Biology Notes
Grade 12 and 10
TOPIC: CHARACTERISTICS AND CLASSIFICATION OF LIVING ORGANISMS
− There are seven vital functions all organisms perform at some time during their
existence.
− These functions are the characteristics which make organisms different from nonliving things.
: LIST AND DESCRIBE THE CHARACTERISTICS OF LIVING ORGANISMS
1 Nutrition: is the obtaining of organic substances [carbohydrates, lipids (fats and
oils), proteins and mineral ions] from which organisms obtain their energy and
their raw materials for growth and tissue repair. Types of nutrition: Autotrophic
nutrition – some organisms manufacture their own food substances from
inorganic raw materials (e.g. Plants). They change energy from one form into
chemical energy of organic molecules, which they make using an organic source
of carbon = photosynthesis. Heterotrophic nutrition – some organisms (e.g.
animals) are unable to synthesize organic compounds to use as food. They
cannot manufacture the energy-storing molecules they need using inorganic
sources of carbon and they rely on consuming ready-made organic molecules.
Heterotrophic organisms: (a) Herbivores = feed on plants (b) Carnivore = feed
on animals (c) Omnivores = feed on both plants and animals. (Rowland, 1998).
2 Respiration:
Respiration
occurs
in
the
cells
[i.e.
in
the
cytoplasm
(mitochondria)] of all living organisms. Cells respire, i.e. the breakdown of
nutrients to release energy so as to power other vital functions. Respiration can
either take place in the presence of oxygen (Aerobic respiration) or in the
absence of oxygen (anaerobic respiration) (MacKean, 1986).
3 Movement: change of position, i.e. whole body (in animal) or moving only
growing parts (in plants) towards or away from influences (stimuli).
4 Reproduction: living organisms can reproduce either by: one parent (asexually)
or two parents (sexually).
5 Growth: Amino acids are used to form new cells resulting in increased number
of cells.
6 Excretion: waste products produced during chemical reactions can be
poisonous to the cells if they are not removed. Examples are carbon dioxide
produced by respiration and urea produced by deamination of excess amino
acids.
7 Sensitivity: living organisms are able to sense and respond to stimuli (changes
in the environment) e.g. light, temperature, water, gravity and chemical
substances.
: DEFINE THE TERMS NUTRITION, EXCRETION, RESPIRATION, SENSITIVITY,
REPRODUCTION, GROWTH AND MOVEMENT
1. Nutrition = intake of nutrients for energy, building up and maintaining living
matter.
2. Respiration = the breakdown of nutrients within the cells to release energy so as
to power other vital functions.
3. Movement = change of position, i.e. whole body (animal) or moving only growing
parts towards or away from influences (stimuli).
4. Reproduction = formation of more individuals either from one parent (asexually)
or two parents (sexually). Ability to produce offsprings.
5. Growth = permanent increase in dry mass, i.e. increase in cell number and size.
6. Excretion = removal of waste products from metabolism (i.e. all chemical
reactions within the cell) and substances in excess.
7. Sensitivity = the ability to sense and respond to stimuli (changes in the
environment) e.g. light, temperature, water, gravity and chemical substances.
NOTE: The seven characteristics of organisms form the basis of the study of Biology.
Activity
TOPIC: CLASSIFICATION AND SIMPLE KEYS
Suggestions for practical work or demonstrations:
•
•
use and/or devise a key to identify six locally occurring organisms, for example
trees, insects
observe and draw organisms found locally, concentrating on diagnostic features
and/or features that adapt them to their environment
Classification
→ Grouping organisms according to structural (physical characteristics) similarities
− Thus, organisms that share similar features are placed in one group.
− The groups are arranged from the largest group (Kingdom) to the smallest group
(Species).
− From the largest to the smallest, the groups are arranged as:
Kingdom→Phylum→Class→Order→Family→Genera→Species (Cambridge
University Press, 2001).
OUTLINE THE USE OF A HIERARCHICAL CLASSIFICATION SYSTEM FOR LIVING
ORGANISMS
Why classify organisms?
− To impose order and a general plan on the diversity of organism
− To reconstruct evolutionary relationships.
− To characterize an organism so as to recognize and distinguish it from the multitude
of similar organisms.
− To point out features that separates an organism from its relatives.
− To comprehend the forces of natural selection.
− To understand why a particular organism does what it does.
− To communicate information about an organism.
− To sort out and compare the diversity of organisms.
− To identify new organisms (Martin Rowland, 1998).
The hierarchical classification system
The hierarchical system of classification (Cambridge University Press, 2001:6)
The science of classification is called taxonomy. It is the branch of Biology that deals
with identification, naming and classification of living organisms into groups or taxa.
− The various groups into which organisms are put are called taxa.
− Taxonomy is the biological classification of species. Thus, the study of the principles,
rules and methods of classification.
− The taxa used in taxonomy are:
(As an example applied to modern man)
Kingdom
Animalia
↓
Phylum
Chordata
↓
Class
Mammalia
↓
Order
Primates
↓
Family
Hominidae
↓
Genus
Homo
↓
Species
Sapiens
NOTE: As you go down the hierarchy, the number of organisms in each taxon
decreases and the similarities between them increase (Michael Roberts, 1998). The
basic unit of biological classification is the species (i.e. a natural group which is
potentially capable of interbreeding to produce viable (fertile) offsprings, or a group of
organisms which have numerous physical features in common and which are normally
capable of interbreeding and producing viable offsprings (Michael Roberts, 1998).
: DEFINE AND DESCRIBE THE BINOMIAL SYSTEM OF NAMING SPECIES
DEFINITION: The system of classifying and naming organisms with a two-word name
(Cambridge University Press, 2001)./ It is one Latin name consisting of two parts. / It is
one scientific name consisting of two parts.
● The binomial name is mostly in Latin.
● It is one Latin name consisting of two parts.
● It is one scientific name consisting of two parts.
●
●
●
●
●
●
●
●
●
●
−
The first designates the genus (generic) name.
The second the species (specific) name.
The generic name comes first, and begins with a capital letter.
It is followed by the specific name which is written with lower case (small) letters.
Conventionally the binomial name is typed in Italics.
When it is hand – written it must be underlined separately.
Closely related organisms have the same generic name. Only their species names
differ.
For convenience, when an organism is referred to frequently, its fully name is given
initially, but in the subsequent mentions its generic name is shortened to the first
capital letter followed by a full stop.
If one refer to Homo sapiens more than once it will be written as H.sapiens.
The binomial name is used globally or internationally by scientists.
Examples: Humans = Homo sapiens
Olive tree = Olea capensis
Puffadder = Bitis arientans
Kamelthorn = Accia erioloba
NOTE: many organisms have local names, but these often differ from locality around
the world.
The species (trivial) name should never be used by itself (Biology Workbook 1, 2007)
− The binomial (two name) system was introduced in 1753 by Carolus Linnaeus, the
Swedish naturalist.
Rules used in the biological binomial system
− The name of the genus (generic name) is written with a capital letter and that of the
species (trivial name) with small letters.
− The whole binomial must be written in italics or underlined if italics are not possible.
− The generic name may be used alone, but the species name must never be used by
itself, e.g. write Bellis, but never peremins by itself.
− The name of the species must be written out in full when used for the first time, e.g.
Bellis peremins, but provided there is no ambiguity, thereafter the name may be
written / abbreviated e.g. B.peremins
− NOTE: many organisms have a common name of the native language, which is not
written in italics (Martin Roberts, 1998).
: USE SIMPLE DICHOTOMOUS KEYS BASED ON EASILY IDENTIFIABLE
FEATURES.
⇒ Convenient methods of identifying and naming organisms (Martin Rowland, 1998).
⇒ Printed or computer aided device that aids the identification of biological entities
such as plants, animals, fossils, microorganisms and pollen grains.
● Biologists use dichotomous keys to identify and name the unknown organisms.
● A dichotomous key is a way of identifying organisms by posing alternative
questions or choosing between alternative statements (D G Mackean, 1998).
● A series of questions asking about features seen on an organism (Biology Workbook
1, 2007
Using the Dichotomous Keys
● Dichotomous key are based on pairs of descriptions.
● It is a series of questions asking you about features one can see on an organism.
● In each case two opposite descriptions are given, and one has to choose the one
that applies.
● The key will tell which pair to go to next.
● The process repeat itself until eventually you arrive at the identity of the unknown
organism.
● Start any key by finding the organism you want to identify, and read the first pair
description
TOPIC: DIVERSITY OF LIVING ORGANISMS (BIODIVERSITY)
: LIST THE MAIN FEATURES USED IN THE CLASSIFICATION OF KINGDOMS
1. Main features of the kingdom Prokaryotae / Monera
− Consists solely of bacteria (archaebacteria & eubacteria)and
cyanobacteriabecause bacteria have prokaryotic cells (i.e. are microscopic,
simple cells and lack nucleus. Genetic material (DNA or RNA) floats freely in the
cytoplasm).
− They are unicellular (single celled) of consisting of very small cells (0.1μm 10μm).
− The genetic material is circular DNA, naked in the cytoplasm (i.e. not inside a
nucleus / prokaryotes).
− They contain cytoplasm but no membrane bound organelles such as
mitochondria, endoplasmic reticulum, Golgi bodies, lysosomes, vacuoles and
chloroplasts.
− Each is surrounded by a cell surface membrane.
− The cell surface membrane is a mesh-like cell wall of murein or peptidoglycan.
− Contain flagella for movement (NNS Biology Module 1)
− Their ribosomes are very small.
− Bacteria are visible with a light microscope.
The structure of a typical bacterium
NB: Bacteria are classified on the basis of criteria which do not necessarily reveal
evolutionary relationships.
− The technique of DNA sequencing may provide a classification which reflects their
true relationships.
2. Main features of Kingdom: Protoctista
− Most members are eukaryotic (i.e. nucleus is surrounded by nuclear membrane)
− Nearly all the protoctists live in water (sea, rivers, lakes)
− Some [e.g. Protozoa (animal like)] and amoeba are unicellular and very tiny.
− Seaweeds and algae (plant like) are multicellular and contain chloroplasts
NB: Algae and seaweeds are not classified as plants because they do not have proper
roots, stems and leaves.
− Euglena and chlamydomonas are single-celled proctists.
− They have chloroplasts and can feed on other microorganisms (NNS Biology module
2:18).
−
Other examples are Trypanosoma, a blood parasite of humans and cattle that is
transmitted by tsetse fly and cause “sleeping sickness’.
− Brown seaweed is another algae that belongs to proctists (Biology Workbook 1,
2007).
− Protista differ from bacteria because they feed in a different ways
NOTE: Protoctista which take in solid or liquid food may be called protozoa (animal like
unicells) and those which posse chlorophyll / chloroplast may be called protophyta.
− Many Protoctista move by means of cilia or flagella.
− Algae look like plants but don’t have proper roots, stems or leaves.
3. Main features of kingdom: Fungi
− Members are eukaryotic (i.e. made of large, complex cells and have nucleus
surrounded by nuclear membrane. Genetic material is enclosed inside nucleus by
nuclear membrane (Martin Rowland, 1998).
− Include organisms such as mushroom, mould, yeast and toadstool.
− Fungi are multicellular. Yeast is single-celled.
− They are plant-like organisms but without chloroplasts with chlorophyll and cannot
carry out photosynthesis.
− Fungus body is known as mycelium and are made of hyphae (thread-like
structures)
− Cell walls are made of chitin (complex polysaccharides)and not cellulose.
− Do not have chloroplast / chlorophyll
− Nutrition:
●Saprophytically = absorb nutrients from dead plant and animal material using
hyphae.
●Parasitically = feed on other living organisms. Penetrate tissues of hosts
− Reproduce asexually by producing spores, which are dispersed by air currents
(Biology Workbook 1, 2007).
Importance of fungi
● Decomposer = release nutrients (Nitrogen cycle)
● Fermentation = provide alcohol for brewers and wine makers.
● Antibiotic producers, e.g. penicilium produce penicillin
● Food, e.g. mushroom (Julian Ford-Robertson, 1979).
4. Main features of kingdom: Plantae
− All plants are multicellular eukaryotes
− Their cells contain chloroplasts with chlorophyll.
