bulb at the end of one neurone
-it triggers movement of vesicles containing chemical transmitters/neurotransmitter
substance
-mitochondria release energy needed for the movements
-vesicles fuse with the bulb membrane and release the neurotransmitter substance into the cleft
-neurotransmitter substance moves across the cleft or synaptic gap by diffusion.
-receptors on the next neurone receive the chemical transmitter
-nerve impulses are generated in the adjacent neurone
1. transmission of nerve impulses is unidirectional at the synapse because vesicles are found on
one neurone and receptors on the other
2. there is a delay of 0.1sec at the synapse due to a change in form of transmission from an
electrical impulse to a chemical; diffusion and then electrical impulse again.
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Sense organs
-these are organs containing specialised cells which detect/sense changes in the environment
1
2
3
4
5
SENSE
ORGAN
Skin
Tongue
Eye
Ear
Nose
STIMULUS DETECTED
Pressure/tough/heat/cold/pain
Salt/sugar/bitter/sour
light
Sound
Chemicals in air
SENSE
OF
Feeling
Taste
Sight
Hearing
Smelling
The Eye
External features of the eye
Eyebrow - stops water or sweat flowing into the eye
Eyelid
- opens and closes the eye
Sclera
- made up of tough material, it maintains the ball of the eye
Iris - the black part; has radial and circular muscles; controls the size of the pupil
Pupil - allows light into the eye
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Internal structure of the eye
1. Cornea – transparent; where major refraction of light takes place
2. Iris - has radial and circular muscles which contract or relax controlling the size
of the pupil, during a pupil reflex.
3. Pupil - allows light into the eye
4. Lens - a crystalline structure capable of adjusting its shape in order to focus
imagesof objects at the retina during accommodation.
5. Fovea/Yellow spot – has a high concentration of cones, it allows us to make
details ofwhat we see
6. Retina – contains light sensitive cells, cones and rods, which enables us to see.
Thefovea is part of the retina
7. Blind spot - this part of the eye does not have cones or rods, so if an image of
anobject falls on this part of the eye, it cannot be seen.
8. Optic nerve - carry electrical impulses to the brain
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Pupil reflex
The pupil diameter increases in dim light and reduces in bright light-this prevents
damage tothe retina/eye
(a). In Bright Light
-circular muscles contract
-radial muscles relax
-pupil diameter reduces
-pupil constricts
-less light passes into the eye
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(b). In Dim Light
-circular muscles relax
-radial muscles contract
-pupil dilates
-more light passes into the eye.
Cones and Rods
The two are light sensitive cells in the eye.
Cones - are more concentrated on the fovea;
-cones make us detect colour in high light intensities;
- three types of cones-red, blue and green- they allow us to detect the three
colours.
-we perceive white colour when the 3 colours mix
Rods - are widely distributed across the retina
-absent on the fovea
-detect low intensity light-important for night vision
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Accommodation
-this is the ability of the lens to change its shape in order to focus near or far away
objects
Far away objects
Near objects
-ciliary muscle relaxed
-ciliary muscle contracts
-suspensory ligaments taut
-suspensory ligaments slacken
-lens becomes elliptical/pulled thin
-lens thicken/becomes spherical
.Focusing light
-light rays travel in a straight line
-light rays travel from the object whose image needs to be focused at the retina
-images of objects are formed at the retina
-light bend when they pass through a different medium- this called refraction
-the cornea causes major refraction of light to allow it pass through the pupil.
-refraction continues at the lens
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-the refraction of the rays makes them to cross behind the retina causing the image
focused to be upside down.
-the brain will interpret it and you see an upright object
Adjusting the focus
-light rays from a faraway object need less bending/refraction compared to light from a
nearby object.
-light rays from a faraway object are more parallel hence less refraction needed
-light rays from a nearby object are diverging, refraction needs to be strong.
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Hormones In Humans
Hormone is a chemical substance produced by ductless glands, carried by blood,
which alters the activities of one or more target organs.
Why ductless?
-they do not have tubes to carry the hormones away.
-they empty their contents direct into the blood stream.
129
Location of ductless/endocrine glands in the body
130
GLAND
Adrenal
gland
HORMONE
Adrenaline
-‘fight/flight/fright hormone- it prepares
thebody for action
Pancreas
Insulin
-produced by beta cells which form islets
inthe pancreas.
-control blood sugar levels- lowers sugar
levelsafter a meal rich in carbohydrates
Testes
Ovaries
Glucagon
-produced by Alpha cells in the pancreas
-control blood sugar-increases sugar levels
intimes of fasting or starvation
Testosterone
-gives secondary sexual characteristics
-production increases at puberty
EFFECT ON THE BODY
• Conversion of glycogen to
glucose
• Increases heart beat and
pulse
• Dilate pupil
• Vasodilation of arteries to
muscles
• Vasoconstriction of arteries
to organs less involved in
action
• Increases breath rate
• Instructs liver cells to
convert excess glucose to
glycogen.
• Instructs liver cells to
convert stored glycogen to
glucose
Oestrogen
-gives secondary sexual features
e.g. menstrual cycle, thin voice, growth of
breasts
• Production of sperm
cells
• Pubic hair, beard growth
• Deepening of voice
• Attraction to opposite
sex
• Widening of chest
• Muscle development
• Production of eggs
• Prepares lining of the uterusmakes it thick and
vascularised.
Progesterone
-gives secondary sexual features
e.g. menstrual cycle
• Keeps lining of uterus
intact
• Maintains pregnancy
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•
•
•
•
•
Adrenaline production increases in the following situations: When startled
Working in the dark
When about to play a match or to run a race
When faced with a vicious barking dog
When provoked e.tc
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Homeostasis
Homeostasis- is the maintenance of a constant internal environment or within
set limits
Example: 1. The body temperature should be around 37oC (36.5-37.5 oC
2. Blood sugar levels 90-100mg/100ml of blood
3. Excess water, ions and urea must be removed from the body
External environment is always changing while the internal one needs to be constant
-this allows cells to function efficiently-enzymes work at an optimum rate
-a constant amount of water prevent damage to cells
-a constant level of glucose-means a constant supply of fuel
-a constant temperature prevents denaturation or inactivation of enzymes
The body uses a mechanism called Negative Feedback to bring back to normal
any deviating factors. This mechanism respect set points (ranges of normal
values)
-this works just like the thermostat of an iron or refrigerator
The brain is the main coordinator in this Negative feedback mechanism.
Sense organs have receptor cells which detect a change in an environmental
factor e.g. a rise in temperature. Information gets to the brain
(Hypothalamus) through nerve impulses or hot blood gets to thebrain.
Nerve impulses are sent to the skin where certain actions occur e.g.
sweating, to make the body lose more heat.
Body temperature drops to normal and the brain send information again to stop
further sweating.
The same applies when temperatures in the environment go down. The
information gets to the brain and it commands correctional measures to bring
body temperature to normal.
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In negative feed back :
-there is a set point-normal level of a factor to be maintained
-there is a “measuring device”- receptors and the brain which keep checking
to make sure the set point is maintained
-there is an effector that bring about action to correct
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Organs involved in Homeostasis
1. Brain
2. Skin
3. Liver
4. Pancreas
THE SKIN
Control of body temperature
-the normal body temperature is 37 oC
-humans are “warm-blooded” and are homoiothermic- are able to regulate their
body temp
-organisms that are not able to control their body temp oC are ‘cold-blooded’
and are poikilothermic.
Body temperature control involves: - heat loss,
-heat gain/conservation
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When it is too hot
-the body must experience heat loss to bring back the temperature to normal
1.Sweating
• The sweat glands elaborate more sweat
• Sweat flows to the surface of the body
• Evaporation of water in sweat uses heat from the body, this brings a cooling
effect
2. Vasodilation
• Arterioles in the skin dilate/increase in diameter-their muscles relax
• More blood is carried to near the skin surface
• Heat in blood is lost by radiation
When it is too cold
-the body has to gain/conserve heat
1.Reduced sweating
• very little sweat is made
• very minimal sweating occurs
• less heat is lost through evaporating sweat
• heat is conserved in the body
2.Vasoconstriction
•
•
•
•
arterioles in the skin constrict/reduce in diameter- their muscles contract
less blood travels near to the surface of the skin
less heat is lost by radiation
heat is conserved
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3. Shivering
• involuntary muscle contractions generate heat in the body
• heat is gained
4. Increased rate of respiration
• more glucose is broken down
• more heat energy is released
5.Insulation
•
•
•
•
a layer of fat under the skin makes the adipose tissue
layer acts as an insulator preventing heat loss
fat people are warmer in winter than thin ones
hairs stand on end when cold and trap air-air acts as an insulator, trapping
heat near the skin
-a reason why we develop goose pimple/bums when cold-this is due to hair
erector muscles contracting in the skin
The Brain and Temperature Regulation
-the part of the brain involved is the Hypothalamus.
-it takes part in the negative feedback mechanism
When too hot, blood passes through the receptors in the hypothalamus
-information is send to the skin inform of nerve impulses to instruct the sweat
glands to elaborate more sweat and also cause vasodilation.
-Heat is lost and blood temperature returns to normal
When too cold, blood passes again through receptors in the hypothalamus.
-information from the hypothalamus, instruct the sweat glands to stop producing
sweat, cause vasoconstriction, causes hair erector muscles to erect and also
stimulate metabolic activities that generate release heat energy e.g. respiration.
-Heat is conserved and gained in the body
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Blood glucose/sugar control
-the liver and the pancreas are the major organs involved
-the blood sugar level must be around 90-100mg/100ml of blood
-any fall or rise has negative impact/detrimental effect on the body
Describe the regulation of blood sugar in a normal person.
o The glucose/sugar level in blood rises after a meal rich in carbohydrates.
o The pancreas detects the rise in sugar level and its beta (β) cells secrete a
hormone called insulin.
o Insulin travels in blood to the liver where it stimulates liver cells to convert
excess glucose to glycogen.
o Glycogen is stored in liver and muscle cells.
o Blood sugar falls back to normal.
o During fasting or after several hours without eating, we feel hungry.
o Hunger is a sign of reduced glucose in blood.
o The blood passes through the pancreas and the alpha(α) cells of the pancreas
secrete glucagon into the blood.
o Glucagon stimulates liver cells to convert stored glycogen to glucose.
o Glucose level rises back to normal.
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Disease associated with blood sugar is Diabetes Type 1
Diabetes Type 1
-an autoimmune disease- lymphocytes recognize beta (β) cells as foreign
-the cells are destroyed and there will be no production of insulin
Effects
-there are very high levels of glucose in blood- level may remain very high after eating
carbohydrates
-patient loses a lot of glucose in urine
-patient feels thirsty as she loses water from cells causing dehydration
-patient feels hungry with a short period after eating
-dry mouth, blurred vision, increased heart rate and breathing rate
-convulsions and coma because less glucose gets to the brain cells
-frequent urination
-weight loss as the body turns breaking down proteins in muscles for energy
-after a long period of not eating the level of blood sugar falls very low
-no enough glucose for respiration - patients experience tiredness -no enough energy
-confusions and irrational behaviour
-unconsciousness
-damage to body organs over time
Treatment and Control
-insulin injections. Two types of insulin
1. Rapid-acting insulin taken just before or soon after meals
2. Long- acting insulin taken daily at a given time to maintain adequate levels of insulin
in the body at all times
-strict diet with very little or no sugar
-regular blood test to check sugar levels
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A biosensor can be used , as shown below
A dipstick can also be use, as shown below
140
Tropic Responses
-plants like animals also detect and respond to stimulus, but not in the same way
-plants experience growth responses to stimuli called tropic responses
Types of growth responses
A. Gravitropism
B. Phototropism
Gravitropism
-a response in which parts of a plant grow towards or away from gravity
1. Positive gravitropism- the part of a plant grows in favour of gravity
-roots grow downwards into the soil in favour of gravity
-this allows plants to absorb water and mineral salts
2. Negative gravitropism- the areal parts of a plant(the shoots system) grow against
the force of gravity.
-this exposes the leaves to sunlight and allow plants to
photosynthesise.
Phototropism
-a response in which a part of a plant grows towards or away from light
1.Positive phototropism- part of plant grows towards the direction from which light is coming from.
-the shoot system (trunk and leaves) grow towards the sunlight
-this exposes plants to sunlight and CO2, allowing them to photosynthesis
andtranspire.
-Positive phototropism is the same as negative gravitropism.
141
2.Negative phototropism-part of a plant grows away from the source of light.
-the roots grow away from sunlight into the soil.
-allowing plants to absorb water and mineral salts
-Negative phototropism is the same as positive gravitropism
Tropic responses in a shoot, are controlled by chemicals called auxins
An auxin is a chemical produced by the growing tip of a shoot or root,
which controls growth.
-it is a plant hormone
142
The role of auxins in shoots
-auxin are produced at the shoot tip
-auxin spread through the plant from the tip
-auxin is unequally distributed in response to light and gravity
-gravity makes auxin to concentrate on the lower surface of a shoot laid
horizontally
-auxin causes elongation of cells on the lower part of the shoot
-the shoot burns upwards opposing gravity
Effects of gravity on the young root
-the auxin accumulate/concentrate on the lower surface A
-auxin inhibit elongation at B on the diagram below
-the tip of root bends downwards C in favour of gravity
143
Effects of light and auxin on a shoot
-light is coming from the right
-auxin is produced at the tip and concentrate on the shaded side(side with no light)
-here auxins cause cell elongation
-shoot bends towards light
144
135
Effects of removing or covering shoot tips to plants exposed to light
A-Removing tips ensures no auxin is present. Shoots do not grow or respond to the
light coming from the right
B- Covered shoots do not respond or grow towards light. Their auxin is evenly
distributed and they grow straight up
C- Shoots are exposed to light. Auxin tend to move and concentrate on the side not
exposed to light. The shoot grows towards the light
15. Drugs
- any substance which when taken modifies or affects chemical reactions in the body
-some drugs interfere with the nervous system e.g., nicotine and heroine (mood
enhancing) or they change the way neurones send impulses
-drugs are broken down in the liver and excreted by the kidneys.
-urine tests are used to detect drugs in athletes and drivers after accidents
-some drugs are detected through the breath
-drug addiction – one’s body will rely on the drug to function, one will crave for the drug
-drug tolerance – the body’s metabolism become used to the drug. The body will
gradually demand more of the drug to attain the same effect as per the first time of using
the drug.
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Example: The liver will start producing more enzymes to breakdown alcohol and one has to
take more and more of alcohol to achieve the same state of euphoria achieved the first time
one took the alcohol
Classification of drugs
• Medicinal drugs
• Recreational drugs
Medicinal drug
-have an active ingredient for medicines
-these are given at clinics, hospitals and pharmacies
Uses of medicinal drugs
- used to treat and cure some diseases e.g. antibiotics
-alter sensory perception and reduce pains e.g. pain killers like paracetamol, aspirin and
morphine
-reduce fever and allergies
Antibiotics
-these are natural chemicals produced by living organisms or synthetic(man-made) that
kill or stop growth of bacteria
-they are used to treat bacterial infections
-antibiotics are produced by fungi and bacteria
-antibiotics are taken orally or by injections
Examples of antibiotics
Penicillin, Amoxylin, Tetracycline e.tc
How antibiotics work
-some inhibit cell wall formation
-others prevent movement of substances across the membrane;
-others stop important reactions e.g., protein synthesis
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Antibiotics cannot be used to treat viral diseases; they have no effects on viruses.
-viruses do not have cell walls, they do not have their own metabolism, they do not make
their own proteins.
Antibiotic resistance
-some bacteria are no longer responding to antibiotics-they are no longer getting destroyed
-MRSA has caused death in hospitals, especially in people with organ transplants as
their immune system is suppressed by immunosuppressant drugs
-antibiotic resistance reduce the effectiveness of antibiotics
-What causes it?
-unnecessary use and over use of antibiotics.
-not completing treatment
-keeping antibiotics for self-treatment
-over the counter purchases of antibiotics
How antibiotic resistance happens
-when an antibiotic is administered, nearly all the bacteria die and just a few, due to
mutation, survive because they will be producing an enzyme that destroy the antibiotic.
This type of bacteria now has enough food and space, it starts to reproduce and grow
without competition. Its population increases and its genes for producing the enzyme are
passed on.
When the same antibiotic is administered, the bacteria won’t get destroyed, all will be
resistant to the antibiotic.
-MRSA (Methicillin Resistant Staphylococcus aureus) is a strain resulting from
antibiotic resistance in the UK and USA.
-this drug Methicillin was over used in the treatment of boils in
the UK and the USA The bacteria, Staphylococcus aureus became
resistant to Methicillin- MRSA
How to reduce antibiotic resistance
Cases of MRSA declined in the UK and USA due to: o Giving antibiotics only when necessary
o Ensuring that people complete courses on antibiotic treatment
o Discovery of new antibiotics
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16.Reproduction
-reproduction is a process whereby individuals produce new organisms similar to
themselves
-new individuals inherit a set of chromosomes from their parents
-chromosomes are long threads of DNA found in the nucleus.
-chromosomes carry sets of instructions called genes
-genes give us our physical characteristics
Types of reproduction
• Asexual reproduction
• Sexual reproduction
Asexual Reproduction
-a type of reproduction where there is no fusion of gametes, only one parent is involved
and offspring are genetically identical to their parents
Examples:
Bacteria- cells divide by binary fission which is similar to mitosis .
New cells are produced containing the same genes as the parent.
-the parent and the new individual are genetically identical
Structure of a bacterium
148
Asexual reproduction in Bacteria
-Cell grows; DNA duplicate; DNA separate
-cell divides into two equal parts forming 2 identical cells/daughter cells-this is binary fission
Asexual reproduction in plants
-farmers and gardeners take advantage of plants reproducing asexually
Advantages of asexual reproduction in crops
• it is quick to produce new plants
• saves energy only one parent is involved
• offspring is genetically identical to the
parent plant
• chances of survival are high
• early maturity
• favourable traits are kept e.g. large attractive flowers, high yields etc
• rapid growth
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Asexual reproduction in plants is also called vegetative reproduction
Examples of vegetative organs used for reproduction by plants
1. stem tubes (potatoes)
2. root tubers (carrots; sweet potatoes)
3. bulbs (onions)
4. corms (yams)
5. rhizomes (grass; ginger)
6. runners (strawberries)
Potato
-reproduce using stem tubers--a stem tuber is an underground stem
Why a stem tuber? -it has eyes or buds from which new shoots and roots grow
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-the tuber stores food made during photosynthesis in leaves
-leaves act as the source.
-phloem vessels carry sucrose and amino acids to the tubers from leaves
-the tuber acts as the sink.
-food is stored as starch and proteins.
-during asexual reproduction the stored food is converted by enzymes to sugars-sucrose and
amino acids, this time the tuber acts as a source
-each potato plant can produce several tubers
-farmers grow and sell potatoes for food
-some potatoes are kept for the next growing season
-potatoes (seed potato) when buried in wet soil during the right season, they shoot and
produce new plants from the eyes
Disadvantages of asexual reproduction in crop plants
-crops are likely to be wiped by diseases and pests since they cluster in one place, diseases
spread easily
• no genetic variation -reduced resistance to diseases and pests
• good traits are lost with time
• competition for nutrients, light and pace
• no hybrid vigor
Advantages in wild species of plants
i. parents genetically identical to offspring
ii. saves energy, only one parent involved
iii. rapid growth
iv. high chances of survival
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Disadvantage in the wild species
-whole population can be wiped off by a disease or pest
-competition for food, water, sunlight and space absence of variation
Sexual Reproduction
-it is a type of reproduction in which two parents are involved and there is fusion of
male and female gamete nuclei to form a zygote
Advantages of sexual reproduction in crops/wild species
➢
➢
➢
➢
➢
➢
genetic variation- the offspring inherit different traits from the two parents
crop may have a better adaptation to environment
new traits can be introduced to the population
resistance to diseases and pests
plants can conquer new localities
spreading of plants is not limited
➢ there is no competition for nutrients, water, space, light
Disadvantages of sexual reproduction/wild species
➢ if only one parent is available, reproduction, cannot take place
➢ diseases can also spread
➢ unwanted traits can also spread
Gametes
-a gamete is a sex cell.
-a gamete is described as haploid
-haploid means having one set of chromosomes
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-a human being has 46 chromosomes in each cell thus two sets
-gametes in humans have 23 chromosomes each (one set).
-gametes fuse together at fertilization forming a zygote
-a zygote is described as diploid, it has 2 sets of chromosomes
-a zygote develops into a new individual
-diploid means having two set of chromosomes
-NB: - haploid and diploid are terms describing number of chromosomes present in a
nucleus-somatic cells are the rest of the body cells and these are diploid
-plants sex cells are also called gametes and they are also haploid
-ordinary cells in the testes, ovary, and anthers divide by meiosis to form gametes
-meiosis is a process of cell division in which the mother cell (diploid cell)
divides to form 4 daughter cells (haploid cells) called gametes
-meiosis only occurs when gametes are formed
-the cells(gametes) are genetically dissimilar.
Sexual Reproduction: Plants
-the flower is the reproductive organ in flowering plants
-the flower above has both male and female parts
Flower parts and functions
Male parts- are called the stamens, -these include the anther and the filament
-filament- hold the anthers in position
-anther - make pollen grains, pollen grains contain the male nucleus/contain male
gamete
153
Female parts - are called the carpel/pistil (stigma, style, ovary and ovules)
-Stigma- where pollination takes place; allow pollen grains to germinate
-Style – hold the stigma in position; allows pollen tubes to develop down to the ovules in
ovary
-Ovary – contains ovules; develop to form a fruit
-Ovules – contain the female sex gametes/ contain the female gametes nuclei;
where fertilisation takes place; develops to form seeds.
Nectaries – produce nectar which attract insects
Petals – large and brightly coloured in insect pollinated flowers-to attract insects
Sepals -protect the flower in its bud
Receptacle -where the flower is attached to the flower stalk
Flower stalk -hold the flower exposing it to agents of pollination
Female and Male gametes
-in humans the female gamete is the egg/ovum- larger and immobile
-in flowering plants- the gametes are inside the ovules/they are the nuclei inside the
ovules
-the male gamete in humans is the sperm- it is smaller and more active/mobile
-in plants is the nucleus inside the pollen grain- carried to the female gamete inside a
pollen tube which grows down the style
154
Pollen grains of insect pollinated flowers
a. have rough surfaces, have spikes to stick to insect hairs and legs
-are heavy and sticky
b. they are smaller, smooth and light
Pollination
-the transfer of pollen grains from the anther to the stigma either by wind or insects
-flowers are classified according to whether they are pollinated by insects or wind
155
Comparison of insect and wind pollinated flowers
Insect pollinated flower
Wind pollinated flower
156
Self And Cross Pollination
Self-pollination -a process where by pollen grains are transferred from the anther to
the stigma of the same flower or stigma of another flower of the same plant
Cross-pollination -a process whereby pollen grains are transferred from the
anther to the stigma of another plant of the same species
-cross pollination brings about variation, which may make the plants to be more
adapted to the ever-changing environment
-wet conditions drive away bees and wet the pollen grains-this can prevent pollination
-this pollination is more successful on a dry sunny day
Self-pollination
Cross pollination
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What happens after pollination?
-the pollen grains germinate forming a pollen tube
-the male nucleus from the pollen is carried at the tip of the pollen tube down the style
to the ovule inside the ovary
-only pollen grains of the right species germinate
-the pollen tube enters the ovule through the
micropyle
-the pollen nucleus is released inside and it fuses with the female nucleus to form a
zygote- this is fertilization
-fertilisation is the fusion of the male and female nuclei to form a zygote
What happens after fertilization?