− Plants
are
autotrophic
organisms
and
manufacture
their
own
photosynthesis.
− Green plants are terrestrial organisms. Some occur in aquatic habitats
food
by
− They reproduce by sexual and asexual means
● NB: the kingdom plantae can be divided into different phyla.Phylum Brophyta
(mosses and liverworts), Phylum Filicinophyta (all ferns), Phylum Coniferophyta
(non-flowering plants / all conifers / needle trees) and Phylum Angiospermophyta
(all flowering plants). Only Phylum Angiospermophyta is discussed here.
− Many angiosperms are herbaceous (non-woody) plants while others are shrubs and
trees.
Phylum Angiospermophyta
− Angiosperms are the dominant plants on earth.
− Have roots, stem and leaves
− Have vascular tissue (xylem and phloem)
− Are multicellular, eukaryotic organisms
− Cells are made up of cell walls, nuclei and chloroplasts (chlorophyll)
− Leaves are elaborate structures with waxy, water-proof cuticle with pores (stomata)
NB: of the features which contribute to plants’ success on land, the most conspicuous is
their flowers.
− Flowers form seeds enclosed in an ovary which develops into a fruit after fertilization
(Biology Workbook 1, 2007)
NB: flowers are the sex organs of plants
− The process of reproduction in angiosperms is sexual (Martin Rowland, n.d :460)
− Angiosperms are divided into two classes according to the number of cotyledons
(seed leaves) which they have in their seeds.
(a) Class Monocotyledons
− One cotyledon in a seed (embryo)
− Parallel veins on leaves (parallel venation).
− Narrow , strap-shaped leaves
− Parts of the flower (petals) occur in 3s
− Vascular bundles are scattered
− Adventitious, fibrous root system
− Often wind pollinated
Examples: grasses, wheat, palms, maize, millet, sorghum.
Monocotyledon (Zea mays)
Class Dicotyledon
− Two cotyledons / 2 seed lobes.
− Network of branching veins on leaves (Net venation)
− Broad leaves
− Parts of the flower (sepals / petals) occur in multiples 2s, 4s or 5s
− Vascular bundle in ring inside stem
− Tap root system. Lateral roots develop from the tap root.
− Often insect pollinated
Examples: Acacias, roses, marula tree, bean plant, etc.
Dicotyledon (Nicotiana tabacum)
5. Main features of kingdom: Animalia (animals)
− Animals are multi-cellular, eukaryotic organisms.
− They do not possess photosynthetic pigments (chlorophyll) and their nutrition is
heterotrophic (i.e. by ingestion).
− Their cells do not have cell walls
− Most animals have muscles and nerves
− Reproduction is mainly sexually
− Have a high level of tissue differentiation, often with specialised organs.
− The kingdom Animalia is divided into several phyla. Only five phyla are discussed
here: Phyla Nematoda, Annelida, Mollusca, Arthropoda and Chordata.
a. Phylum Nematoda
− Are described as round worms.
− Have slender, long; round / cylindrical narrow bodies that are pointed at the ends.
− The body is not segmented and is covered by a thin, elastic protein cuticle of fibres.
− Have two openings in the body: mouth (anterio) and anus (posterior).
− Triploblastic body plan with ectoderm, mesoderm and endoderm.
− Body has no true coelom = pseudocoelomate.
− May live in many different habitats. Many live in the soil. Some are parasites.
Examples: tapeworms and hookworms.
b. Phylum Annelida
− Annelids are segmented worms
− Most are aquatic but some live in moist environments on land.
− Have long cylindrical bodies divided into metameric segments (i.e. each segment
contains the same pattern of muscles, nerves, blood vessels and excretory organs).
− Do not have a hard exoskeleton or endoskeleton ↔ have adapted to their
environment by having some fluid inside their bodies to keep their shape (=
hydrostatic skeleton).
− Have mucus on their skin to protect them from being damaged (dehydration).
− Some have a row of bristles (chaetae) on the underside of each segment, which grip
the surface when they move through burrows.
− Example: earthworm (Lumbricus terrestris)
c. Phylum Mollusca
− Contains the largest animals without a backbone (invertebrates) known to exist.
− Are soft bodied animals with a limey shell.
− Body divided into head, muscular foot (for creeping / locomotion / digging), and a
visceral hump covered by the mantle, which secretes the shell (martin Rowland,
1998).
− They are mostly aquatic (marine / sea water or fresh water), but snails live on land
(terrestrial).
− Triploblastic body plan.
− Principal body cavity is represented by a blood-filled cavity (haemocoel).
− Molluscs have a central nervous system.
− Have gills and lungs in the mantle cavity.
− Most have a rasping tongue-like radula used for feeding.
− Have unsegmented soft bodies with slimy skin.
− Most have one coiled or uncoiled hard shells.
− Slugs and octopus have no external shell or have a much reduced shell. Shells
protect their soft bodies.
− Heads are well developed with tentacles and eyes (NNS Biology Module 1).
− Reproduction is sexual.
Examples: octopus, mussels, snails, slugs and squids.
d. Phylum Arthropoda
− Arthropoda are so called because they have jointed legs. All have jointed legs.
− Are terrestrial and aquatic organisms.
− Are segmented with a hard chitin exoskeleton. The exoskeleton covered by a
waterproof cuticle protects, supports the body and allows movement to occur.
− Most numerical successful group and contain most of the world’s species of
organisms, i.e. largest Phylum.
NB: about half are insects and it is estimated there may be up to 9 million more species
of insects yet to be identified (Martin Rowland).
− They are invertebrates (i.e. no backbones).
− Majority have sexual reproduction.
− Divided into several classes. Important four are classes:
● Class Insecta
− Insects are terrestrial animals
− Body divided into: Head (six fused segments), thorax (three segments) and
abdomen (11 segments) [Biology Workbook 1, 2007].
− Wings can be one or two pairs or can be absent.
− Paired limbs adapted as mouth parts.
− One pair of compound eyes. One pair of antennae.
− Gas exchange through trachea (system of tubes).
− Exoskeleton prevents desiccation (drying out).
NB: wings help fly away from predators, environmental calamities or fly long distance to
seek food.
− Different colours are for camouflage.
Examples: locust, butterfly, beetles, cockroaches, mosquitoes, flies, wasps.
● Class Arachnida
− Terrestrial organisms
− Four pairs of jointed legs.
− Body divided into two sections: Cephalothorax (head and thorax) and abdomen.
− Lack sensory antennae
− Chelicerea hold the prey
− Leathery exoskeleton.
− Several pairs of simple eyes.
− Gas exchange through book lungs.
NB: Arachnids are carnivores. Scorpions have pincers for catching and holding prey.
Spiders, ticks and scorpions use their stings to inject and paralyze prey with poison.
Examples: Scorpions, spiders, ticks.
● Class Crustacean
− Mainly aquatic. Woodlouse (singular) is terrestrial crustacean
− Body divided into two sections: cephalothorax (i.e. head is not clearly defined ↔
head and thorax fused).
− Distinguished by two pair of antennae and compound eyes.
− More than four pairs of jointed legs.
− Have a thick, hard exoskeleton made of calcium (hence calcareous exoskeleton)
that protects their bodies.
− Have long pincers used to catch prey.
− Gas exchange through gills.
− Examples: crayfish, lobsters, crabs, woodlice (plural).
● Class Myriapoda
− Flattened bodies divided into segments = centipede.
− Rounded bodies = millipedes
− Body divided into two sections: head and abdomen
− One pair of legs per segment (Centipedes). Two pair per segment (Millipedes).
− One pair of antennae.
− Centipedes are carnivores. Millipedes are herbivores.
Examples: centipedes and millipedes.
e. Phylum Chordata
− Are animals with a supporting rod running along the length of the body.
− Most familiar ones have a backbone and are called vertebrates
− Vertebrates are divided into five classes: Pisces, Amphibians, Reptilian, Aves and
Mammalia.
● Class Pisces
− Mainly aquatic (marine/sea water and fresh waters).
− Body covered with scales.
NOTE: scales overlap and face backwards to reduce friction.
− Streamlined bodies cut the water easily for free movement.
− Gas exchange through gills. Gills are covered by operculum (gill cover).
− Lateral line contains sense organs that detect vibrations in water.
NB: fish are weightless in water because they contain a swimming bladder (air-filled
structure, like balloon). Swimming bladder helps with buoyancy (float) in water.
− Flexible vertebral column allows fish to manoeuver from side to side to produce
forward movement.
− Fins help with maintaining balance and steering.
o Dorsal fin = keep fish upright (balance) and move in straight line.
o Caudal fin = propel fish through water.
o Anal fin = keep fish upright.
o Pectoral fins and pelvic fins = used to steer, brake, move up and down and
even back.
Examples: Dolphin (Coryphaena hippurus), Cape hake (Merluccius capensis),
Soupfin shark (Galeorhims galeus), Pilchard (Sardinopus sagax).
● Class Amphibia
− Terrestrial and aquatic organisms.
− Have smooth, moist and thin skin with no scales.
− Have four limbs.
− Lay eggs in water. Jelly-like layer protect eggs. Eggs are fertilized externally in
water.
− Tadpoles (larvae) breath through gills. Adult frogs breathe through lungs and moist
soft skin.
− Undergo metamorphosis (i.e. change process from larva into adult).
− Eardrum (tympanum) externally visible.
− Body mucus prevents desiccation (drying out).
− Nostrils mounted high on top of head = exposure to oxygen.
− Eyes have transparent membranes = cover the eyes and enable them to see clearly
in water.
NOTE: Amphibians are poikilothermic (i.e. their body temperature varies with that of
the environment) = exothermic (“cold blooded”).
Examples: frogs, salamanders.
● Class Reptilia
− Mainly terrestrial. Others live in water.
− Have tough, dry, scaly, waterproof skin.
− Four legs, except snakes.
− Lay eggs with tough, leathery shell.
− Gas exchange through lungs.
− Poikilothermic animals (i.e. their body temperature varies with that of the
environment)
NOTE: Reptiles are adapted to their environment by having scales that protect their
bodies against desiccation
Examples: Crocodiles, snakes, lizards, turtles, gecko.
● Class Aves
− Terrestrial and aquatic organisms.
− Body covered with feathers.
− Have beaks for perking and tearing food.
− Scales on lower parts of legs.
− Wings are for flight.
− Lay eggs with hard, waterproof shells.
− Streamlined bodies minimize air resistance.
NOTE: Theory of evolution = birds and reptiles evolved from same ancestors
− Homeothermic animals = endothermic (“warm blooded”).
Examples: Eagles, ostrich, pigeons.
● Class Mammalia
− Terrestrial and aquatic
− Body covered with hair or fur = trap air and serve as insulator. Sweat glands produce
sweat = lowers body temperature.
− Females have mammary glands (breasts).
− Have pinnae (flap of skin) on ears.
Examples: Elephant, humans, cattle.
Viruses
− Viruses are not included in any of the five kingdoms (WHY?)
− Extremely small (30nm to 300nm), i.e. 1/100 size of bacterium.
− Not made of cells (i.e. non cellular = lack organelles).
− Consists of a single strand of a nucleic acid (either DNA or RNA) surrounded by a
protein coat (capsid).
− Are parasites. No metabolism of their own.
− Most are pathogens (cause diseases)
NB: there are arguments for and against classifying viruses as living.
Arguments against
− They are non-cellular in organization.
− They do not have the cytoplasm
− They do not have organelles
− They do not perform any of the seven characteristics of livings organisms by
themselves (i.e. use host cells).
Arguments for
− They have genetic material (DNA and RNA).
− They can produce with the help of the host cell.
− Use all the organelles of the host cells.