-the stigma, style, filaments and anthers dry up and fall off
-the zygote divides by mitosis and develop into a seed
-the ovary matures into a fruit
Seeds
- a seed is a mature ovule
- the becomes dehydrated
- it becomes dormant (having no metabolic reactions), but remain viable
- dormancy allow seeds to survive harsh conditions (cold or drought)
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Germination
- A process when a seed starts to grow into a new plant
- The seed absorbs water through the micropyle
- The seed swells and enzymes are activated
- Enzymes break down stored food
1. Amylase breaks down starch to maltose to glucose
2. Proteases break down proteins to amino acids
3. Lipase breaks down lipids/fats to fatty acids and glycerol
-the end products of digestion-glucose, amino acids, fatty acids and glycerol are
used by the developing young plant for energy, growth etc
Conditions necessary for germination
1. Moisture/water – chemical reactions takes place in the presence of water
-cell expansion and elongation are enhanced
when cells absorb water
-water transport digested food in the seed
2. Suitable temperature – enzymes are denatured by very high temperature
and are inactivated by very low temperatures
-seeds require favourable temperature to germinate
3. Oxygen – germinating seeds respire. Oxygen is a gas needed during respiration
Investigation to show that water(moisture) is important for germination
i. Set up the apparatus as shown below
ii.
iii.
Leave the set up for 5 days
Make observations
A- seeds dry up before completing germination- no enough
moisture B- seeds germinate- enough moisture
C- seeds decompose- too much water which cut down oxygen supply
159
Investigation to show that oxygen is needed during germination
i
ii.
iii.
Set up the apparatus as above
Leave the apparatus for 5 days
Make observations
A- Seeds fail to germinate- pyrogallic acid absorbs
oxygen B- Seeds germinate -oxygen is available
Investigation to show that suitable temperature is needed during germination
i.
Soak a number of seeds. Divide them into 3 groups.
ii.
Roll each group between moist blotting paper and enclose them in polythene bags, as
below
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iii.
iv.
v.
Put one polythene bag in a refrigerator at 4oC, put the other bag in an oven at 30oC
and the last bag leave at room temperature in a dark cupboard
Leave the experiment for a week
Make observations
-In refrigerator- seeds fail to germinate. Temperature too low for enzyme activity
-In oven- germination takes place and advanced growth is observed compared to
those left at room temperature. 30oC proved to be more suitable for germination of
maize seeds
-at room temperature – germination takes place but the rate is not as at 30oC
Sexual Reproduction In Humans
-two sexes are involved- male and female
-each produces a haploid gamete-thus a sex cell with 23 chromosomes
-the male gamete is the sperm and the female one is the egg/ovum
-systems of organs are involved in sexual reproduction
The male Reproductive organs
-the male system is made up of the following organs
• Penis
• Urethra
• Testicles/Testes (testis=one)
• Epididymis
• Sperm duct
• Prostate gland and seminal vesicle
The male reproductive system is connected to the urinary system
NB:- the kidneys, bladder, ureters are part of the urinary system not the reproductive
system
161
-the two systems share the urethra
Functions of male parts
i. Scrotum
-sac like structure containing the testes/testicles
-the scrotum allows the testicles to hang out side to maintain a lower temperature
needed for sperm cell production, 2oC lower than body temp.
ii.
iii.
iv.
v.
vi.
vii.
Testes
-they have two functions-producing a hormone called testosterone and sperm cells
-testosterone gives secondary sexual characteristics
-sperm cells are gametes
Epididymis
-stores sperm cells temporarily
Penis
-an organ for mating/copulation/sexual intercourse
-it has erectile tissue to allow it to erect and penetrate into the vagina
Urethra
-a tube which allows semen and urine to come out
-in females it allows only urine to come out.
Sperm duct
-a tube which allow sperm cells and later semen to move by peristalsis towards the
urethra.
Prostate gland and seminal vesicle
-these two glands add fluids containing nutrients and enzymes to activate sperm cells
-the fluids plus sperm cells make semen
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Female Reproductive System
-there is no sharing of functions between the urinary system and the reproductive system
-the two systems open to the outside in the vulva
The female sexual organs
1. Ovaries
-there are two ovaries
-they start producing eggs/ova at puberty-eggs fuse with sperm cell at fertilisation
-they also produce two hormones-oestrogen and progesterone
-the two hormones take part in the menstrual cycle
-progesterone also maintain pregnancy
2. Oviducts/Fallopian tubes
-where fertilisation takes place
-allows movement of the egg and zygote by action of cilia
3. Uterus/Womb
-it is pear shaped
-where implantation and pregnancy take place
4. Cervix
-separates the vagina from the uterus
-it has some circular muscles which close and open the entrance to the uterus
5. Vagina
-an organ for mating/copulation/sexual intercourse
-it’s a muscular tube which allows discharge of the menstrual flow
-it also serves as the birth canal
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The male and female gametes
Sperm
Egg/Ovum
-10x smaller than an egg
-has an acrosome which contain enzymes to
digest into the jelly coat of the egg
-10x larger than a sperm
-no acrosome
-has a head, middle piece and a tail
-it is mobile (it swims using its tail
-does not have a food storage
-life span-3days in the oviduct
-millions are produced in one
ejaculation
-it has an oval or spherical shape
-it is immobile
-has a food storage
-1 day(24hrs)
-one is produced monthly
Adaptations of the sperm cell to its function
• has an acrosome which contains enzymes to digest a way for the sperm cell
through the jelly coat (zona pellucida)
• has a flagellum or tail to allow it to swim
• has a lot of mitochondria to release energy needed for swimming by the cell.
Adaptations of the egg cell to its function
• has a food store to which supplies energy for the first stages of development of
the zygote into a ball of cells
• has a jelly coat that changes at fertilisation forming a fertilisation membrane which stops
any other sperm cell to penetrate
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The Menstrual Cycle
-starts at puberty (12yrs)
-ends at 45-50yrs (Menopause)
-takes 28 days to complete
-a girl child has all her eggs at birth, though not matured.
Stages of the cycle
1. Follicle; 2. Ovulation ; 3. Corpus luteum; 4.Menstruation
Stages which bring changes to the ovaries are 1, 2 and 3
Stages which bring changes to the uterus are 1,3 and 4
Follicle stage
-the pituitary gland secretes FSH (Follicle Stimulating Hormone) into the blood
-its target organ is the ovary
-FSH stimulates the growth of a follicle
-a follicle is a group of cells which start to divide and increase in number
-the cells secrete a hormone called Oestrogen.
-Oestrogen travels in blood to its target organ the uterus and causes vascularisation and
thickening of the uterus lining
-vascularised means having an increased number of blood vessels
-Oestrogen prepares the lining of the uterus for implantation
-among the follicular cells will mature an egg/ovum
Ovulation stage
-maturity of the egg triggers release of LH (Luteinising Hormone) from the pituitary gland
-LH triggers ovulation- that is the release of the mature egg from the ovary at day 14 of the
cycle
-the egg is ushered into the oviduct and starts to be moved along by the cilia
Corpus Luteum stage
-the scar left on the wall of the ovary by the egg at ovulation is called the yellow body, it starts
to secrete a hormone called progesterone
-progesterone gets to its target organ, the uterus and maintains the lining of the uterus intact
awaiting implantation
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Menstruation stage
-if the egg is not fertilized within 24hrs, it dies
-the level of progesterone falls and the lining of the uterus break down
-dead tissues, blood and the dead egg comes out as the menstrual flow
-this flow or menstrual discharge comes after day 28 of the cycle
-the first day of discharge is day 1 of the new cycle
-discharge continues for 4-5days
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NB:- after the discharge, secretion of Oestrogen starts again.
Fertilisation
-takes place in the oviduct
-this is the fusion of the sperm and egg nuclei to form a zygote
-steps a-e show events leading to fertilisation.
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Fertilisation and early development
-the nucleus of the sperm and that of the egg meet and fuse together to form a zygote
-the zygote is a single cell which then start to divide by mitosis forming a ball of cells
-the ball of cells implants/sinks into the lining of the uterus.
- a process whereby a ball of cells sink/embeds into the lining of the uterus is called
implantation
-pregnancy starts as soon as implantation is successful
-the ball of cells transforms into an embryo
-finger-like projections grow from the embryo into the lining of the uterus forming the
placenta
-a membrane called the amniotic sac develops around the embryo and it secretes a fluid
called the amniotic fluid
-the embryo develops to form a fetus. A human fetus has all the parts of a human beingsmall hands, legs, eyes, ears e.tc
-during the early stages of development there increase in complexity- one cell(zygote) to
ball of cells to an embryo and then a fetus
-later stage is only characterized by increase in size-the fetus just grows big until birth
-an umbilical cord extends from the fetus to the placenta
The placenta
allows exchange of substances between the embryo/fetus and the mother
-nutrients, oxygen, antibodies, water, salts, including drugs (nicotine or alcohol) and
pathogens
e.g. rubella virus can pass from the mother to the embryo or fetus
-carbon dioxide, excess salts and water, urea e.tc pass from the embryo/fetus to the
mother
takes over the production of progesterone
Acts as a barrier- there is no mixing of the maternal and fetal blood at the placenta.
Why?
-the mother might be of a different blood group, and if mixing was allowed this could
cause death of both the fetus and mother
-the mother’s blood has a higher pressure, this would kill the fetus
-there would be an unlimited transfer of pathogens from the mother to the fetus
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The umbilical cord
-has two blood vessels inside it
-the umbilical artery carries deoxygenated blood containing urea, excess water
and salts to the placenta from the embryo/fetus
-the umbilical vein carries oxygenated blood, nutrients, antibodies and water
from the placenta towards the embryo/fetus
Amniotic sac and amniotic fluid
Amniotic sac
- is a membrane which surrounds the embryo or fetus
-it secretes the amniotic fluid
Amniotic fluid
- acts as a shock absorber protecting the fetus from mechanical damage.
-it maintains a constant temperature,
-it allows free movements for the fetus,
-it can be used by doctors to detect diseases in the fetus
-lubricates the birth canal during birth
Sex hormones in humans
-the female hormones Oestrogen, progesterone, FSH and LH take part in the
menstrual cycle
-Oestrogen is produced by the follicle in the ovary
-Oestrogen gives secondary sexual characteristics e.g. widening of hips,
development of breasts, feminine voice, attraction to opposite sex, controlling
the menstrual cycle
-progesterone is produced by the yellow body-it maintains the lining of the uterus
intact
-during pregnancy progesterone is produced by the placenta and it maintains
pregnancy
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-a sudden fall in the level of progesterone triggers MPs (menstruation)
and if this occurs during pregnancy it causes a miscarriage.
-both Oestrogen and progesterone inhibit production of FSH and LH
-FSH stimulates growth of follicles
-LH causes ovulation
-Testosterone is the male hormone produced by the testes/testicles
-it controls secondary sexual characteristics in males such as growth of a beard,
production of sperm cells, deep voice, widening of chest, development of muscles,
attraction to opposite sex.
Sexually Transmitted Infections (STIs)
-STIs are infections as result of sharing fluids during sexual intercourse
-an example is HIV/AIDS
HIV/ AIDS
-HIV stands for Human Immunodeficiency Virus
-HIV infection may lead to AIDS
-AIDS stands for Acquired Immune Deficiency Syndrome
-‘syndrome’ -several signs of different diseases appear/ a combination of signs and
symptoms
e.g. coughing; fever; loss of appetite; diarrhoea; headache; swollen lymph nodes; hair
loss e,t.c
How HIV is spread
Unprotected sexual intercourse- vaginal or anal Sharing needles during drug abuse by
injections Through the placenta
Through breast feeding
Through contaminated blood on cut skin surfaces
e.g. open wounds
Signs and Symptoms of HIV/AIDS
…………………………………………………………………………………………..
Treatment and Cure of HIV/AIDS
…………………………………………………………………………………………..
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Prevention/Control of STIs
-avoid sexual intercourse with people whom you are not sure of such as
i.
Known prostitutes who offer sexual intercourse for money
ii.
People who are known to have had sexual contacts with many people
iii. People whose sexual backgrounds are not known
iv.
Be faithful to one partner
v.
Get tested for HIV-both partners
vi.
Use of condoms and femidoms
vii. Get treatment early-an antiviral dose can be used to victims of rape to prevent HIV
infection
viii. Use of antibiotics to treat early signs of gonorrhea and syphilis
17.Inheritance
Chromosomes, Genes And Proteins
Inheritance is the transmission of genetic information from one generation to the next
The study of inheritance is called genetics
Definitions of terms
1.Chromosome -a thread-like structure made up of DNA and proteins which carry
genetic information in the form of genes.
-Chromosomes are invisible in a cell at rest, they become visible as two
chromatids, joined by a centromere during cell division.
-chromosomes are found in the nucleus
Organism
Human
Chimpanzee
Indian
muntjac deer
Fruit fly
Adders
tongue fern
Number of
chromoso
mes
46
48
6
8
1400
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Gene: - a length of DNA coding for a particular protein.
-each protein affects a feature of an organism.
-genes are like beads along chromosomes.
-genes control specific characteristics.
-genes are shared evenly in daughter cells
-20 different amino acids exist on earth
-their different sequences result in different several types of proteins in organisms
-sequences of bases result in different proteins of different shapes
-a shape of a protein determines its function
-enzymes have specific shapes which form their active sites
-a faulty protein may have a different shape and if it’s an enzyme no substrate will fit
its active site
-for a gene to be able to code for a protein, the code is in form of a sequence of bases
in its DNA. The protein produced then determines one or more features of an organism.
DNA (deoxyribonucleic acid)- is the genetic material
DNA controls how a cell functions- by deciding the shape and therefore function of the
protein e.g. an enzyme
-it is responsible for the production of other proteins like receptors and carrier proteins in
cell membranes
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-has 4 nucleotides, each containing either one of the bases-A; G; T and C.
173
.
Proteins synthesis by genes
-the gene coding for the protein remains in the nucleus
-the gene is copied onto a messenger RNA (mRNA)
-mRNA carries the copy of the gene into the cytoplasm
-mRNA passes through a ribosomes
-ribosomes assemble /link amino acids into desired proteins according to the base
sequence
on the gene in the nucleus.
-the order of amino acid is determined by the sequence of bases on the mRNA
Cell Division
Cell division can result in cells with either diploid or haploid nuclei.
Diploid and haploid refer to number of chromosomes present in the nucleus
Diploid nucleus: a nucleus with a full set/two sets of chromosomes.eg. 46 in all
somatic /body cells in humans.
-46 is the diploid number of chromosomes in humans.
-Diploid cells have two alleles of each gene.
-The alleles are in their pairs.
-a diploid nucleus is produced during Mitosis
Haploid nucleus: a nucleus with one set of chromosomes
e.g. 23 chromosomes in human gametes/sex cells.
- Haploid refer to the nucleus of gamete
- a haploid nucleus is produced during Meiosis
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Nuclear Division
- this is a process whereby the nucleus and later the
cytoplasm separate forming new individual cells from one
original cell
-there are two types of nuclear division namely mitosis and meiosis
Mitosis: nuclear division producing to genetically identical cells.
-mitosis produces a diploid number of chromosomes
-copies of chromosomes separate- this maintains the chromosome number.
Mitosis is important for: -Repair and replacement of tissues
-Growth
-Asexual reproduction
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Specialised Cells and Stem Cells
-all body cells have the same number of genes
-they are all genetically identical because they all a result of mitosis from one zygote
-not all cells make use of the genes in them, because they do not need the all the
proteins
produced by them
-a cell in the skin may require only the genes to make keratin (protein to make hairs)
and melanin (for complexion)
-a neurone does not require the protein above; it requires genes to make protein
receptors and neurotransmitters
NB: - though cells have all the genes, not all genes are expressed
-Specialised cells express only specific types of genes that enable them to carry out
their functions.
- a red blood cell has haemoglobin; it is a specialised cell to transport oxygen
- a muscle cell has contractile protein, allows it to effect movements
Stem Cells
What are stem cells?
-unspecialised cells which differentiate to form cells of specific structure and function
like skin cells, brain cells, muscles, blood cells.
Types of stem cells: 1. Embryonic stem cells- cells in an embryo (an embryo develops by mitosis from a
zygote. These cells can change/specialise to form any cell of the body
2. Adult stem cells- these are limited to change / specialise to form limited types of
cells and tissues.
-they are found in the bone marrow - to make blood cells.
-they are found in the brain- to make neurones
Note: - stem cells are used to treat diseases like type 1 diabetes.
-all body cells contain the same genes, but certain genes are switched on/off.
-genes for hair production are activated in the armpit and on the head, but not on the
forehead.
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Stem cells divide by mitosis to form specialised cells
Meiosis: cell division in which a cell divides to produce four daughter cells having
half the number of chromosomes.
-a reduction division in which the chromosome number is halved from diploid to
haploid resulting in genetically different cells.
-meiosis produces a haploid number of chromosomes
Importance.
-formation of gametes
-brings about genetic variation
177
Inheriting Genes
Gene: - a segment of DNA that codes for a specific protein
Allele: - an alternative form of a gene.
- gene for height has two forms –one allele for tallness and the other for shortness.
- a gene for eye colour has an allele for brown eyes and one for blue etc.
-alleles occupy the same positions called loci on homologous pairs of
chromosomes. Homologous chromosomes: are chromosomes of the
same length and same number of genes on corresponding positions
called loci.
-alleles are represented by letters of the alphabet.
-the same letter is used for the pair of allele.
- the gene for height can be TT, Tt, tt or HH, Hh, hh.
-capital letter standing for the dominant allele and the smaller the recessive allele.
Dominant allele: allele which expresses itself in the phenotype, suppressing the
effects of the other allele of the pair. Tt - the allele T of the pair is dominant
over the allele t
Recessive allele: allele which cannot express itself in the presence of a dominant
allele.
-expressed only in a homozygous state e.g. tt, hh, gg. .
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-One of the chromosome comes from the male parent and the other from the female
parent
Genotype:-genetic makeup of an individual/all the alleles which control all the
characteristics of an individual.
Homozygous: having a pair of identical alleles of a gene
- pure breeds have a pair of identical alleles.
-alleles may be all dominant (TT, HH, GG,)
-may also be recessive (tt, hh, gg)
Heterozygous: having a pair of contrasting alleles of a given gene as is in hybrids.
-hybrids have one dominant and one recessive allele
e.g. Tt, Hh, Gg etc
NB:-The genotype controls the phenotype.
Phenotype: physical appearance /outward expression of a gene.
-e.g. tallness, shortness, dark complexion, rolling the tongue
Monohybrid Inheritance
- inheritance of only one characteristic/single-factor inheritance.
Monohybrid cross: The way in which a single characteristic e.g. eye
colour is passed from parents to offspring.
-brown eye colour is dominant over blue eye colour.
-B = a brown eye colour allele
-b= a blue eye colour allele
-Brown eye and blue eyes are two phenotypes.
Possible genotypes can be as follows
Genotype
Homozygous
dominant
Heteroz
ygous
Homozygous
recessive
BB
Bb
bb
Brown
Brown
blue
Phenotype
Pure Breeding
Crossing means allowing fertilisation to take place. Gregory Mendel did genetic
crosses using pure breeding
garden peas
179
Pure breeds-these are organisms that always produce an offspring with the same
features. Tall plants always produce tall plants when crossed.
-pure breeding tall pea plants and short/dwarf pea plants were crossed.
-he obtained tall pea plants in F1 generation
F1 generation: The off spring resulting from crossing pure breeds, they are always
heterozygous
F1 generation = first filial generation
-tall plants produced are hybrids—mixed alleles.
-Mendel wondered what happened to the ‘factor’ for shortness
-He crossed plants of the F1 generation and he obtained a ratio of 3 tall plants
to 1 short plant [3:1], in the second filial generation (F2)
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-the factor for shortness reappeared, it was not destroyed
NB: From Mendel’s experiments, modern genetics deduce that
• The ‘factor’ referred to by Mendel is the allele
• The factor for tallness was dominant
• The factor for shortness was recessive and was suppressed in the F1 generation.
• The 3:1 ratio is the monohybrid ratio
A ratio of 3:1 is only obtained when heterozygous
individuals are crossed
The monohybrid ratio is a mathematical probability, which is verified using large
population of plants or animals. It may not be proved using few numbers of
individuals
A cross between a heterozygous tall plant and a homozygous recessive plant.
A ratio of 1:1 is only obtained when a heterozygous cross with a homozygous recessive
A Test cross - a cross undertaken to determine the genotype of an individual
showing dominant features.
-Given that in rabbits grey fur is dominant over white fur. One cannot tell the
genotypes of two grey rabbits using their eyes, instead a test cross with a white one is
done.
Possible crosses:
181
Cross 1
Parental phenotypes: Grey
Parental genotypes: GG
Gametes:
Offspring genotypes :
Offspring phenotypes:
Cross 2
Parental phenotypes:
Parental genotypes:
Gametes:
Offspring genotypes:
Offspring phenotypes:
Ratio of grey to white:
x
white
gg
G
g
Gg
All grey
Grey
Gg
G
x
g
white
gg
g
Gg
1 grey
gg
1white
1:1
Explanation of test cross results
-If the offspring are all showing dominant features (GREY), as in cross 1, the
unknown genotype of the rabbit is homozygous dominant.GG
-If the offspring are in the ratio of 1:1 as in cross 2, the unknown genotype of the
rabbit
is heterozygous, Gg
Codominance-it is when alleles are expressed equally in the phenotype and intermediate features
are produced.
-no allele is dominant over the other
-offspring show shared features
182
-Monohybrid inheritance, where one allele is dominant over the other is called
Complete dominance
Codominance In Plants
A four o’clock plant has red or white flowers.
Crossing a pure breed red flowered and a pure breed white flowered plant gives pink
flowered plants
Parent phenotypes:
Parents genotype:
Red flowered
CRCR
x
White flowered
CWCW
CR
Gametes:
CW
CRCW
Pink flowered
Offspring genotypes:
Offspring phenotypes:
Codominance In Cattle
Red bulls cross with a white cow to produce calves with roan colour (roan:
mixture of red and white)
Parent phenotypes:
Parents genotype:
Red bull
CRCR
CW
CRCW
Roan calves
Offspring genotypes:
Offspring phenotypes:
Codominance In Humans
-Occurs in blood groups A and B
-There are 4 blood types/groups.
-The gene for blood has 3 alleles.
A
White cow
CWCW
CR
Gametes:
Blood
group
x
x
Genotypes
B
IAIA ; IAIO
IBIB ; IBIO
AB
IAIB
O
IOIO
Alleles
IA ; I B ; I O
183
-Blood group AB is universal recipient —can receive blood from any other blood group.
-Blood group O is a universal donor —can donate blood to any other blood group.
-Blood of different types (A and B, A and AB, B and AB) cannot mix, reaction between
antigens and antibodies cause blood to clot.
-antigen: - protein specific to each individual found in the cell membrane. Antigens allow
cell identification.
-antibodies: -chemicals in plasma produced by lymphocytes which destroy pathogens and
neutralise toxins.
-antigens are on membranes of red blood cells
-antibodies are in the blood plasma
A man of blood group A married a woman of blood group B and they have children of
blood group O.
Genetic diagram showing how blood groups are inherited.
Parent phenotypes:
Parents genotype:
Gametes:
Man
IAIO
IA
Offspring genotypes IA IB
Offspring phenotypes: AB
x
x
IO
Woman
IBIO
IB
IO
IA IO
IB I O
IO IO
A
B
O
-alleles A and B are dominant over allele O
-allele A and B are codominant- they express themselves equally hence blood group AB
184
Inheritance Of Sex In Humans
Sex is determined by the 23rd pair of chromosomes in
the karyotype
Male sex chromosomes = XY Female sex chromosomes = XX
Male sex cells/Sperm cells
-contain either a Y or an X
chromosome.
Female sex cell/Egg/ovum
- contains an X chromosome
185
There are 50% chances of having a boy or a girl. A man married to have children. Find the
ratio of boys to girls
Parent phenotypes:
Parents genotypes:
Gametes:
Offspring genotypes
Man
XY
x
Woman
XX
X
Y
X
X
XX
XX
XY
XY
Offspring phenotypes: 2girls
Ratio:
2boys
1;1
The probability of having a boy or girl child 1:1/ ½ /50%
Ratios in inheritance are just mathematical probabilities, and results may not come out as
expected in real life situations.