− When inside the host they can perform some living functions
SECTION II
ORGANISM
–
ORGANISATION
AND
MAINTAINANCE
OF
TOPIC: THE MICROSCOPE
Objective: Identify and state the functions of the different parts of a
simple microscope
Cells are too small to be seen with our naked eyes, are even too small to be seen even
with a magnifying glass or a hand lens. The name’ lightmicroscope’ means light
passes through the specimen that is being studied
The functions and parts of the microscope
1. Tube-connects the eyepiece to the objectives and imaged is viewed through
2. Revolvingnosepiece/turret-holds two or more objective lenses and can be rotated
3. Lowpowerobjective- magnify objects with low power
4. Mediumpowerobjective-magnify objects with medium power
5. Highpowerobjective-magnify objects with high power
6. Stageclips-hold the specimen on the stage in position
7. Condenserlens-focuses the light onto the specimen
8. Lightsource-supplies light
9. Eyepiece –to produce the final image seen by the eye
10. Arm-support the body tube and is the part you can grasp to carry the microscope
11. Stage-supports the slide for magnification and the stage has a hole to allow light to
shine up through the specimen
12. Courseadjustmentknob-move the tube and lenses up and down to the right
position so that the specimen is in focus. This is used only with the low power objective
lens
13. Fineadjustmentknob-moves the tube and lenses up and down to put the specimen
at the right position so that the specimen is perfectly focused. It is used to achieve fine
focus with high and medium power objectives.
14. Base-acts as a stand for a microscope and gives the microscope a firm, steady
support
Many microscopes have a rotating disk under the stage, called the diaphragm or iris
and have different sized holes. Iris regulates the amount of light that goes through a
specimen on the stage. It collects light and illuminates the specimen
Objective: Calculate the magnification and size of biological specimen using
millimetres as units
Magnification
Making things appear big
To determine microscope magnification…you just multiply the ocular lens by the
objective lens
Ocular 10x Objective 40x e.g. 10 x 40 = 400
● The total magnification is the eyepiece magnification multiplied by the objective
magnification
● The maximum magnification of a light microscope is x1500
● What can it be used for?
● What can it not be used for?
How to calculate the magnification of your drawing
Magnification= size of the drawing
size of object
Hints: always put X with the answer, e.g. 10 X 40 =400x
Hints on biological drawing
✓ Make your drawing as large as possible to fill the available space and draw with
pencil
✓ Do accurate observation, correct proportions, clear, sharp outlines and labels
✓ If you are drawing a feature such as the outline of a cell, the lines should be
clear, sharp and join smoothly
✓ Do not shade or colour your drawing. This is because shading or colouring may
cover up details and make the drawing less accurate.
✓ If you are drawing an organism with a complicated, reaping structure. You do not
need to draw them all. Draw only one or two to show details. Do not forget to
label the features on the drawing and give title
✓ Label lines: Must be in pen
Must touch the part you want to identify
May not cross
Should be on one side of the drawing only, if possible
Must be straight lines-no arrows
✓ Labels must be printed in pen
TOPIC: CELL STRUCTURE AND ORGANIZATION
Objective: Describe the structure of a prokaryotic and eukaryotic cell
Cell theory
• All living things are composed of cells and cell products
• New cells are formed by the division of pre-existing cells
• The cell contains inherited information (genes) that are used as instruction for
growth
• The cell is the functioning unit of life
• The chemical reactions of life take place in cells
−A
cell is the smallest unit that is capable
of performing life functions.
▪
▪
▪
●
1. The prokaryotic cell
Bacteria cells are described as prokaryotic cells
Prokaryotic cells are microscopic, simple cells and they have nonuclei
The genetic material (DNA or RNA strands) is coiled up and floats
cells without membrane-bound structures
Structure of the prokaryotic bacteria cell
2. The eukaryotic cells
● The cells of fungi, plants and animals are described as eukaryotic cells.
● The eukaryotic cells are large, complex and contain nuclei.
● Genetic material is found inside the nucleus, unlike in the case of
prokaryotic cells that do not have nuclei
Structure and function a cell
CELL MEMBRANE



Outer covering, protective layer
around ALL cells
For cells with cell walls,the cell
membrane is inside the cell wall
Allows food, oxygen, & water
into the cell & waste products
out of the cell.
CYTOPLASM



gelatin-like inside cell membrane
constantly flows
aka protoplasm
NUCLEUS




Directs all cell activities
Contains instructions
for everything the cell
does
These instructions are
found on a hereditary
material called DNA
Usually the largest
organelle
NUCLEAR MEMBRANE


separates nucleus from
cytoplasm
controls movement of
materials in & out of
nucleus
NUCLEOLUS


Aka “little nucleus”
Found in the nucleus
CHLOROPLASTS
 Green organelles that
make food
 found only in plant
cells
MITOCHONDRIA
 Organelles that release
energy from food
 This energy is released
by breaking down food
into carbon dioxide
 AKA the powerhouse
b/c they release
energy from food
 Some muscle cells
have 20,000
mitochondria
RIBOSOMES
 Make proteins
 Float freely or attached
to the endoplasmic
reticulum (ER)
 Ribosomes are made in
the nucleolus
ENDOPLASMIC RETICULUM
 A series of folded
membranes that move
materials (proteins)
around in a cell
 like a conveyor belt
 Smooth ER – ribosomes
not attached to ER
 Rough ER – ribosomes
attached to ER
GOLGI BODIES (GAWL jee)
 Stacked flattened
membranes
 Sort and package
proteins
VACUOLES
 Temporary storage
spaces
 Store food, water,
waste
LYSOSOMES (LI suh sohmz)
 The word "lysosome" is Latin for "kill
body."
 The purpose of the lysosome is to digest
things. They might be used to digest food
or break down the cell when it dies.
 Break down food molecules, cell wastes &
worn out cell parts
CELL WALL




protects the cell
gives shape
is made of cellulose
A cell wall is found in plants, algae, fungi, & most
bacteria.
Table to compare and contrast the structure between typical animal and plant
cells
Plant cells
Animal cells
Have cellulose cell wall
Do not have cellulose cell walls
Have chloroplasts with chlorophyll; Do not have chloroplasts with chlorophyll
starch grains in chloroplasts
Always have large permanent vacuole Have a number of small vacuoles or no
with cell sap
vacuoles at all; no permanent vacuoles
Have regular shapes
Have irregular shapes
Mitochondria present
Many mitochondria present
Cell surface membrane always present Cell surface membrane always present
Nucleus with nuclear membrane and Nucleus with nuclear membrane and nuclear
nuclear pores present
pores present
Nucleus located more to the edge
Nucleus centrally located
Cytoplasm present
Cytoplasm present
Cytoplasm forms a layer at the edges Cytoplasm found throughout the cell with
of the cell with more to the edge
nucleus more on the middle
✓ Test yourself
Tick in the correct space
Structure
Animalcells
Nucleus
✓
Cell wall
Cytoplasm
Chloroplasts
Large sap vacuole
Starch granules
Mitochondria
Plantcells
TOPIC: LEVELS OF ORGANIZATION
Define tissue as a group of similar cells working together to perform a particular
function.
Examples of tissues: in animals
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Liver tissues
Epithelial tissues
Bone tissues
Muscle tissues
Nerve tissues
Red blood cells
Examples of tissues: in plants
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Phloem
Endodermis
Xylem
Palisade mesophyll
Spongy mesophyll
Epidermis
Definition: organs are group of different tissues working together to perform a
particular function
Examples of organs: in animals
●
●
●
●
●
●
Heart
Lungs
Brain
Stomach
Kidney
Eye
Examples of organs: in plants
●
●
●
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●
Leaf
Root
Ovary
Storage organs
Flower
Definition: organ system is a group of organs performing several closely related
functions.
Examples of organ systems: in animals
●
●
●
●
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Endocrine (hormonal) system
Support/skeletal system
Support/ muscle system
Nervous system
Circulatory system
Respiratory system
Excretory system
Lymphatic system
Digestive system
Female reproductive
Male reproductive
Definition: an organism is a complex, functioning whole being that is the sum of
all its component parts.
● Some organisms consist of only one cell (unicellular), e.g. bacteria, amoeba,
paramecium
● Other organisms consist only of tissues, e.g. jellyfish, sea anemone
● Other organisms consist of organ systems, e.g. plant, chicken, fungus, cat
Objective: relate the structure of the following to their functions and locations
Ciliated cells
The cells that line the respiratory tubes in the lungs are covered in a special tissue
made of ciliatedcells. Ciliated cells are also found lining the oviduct (fallopian tube), the
trachea (windpipe), bronchus and bronchiole
Structure of ciliated cells
● Have tiny thread-like extensions called cilia.
● Cilia beat and make flicking movements
● They contain many mitochondria to release energy for cilia to beat.
Importance (function) of cilia
● They move rhythmically in a wave-like motion and move materials from one
place to another.
E.g
✓ In respiration, cilia sweep dust trapped by mucous towards the throat
away from the lungs.
✓ In the oviduct, an ovum swept towards the uterus along the fallopian tube
Ciliated cells
Root hair cells
very thin, delicate cells, which grow out of the side of the root in the soil.
Functions of root hair cells
● Increase the surface area for intake of water
● Absorb water and inorganic salts from the soil
How root hair are adapted for the absorption of water
● Has long, thin extension growing out into the soil, this gives each cell a large
surface area for absorption.
● There are a large number of root hairs in contact with the water around the soil
particles
● They do not have a cuticle and their cell wall is thin and allows water molecules
to penetrate
● Root hairs are sticky and stick to soil particles
● Root hairs grow fast and so penetrate soil particles easily
Xylem vessels—conduction and support
Definition: a structure made of many xylem cells arranged end to end; the cells are
dead and hollow but very strong and they carry water and salts up the plant.
Xylem vessels
How the structure of the xylem vessels are related to their functions
● Xylem vessels form a continuous transport system inside a plant.
● Xylem vessels are made of long hollow tubes connected end-to-end to form a
long continuous column
● They contain no cytoplasm and organelles (i.e. the cells are dead), so there are
no obstructions for the flow of water and mineral ions
● The walls are thickened with lignin (lignified walls) to provide strength and to
prevent the cell from collapsing – supporting the plant
● Xylem walls have unlignified areas called pits for lateral movement of water
Functions of the xylem vessels
● To transport water and inorganic salts
● To provide support to plants
Muscle cells-contraction
How the structure of the muscles cells are related to their functions
● Muscle cells are found in voluntary skeletal muscles like the organs biceps and
triceps
● They are made of long muscle fibre cells which are made up of contractile
proteins
● Muscle gets shorter because the protein molecules in the cell slide past each
other.
● Muscles have the effect of shortening the muscles and of developing a very
strong force.
● The contraction results in movement of the organism or organ by itself.
Red blood cells-Transport
How the structure of the red blood cells are related to their functions
● Red blood cells are found floating in the plasma of blood
● Contain haemoglobin, a molecule specially designed to hold oxygen and carry it
to cells that need it. Haemoglobin combines easily with oxygen to form
oxyhaemoglobin
● Red blood cells transport oxyhaemoglobin to the body tissues
● They are the smallest cells in the body to be easily pumped into the fine
capillaries
● They are biconcave in shape, that is, round and flat without a nucleus
● They have elastic walls, making the flexible enough to change shape when
squeezed inside capillaries
Topic: Passage of substances: Diffusion
Definition: diffusion is the movement of molecules from a region of their higher
concentration to a region of their lower concentration down a concentration
gradient.
Objective: Describe the importance of gaseous and solute diffusion, and of water
as solvent
Diffusion in living organisms
Example1: Diffusion in the Alveoli:O diffusing into the
2
bloodandCO diffusing out of the blood
2
● Oxygen enters your body by diffusion
● Carbon dioxide enter the leaf by diffusion
Example 2: Some digested food diffuses across the gut wall into the blood
The importance of diffusion in gases and solutions
● Diffusion of molecules such as oxygen, carbon dioxide and water down the
concentration gradient makes it possible for the cells to obtain substances they
need and get rid of waste products and toxic substances.
● Waste products diffuse out the organism
Importance of water as a solvent
● All metabolic reactions in cells occur in solution. Substances diffuse in and out in
solution. This means that substances dissolve in a liquid to diffuse inefficiently.
Water is a solvent.
The role of water as a solvent in transport and cooling mechanisms
● Water transport substances in blood, lymph, sweat and urine. It helps to
distribute and regulate body heat when your body loses water through
perspiration, urination and breathing.
● Water is also important in plants for transport and cooling.
− Plants absorb minerals ions dissolved in water in the soil and transport
them in xylem vessels.