Sex-linked characteristic
-gene responsible is on a sex chromosome and it can be common in one sex.
-found on the non-homologous parts of the X and Y chromosomes
-X chromosome has more genes than Y chromosome
Red – green colour blindness- a sex linked characteristic
-three types of cone cells are controlled by one gene.
-a recessive allele, b, results in only two types of cone cells being made.
-a person who is bb cannot tell the difference between red and green colours.
-the person is red-green colour blind.
-common in man
Example
A normal man married a normal woman and got a red- green colour blind boy child. Show
a genetic cross for the couple.
Let B represent normal vision allele
Let b represent red-green colour blindness allele
Parent phenotypes:
Parents genotype:
Gametes:
Normal man
XB Y
XB
x
Normal woman
XB Xb
XB
Y
Offspring genotypes: XB XB XB XB
Offspring phenotypes: Normal Normal
XB Y
Normal
Xb
Xb Y
red- green
-the results predict that about ½ of their male children will be red-green colour blind.
186
18.Variation and Selection
Variation
-is the differences that exist between organisms of the same species and even different
species.
Variation occurs in:
-complexion; ability to roll the tongue; shape of earlobes; blood groups; sex; height;
intelligence, sex, height, body mass, etc
Two types of variation:
Continuous variation and Discontinuous variation
Continuous variation: - individuals show a range of phenotypes between two extremes.
e.g. in height - very short and very tall.
-occurs in height; weight; length of leaves; size of feet; number of seeds in a pod;
intelligence etc.
A histogram can be used to show the frequencies of heights in class.
187
A normal distribution curve can be drawn as below
▪
▪
Discontinuous variation: - it is where individuals are grouped into limited
distinct phenotypes with no intermediates e.g. A, B, AB and O blood groups and
sex in most organisms
it is influenced by genes alone.
occurs in Sex; Blood groups; Ability to roll the tongue; Hitch hiker’s finger; Shape of
earlobe etc.
A bar chart is used to show the frequencies e.g. of blood groups.
Causes Of Variation
-the genes making the genotypes/alleles of an organism
-the environment which surrounds an organism
-genes brings about genetic variation
-environment brings about environmental variation
188
What causes genetic variation?
*Mutations
*Meiosis
*Random mating
*Random fertilisation
A. Mutations
-a mutation is an unpredictable change in a gene or a chromosome.
-often harmful or bring uncalled for suffering in both people and animals.
-bring about new alleles & phenotypes in the population
-happen spontaneously
Causes:
1. ionizing radiation by X-rays; gamma, beta and alpha radiations;
-DNA base sequences are damaged
-such damage in gamete producing cells of the ovaries and testes and result in
mutations being passed to the next generations
2. Chemicals such as lead, mercury, and those in tobacco smoke
-chemicals causing mutations are called mutagens
-mutagens causing cancer are called carcinogens
Mutations bring about changes in DNA base sequences, hence changes in proteins
produced which can be harmful or not functional causing different conditions
Examples:
Albinism
Down’s syndrome
Sickle cell anaemia
Some mutations can be of benefit in some organisms
Adaptive Features
-an adaptive feature is that caused by an organism’s genes, making it to survive and
reproduce in its environment
-some adaptive features are obvious e.g. fish has gills for gas exchange
-others are amazing
189
-Camouflaging –bodies having colour blending with the environment, it is against
predation
-leaf tailed gecko blends with dry leaves and can easily catch its pray
-seahorses blend sea fans to derail predators
-some insects look like leaves
-tuna fish is streamlined and has strong muscles for swimming very fast to catch its prey
-springboks have long thin strong legs to jump and flee from danger, brown and white fur
for camouflage
-giraffes – have long legs and necks to reach for leaves, skin furs designed to blend with
trees and bushes
- lions- strong legs and strong jaws and teeth to fight and to kill prey
-cheetah- light and swift body to catch prey
-organism best suited (fit) to its environment survive
-fitness is the probability of an organism to survive and pass on its genes to the next
generation in a given environment
190
Xerophytes: - plants surviving in very dry/desert conditions.
Adaptation of xerophytes
closing stomata
waxy cuticle
hairy leaves
reducing surface area of the leaves
➢ deep or spreading roots
➢ sunken stomata on underside of leaves
➢
➢
➢
➢
Closing stomata
-deserts have very high afternoon temperatures
-stomata close to prevent excessive water loss by transpiration
Waxy cuticle
-leaves have a thick layer of waxy cuticle secreted by the epidermal cell
-the cuticle prevents loss of water by evaporation
191
Hairy leaves
-hairs trap a layer of moist air around the leaf reducing loss of water vapor by transpiration
-a micro humid environment is created around the leaf
Reducing surface area of the leaves
-the smaller the surface the les water vapour will be lost by diffusion
-cacti has very tiny leaves, others reduced to thorn
-spines act as deterrents, animals will not eat them
-cactus us chloroplast in its stems for photosynthesis
deep or spreading roots
-deep roots to reach water deep down in the soil
-roots spread covering a wider area to capture as much water as possible soon after
flash floods
192
Sunken stomata on underside of leaves
-xerophytes have very few stomata in their leaves
-stomata are in pits on the lower side of the leaves
-pits trap water vapour
-diffusion gradient is reduced and less water is lost to the environment
Though plants elsewhere also have stomata on the lower’s surfaces of leaves, have cuticle,
have deep or spreading roots, desert plants display more.
Hydrophytes: - plant that survive in very wet places
-no water problems
-no need for adaptations to conserve water
e.g. the water hyacinth and water lily.
-no deep roots- roots just fix the plant into the soil under water
-stalk and leaves have hallow spaces-filled with air.
-air spaces for floating and expose their leaves to light for photosynthesis.
-stomata are mostly on the upper surfaces
-thin cuticle on leaf surfaces
193
-below is a photograph of water lily
Selection
Natural Selection
-natural selection is when nature decides which organism survives and pass on its genes to
next generation.
-organisms best suited to the environment, thus organisms with advantageous adaptive
features survive and pass on their genes/alleles to the next generation.
-natural selection is happening all the time
Summary of natural selection
1. Variation: - some mutations bring some selective advantage which causes other
organisms to survive and breed.
- camouflaged moths survived in Britain in 1918 than their white counterparts
-gene mutations, meiosis and fertilisation give rise to new individuals with better
adaptations
2. Overproduction: - production of large numbers of eggs by Sockeye salmon fish,
ensures that enough offspring survive and breed.
-Overproduction is to cater for those which are consumed by predators.
-zebra foals are in large numbers in spring, only a few reach adult age, due to predation
3. Survival of the fittest -plants compete for light, water, nutrients and space, animals
compete for food, water, space and mates.
*Organisms that are able to fight in this struggle for existence will survive and breed.
*Competition is fiercest among organisms of the same species
*They have the same structures and ways to get those resources.
4. Passing on of alleles for useful adaptations
-best adapted individuals survive and reproduce.
-best alleles increase in the population and others decrease
Stabilising selection
194
-individuals at the extremes do not survive, they are not well adapted e.g. female sparrows
with very long or very short wings are often killed in stormy weathers.
-natural selection does not always bring change.
-changes come when there is a change in the environment or if there is a mutation.
-natural selection keeps populations the same.
Mutation
-a new allele coffering an advantage to an individual -giving it new adaptive features
will make the organism to survive and pass on the allele
Change in the environment
-probably a feature that used to give an organism an advantage over the others no longer
save the purpose. In normal African environments grass and the environment in general
have a greyish-brownish look. Rabbits with grey or agouti colour are well camouflaged.
The allele for grey or Agouti favour and selected for, unlike the allele for white fur.
Suppose the climate changes and Africa starts to experience snow (a new ice age), white
fur allele to enjoy a selective advantage. White rabbits start to multiply as they get
camouflaged by the ice.
Examples of natural selection
*Distribution of the dark and pale peppered moth in Britain
*Antibiotic resistance
Distribution of the dark and pale peppered moth in Britain
-before the industrial revolution of the 19th century Oak trees where of a normal bark
of greyish colour with lichens contributing to the colour.
-the peppered moth is a nocturnal fly. Day times in perches on tree trunks and branches
-the moth has two phenotypes- dark and pale colours
-the dark colour is controlled by a dominant allele, but is due to a mutation
-the normal pale colour is controlled by a recessive allele
The pale peppered moths were very common before the industrial revolution
-they were more camouflaged by the Oak tree background. Predation by birds was
very low, they were not very visible.
-the mutant dark moths were scarce due to predation-they were darker against a clear
background
-natural selection was in favour of the recessive allele.
195
A lot of soot from burning coal, darkened the Oak tree trunks during the 19th century as
industry boomed
-the dark peppered moth started to enjoy a selective advantage and their numbers increased
compared to those of the pale peppered moth. The dark moth became camouflaged.
-this is an example of a change in the environment
An investigation to measure the survival of the dark and pale moths in polluted and
unpolluted environments
196
Antibiotic Resistance In Bacteria
-the process by which adaptive features develop gradually to make an organism fit to
survive in its environment is called adaptation
-bacteria can also develop adaptive features to survive in a changing environment, though
to the disadvantage of men
-drugs are chemicals used to ease symptoms or cure a disease, they affect metabolic
reactions in the body
-medicinal drugs, e.g. antibiotics are drugs that keep us healthy
197
-Antibiotics are chemicals used to kill bacteria or inhibit their growth, without damaging
our cells
-Discovered in 1940s
-antibiotics are not used against viral infections—viruses do not have metabolism of their
own(like protein synthesis); they do not have cell walls.
Penicillin is an example of an antibiotic
-it stops cell wall formation in bacteria, the bacteria absorb water and burst.
-among the huge population of bacteria, one or two may have an allele giving them
resistance to penicillin-they will have a selective advantage
-they multiply/reproduce passing on the allele
-others die
-the new generation of bacteria will be penicillin resistant
Applying an antibiotic, can kill most of the bacteria, but a few may undergo a mutation
which give them a resistance to the chemical.
They may produce an enzyme that break down the antibiotic
These bacteria will then multiply successfully in the absence of their competitors
They reproduce passing on the gene for resistance
New strains of resistant bacteria survive today
e.g. Staphylococcus aureus, normally lives on our skins, can cause infections resulting in
boils.
-Drugs like penicillin, oxacillin, Amoxylin and methicillin were used successfully to kill
Staphylococcus aureus.
-the new strain is called MRSA (Methicillin Resistant Staphylococcus Aureus)
-the bacterium goes through random mutation and natural selection
-more antibiotics used, more resistance occur.
198
How to conquer bacterial resistance?
-restrict use of antibiotics (no antibiotics for flu and cold, even for minor bacterial
infections)
-Patients should complete prescribed courses
-Doctors should stop unnecessary prescription of antibiotics
-New antibiotics should be made
-Use combinations of antibiotics
Artificial selection
Selective Breeding
-this is when man choses/decides which type of animal to breed or plant to grow basing on
their favourable/desirable features.
-humans are the selective agents not nature as in natural selection
-Man is after the best out of the crops and animals he keeps
-Man considers the following:
*High meat; milk and wool yielding
*Early maturity
*Rapid/fast growth
*Disease resistance
*Drought resistance
Animals and plants showing these features are bred over a period of time
Those which show an improvement in the desired features are kept for breeding.
Example:
A farmer has a herd of cattle. He always wants to improve one or two features of the herd
e.g. milk production
1.
2.
3.
4.
he chooses cows producing the most milk
chooses a bull whose mother and sisters produce more milk
breed the chosen cows with the chosen bull
the resulting calves are allowed to grow and those yielding more milk are selected and
bred with the best bull
5. he repeats for generations
He can also combine two or more desirable features like high milk yielding capacity
and docility.
-the act of choosing which animals or plants to breed is called artificial selection or
selective breeding
Dangers of selective breeding:
Inbreeding causes harmful recessive alleles to spread in the population.