− Food produced in the leaves by photosynthesis is also translocate in the
phloem tubes in a solution
− Plants lose water through the stomata of their leaves during transpiration;
this helps the plant, especially the leaves to remain cool on a hot day.
Topic: Passage of substances: Osmosis
Definition: osmosis is the passage of water molecules from a region of their
higher water potential to a region of their lower water potential, through a partially
permeable membrane
− Hypotonic Solution - One solution has a lower
concentration of solute than another.
− Hypertonic Solution - one solution has a higher
concentration of solute than another.
− Isotonic Solution - both solutions have same
concentrations of solute.
Explanation of terms
● Selectively / partially permeable – a cell membrane where some substances can
pass through while others cannot. In other words, the cell is “picky” about what it
lets into and out of the cell.
● Water potential – this is the tendency for water molecules to move from one
place to another
● High water potential: when a solution has lots of free water molecules, i.e.
diluted, weak, hypotonic solution. Distilled water has a high water potential
● Low water potential: when a solution has less free water molecules, i.e. a
concentrated, strong, hypertonic solution. Sugar or salt has a low water potential
● If water enters a cell = endosmosis
● If water moves out of cell = exosmosis
Osmosis process
●
●
●
●
Osmosis is a passive process – no energy is required
Water moves into and out of cells by osmosis
Plants absorb water from the soil by osmosis
Osmosis is important for keeping the soft stems of seedlings and herbaceous
stems (non-lignified) upright (turgid)
● Osmosis prevents leaves from wilting and prevents cells from becoming flaccid.
Objective: Describe the effects of osmosis on plant and animal tissues
● If one places a plant cell in distilled water, water moves into the cell by
endosmosis
● The vacuole swells and the cell will become turgid but will not burst, because of
the cell wall.
● If one places an animal cell into pure water, water moves into the cell by
endosmosis
● The cell will become turgid and will eventually burst (lyse) because it is not
surrounded by a cell wall.
● If one places a plant cell in a salt solution, the water moves out of the cell by
exosmosis
● The cell membrane tears away from the cell wall, the cytoplasm and vacuole
shrink and the cell will plasmolyse and become flaccid.
Topic: Active transport
Objective: Define active transport and discuss its importance as an energyconsuming process by which substances are transported against a concentration
gradient, e.g. ion uptake by root hair and uptake of glucose by epithelial cells of
villi
Definition: active transport is the movement of molecules, atoms or ions from a
region of low concentration to a region of high concentration against a
concentration gradient through a partially permeable membrane with the aid of
carrier proteins.
Active transport process
● This is an energy consuming process which uses energy
● It is an active process – requires energy
● Amino acids, glucose, minerals, vitamins, urea and iron move by active transport
into and out of cells
● Active transport takes place through the carrier proteins
● Mineral ions such as iron move into root hairs by active transport. The soil has a
low concentration of iron while the root has a high concentration. The iron ions
move from a low concentration in the soil to a high concentration in the root hair
cell against a concentration gradient. Active transport requires energy (ATP). The
carrier proteins of the cell surface membrane assist with active transport.
● Uptake of amino acids and glucose by the epithelial cells of villi in the ileum is by
active transport. The ileum has a low concentration, while the blood in the villi
has a high concentration.
Topic: Enzymes
Definition: enzymes are proteins that function as biological catalysts.
Properties of enzymes
● Are proteins
● Are specific in the reactions they catalyse; one enzymes will affect the rate of
only one reaction
● Are not changed by the reaction they catalyse
● Help cells to carry out chemical reactions quickly and efficiently at relatively low
temperatures; this would not be possible without the help of enzymes
Metabolic reactions
Metabolic reactions are all chemical reactions that occur in cells. They include reactions
that are catalysed by enzymes.
Type of metabolic reactions
● Anabolic reaction build up complex compounds from simpler ones; e.g. making
sugar from carbon dioxide and water during photosynthesis
● Catabolic reactions break down complex compounds into simpler one with a
release of energy’ e.g. digestion of food reserves to release energy during the
germination of seed.
Substrate and products
● Substrates are substance present at the beginning of the reaction.
● Product-substance it is changed into
Active sites and enzymes specificity
-Enzymes are specific in the reactions they catalyse because of their unique threedimensional shape.
-Active site – this is a site on the surface of an enzyme molecule that binds the
substrate molecule
Rate of Reaction = Amount of substrate changed (or amount product formed)
LOCK AND KEY
Some enzymes, their substrates and products
enzyme
substrate
amylase
maltase
lipase
sucrase
pepsin
trypsin
starch
maltose
lipids (fats & oils)
sucrose
proteins
polypeptides
product
maltose
glucose
fatty acids & glycerol
fructose & glucose
polypeptides
amino acids
Objective: Describe the effect of changes in temperature and pH on enzyme
activity
● Each enzymes works best at an optimum temperature and an optimum pH
The effect of temperature on enzyme activity
Enzymes and temperature
● Each enzyme has a temperature at which the rate of reaction (rate of enzyme
activity) is greatest – optimum temperature
● At low temperatures, the rate of enzyme activity is very slow. Enzymes can be
completely inactive at very low temperatures
● When temperature is low, molecules move slowly and few collisions occur
between enzymes and substances because there is less kinetic energy
● This is reversible because the enzyme is not denatured and is still active
● The rate of activity of enzymes decreases when the temperature decreases
● There is decreased kinetic energy
● When the temperature goes up, an increase in kinetic energy causes the enzyme
to vibrate very quickly
● When the temperature goes higher than the optimum, excessive kinetic energy
causes the enzyme to vibrate too much
● This breaks the bonds (hydrogen, disulphide and sulphur) and causes changes
in the tertiary 3D structure of the enzyme
● The active site changes shape
● The substrate will not fit into the active site and no ESC (enzyme-substrate
complexes) can form
● The enzyme is said to be denatured and the reaction rate will decrease or stop
● It is a permanent change and enzyme will never be active again.
Effect of pH on enzymes activities
● Use a pH scale to measure the strengths of acid and alkalis in a solution. The pH
scale has a of number from 1 for strong acids to 14 for strong alkalis;
● Some enzymes work best in alkaline some in acid, different enzymes work best
at different levels of pH
● Enzyme which is inactivated by low pH will resume its normal activity when its
optimum pH is restored
● Extreme of pH may denature some enzymes irreversibly
● The pH or temperature at which an enzyme works best is often called its
optimum pH or temperature
Graph below shows the effect of pH on the rate of enzyme activity of three digestive
enzymes
Pepsinamylaselipase
1 2
3 4 5 6 7 8
9 10 11 12 13 14
● Pepsin the enzymes produced in the stomach work best at a pH of 2 which is
acidic, digest proteins
● Amylase , the enzyme found in human saliva , work best at pH of 7.0 to 7.5,
digest carbohydrates
● Lipase, the enzyme produced by the pancreases work best in pH 11
Objective: Describe the role of enzymes in the germination of seeds and their
uses in biological washing products and in the food industry
Role of enzymes in the germination of seeds
● Seed contains food stored for a n embryo to use when germinating
● Starch stored in seeds is insoluble and the embryo cannot use it as food supply
unless it is changed into a soluble substance.
● Seed contain the enzyme amylase, this change starch into maltose. Maltose is
soluble, and can dissolve in water in the seed and be carried to the embryo plant
● Stored proteins is also changed to a soluble substance by an enzyme called
protease
● Amylase and protease in seed will only work until the seed start to germinate.
● Water soaking into the seed start the enzymes working
Enzymes in biological washing powder
● Biological stain on clothes such as blood, sweat, egg and wine are very difficult
to remove especially with ordinary washing powder
● Biological washing powder contains protein-digesting enzymes and detergents.
● Stains cannot be removed by detergents only
● Detergents remove greasy dirty from the clothes while enzymes remove organic
stains from clothes (blood, egg and fat stains)
● Enzymes break down proteins in the stain, producing smaller molecules which
are not coloured and which are easily removed by the detergent in the powder.
● After washing, the products are soluble
● Biological washing powders work best in warm, rather than hot water.
Enzymes in food industry
● Enzymes are used in the food industry, in the baking and dairy industries and in
the making of fructose syrup, baby foods and fruit juices
● Fructose syrup can be produced from starch in maize. The enzyme amylase
convert the starch into glucose, and then another enzyme converts the glucose
into fructose, fructose is used to make a very sweet fructose syrup that has a low
caloric value
● In baking industry, enzymes are used to produce white bread, buns and rolls.
Enzymes speed up the breakdown of starch in flour into sugar; Yeast can then
act more easily on the sugar to release carbon dioxide and cause the dough to
rise
● In the dairy industry,an enzyme (renin) is used to clot milk in the making of
cheese, and help in the ripening of blue-mould cheeses, such as Danish blue.
Rennet, a commercially prepared enzyme, is used to solidify the protein in milk
during cheese production.
● In baby food, to partially break down food for easier digestion in the digestive
system of the baby
● In fruit juices, to keep the juice clear
● In the brewing industry, sugar – fermenting enzymes change sugar into alcohol
and carbon dioxide
Topic: Nutrition
Definition:Define nutrition as the obtaining of organic substances and mineral
ions from which organisms obtain their energy and their raw materials for growth
and tissue repair.
Objective: distinguish between autotrophic and heterotrophic nutrition
● Autotrophic nutrition uses inorganic materials (carbon dioxide and water) and
an external source of energy (sunlight) to build organic molecules like starch and
glucose
● It occurs in plants (producers) during photosynthesis
● Autotrophic nutrition –
➢ Auto (self)
➢ Trophic (refers to feeding and nutrition)
➢ “Self feeding.”
➢ Organisms that make their own organic compounds
● Heterotrophic nutrition takes organic molecules (proteins, starch and other
carbohydrates) into the body during nutrition
● Organisms use it as a source of energy and for growth (building materials)
● This type of nutrition occurs in animals
● Heterotrophic nutrition –
➢ Hetero: other
➢ trophic: (refers to feeding and nutrition)
➢ “Fed by others.”
Objective: List the chemical elements that make up, carbohydrates, fats and
proteins
● Carbohydrates is made of carbon (C), hydrogen (H) and oxygen (O)
● Proteins is made of Carbon, hydrogen, oxygen, nitrogen, phosphorous and
sulphur
● Fats is made of carbon, hydrogen and oxygen
Objective: Describe the synthesis of large molecules from smaller basic units, i.e.
simple sugars to starch and glycogen; amino acids to proteins; fatty acids and
glycerol to fats and oils
Synthesis of simple sugars to starch and glycogen
●
●
●
●
●
Glucose and sucrose are examples of sugars.
The glucose molecule (C6H12O6) is described as a simple sugar
It is very small, soluble and tastes sweet
When two glucose molecules join together, a larger molecule, sucrose, is made
Very large, complex molecules are made when many thousands of simple sugar
molecules join in a long chain – these are starch found in plants and glycogen
found in animals.
Synthesis of amino acids to proteins
● Protein molecules are made of long chains of smaller molecules called amino
acids
● A short chain of amino acids is called a polypeptide
● A chain of polypeptides is called a protein
Synthesis of fatty acids and glycerol to fats and oils
● Fats are made of glycerol and fatty acids
● A molecule of fat is made of four molecules, one molecule of glycerol joined to
three long molecules of fatty acids
Objective: Outline the role of carbohydrates, fats/oil and proteins in living
organisms
Role of carbohydrates
● Structure and function: Carbohydrates are sugars and starches that the body
uses for ENERGY!
● PLANTS are the major source of carbohydrates in the food we eat.
● It is a building block for larger carbohydrate molecules (starch, glycogen,
cellulose)
● It is the starting molecule for building other molecules such as fatty acids, amino
acids, vitamins and chlorophyll
Role of fats/oil
●
●
●
●
●
●
●
●
●
ENERGY source for the body (more than carbohydrates and proteins)
Help protect and cushion vital organs as well as joints
Insulate the body against heat loss
Used for energy storage in organism, where they act as important sources of
fuel reserves that are rich in energy
Fats serve as a structural component of cell membranes. It forms the
phospholipids
Fats form the outer covering of nerve cells known as the myelinsheath
Forms a waterproof cuticle on leaves of plants to reduce transpiration.
Insects have waxy cuticle over their bodies to prevent too much water loss
through evaporation.
Birds spread oil over their feathers to help them repel water.
Role of proteins
●
●
●
●
●
Provide the building materials your body needs to grow and repair itself
Enzymes are globular proteins that act as biological catalysts
Hormones, immunoglobulin’s and haemoglobin are globular proteins
Carrier and channel proteins are contained in cell surface membranes
Keratin is a fibrous protein that forms the structural parts of hair, nails, wool,
claws, beaks and horns
● Fibrin is a fibrous protein found in blood plasma.
● Collagen is a fibrous protein in tendons, ligaments, connective tissue, blood
vessels and bones to provide tensile strength. In blood vessels it prevents
overstretching and bursting and helps to withstand high pressure.
Objective: describe the role of water as a solvent, in transporting and cooling
mechanisms
● Water isthe transport medium in the blood for moving nutrients and metabolic
wastes to and from cells; and in xylem for mineral ions
● It transports undigested and unabsorbed food from the body
● It is a major component of blood plasma
● It provides a fluid medium in which chemical reactions can occur and in which
biochemical compounds can dissolve, so it acts as a solvent for chemicals
● It is a reactant in hydrolysis when food is broken down into smaller molecules
during digestion
● It is also a reactant when large molecules are formed during condensation
● It is a product of respiration
● It is used in cooling
● When sweating or panting occurs, the body is cooled down
● This remains a stable body temperature which is needed for enzyme
reactions
● Water is used in body fluids such as digestive juice, milk and urine
● It is part of cytoplasm in all cells
● It is used in joints for lubrication
● It is part of mucus that plays a role in protection of the body
● It is needed for photosynthesis
● It keeps the plant cells turgid and prevents plants from wilting
● It keeps herbaceous plants and seedlings upright
FOOD TESTS
This is a simple test carried out on foods to find out what nutrients they contain. Each
type of nutrient has its own food test
Procedures to be followed whenever a food test is being carried out
● A standard test should always be done first. E.g. if food s are being tested for
simple sugar, a known simple sugar should be tested. The results of this can be
compared with other results from other foods.
● Foods should be kept completely separate from each other; this means using
clean containers, and so on for each kind
● The same amount of reagent should be used for each test.
NB: Reagent is a chemical substance used in a chemical test
Objective: describe test for: Benedict’s test for reducing sugars (qualitative only)
● This test uses a chemical called Benedict’s solution. Benedict‘s solution contains
copper salts and therefore has a blue colour.
● Crush a piece of food into very small pieces and put it in a test -tube
● Add some water (approximately 2 cm³) and shake the tube to help the food
dissolve and make a solution
● Add the same volume of Benedict’s solution
● Heat the solution carefully
RESULTS
● If large amount of reducing sugar is present in the food, Benedict’s solution will
turn an orange-red colour
● If small amount of reducing sugar is present in the food, Benedict’s solution will
turn a greenish-yellow colour
NB: Simple sugar reduces the blue copper salts in the Benedict’s solution to a red
compound. Sugars that do this are called reducingsugars. All simple sugars are
reducing sugars, as are some complex sug
Objective: describe the iodine test for starch
●
●
●
●
Crush a piece of food into very small pieces and put it in a test tube.
Add some water and boil the mixture to make a clear solution
When the solution is cold, add 3 or 4 drop of iodinesolution
Dark blue could should be produced
The biuret test for proteins
● Two chemicals, potassium hydroxide solution and copper sulphate solution
are used
● Put some food into a test-tube and add little some water
● Add some potassium hydroxide solution
● Then add two drops of copper sulphate solution
● When the tube is shaken gently, a purple colour appears if protein is present. If
colour remain blue , no protein
Objective: describe the ethanol test for fats (the emulsion test)
●
●
●
●
●
Ethanol is used to test for fats. Fats will dissolve in ethanol but not in water
Add ethanol on food and shake it thoroughly
Put some water in another container
Pour some of the liquid from the first container into the water
If solution of fat in ethanol is added to water, the fat forms tiny globules, which
float in the water. This is called an emulsion. The globules of fat make the water
look milky
Objective: describe the DCPIP test for ascorbic acid (vitamin C) and be able
toevaluate the results
● Test for vitamin C uses a blue reagent , DCPIP, which is made colourless by
vitamin C
● Put a standard volume of the same concentration DCPIP in a test tube
● Place one fruit juice sample in a dropper or syringe
● Add the fruit juice drop by drop to the DCPIP
● Shake the DCPIP after each drop of fruit juice is added
● When the DCPIP goes clear, record the number of drops of fruit juice you added
● Repeat the test with other fruit juice samples
● The fewer the drop needed to remove the blue colour from the solution, the more
concentrated the vitamin C in the food sample
Topic: Plant Nutrition
Leaf structure
Objective: Identify the cellular and tissue structure of a dicotyledonous leaf, as
seen in cross-section, and demonstrate the significance of these features in
terms of function, i.e. distribution of chloroplast for photosynthesis; stomata and
mesophyll cell for gaseous exchange;, vascular bundles (xylem and phloem) for
transport
Definition of Leaf
Leaf is the flattened outgrowth of Stem or a branch that develops at node & has a bud in
its axel. These are the dissimilar organs & are meant primarily for Photosynthesis,
Respiration & Transpiration.
Leaf structure
● Cuticle: a waxy, waterproof layer secreted by the epidermis, covering the lower
and upper epidermis. It stop water from evaporating from the leave
● Upper and lower epidermis: transparent layers of cell that protect inner layers of
the leaf. It allow maximum penetration of sunlight into the mesophyll layer
● Mesophyll layer: middle layer of the leaf, Divided into two layers palisade and
spongy
(a) Palisade layer-top layer of the mesophyll and are rectangular-shaped and
arranged in a regular pattern. This layer contain more chloroplast, therefore
most photosynthesis takes place here.
(b) Spongy mesophyll layer-lower layer of the mesophyll and cells here are round
and loosely arranged with large air spaces between them, like a spongy. Air
space is for gaseous exchange. This layer contains chloroplast, so
photosynthesis takes place here as well.
● Vascularbundle (veins) this is made of xylem and phloem. Xylem vessel carries
water whereas phloem tube carries food
● Stomata. Small pores on leaf and allow for gaseous exchange
How carbon dioxide enters the leaf
✓ By diffusion through the stomata
Mechanics of water uptake in the plant
✓ From the soil, water is absorbed by root hair cells by osmosis and
transported up the stem to the leaves by xylem vessels
Topic: Mineral requirements
Objective: Describe the importance of nitrate ions for protein synthesis and
magnesium ions for chlorophyll synthesis
● Nitrogen is a macronutrient. Plants use it in the form of nitrates.
● Nitrate ions are needed by plants to make amino acids, which combine to form
proteins
● They are used to synthesise chlorophyll
● Nitrates are used to synthesise nucleotides which form nucleic acids
● Some plant hormones, like auxin, contain nitrogen
● If plants are nitrogen deficient, yellowing of all leaves will occur, as well as
stunted growth
● Magnesium ions are needed by green plants to make chlorophyll
● It acts as enzyme activator
● It forms part of the middle in plant cells
Objective: explain the effects of nitrate ions and magnesium ions deficiency on
plant growth
● Lack of Nitrate ions results in plants having yellow leaves and poor growth as
plants do not build up amino acids
● Magnesium or iron ions, lack results in yellow of the older (lower) leaves and
spear stunted
Topic: Photosynthesis
Definition: photosynthesis as a process by which light energy is trapped in
chloroplasts and used to reduce carbon dioxide to form carbohydrates
Objective: state the balanced equation for the production of simple sugars and
oxygen (in symbols and words)
● Carbon dioxide + water + (Chlorophyll +light energy) = glucose + oxygen
6CO2＋ 6H2O →
● C6H12O6 + 6O2
Objective: describe the intake of the raw materials, the trapping and storing of
energy (conversion of light energy into chemical energy, the formation of food
substances and their subsequent storage (no detail required)
● Light energy from the sun, carbon dioxide and water combine and form sugars,
such as glucose during photosynthesis.
● Glucose is organic because it is made by green plants
● Water , carbon dioxide and sunlight are raw materials
● Light energy is changed to chemical energy in the leaf
● Light is trapped by chlorophyll in chloroplast
● Glucose is stored as starch
Objective: define the term limiting factor (as factors that affect photosynthesis)
and interpret the effects of light intensity and carbon dioxide concentration on
the rate of photosynthesis
● Limiting factor is any environmental factors that can slow down the rate of a
reaction if they are in short supply or in excessive amounts
Light intensity as a liming factor
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Light is a requirement of photosynthesis
A certain amount of light must be available
As light intensity increases, so does the rate of photosynthesis
It increases until the optimum light intensity is reached
At this point the photosynthetic rate is at its maximum
A further increase in light intensity does not bring about any further increase in
the rate of photosynthesis
Carbon dioxide as a limiting factor
● Photosynthesis requires carbon dioxide
● At low carbon dioxide levels the rate of photosynthesis will be slow
● Themore carbon dioxide a plant is given, the faster it can carry out
photosynthesis
● It increases until the optimum is reached
● At this point the photosynthetic rate is at its maximum
Objective: Explain the use of carbon dioxide enrichment, optimum light and
optimum temperatures in greenhouse systems
● If light intensity, temperature is low in some seasons,, a greenhouse can be used
to increase carbon dioxide, temperature or light intensity. Artificial lighting can be
used to improve crop production
Control of carbon dioxide concentration
● Carbon dioxide can be increased (carbon dioxide concentration) by burning of
fuels
● Bottles of carbon dioxide can be used to increase its concentration
● Ventilators can allow fresh air with carbon dioxide to enter the greenhouse
● A higher concentration of carbon dioxide means faster photosynthesis
Control of light intensity
● Position the greenhouse to receive maximum light
● Additional light can be supplied by artificial light (bulbs)
● If the light is too intense, it can be reduced by blinds which can be closed
● Reflectors inside the greenhouse can reflect light directly onto plants
● As light intensity increases, so does the rate of photosynthesis
Control of temperature
● Temperature can be increased by heaters or by burning fuels
● Temperature can be decreased by using fans
● Increasing ventilation rates bring cooler outside air into the greenhouse
● The decrease of temperature on hot days will prevent plants from overheating,
denaturing of enzymes and wilting.
Topic: Nutrition in humans
Nutrients and diets
Objective: list the principal food sources and describe the importance of
carbohydrates, fats, proteins, vitamins (A + C only), mineral salts (calcium, iron
and iodine only) fibre (roughage) water
What are nutrients?
Essential substances that your body needs in order to grow and stay healthy
Six categories of nutrients:
● Carbohydrates
● Proteins
● Minerals
● Vitamins
● Fats
● Water
Carbohydrates are sugars and starches that the body uses for ENERGY!
PLANTS are the major source of carbohydrates in the food we eat
Sources of carbohydrates:
● Sugars: jam, sweets, honey, sucrose (table sugar), fruit, cool drinks,
pancakesyrup.
● Starches: potatoes, (like French fries), maize, rice, pasta, wheat, bread,
mahangu.
Sources of lipids (fats and oils:
● Animal fats: butter, fat meat, cheese, oily fish, fish liver oil.
● Plant fats: olive oil, sunflower seed oil, peanut oil, avocado, margarine.
Sources of proteins:
● Animal proteins: eggs, meat, milk, cheese, fish, chicken.
● Plant proteins: beans, peas, lentils, soya, peanuts.
Sources of vitamin A (retinol)
● Vitamin A is a fat soluble vitamin, that is stored in the liver
● Fat soluble – butter, cheese, milk, oily fish, fish liver oil, liver, egg yolk
● Carotene – (orange pigment in fruit and vegetables) converted to retinol in the
body
● Beta-carotene – in carrots, green leafy vegetables, apricots.
Sources of vitamin C (ascorbic acid)
● Vitamin C is a water soluble vitamin that cannot be stored and daily intake is
needed
● Blackcurrants, citrus fruits (oranges, limes, lemons and grapefruit), strawberries,
melons, kiwi fruit, guavas
● Green vegetables (cabbage, spinach, lettuce, broccoli), new potatoes, green
peppers, tomatoes.