Reduced variation
Individual animals cannot survive in the wild
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Comparison of Natural Selection and Selective Breeding
Natural selection
Selective Breeding
For both: certain individuals survive and breed
1. environments chooses/selects
Humans choose
2. random mating
Only selected animals and plants
cross
3. survive due adaptive features
Survive due to features desired by
breeder. The features often reduce
survival of the animal in the wild
4. any animal or plant has a chance to
Only a plant or animal with best
survive even with the least
features survive
adaptive features
5. greater variation
Reduced/limited variation
6. slow change in population
Rapid change in population feature
over a short period of time
19.Organisms And Their Environment
Ecology: - the study of living organisms and their environment.
Habitat: -a place where an organism lives and it has adaptive features to survive in that
area. Tadpoles live in a pond
Population: - a group of organisms of the same species living in the same habitat at the
same time. Many tadpoles make a population in the pond
Community: -populations of different species in an area.
Ecosystem: -is a community of organisms interacting among themselves and their physical
environment
Niche: - the way an organism lives its life and the role it plays in an ecosystem. Tadpoles
eat algae and weeds, excrete ammonia, they breath oxygen and breath out Carbon dioxide
in the water, they disturb pebbles and mud at the bottom of the lake
Physical factors in the environment:
Sunlight
Wind
Water
PH
Temperature
Ecosystems provide habitats for different organisms.
Examples of habitats are:
pond
lake
dam
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shrub
tree
rotting log
sea shore etc.
Energy Flow
-the energy comes from the sun
Organisms involved in energy flows
Producers
Consumers
Decomposers
Producers
-organisms which make their own food, using simple inorganic substances. e.g. plants and
bacteria.
Plants: use sunlight to convert water and carbon dioxide to sugars.
Bacteria: use energy from simple chemical reactions.
-Producers make food for other organisms (glucose, starch; proteins and fats)
-sunlight energy is converted to chemical energy in the food mention above
Consumers
-depend on plants directly or indirectly
Herbivores: - these feed on plants only e.g. cattle; goats; impala; elephants etc.
- are also called primary consumers (they are first consumers)
Omnivores: - these feed on both plants and animals
e.g. baboons; monkeys; humans; fish
-can be both primary and secondary consumers.
Carnivores: - These feed on animal meat only. e.g. hyena; lion; cheetah e.tc.
-they secondary, tertiary and quaternary consumers.
- the birds of prey which even feed on carnivores e.g. vultures and eagles are carnivores
and can be tertiary or quaternary consumers.
Decomposers (Bacteria and fungi)
feed on dead plants and animals.
-cause the decay of organic materials
Trophic Levels
-made up of producers; consumers and decomposers.
-trophic is a Greek word for ‘feeding’.
-a trophic level is a feeding position of an organism in a food chain.
Food chains
-A food chain is a feeding relationship showing the flow of energy from one trophic level
to another.
-the sequence of energy flow in form of a chemical from one organism to the next
-The flow of energy is non-cyclic— energy comes from the sun and never returns to the
sun.
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Sun → Producers→ Consumers
Sun light to chemical energy to heat energy
-the arrows show flow of energy
The sun is not part of a food chain.
Why: it is not food. Examples of a food chains: Grass → Hair →Jackal
Leaves →Goat →Man
Cabbage →Aphids →Bird →Eagle
Grass →Bird→ Snake →Eagle
Seeds →Mouse → Cat→ Eagle
Decomposers form their own food chains.
Food web
-it is a network of interconnected food chains
-it is a more realistic way of showing feeding relationship between organisms.
- It shows that an organism may not rely on one source of food.
-An ‘→’ shows flow of energy
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Seeds → Squirrel →Ocelot.
Seeds are eaten by a squirrel and a squirrel is eaten by the ocelot
Another food web
Trophic Levels.
a). Pyramid of numbers
-shows the relative numbers of organisms found in each trophic level.
-producers are more than the consumers
-primary consumers are more than secondary consumers,
-area of each block is represent the number of organisms at that particular trophic level
-the pyramid resembles a real pyramid— wider base and a narrow top.
-the pyramid shows that energy is lost at each trophic level
-very little energy is available for the tertiary consumers, hence their numbers will be the
least in the pyramid
Problem:
- Pyramid of numbers do not take into account the size of organisms.
-One plant can be a producer e.g. a cabbage and the pyramid is inverted.
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Pyramid of biomass
-much better than pyramid of numbers because:
* It takes into account the actual mass or dry mass of organisms involved.
*Gives a better idea about the energy transferred at each trophic level
-Dry mass of the organisms at each level is found.
-Dry mass is obtained by killing; drying and weighing organisms.
-Drying is done by repeated heating in an oven.
-In animals, an estimate of 65% is dry mass, animals do not change much like plants.
-Dry mass = mass of an organism - water.
-Biomass pyramids in phytoplankton and zooplankton are inverted.
-Biomass also varies with seasons.
Biomass is at its peak during the growing season.
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Pyramid of Energy
most reliable method.
-shows the energy transferred from one trophic level to the next.
-Producers have more energy and this energy falls as it passes from one feeding level to the
next.
-it is very difficult and time consuming to produce a pyramid of energy
-it also involves killing, drying and then burn the organisms to measure the amount of
energy released
Energy losses
The undigested/unabsorbed and waste—these pass out through the anus
The uneaten—herbivores do not eat all the plant material, tree branches, stem and roots
Respiration—when glucose is broken down in cell, some energy is lost as heat
-organisms only pass that energy in their biomass.
-only 10% of energy is passed on to the next trophic level
-2 to 5% of the sunlight energy reaches the leaves
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-very little of this energy is used during photosynthesis since some will be:
*Reflected
*Some will pass straight through
*Some cannot be absorbed e.g. green light
-Respiration in plants is only 40% efficient
-60% of the energy is lost as heat.
-Only 10% of energy is passed from plants to primary consumers.
Why?
Not all parts of the plants are edible or
easy to digest. 60% is lost in the plant as
heat
Only 10% of the energy is passed on by consumers.
Why?
Movements
Respiration-energy lost as heat
Passing out urine and faeces-energy lost to decomposers.
-Food chains are limited to less than 5 trophic levels
Reason: -very little energy will be available to support the 5th trophic level
-Few organisms mean enough energy available for the consumers
Energy efficiency
-Its more energy efficient to feed people directly to wheat than to feed on beef and dairy
products
Wheat →Man
-more people fed.
-but not all the energy in wheat is available to us—we are not able to digest cellulose and
therefore we cannot release the energy in it, the cattle can
-Soya beans can yield a higher protein content efficiently and cheaply, its more efficient
for humans to feed on soya beans than beef than beef
Wheat →Cattle →Man.
-Less people fed
-More energy lost as heat during respiration.
-Energy in urine and faeces from cattle not used.
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A vegetarian diet supports more people
-90% of energy constitute the uneaten; undigested and heat and is lost between
trophic level.
Nutrient Cycles
Carbohydrates; Proteins; Fats contain the elements: Carbon and Nitrogen
- Bacteria and fungi recycle the elements
-they feed on dead and decaying matter-acting as decomposers.
-Decomposers release carbon in form of carbon dioxide and nitrogen in form of
ammonia and nitrates.
- plants absorb carbon dioxide during photosynthesis and make new carbohydrates.
-Plants also absorb ammonium ions and nitrates and make new proteins
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The Carbon Cycle
-Carbon makes part of: - Carbohydrates; Proteins; Fats DNA
-Carbon comes from carbon dioxide in the air.
Describe the carbon cycle
-Carbon is in form of carbon dioxide in the air.
-Carbon dioxide is 0.04% of the air
-plants absorb carbon in form of carbon dioxide and make carbohydrates.
-Animals obtain carbon when they feed on plants.
Plants and animals respire and release carbon dioxide.
-Decomposers act on dead plants and animals, urine and faeces and release carbon dioxide.
-Combustion of wood and fossil fuels to release more carbon dioxide.
-Photosynthesis brings carbon to the living matter.
-Photosynthesis, respiration and combustion-maintain levels of CO2
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The Nitrogen Cycle
Describe the nitrogen cycle
-Nitrogen constitute 78% of air
-Plants and animals cannot use nitrogen as an element
-It must be fixed first by 3 ways:
1.Nitrogen fixation: fixing bacteria in root nodules in legumes, convert the nitrogen in air to
nitrates.
2.The Haber process: - react hydrogen and nitrogen to make ammonia used in making
fertilizers.
-Fertilisers (ammonium nitrate) add nitrates to soil.
3. Lightning convert nitrogen gas to nitrates during a thunderstorm.
-Plants absorb and convert nitrates to proteins.
-Animals get nitrogen in form of proteins when feeding.
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*Decomposers act on urine, faeces and dead plants and animals releasing ammonium
compounds.
*Nitrifying bacteria breakdown ammonium compounds to nitrites then to nitrates
*Denitrifying bacteria break down nitrates to nitrogen gas in swamps or water-logged
areas
-The nitrogen gas gets back to the air.
Populations
-Most populations maintain or remain the same size.
Factors affecting size of population
1. Availability of food
2. Availability of water
3. Predators
4. Diseases
5. Birth and death rate
-more food and water mean an increase in population
-competition for food and water in a large pop leads to death of the weak ones
-predators hunt down the young and the weak individuals leading to a decrease in pop.
-Only the best suited to the environment survive.
-diseases tend to spread fast in a large population than a small population
-the higher the birth rate than death rate the greater the pop
Population growth is shown on a sigmoid curve
-sigmoid means ‘S’ shaped
The Sigmoid curve
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-The growth curve above is of yeast cells.
-Bacteria and Yeast are easy to use to show the pattern of growth because they reproduce
and grow quickly
Phases on a sigmoid curve: 1. Lag phase (phase A): -insignificant growth observed as the yeast cells are very few
- organisms getting accustomed /acclimatized to the new conditions.
-for other organisms, they might still be looking for mates
2. Log /exponential phase (phase B)
-rapid growth experienced
-reproduction is at its peak
-plenty of food available (no limiting factors)
-no competition
3. Stationary phase (phase C)
-growth slows down
-population remains constant
-limiting factors-food; toxins(high levels of ethanol in case of yeast);
-diseases slow pop growth
-competition is stiff
-death rate = birth rate
4. Death phase (phase D)
-no more growth
-death rate is greater than birth rate
-too much toxins, lack of food; diseases
-high levels of competition
-higher levels of predation in some other organisms
NOTE: - limiting factor is a factor that is in short supply, which can either slow or stop a
reaction/activity
-These factors can be:* food supply
*buildup of toxins
*water supply
*predation
*shelter/space to live
*diseases
Predator-Prey Relationships
211
The graph was created using the data from the trading of snowshoe hare and lynx fur
between 1845 and 1925 in Canada
-the populations of the and that of the lynx vary from year to year
-it is all about food supply and predation
-increasing food supply for the hares resulted in increase in the hare population
-an increase in hare population means enough food for the lynx
-lynx population rises afterwards
-a drop in the numbers of hares was followed by a drop in numbers of lynx
Human Populations
-Human population was very low long back
Why?
• Diseases reduced life expectancy
• Limited food supply/famine
• Wars
• Natural disasters
World population has experienced a growth spurt.
Why?
Medical advancement- reduction of death by diseases and invention of drugs e.g.
antibiotics and introduction of immunisation programs, typhoid, dysentery wiped of
USA and Europe,
• Improvement in Agricultural methods and machinery- more food supply, more land
farmed
• Clean water supply
• Sewage treatment
• Hygienic food handling
•
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•
High birth rate and low death rate
Population pyramids
a population pyramid shows the number of people in a country by age and sex.
-the males are on the left and the females on the right
-they used to see whether the pop is shrinking or growing
Developed countries
Sweden; Great Britain; Canada etc.
-pyramid has a narrow base and bulging or wider top
-Narrow base - birth rates are very low
-Wider top - more people are surviving to old age.
-there is a higher life expectancy.
-there is an even spread of ages
-same BR and DR
-pop remains relatively constant
Developing Countries
Zimbabwe; Botswana; Zambia; Sudan etc.
-Wide base (bottom heavy pyramid)- birth rates are very high
-more dependents
-Narrow top - less people get to old age
-low life expectancy
-sign of an increasing pop
-more young people than older ones
-BR is greater than DR
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20. Biotechnology & Genetic Modification
What is biotechnology?