Sources of calcium
● Milk, cheese, yoghurt, dairy food
● Nuts, green vegetables (cabbage, lettuce, broccoli, spinach)
● Bones of tinned fish, hard water (water with a high mineral content)
Sources of iron
● Liver, kidneys, red meat, eggs, soya beans
● Spinach, raisins, dried fruit, curry powder, cocoa and plain chocolate
● Green leafy vegetables (cabbage, spinach, lettuce, broccoli)
Sources of iodine
● Seafood (fish, lobster) and shellfish (mussels, oysters), kelp
● Iodised table salt (when potassium iodide is added to table salt)
● Present in most vegetables, provided that the soil in which it grows is not
deficient in iodine
Sources of dietary fibre
● Green leafy vegetables (cabbage, lettuce, broccoli, spinach), fruit skins, seeds,
nuts, celery, potato skins, dried fruit, maize, oranges
● Wholegrain breakfast cereal, brown rice, whole meal pasta, wholemeal bread,
oats, bran flakes
Importance of:
a) Carbohydrates
● They provide the body with energy
b) Fats
● ENERGY source for the body (more than carbohydrates and proteins)
● Help protect and cushion vital organs as well as joints
● Insulate the body
c) Proteins
● Provide the building materials your body needs to grow and repair itself
d) Vitamins A
● Vitamin A is required in the formation of rhodopsin, the visual pigment in the
retina of the eye
● It aids vision in dim light
● It promotes healthy skin
● It promotes moist mucous membranes (e.g. the cornea, in digestive tract and
respiratory tract)
e) Vitamin C
● Vitamin C promotes wound healing
● It keeps gums and skin healthy and prevents bleeding gums
● It helps the immune system to prevent colds and flu
● It prevents teeth loss
● Vitamin A is needed in the formation of collagen which keeps epithelial cells
together
● It is needed in the production of healthy walls of blood vessels
● It helps with absorption of iron
f) Fibre
● Fibre absorbs water in the colon and retains water, making faeces soft
● It makes faeces bulky and makes it easier to expel (defecate) regularly
● Its bulk stimulates intestinal muscles and promotes peristalsis
● Its bulk provides something for muscles to grip onto and push faeces along the
length of the colon
● Fibre prevents constipation
● It removes toxins and prevents them from being absorbed into the blood
● It reduces the likelihood of colon cancer
g) Water
● All chemical reactions occur in water.
● Water is used as a solvent for many substances to be transported around the
body in blood plasma which is mostly water
● The evaporation of water from the body cools down the body
● Waste products like urea, uric acid and carbon dioxide are transported in blood
plasma to be excreted
Objective: describe the deficiency symptoms for: vitamins (A + C only) mineral
salts (calcium, iron and iodine only)
Deficiency symptoms for: vitamin A
● Deficiency of vitamin A results in an inability of the body to make rhodopsin which
causes reduced vision in dim light
● Deficiency of vitamin A : night blindness
● Deficiency of vitamin A also causes dry skin and dry and inflamed membranes in
the front of eyes (ulcerated cornea)
Deficiency symptoms for: vitamin C
● Deficiency disease: scurvy (gums become spongy and bleed)
● A deficiency causes spontaneous bruising as small vessels break
● It leads to slow wound healing
● It can cause the loss of teeth
● Fractures can occur, because a deficiency in vitamin C causes insufficient
connective tissue to form
Deficiency symptoms for: calcium
● Deficiency disease: rickets (bow legs, knock knees, bones set in bent shape) and
osteoporosis
Deficiency symptoms for: iron
● Deficiency disease: anaemia
Deficiency symptoms for: iodine
● Deficiency disease: goiter
Objective: discuss the use of microorganisms in the food industry, with reference
to yoghurt, bread and single cell protein
Use of microorganisms in yoghurt production
● Milk (from cows, sheep or goats) can be changed into by adding bacteria
(harmless to humans, e.g. Lactobacillus bulgaricus)
● These bacteria use lactose, the sugar in milk, as an energy source
● As a result, lactic acid is produced
● This acid lowers the pH which causes the milk to thicken (solidifies or coagulates
the milk) and form yoghurt
● Other by-products like ethanol give yoghurt a sharp taste
● Fruit pulp, colourings and flavourings are added to yoghurt
Use of microorganisms in bread making
● Yeast produces glucose (in dough) during respiration for energy
● This produces carbon dioxide (bubbles) and ethanol (alcohol)
● The carbon dioxide bubbles cause the sticky dough to rise
● During baking the bubbles expand
● These form air spaces in the bread making it porous and light
● Alcohol evaporates during baking
Use of microorganisms in production of single cell protein
● High protein foods are produced from bacteria and fungi
● Microorganisms can be produced or cultured in large quantities so that it can be
used as human or animal food
● They can be grown in fermenters, so a lot can be produced in a very small space
● They are non-pathogenic to humans and animals
● These microorganisms grow quickly, are cheap, can be eaten by vegetarians,
are high in proteins and low in fats
● People are reluctant to eat food bacteria
● This food is tasteless, but can be flavoured
● Microorganisms can be pressed into cookies
Objective: discuss the uses, benefits and health hazards associated with food
additives, including colouring
Definition: a food additive is anything which is added to a food product during
manufacturing to improve colour, flavour and texture, and to prevent food from going
bad.
Benefits of food additives
● Preservatives give food a long shelf life or storage time
● Flavourants improve taste or flavor
● Colouring improves colour and appearance
● They contain antioxidants, which stop food from combining with oxygen to cause
discolouring (apples turn brown) and spoil food
● They contain stabilisers, which stop food from (such as ice cream) from
separating into watery and fatty components
● Additives can improve the texture of food
Health hazards associated with food additives, including colouring
● Food additives can cause hyperactivity in children
● They can cause mood swings and tantrums
● They can cause cancer (they are carcinogenic)
● They can cause migraines and headache
● Some people can be allergic to certain additives
● Additives can aggravate the symptoms of asthma
● They can cause skin rash (dermatitis)
Definition: a balanced diet is the sufficient intake of nutrients to meet the body’s
energy, growth and repair requirements.
Objective: Describe a balanced diet related to age, sex and activity of individual
Age:
− growing children need plenty of proteins for making new cells during growth,
repair and hormone production.
− Teenage need more energy than babies because they are larger and more active
− Older persons require less proteins and energy
− Children need extra calcium for growing bones and vitamin D to help calcification
of their bones
− Children need extra iron for formation of red blood cells
Sex
– Males use more energy than females of the same age, even if they are doing the
same work. This is because male have more muscle mass and are generally
larger
Activities
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When doing sport, more protein for building muscles and more carbohydrates for
energy.
A person doing heavy or physical requires more energy than a person doing light
work
Objective: Describe the role of a balanced diet for HIV positive and AIDS persons
● High proteins food that stimulates weight gain by building up the muscles. Foods
like meat, chicken, fish, yoghurt, beans, nuts, and dairy products
● Vitamins are needed to help the immune system fight infectious diseases. Food
like fruits and vegetables such as orange, carrots, pumpkin and spinach
● Carbohydrates are also necessary to provide energy. Food like cereals such as
rice, millet, macaroni and brown bread.
Objective:Describe the effects of malnutrition in relation to starvation, coronary
heart disease, constipation and obesity
Malnutrition: is caused by not eating a balanced diet, even though the quantity of food
is adequate.
Starvation: is caused by not getting enough food for sufficient growth and energy.
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Kwashiorkor: caused by lack of protein
Marasmus: is caused by not eating food with enough proteins and carbohydrates
Scurvy: lack of vitamin C
Rickets: lack of calcium, phosphorus, vitamin D and lack of exposure to ultraviolet light
Night blindness: lack of vitamin A
Goitre: lack of iodine
Constipation and colon (bowel) cancer: not consuming sufficient amounts of
dietary fibre
Obesity: consuming too much carbohydrate, fat and protein.
Obesity plus too much cholesterol and salts can lead to coronary heart diseases
Objective:Discuss the problems that contribute to famine (unequal distribution of
food, drought and flooding, increasing population)
● Unequal distribution of food: although sufficient food is available to all, some
areas do not receive their share. Too many people results in food resources
decrease
● Increasing population: farms and factories are unable to supply sufficient
amounts of food for everyone. More people move to cities and no one to cultivate
in the village and this increase the prize of food.
● Drought and flooding cause crop failures. Lack of rain result in lack of food. And
too much water destroy crops
Topic: Human alimentary canal
Objective: Identify the gross structure of the alimentary canal and associated
organs (mouth, oesophagus, stomach, small intestine(duodenum and ileum),
large intestine (colon and rectum), anus, pancreas, liver)
The alimentary canal (or gut) is the tube within the body through which food passes
and is processed in various ways
Objective: Define ingestion, digestion, absorption, assimilation and egestion
● Ingestion: intake of food through the alimental canal
● Digestion: the breakdown of large, complex, insoluble molecules to form small,
simple, soluble molecules by the actions of enzymes
● Absorption: the uptake of small molecules, following digestion, through the walls
of the alimentary canal and into the blood vessels which carry them around the
body
● Assimilation: the transfer of these molecules from the blood vessels into the
body cells and their use by the cells
● Egestion: the removal of undigested waste products from the alimentary canal
as faeces from the anus
Objective: Describe the functions of the alimentary canal’s various parts in
relation to ingestion, digestion, absorption, assimilation and egestion of food
In the mouth
Salivary gland
Starch
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maltose then into glucose
Broken down into glucose later by other amylases
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Teeth assist the mechanical breakdown of food
Saliva is mixed with food during chewing
Saliva contains the enzyme amylase, which starts the digestion of food
Saliva contains mucus that keeps the mouth moist and lubricates food for
easier swallowing
In the stomach
Pepsin
Proteinamino acid
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Broken down into amino acids later by other proteases
In the pancreas
Pancreatic lipase
Fat
fatty acids and glycerol
Small intestine
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Small, soluble food molecules are absorbed through the wall of the small
intestine
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To absorb food molecules efficiently the small intestine has three main
adaptations…….
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The small intestine is very long 6m long
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The inner surface on the intestine is folded covered with many finger-like
projections called villi -greatly increase the surface area in contact with digested
food
Thin wall of villi
Thin wall each villus has an extremely
-only one cell thick
-rapid absorption
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Each villus is supplied with blood vessels to receive the absorbed foods
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glucose/amino acids/vitamins/minerals are absorbed into blood capillaries
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products of fat digestion absorbed into lacteal
Topic: Digestion
Define digestion as the process where large insoluble molecules can be broken
down into smaller more soluble forms for easy absorption
Objective:Identify the types of human teeth and describe their functions
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There are 4 different types of tooth
-incisors
-canines
-premolars
-molars
These different teeth have different jobs!
Incisors
These are cutting teeth used for cutting and biting off pieces of food
Canines
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These are long and sharp teeth that are used to hold and tear at food
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Premolars
These teeth are used to crush and grind soft food
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Molars
These teeth are used for chewing and grinding hard food
Objective: State the causes of dental decay and describe the proper care of teeth
Causes of dental decay
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A combination of bacteria and food cause tooth decay.
– A clear, sticky substance called plaque that contains bacteria is always forming
on your teeth and gums
– Bacteria in the mouth digest food (such as sugar) which remains between the
teeth
– As the bacteria feed on the sugar in the food you eat, they form acids that attack
the teeth for 20 minutes or longer after eating
– Over time, these acids dissolve the enamel and dentine, causing cavities (holes)
– When cavities reach the pulp it causes toothache.