-use of organisms to carry out processes that produce substances we want.
-bacteria and microscopic fungi are used
Why using these microorganisms?
-they are small and easy to grow in labs
-take little space
-reproduce quickly
-produce a variety of chemicals
-no ethical issues over manipulation and growth of these microorganisms (no one minds)
-genetic code shared with all other organisms
-a human or plant gene can be placed in bacteria
-presence of plasmids. - genes are moved in plasmids
Use of Yeast
-a single celled fungus
-respires anaerobically producing CO2 and ethanol. Glucose → ethanol + carbon dioxide
-this is fermentation
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Biofuels/Bioethanol
-plants produce fuels for vehicles and engines
-yeast is used.
ground maize is mixed with amylase in a solution
amylase breakdown starch to glucose
yeast is added to ferment glucose to ethanol
ethanol is separated by distillation
ethanol is mixed with petrol to make a blend which release more energy per litre than
ethanol alone.
Advantages of biofuels/bioethanol
-sustainable resource-more maize grown, more fuel
-reduce CO2 through photosynthesis
-fossil fuels add CO2 without removing it
Disadvantages
-more land is used to grow maize for biofuel rather than for food
-food becomes expensive
-reduced biodiversity
Making bread
-wheat flour contain starch and gluten (a protein)
-flour, water and yeast are mixed to make a dough.
-amylase break down starch to maltose and glucose
-yeast enzymes break glucose to carbon dioxide and ethanol.
-bubbles of CO2 rise through the dough making the dough to rise.
-gluten makes the dough stretchy
-the dough is baked in an oven at 1500C
-alcohol evaporates and the yeast dies.
Making use of enzymes
- in industry enzymes come from microorganisms
-microorganisms are grown in fermenters
-oxygen, nutrients and suitable pH are availed to the fermenter.
-the enzymes are extracted from the solution and purified.
1. Biological washing powders
-contain enzymes and detergents
-detergents make greasy dirty to mix with water
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-enzymes digest stains of plant and animal origin-stains by blood, eggs, fats etc.
-proteases digest proteins to amino acids
-lipases digest fats to fatty acids and glycerol
-the products of digestion dissolve in water and are washed away.
-the enzymes are packed in microscopic capsules to prevent them from attacking skins of
those handling the washing powders.
-capsules only break in water during washing
-before biological washing powders were used at 400 C, today proteases from host spring
bacteria are used
2. Pectinase
-an enzyme which breakdown pectin making it easier to squeeze juice
-pectinase together with cellulase breakdown suspended carbohydrates which make the
juice cloudy, this makes the juice clear.
-pectin is a cementing substance between cell walls of adjacent cell
-production of juice increases when pectin is broken down
3. Lactase
-an enzyme that break down milk sugar lactose to glucose and galactose
-glucose and galactose are used to make sweets
-Asians and other people may stop production of lactase at adult age.
-these people cannot digest lactose –they get ill if they consume milk and its products.
-this is called lactose intolerance.
-milk is passed through immobilised lactase, lactase digest lactose making it free of lactose
-lactose tolerant people will now be able to feed on milk and milk products
-lactase also break milk to glucose and galactose to make sweets.
NB: - immobilised lactase is used because: -it will not mix with products
-the lactase remains fixed on alginate beads
-the little beads can be used again and again.
Growing Microorganisms in Fermenters
-bacteria and fungi are grown in fermenters
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-fermenters allow large scale production of the useful substances
What is done with regards to use of a fermenter?
1. Sterilisation
-washed first and steam is passed into the fermenter steam
-washing and steaming kill other microorganisms, preventing contamination of the
culture
-a culture is a mixture of the microorganism of our choice and their nutrient supply
2. Providing nutrients
-bacteria or fungi need nutrients in order to grow and produce the substances we want
-nutrients include water- a medium for chemical reactions; glucose for respiration;
amino acids- a source for nitrogen to make proteins
3. Providing Air
-fermentation has an earlier stage which requires oxygen
-oxygen is required during the multiplication stage
-oxygen is used during respiration to release energy needed by the microorganisms for
growth
-oxygen passes into the fermenter through an inlet
-waste gases escape through an outlet at the top of the fermenter
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4. Mixing the contents
-a motor turns paddles which keep the contents agitated to prevent settling
-through mixing happens to distribute nutrients and microorganisms evenly
-paddles may not be used in a fermenter where a fungus with hyphae is used, this
would cause entanglement
-air bubbles are used to mix contents instead
5. Adding the microorganisms
-these are added through an inlet at the top
6. Measuring and maintaining temperature
-a temperature probe is used
-a constant temperature ensures optimum enzyme activity
-reactions in the fermenter are exothermic—respiration releases heat
-cold water running around the ferment in a water jacket cools the fermenter
-hot water/steam can be used to raise the temperature
7. Measuring and maintaining pH
-a pH probe monitors pH levels
-enzymes in both bacteria and fungi work best at given pH values
-reactions releasing CO2 reduce pH
-smaller quantities of acids or alkaline liquids are added
8. Harvesting the product
-the solution is tapped out at the bottom and is filtered
-the fermenter can be emptied or product is removed in stages
9. Purifying the product
-the solution tapped from the fermenter still contain microorganisms, other residues
including the substance we want
-extraction of product happens here-separating it from the rest and then pack it in
suitable containers
Examples of substances produced commercially using fermenters
*insulin from GM bacteria
*antibiotic penicillin from penicillium
*mycoprotein from a fungus Fusarium
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Production of penicillin
-penicillin is an antibiotic used to kill bacteria
-produced by a fungus called penicillium
-a culture of penicillium, carbohydrates and amino acids are fed into the fermenter
Stage 1: - the penicillium grow in aerobic conditions and multiply for 15-24hrs.
Stage 2: - fermentation takes place
-the penicillium produce penicillin
-a small amount of sugar is continually added for a steady production of penicillin
-production goes on for even a wk.
Stage 3: penicillin is filtered and purified
NB: - a water jacket is used to control temperature
-the reactions inside are exothermic
-the paddle continues agitating the solution to mix it
Production of mycoprotein
-produced by a fungus Fusarium graninearum, in fermenters
-myco means fungus
-mycoprotein is produced by continuous culture – nutrients are continually added,
product is continually removed, no need to empty and sterilise the fermenter as in batch
culture.
-oxygen, glucose (energy source); minerals salts and ammonia (source of nitrogen for
production of amino acids) are added to the fermenter
-temperature 300C
-the hyphae give a meat like texture, with a bland taste
-flavourings are added to make products like burgers, sausages and pies
-mycoprotein is a good substitute for meat, it has high protein, low fat content and high
fibre content
-its consumption reduces chances of obesity, diabetes and heart diseases
-single proteins from bacteria have also been tried, though without success
Genetic Modification
- is the transfer of a gene from one species to another species e.g. from humans to bacteria
and bacteria to plants
-a gene is a segment of DNA which codes for a particular protein
Where is genetic engineering used?
1. Improving nutritional qualities of crops
-white rice lacks vitamin A
-severe vitamin A causes blindness
-millions of children die due to vitamin A shortage
-genes from maize and bacteria are used to make carotene in rice
-carotene is converted to vitamin A in the body
-carotene produces a yellow pigment in carrots and in Golden Rice
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2. Producing crops resistant to herbicides
-herbicides kill weeds
-most of the herbicides can kill even the crop plants
-some plants like soya plants have been modified to resist the impact of glyphosate
-glyphosate is a strong herbicide, but in this case when sprayed, it will kill weeds only.
3. Producing plant resistant to pests
-insect pests reduce yields and also destroyed stored grain
-traditionally farmers use pesticides to kill pests—but, these chemicals can also kill
harmless insects like bees and are very expensive
-genes from bacteria that produce a toxin called Bt, have been added to cotton and
maize.
-insects are killed when they try to feed on the leaves or stems of maize and cotton
or cotton fruits and maize seeds
1.
2.
3.
4.
5.
6.
7.
Advantages and disadvantages of GM crops
Advantages
Disadvantages
Golden rice gives an
1.Golden rice not wanted. Eradicate
immediate relief, unlike
poverty the cause of vitamin A deficiency
removing poverty which can
take ages
Quality crops and yields
2.Seeds for GM crops are very expensive
increased using GM crop seeds
-Farmers in developing countries cannot
not afford to buy them
3.there is serious monopoly by big
companies-farmers not allowed to keeps
and use seeds they harvest; new seeds must
be bought
Herbicide resistant crops
-herbicide resistant gene can be passed to
Reduces the number of times
other plants producing superweeds,
farmers have to apply
herbicides-less chances of
contamination
Increases yields
Reduces labour costs
Cheaper food produced
The issue of superweeds must
be a distant worry for none
have been discovered despite
huge commercial production
going of GM crops
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8. Bt maize
-the Bt protein binds to
receptors in the gut of insects
not humans
-numerous tests proved that
there is no harm can be caused
to people or other animals
-studies show that there are no
effects on other insects
-reduced use of traditional
pesticides which cause serious
pollution.
-Bt crops can be grown side by
side with non-Bt crops , this
reduces the selection pressure
for resistance to Bt.
-people feel that Bt maize can cause harm
-long term effects of GMOs not known
-insect resistant crops can harm other
insects apart from pests
-Bt toxin resistant insects are evolving
4. Human insulin production
-this is an example of genetic engineering.
-Insulin is a hormone which regulates blood sugar.
-failure to produce insulin in the body by the pancreas leads to a disease called diabetes
type 1.
Diabetics: -experience a sharp increase in sugars in blood after taking in carbohydrates
-they discharge a lot of glucose in urine leading to a sharp decline in amount of sugar in
blood; frequent urination ;blindness if not treated; sweating; poor healing of wounds,
leading to ulcerations; getting hungry quickly; dizziness when sugar levels drop; poor
mental stability; anxiety
Before 1970s:
- Sources of insulin-pigs and cattle slaughtered for meat.
-this did not meet the demand as diabetics increased.
-high chances of spreading of diseases from animals to humans and allergic reactions.
Late 1970s: - human insulin gene isolated
-mass production of insulin using bacteria
-this proved to be cheap and reliable.
-pure insulin from GM bacteria
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Steps in Insulin production using Bacteria
(How genetic modification is done)
1. Insulin gene is identified in a human pancreatic cell.
2. Restriction endonuclease enzyme cuts the gene from the human chromosome, leaving
sticky ends. Sticky ends are unpaired bases at the ends of the cut gene.
3. A circular DNA called a plasmid is removed from a bacterium and is cut using the same
restriction enzyme that leaves sticky ends.
4. Human insulin gene is joined to the plasmid using an enzyme called DNA ligase.
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-the sticky ends on the insulin gene and plasmid are complimentary.
-a recombinant plasmid is formed.
5. Plasmid is put back into the bacterium—form GM bacteria
6. The GM bacteria, ammonium sulfate and sugars are added to a fermenter
7. Bacteria multiply and later ferment the nutrients and express the human insulin gene—
thus they use the code on the gene to produce the human insulin.
8. Insulin is extracted; purified and packed in bottles.
-Patients inject themselves with insulin injections.
21. Human Influences On Ecosystems
-the human population has grown
Humans have negative influence on the ecosystem
-destruction of rain forests(habitats)-land cleared for settlement and farming
-killing thousands of species of animals and plants
-pollution on land; oceans and rivers.
Man is destroying his environment.
How humans have impacted on the natural environment
1. Food Production
-the world’s food supply comes from crops and animals
-food productions have increased
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Reasons for increased food production
a. Agricultural machinery
-tractors, combine harvesters—more land tilled, more crops harvested
b. Agricultural chemicals
-fertilisers; insecticides and herbicides
-fertilisers increase soil nitrates, phosphates etc
-insecticides kill pests
-herbicides killed weeds-selective herbicides kill weeds and leave crops
-there is a general increase yields and improved crop quality
c. Selective breeding increased amount and quality of crops and animals
- new plants and animals have been produced which survive harsh conditions
Monocultures –
-Large piece of land is used to grow one type of crop
Advantages
-working on one large piece of land using agricultural machinery is faster and more
efficient.
-a uniform crop grows at the same height and harvesting happens at the same time
-one herbicide or pesticide can be used in the same way at the same time.
-large quantities of crop can be produced at once, making selling easier
Disadvantages
-Biodiversity is reduced
-Biodiversity is the existence of many different species of organisms in one area
-There is an increase in one type crop pest e.g. leafhoppers this reduces yield—mixed
cropping is being employed to reduce spread of pests
-Spread of diseases is high
-Spraying of leafhoppers and other pests- kill harmless insects e.g. bees
-Resistance to pesticides also occur
-reduced soil fertility—plants of the same type grown year after year will exhaust all the
nutrients; more fertilisers are used, crop rotation is the best way to improve nutrient levels,
intercropping with legumes increases nitrate levels in the soil
Intensive livestock production
-production of animals in a small piece of area which normally is enough for few animals.
-farmers use high inputs e.g. high energy expensive foods; medication (drugs) to prevent
and treat disease; temperature controlled buildings to maximize growth
Advantages
-more food is produced
-food can be cheaper
-less land used than in extensive farming—more land to provide habitats for other species
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Disadvantages
-welfare issues- animals overcrowded
-diseases spread easily
-high risk of antibiotic resistance
-wastes pollute water and land
-food supposed to be fed to people is given to animals
-excessive use of energy to transport animal feeds or maintaining warm temperatures in
building
-High water demand
Habitat Destruction:
-habitat is a place where organisms live
-animals have adaptive features to survive in their habitats
-destroying habitats is a direct cause for extinction
How habitats are destroyed
-cutting down of native vegetation- creating land for farming, factories, settlement, for
roads
- mining explorations for metals, for coal, for sand and gravel; toxic run off can pollute
water and land
-pollution (fertilisers, pesticides, eutrophication and bioaccumulation)
-removing key species in food chains and webs e.g. corals
Deforestation: -this is the careless cutting down of trees:
-trees are cut for wood and building materials
-the rainforest in the temperate and tropical regions is threatened with deforestation
Effects of deforestation
*Extinction –animals lose habitats and food & die.
-Plant are destroyed
-Burning cut down trees kill more animals and plants.
*Reduction of species diversity
*Soil erosion: -land is left bear exposed to effects of raindrops
-top soil is washed away (no roots to hold soil).
-no soil to support new plants.
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How to reduce soil erosion?
-stop careless cutting down of trees
-afforestation- planting more trees
-reduce number of livestock grazing in an area
-terracing on slopes
-ploughing across slopes
-use of contour ridges
-planting grass- vetiver or lawn
-gully reclamation-blocking them & planting trees
*Flooding: -due to siltation which raises river beds and dam floors, water over flows their
banks.
-floods kill animals and people
*Reduced absorption of CO2.
- CO2 forms a layer which traps heat creating ‘the enhanced greenhouse effect’-which
leads to global warming
Greenhouse
-made up of transparent materials- glasses or plastics
-the glass or plastic allows the sun’s radiation of short wavelength to pass
-the radiation has enough energy to pass
-reflected heat from the earth is of long wavelength and has less energy to pass through the
glass
-the heat is used to warm the greenhouse
-crops are grown
-all conditions are controlled artificially in the greenhouse
-yields are very high.
Examples of greenhouse gases
Gas
Contribution %
Source
CO2
Methane
55
15
CFCs
24
Nitrogen
Oxides
6
Fossil fuel
-Natural gas leaks
-Digestive
system(cattle)
-Paddy fields
-Waste tips/Land
fills
-refrigerators
-air conditioners
-plastic foams
-fertilisers
-fossil fuels
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Greenhouse effect
- the earth is warmed up by trapping of radiant by greenhouse gases.
-there is an ever increase in the concentration of greenhouse gases in the atmosphere,
hence more heat is being trapped.
-Excess heat is supposed to escape into space and this is barred by the thick layer of CO2;
Methane; CFCs and Nitrogen oxides
-enhanced greenhouse effect results which brings about global warming.
What is global warming?
The overall increase in environmental temperature.
Possible effects of global warming:
Sea levels rises
-melting of ice in the Arctic and Antarctic regions—137giga tonnes of ice being lost each
year
-average sea level rose by 7.5cm between 1993 and 2017
-flooding is leading to submergence of low-lying towns and cities (New York; Mumbai
and Singapore) and countries like Marshall Islands; Kiribati; Tuvalu; the Maldives.
-floods destroy habitats.
More extreme weather events
-rising temperatures cause climate change
-wind patterns change and different weather systems are created e.g. hurricanes and
cyclones becoming more stronger in the future
-drought in most low rainfall areas. e.g. desert areas—lasting longer, more fires are
occurring killing wild life e.g. in Australia recently
-rainfall pattens changing and becoming too heavy causing floods in China, Germany and
India
How to reduce greenhouse gas emissions
-reduce burning of fossil fuels (very difficult to implement)—most countries still rely on
coal for energy
-Using alternative sources of energy such solar energy
Pollution
-is making the environment uninhabitable by man
-water pollution by raw sewage and fertilisers is a major issue for concern
Eutrophication
-inorganic fertilisers help crops to grow effectively.
-poor farming methods lead to washing of fertilisers into lakes and rivers
-fertilisers are leached -washed through the soil and carried by underground water to rivers
-fertilisers cause eutrophication.
-Nitrates and phosphates are limiting factors for growth of aquatic plants—their sudden
high levels, in water result in rapid growth of aquatic plants e.g. algae
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BIOLOGY 0610 NOTES 2023-2025
Describe eutrophication in dams and lakes
-it is a result of excessive use of fertilisers by farmers
-the fertilisers are washed into lakes and dams
-the nitrates and phosphates provide nutrients for aquatic plants e.g. algae, water lilies and
other single celled plants.
-these plants over-grow and die.
-they also block sunlight leading to death of those plants at the bottom.
-Aerobic bacteria decompose the dead plants using all the oxygen.
- fish, frogs, tadpoles etc. suffocate.
-the water becomes unpotable and smelly.
Sewage also causes eutrophication
-sewage is a mixture of faeces, urine and waste waters from homes and industries
-sewage mainly provides food for many aerobic bacteria which use a lot of dissolved
oxygen in the water bodies
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BIOLOGY 0610 NOTES 2023-2025
To reduce eutrophication
1. Apply fertilisers the time the plants are growing
2. Apply amount enough to be used by plants
3. Do not apply fertilisers just before rains
4. Avoid stream bank cultivation
5. Use organic manure-not easily washed away
6. Manure supply nutrients steadily for a longer time
7. Do not discharge raw sewage into water bodies (treating sewage also prevent spread of
diseases causing pathogen like cholera
Sewage must be treated to prevent eutrophication and spread of diseases
Air pollution
-Carbon dioxide from burning fossil fuels and wood
-Methane from cattle; paddy fields and extraction of coal and oil
-CO2 and Methane are greenhouse gases contributing to enhance greenhouse effect
resulting in global warming and climate change
Non-biodegradable plastics
-plastics are light weight, cheap, can be made into any shapes
-the problem is they are non- biodegradable- they cannot be decomposed or they take a
very long time to decompose.
-they can litter around- creating an eye sore on both land and water surfaces
-Can be mistaken for jelly fish by turtles –they accumulate in their stomach
-Trap, entangle and kill aquatic organisms and land animals
-crabs can be trapped inside bottles and die—526 hermit crabs found dead in one bottle
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Resources
-all that we get from the environment and utilise to meet our demands Resources include:
-Fossil fuels—coal; oil; gas; diesel Food
-Land for housing; agriculture; dumping
-Water
Categories of raw materials
-renewable resources
-non-renewable re s o u r c e s
*Renewable resources: - those that can be replaced or are readily available, plants;
animals; solar; wind and hydroelectric power
-these are also referred to as sustainable resources – resources that we can use without
them running out e.g. fish as long as we do not over fish; trees as long as we plant new
trees.
*Non-renewable resources: - those that cannot be replaced e.g. fossil fuels (coal; gas; oil;
nuclear power)
Conservation
-the management of ecosystems and resources to meet changing conditions and needs.
-it attempts to maintain or increase biodiversity of an area and to prevent extinction
Reasons for conservation
*Ecosystems provide food; fuels; recreation and tourism
*For future generations-prevents extinction
*Ecosystems provides the balance of life and nutrient cycles
*To protect habitats for animals
*Observing rights for all living things
*Provides a large gene pool for research
*to maintain water cycles
How to conserve forests
-passing laws to protect certain forests
-licensing to regulate the cut down of trees
-selective felling-this allows most forests to recover—roads; large machinery used and
disturbances by workers—still cause harm to the environment
-coppicing- deciduous trees are cut down to about 1m, this allows them to regrow fast
-afforestation -cutting and replanting trees- but must not cut down the primary forest
-educating the masses—that other source can be used e.g. solar cookers.
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How to conserve fish stocks
-populations of fish used for food are getting less.
-it’s difficult to draw up and enforce international laws against over fishing.
* Imposing quotas-only a certain quantity is allowed to be caught- more of unendangered
species and less of those in danger-boats are visited by inspectors at sea.
*Breeding in fish hatcheries for restocking
*Observing breeding periods when fishing is prohibited
*Seasonal fishing—certain areas closed to allow breeding of fish
*Restriction on the types –ban dredging nets and bottom trawls
*Restriction on sizes of mesh /net holes to use
*Monitoring should be done at sea—fitting electronic position sensors on fishing boats and
inspectors to check fishing boats for illegal fishing practices.
Endangered species
-extinct species have no individual surviving
-these are species whose numbers have declined that they are at the point of extinction.
-the larger the pop, the greater the variation
-the smaller the pop, the little the variation hence reduced chance of survival
-Paleontologists- people who study fossils have indicated periods of mass extinction
-major climatic changes could have caused mass extinction
-the changes could have been due to massive continuous volcanic eruptions in Siberia or
an asteroid hitting the earth that time
How are we causing extinction today?
-Destruction of habitats
-Hunting-the dodo has been hunted to extinction
-Pollution -habitats destroyed for the polar bear
-Introduced species-these outgrow the native species or hunt down the native vertebrates.
-overharvesting/overfishing
-climate change
-introduction of new species/alien species- these can turn out to be serious predators and
invasive /breeding out of control
-in Australia introduced rabbits bred out of control
-possums introduced escaped and preyed on eggs of ground nesting birds
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Conserving endangered species
-birds e.g. the echo parakeet-rats and monkeys took their eggs
-1973 an intensive conservation program of the Mauritian parakeet was started
-breeding in captivity
-in 2012, 600birds were now existing from only 10 in 1970s
-it was made successful by public awareness including visits to schools
-But genetic diversity has been lost -today birds rose from the 1970, 10 birds
How is conserving endangered species is done?
-Monitoring and protecting species in their habitats – National parks
-Captive breeding
-Educating local people
- Building seed banks
-Zoos and Botanical Garden and reintroduction into the natural environment
- Preventing trade in endangered species. CITES- banned trade of ivory in 1989
Problems associated with captive breeding
-males and females fail to recognize each other as potential mates—this can be bypassed
by use of artificial insemination (AI) and In Vitro Fertilisation (IVF)
-hormonal control of endangered species not known
-animals and plants failing to adapt when reintroduced into the wild
Maintaining genetic diversity
-genetic variation is of paramount importance
*Increases chance of survival in pathogen outbreaks
*Increases chances of adapting to changing environment
-variation allows some organisms to survive
-low population=low genetic variation-extinction is inevitable.
-harmful recessive alleles likely to be passed on easily- reducing chances of survival
*the green parakeets of Mauritius have been raised from only 10 individuals through
captive breeding—there is little genetic variation
To maintain genetic variation
1. Seed banks store seeds collected from various individuals of the same species
2. Seeds are germinated and plants with different genotypes are crossed
Reasons for conservation programs
Animals and plants have rights
For future generations
Plants and animals are sources of food
Plants are sources of oxygen and rainfall
Maintain health food chains and webs
Plants are a source of drugs
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The wild provides a gene pool for scientific investigations
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