The proper care of teeth
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Brush and clean with dental floss after every meal
Not eat sticky and sugary food
Not drinking fruit juices between meals
Using a fluoride toothpaste/mouthwash
Visiting the dentist regularly
Use anti-bacterial mouthwash
Eat food containing calcium, phosphorus, vitamin D and vitamin C
Rinse mouth with water after eating
Don’t open bottles with teeth
Eat apples or crisp foods
Brush or massage your gums
Fluoride can be added to drinking water
Objective: Explain the probable action of fluoride in reducing tooth decay and
present arguments for and against its use
● Fluoride inclusive in water reduces the percentage of tooth decay
● Fluoride can produce dark coloration on the teeth and many thinks it is an natural
to add it to drinking water
FOR:
● Fluoride can be added to drinking water (fluoridation) and can prevent toothe
decay between 30 and 70%
● It is a safe, simple, effective way to improve dental health
● Preventing tooth decay can save your family the pain and discomfort of
toothache, and also saves the expense required to treat dental disease
AGAINST:
● Too much fluoridation can cause discolouration or mottling of teeth (white
patches - flourosis)
● Where fluoride has been added to water, it often affects large numbers of people
without their consent
Objection: Describe the process of chewing (mechanical digestion)
● Chewing of food occurs in the mouth
● Chewing makes swallowing easier, to increase the surface area for enzyme
activity and to mix the food with saliva
● Chewing is mechanical digestion
● Salivary glands produce saliva with water and mucus to soften, moisten and
lubricate dry food and the oesophagus
● Food remains in the mouth cavity for a few seconds and little digestion occurs
here
● Chewed food is rolled into a ball called a bolus by the tongue and the tongue
pushes it into the pharynx.
Objective: Describe the process of peristalsis
● Peristalsis comprises of the rhythmical contractions which take place in the
alimentary canal to push the food downward
● The circular muscles behind the food bolus contract, while the longitudinal
muscles relax
● Then the circular muscles ahead of the bolus relax while the longitudinal muscles
contract
● It is called the antagonistic muscle action
● This action forces or squeezes the food bolus through the alimentary canal
Objective:Describe digestion in the alimentary canal
In the mouth
● Food is crushed and ground up by teeth
● The salivary glands make saliva which makes the food moist and easy for
swallowing
● Amylase enzyme (in saliva) breaks the carbohydrate starch down into glucose.
Stomach
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Stomach muscles contract and relax to mechanically break down the food
They also mix the food up with gastric juice and hydrochloric acid
The acid kills germs in the food
The gastric juice contains the protease enzyme PEPSIN to digest protein into
amino acids
● Food spends about 3-4 hours in here.
Duodenum
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The first part of the small intestine is called the duodenum.
Food, still mixed with gastric juice is squirted into it from the stomach.
The food is now a semi liquid, highly acidic mush.
It needs to be neutralized and digestion needs to be continued…
Small intestine
● The small intestine has 3 enzymes to complete digestion:
● Amylase breaks starch down into glucose.
● Protease breaks protein down into amino acids and Lipase breaks fats down
into fatty acids and glycerol
Absorption
● The food is then ABSORBED through the wall of the small intestine into the
blood stream.
● To do this effectively, the small intestine needs to have a large surface area.
● This is achieved in the following ways:
● The inner wall of the tube has bends in it
● The wall is covered in villi (small finger-like structures)
After absorption
● Once the products of digestion have been absorbed, they travel in the blood to
the LIVER.
● The liver has many functions. Read about them on page 131 in your text book
● Answer questions 4 – 7 in full sentences.
Egestion
● Any indigestible food (e.g. fibre) passes into the large intestine (colon).
● Water is absorbed back into the body.
● Where has this water come from?
● The food becomes solid waste-called faeces.
Faeces are stored in the rectum and removed through the anus. This removal is called
EGESTION
Objective: Describe the functions of a typical amylase, protease and lipase,
listing the substrate and end-product
Substrate
Enzyme
Product
pH mouth 7-8
Stomach pH 2
Small intestine 7-8
Starch
Amylase
Maltose
Maltose
Maltase
Glucose
Protein
Pepsin
Peptides
Peptides
Protease
Amino acids
Fats
Lipase
Fatty Acids and Glycerol
Objective: Describe the action of amylase in the mouth
● Saliva contains the enzyme amylase
● Amylase hydrolyses insoluble starch into soluble maltose
● The digestion (hydrolysis) of starch to maltose is the first stage of starch
digestion
Objective: Describe the secretion of gastric juice containing hydrochloric acid
and a protease, and explain its role in digestion
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Gastric juice contains hydrochloric acid (HCI) to create acid conditions (pH 2-3)
Gastric juice contains an inactive enzyme, pepsinogen
Hydrochloric acid activates pepsinogen into its active form, pepsin
Pepsin begins protein digestion by the hydrolysis of protein into polypeptides
Pepsin requires acidic conditions
Objective: Describe the role of pancreatic juice (secreted by the pancreas) and
bile (secreted by the liver) in the duodenum
● Cells in Pancreatic juice secretes pancreatic juice, which contains amylase,
lipase and protease ( all these enzymes need alkaline pH
● The pancreatic juice contains also sodium hydrogencarbonate, which neutralizes
the acids pH in the food from the stomach
● Bile-is not an enzyme, but it help to breakdown (emulsification) fats into smaller
fat droplets to increase its surface area so that lipase enzymes can easily act on
them.
● Bile is produced by the liver and stored in the gall bladder
● Two functions of bile are: to help with the absorption of lipids and to emulsify fat
TOPIC: ABSORPTION AND ASSIMILATION
Objective: Identify the small intestine as the region for the absorption of digested
food
● The alimentary canal (or gut) is a long tube inside the body
● Any food in the alimentary canal is still outside the cells of the body
● To get inside the molecules of the food have to be able to pass through the wall
of the alimentary canal
● Small, soluble food molecules are absorbed through the wall of the small
intestine
Objective: Describe the significance of villi in increasing the internal surface area
● The inner surface on the intestine is folded covered with many finger-like
projections called villi
● greatly increase the surface area in contact with digested food
Objective: Describe the structure of a villus, including the role of capillaries and
lacteals
● Finger-like folds in the surface of the small intestine’
● Each villus has an extremely thin wall, only one cell thick for rapid absorption
• Each villus is supplied with blood vessels to receive the absorbed foods,
glucose/amino acids/vitamins/minerals are absorbed into blood capillaries
• products of fat digestion absorbed into lacteal
Objective: Indicate the role of the hepatic portal vein in the transport of absorbed
food to the liver
● Hepaticportalvein: carries glucose and amino acid to the liver from the small
intestine
● All nutrients which are taken up by the stomach and the capillariesof the villi are
first taken by the hepatic portal vein to the liver
Objective: Describe the role of the liver in the metabolism of excess glucose and
in the breakdown of excess amino acids
● Absorbed nutrients has to go to the liver first
● Glucose metabolism: liver convert surplus glucose to glycogen, and when
blood glucose level drops, the liver convert glycogen back to glucose
● Amino acid metabolism: body cannot store amino acids as amino. Excess
amino acids not assimilated by the cells are broken down by the liver cells into
urea, this is called deamination.
● Some amino acids molecules is changed by liver cells into fats or carbohydrates
molecules that can be used to released energy
Objective: Describe the role of fats as a storage substance
● There are no limits to the amount of fats stored and because of its high-energy
value; it is an effective ‘long –term store.
● The fat is stored in adipose tissue in the abdomen, round the kidneys and under
the skin.
● These are fat depots
● Fats provide insulation for the body
● Fats are metabolized to release greater amounts of energy
● They are also important for storing certain vitamins like vitamins A, D, E and K
which are soluble in fats and not in water
● They help protect vital organs such as the heart, kidneys and liver
TOPIC: TRANSPORTATION: TRANSPORT IN PLANTS
Objective: Identify and describe the structure of a dicotyledonous root and stem
as seen under a light microscope (epidermis with root hairs, cortex, phloem,
xylem vessels)
Xylem vessel
● Hollow dead tubes
● Water and minerals transported in an upwards direction
● Made of lignin
● Very strong so help support the plant
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Phloem tube
Transports sugar around plant
Made of living cells
Companion cells provide the energy for the tube cells.
The end walls of the tube cells have pores through which food is transported
from cell to cell in the form of dissolved sugars
Cortex
● This is the tissue between the vascular bundles and the epidermis
● It store starch,
● In green plants, the outer cortex contains chlorophyll and make food by
photosynthesis
Root hairs
Objective: Describe the uptake of water by osmosis
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Water enters the root hairs of the epidermis of roots by osmosis
Water moves from a high water potential to a low water potential
The root hairs provide a large surface area for osmosis.
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POINTS TO REMEMBER
THE SOIL WATER IS THE DILUTE SOLUTION
THE CELL SAP HAS CONCENTRATION SOLUTION BECAUSE OF HIGH
CONCENTRATION OF SALTS.
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THE CELL MEMBRANE AND TONOPLAST IS SEMI-PERMEABLE MEMBRANE
OSMOSIS: MOVEMENT OF WATER MOLECULES FROM HIGH
WATER
POTENTIAL TO THROUGH SEMI PERMEABLE MEMBRANE.
Objective:Describe the pathway by which water enters a plant, crosses the root,
moves up through xylem vessels, enters leaf cells, and leaves the plant through
stomata
Objective:Describe the mechanism of water uptake and movement in terms of
‘pull’ from above, creating a water potential gradient through the plant
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Forces responsible for the upward movement of water
Transpiration pull
Root pressure
Capillarity
Transpiration Pull:
Water evaporates from leaves
Creates diffusion pressure gradient between outside air and xylem
Tension exists in the water column extending from the roots to the leaves
Adhesive and cohesive forces keep the column continuous
Thus water is continually being pulled upward as water evaporates from the
leaves
Upward pull = transpiration pull
Root pressure
Cell sap of root hair always has low water potential when compared to soil water
Water enters root hair by osmosis
Continuous osmosis causes pressure forcing water a short distance up the stem
Capillarity
Spontaneous movement of water up narrow tubes because of adhesion and
cohesion is called capillarity
Lumen of xylem vessels and tracheids are very narrow therefore capillarity takes
place
Upward distance is very short
Objective: Define transpiration as the loss of water vapour from a plant (mostly
from the leaves)
Objective: Describe how the loss of water vapour is related to cell surfaces, air
spaces and stomata
● Water moves out of the leaves through the stomata
● Most leaves has more stomata on the lower surface than on the upper surface
Objective: Describe the effects of variation of temperature, humidity and light
intensity on transpiration rate
● Humidity:High humidity decreases transpiration rate
– Low humidity increases the rate of transpiration, because there is less water
vapour outside the leaf and more water vapour inside the leaf
– This creates a water potential gradient between the moist air in the leaf and the
dry air outside the leaf
– When the external air has a high humidity the gradient is reduced and less water
is transpired.
● Temperature:Increases evaporation and thus transpiration
– An increase in temperature causes an increase in transpiration
– Higher temperature causes an increase in kinetic energy of water molecules and
so increases the rate of transpiration
– Water molecules move faster when heated
– Air with a high temperature can hold more water molecules
– High temperatures increase the relative humidity of air
– A fall in temperature has the reverse effect, that is, a decrease in transpiration
● Light intensity:generally causes an increase in the rate of transpiration
– Stomata open in light and close in the dark
– An increase in light intensity increases the transpiration rate and vise versa.
Objective: Describe the methods by which xerophytic plants can reduce
transpiration rate, with reference to two named examples (e.g. Aloe, Euphorbia,
Quiver tree)
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Plant adaptations to habitats
Plants in different habitats possess different adaptations:
Mesophytes:plants adapted to a habitat with adequate water
Xerophytes:plants adapted to a dry habitat and can withstand periods where
water is unavailable, e.g. Aloe, Euphorbia,Quiver tree
– Halophytes:plants adapted to a salty habitat
– Hydrophytes: plants adapted to a freshwater habitat
Xerophytes
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Stomata sunken in pits creates local humidity/decreases exposure to air currents;
Presence of hairs creates local humidity next to leaf/decreases exposure to air
currents by reducing flow around stomata;
• Thick waxy cuticle makes more waterproof impermeable to water;
• Stomata on inside of rolled leaf creates local humidity/decreases exposure to air
currents because water vapour evaporates into air space rather than atmosphere
e.g. British Marram grass
• Fewer stomata decreases transpiration as this is where water is lost
Objective:Describe how willing occur
● Wilting: Loss of turgidity of the cells results in leaves and sometimes the stems,
becoming limp, causing them to droop.
● Then the plant is called wilting.
● Guttation: Loss of liquid water through tiny pores, called hydathodes on margin of
leaf.
● Wilting occurs when the turgor pressure in non-lignified plant cells falls towards
zero
● The cells lose their turgidity and become flaccid
● If the soil around the roots lacks water, the cells in the plant will contain less
water and fail to support the plant and the leaves and stems become soft
Objective: Discuss the adaptations of the leaf, stem and root to different
environments, with emphasis on local examples
Xerophyte adaptations summary:
Adaptation
Example
How it works
thick cuticle
stops uncontrolled evaporation
through leaf cells
small leaf surface
area
less surface area for
evaporation
low stomata density
smaller surface area for
diffusion
sunken stomata
maintains humid air around
stomata
marram grass, cacti
stomatal hairs
(trichores)
maintains humid air around
stomata
marram grass, couch
grass
rolled leaves
maintains humid air around
stomata
marram grass,
extensive roots
maximise water uptake
cacti
conifer needles, cactus
spines
Objective: Define translocation in living phloem sieve tubes as the movement of
sucrose and amino acids from regions of production or of storage to regions of
utilization in respiration or growth
Objective: Describe the translocation of applied systemic pesticides in phloem
throughout the plant
● Pesticides are used to kill insects and pests that can damage plant crops.
Systematic pesticides are carried in the plant’s phloem
● Systemic pesticides are sprayed onto plants
● Pesticides are absorbed into the leaves or stems of the plant
● The pesticides will be translocated in the phloem sieve tubes
● The pesticides move into the phloem sieve tubes by active transport
● Aphids and other sucking plant pests suck plant sap with amino acids and
sucrose from the phloem sieve tubes
● The pests remove poisonous sap from the phloem sieve tubes and die
TOPICTRANSPORT IN HUMANS:
SUB-TOPIC: HEART
Objective: Describe the heart in terms of its gross
structure and its function
● The heart is a muscle that pumps blood around the
body
● The pulmonary veins pump oxygenated blood from
the lungs to the left atrium
● The left atrium receives oxygenated blood from the pulmonary veins and pumps
it through the bicuspid valve into the left ventricle which pumps it through the
semi-lunar valve into the aorta
● The semi-lunar valve prevents the backflow of blood from the aorta to the left
ventricle
● The aorta carries oxygenated blood from the left ventricle to the body
● The inferior vena cava carries deoxygenated blood from the lower parts of the
body to the right atrium while the superior vena cava carries deoxygenated blood
from the upper parts of the body to the right atrium
● The right atrium receives deoxygenated blood from the vena cavae and pumps it
through the tricuspid valve into the right ventricle
● The right ventricle receives deoxygenated blood from the right atrium and pumps
it through the semi-lunar valve into the pulmonary artery
● The pulmonary arterypumps deoxygenated blood from the body back to the
lungs where it will be oxygenated
● The semi-lunar valve prevents backflow of blood from the pulmonary artery to the
right ventricle
● The blood is carried by the pulmonary veins from the lungs to the left atrium
● The right side of my heart pumps blood to my lungs
● The left side of my heart pumps blood to the rest of my body
● The heart contains four valves to stop the backflow of blood
Veins of the heart
● Vena cava
● Pulmonary vein
● Coronary vein
Arteries of the heart
● Aorta
● Pulmonary artery
● Coronary arteries
Atria (or auricles) of the heart
o Right atrium
o Left atrium
Ventricles of the heart
• Right ventricle
• Left ventricle
Valves of the heart
● Bicuspid valves
● Tricuspid valve
● Semi-lunar valves
Four chambers of the heart
● Right atrium
● Left atrium
● Right ventricle
● Left ventricle
Objective: Describe the effect of exercise on heart beat
● Heart Rate can be determined using a Stethoscope
● During excise, the heartbeat increase due to the high demand of oxygen.
● This means that faster respiration occurs in the muscle cells
● The faster respiration means that more energy is released for the muscle cells
during exercises
● The faster heartbeat means that more carbon dioxide is pumped to the lungs for
faster excretion.
Objective: List the likely causes of a heart attack (diet, smoking and stress), and
preventive measures
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A genetic predisposition (disease resulting from factors inherited from parents)
A high cholesterol diet
Overweight/obesity
Stress (tension, anxiety, fear)
Smoking cigarettes and second – hand smoke
Not exercising regularly
Atherosclerosis in the coronary arteries
− A build – up of fatty deposits occurs on the lining of the coronary arteries
− It causes narrowing of arteries and reduces or obstructs blood flow to the
heart muscles
− This build – up causes a blockage in the coronary arteries
− This results in less or no blood flow through the arteries
− The heart muscle does not receive sufficient amounts of oxygen and glucose
− Anaerobic respiration occurs and there is not enough energy available
− Less or no removal of lactic acid and carbon dioxide occurs
− The cardiac muscle contracts less powerfully or stops contracting
− The result is pain in chest or a heart attack (cardiac arrest)
Preventive measures of a heart attack
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Follow a low cholesterol diet
Avoid being overweight (obese)
Reduce stress levels
Do not smoke
Exercise regularly
Reduce salt intake
Avoid excessive sugar intake
Reduce alcohol intake
SUB – TOPIC: BLOOD VESSELS
Objective:Describe the structure and functions of arteries, veins and capillaries
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A blood vessel is a tube with a space in the centre, called the lumen
Mammals have three types of blood vessels.
Arteries carry blood away from the heart
Veins carry blood towards the heart
Linking the two, forming networks of tiny tubes in the tissues are capillaries.
Arterioles are small arteries. As an artery gets closer to the tissue to which it is
delivering blood it divides to form many smaller vessels, which are similar to
arteries (less elastic as blood flow has become smoother)
Venules are small veins which collect blood after it has flowed through a
capillary bed.
So blood leaves the heart through arteries, which in turn give way to arterioles
and then capillaries where the oxygen is delivered and exchanged for carbon
dioxide. The capillaries then become larger venules and then veins which then
deliver the blood back to the heart.
Blood pumped out of the heart is at a very high pressure, so the structure of the
arteries must be adapted to this.
They can withstand high pressure by having very thick walls made up of elastic
fibres and smooth muscle.
The elastic fibres increase its elastic strength.
The smooth muscle can change the diameter of the lumen, especially in the
smaller arteries.
Lumen is relatively narrow.
The tunica media layer is thicker in arteries than in veins
tunica intima In arteries this layer is composed of an elastic membrane lining
and smooth endothelium that is covered by elastic tissues.
Veins carry blood from every tissue in the body to the heart.
As the pressure is so much lower in the veins than in the arteries, there is little
need for the elastic fibres and smooth muscle in the walls.
● they have a larger lumen that arteries, to reduce the resistance to flow
● They also have semi-lunar valves to stop the blood flowing backwards
● Capillaries are where the transported substances actually enter and leave the
blood
● No exchange of materials takes place in the arteries and veins, whose walls are
too thick and impermeable.
● Capillaries are very narrow and thin-walled, but there are a vast number of them
(108 m in one adult!),
● so they have a huge surface area : volume ratio, helping rapid diffusion of
substances between blood and cells.
● Capillaries are arranged in networks called capillary beds feeding a group of
cells, and no cell in the body is more than 2 cells away from a capillary.
● A capillary wall is very thin and composed of (endothelium only) single layer of
cells as it does not have to withstand high internal pressure.
● A capillary wall is often highly permeable, partly because it is very thin and partly
because of holes in and between cells in some capillaries (particularly those with
high demand of exchange e.g. endocrine glands)
● Capillary diameter is very small.
● A typical small artery or vein may be 5mm (in diameter in a human)
● But capillaries are approximately 10 micrometer about the size of a red blood cell
(erythrocyte)
Objective: Describe the double circulatory system ( names of the following blood
vessels are required; aorta, pulmonary arteries and veins, vena cava, renal artery
and vein, hepatic artery and vein and hepatic portal vein)
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Aorta: carries blood away from the heart to the body
Pulmonaryartery: carries blood from heart to the lungs
Pulmonaryvein: carries blood into the heart from the lungs
Venacava: brings blood to the heart
Renalartery: bring blood to the kidney
Renalvein: carries blood away from the kidney
Hepaticartery: brings blood to the liver
Hepaticvein: carries blood away from the liver
Hepaticportalvein: carries blood containing absorbed products of digestion from
the intestine directly to the liver
The human circulatory system
This diagram is drawn as though you were looking at a person who is facing you.
● The pump, the heart, pushes a fluid, blood, along tubes called vessels.
● As the blood passes twice through the heart on this single complete journey
around the system, it is called a doublecirculatorysystem.
● By returning to the heart after picking up oxygen in the lungs there is enough
pressure to ensure that every cell in the body gets enough oxygen.
SUB – TOPIC: BLOOD
Objective: Identify and describe blood cells, as seen under a light microscope
Red blood cells
● a biconcave disc that is round and flat withoutanucleus
● Can change shape to an amazing extent, without breaking, as it squeezes
single file through the capillaries.
● Contain haemoglobin, a molecule specially designed to hold oxygen and carry it
to cells that need it.
White blood cells
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There are many different types and all contain a big nucleus.
the two main ones are the lymphocytes and the macrophages/PHAGOCYTES
Macrophages ‘eat’ and digest micro-organisms.
Some lymphocytes fight disease by making antibodies to destroy invaders by
dissolving them.
● Other lymphocytes make antitoxins to break down poisons.
Platelets
● Platelets are bits of cell broken of larger cells
● Tiny fibrinogenfibres to form a net.
● This net traps other blood cells to form a blood clot
Plasma
A straw-coloured liquid that carries the cells and the platelets that help blood clot.
Composition of blood plasma:
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carbon dioxide
glucose
amino acids
proteins
minerals
vitamins
hormones
waste materials like urea
Objective: Describe blood in terms of its components and its functions
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Functions of the blood
Oxygen is carried in the red cells
Carbon dioxide is carried in the plasma
digested foods are carried in the plasma
Urea (waste substance)is carried in the plasma from the liver to the kidneys
Hormones are carried in the plasma
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Heat is carried in the blood
Objective: Describe the process of clotting (fibrinogen to fibrin only)
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Platelets collect at the site where damage to the blood vessels occurred
Platelets release enzyme that set up a chain of chemical reactions in the blood
These reaction change fibrinogen, a soluble plasma protein, into a network of
insoluble fibrin threads
Objective: Describe the transfer of nutrients between capillaries and tissue fluid
● Capillaries are where the transported substances actually enter and leave the
blood
● No exchange of materials takes place in the arteries and veins, whose walls are
too thick and impermeable.
● Capillaries are very narrow and thin-walled, but there are a vast number of them
(108 m in one adult!),
● So they have a huge surface area : volume ratio, helping rapid diffusion of
substances between blood and cells.
● Capillaries are arranged in networks called capillary beds feeding a group of
cells, and no cell in the body is more than 2 cells away from a capillary.
SUB – TOPIC: DEFENCE AGAINST DISEASES
Objective: Describe the immune system in terms of antibody production, tissue
rejection and phagocytosis
● Immunity: The ability of the body to fight infection and/or foreign invaders by
producing antibodies or killing infected cells.
● Immune System: The system in the body responsible for maintaining
homeostasis by recognizing harmful from non-harmful organisms and produces
an appropriate response.
How antibody operates
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Antibodies
Y-shaped protein molecule.
Made up of variable and constant regions.
Made up of Heavy and Light chains.
Produced by B-Lymphocytes
Function: Recognize antigens, bind to and deactivate them.
o Note: Variable region recognizes the antigens
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Step 1
Pathogens eaten by Macrophage
Step 2
Displays portion of Pathogen
on surface
Step 3
Pathogens
Helper-T cell recognizes
Pathogen
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Tissue rejection
Transplanted organs are recognized as foreign by lymphocytes
The body try to reject the transplant
Overcame transplant rejection, receipt receive immunosuppressant drugs to kill
their own lymphocytes
The body cannot produce antibodies and cannot reject the new organ
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Phagocytes
Produced throughout life by the bone marrow.
Scavengers – remove dead cells and microorganisms.
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If cells are under attack, they release histamine.
Histamine plus chemicals from pathogens means neutrophils is attracted to the
site of attack.
• Pathogens are attached to antibodies and neutrophils have antibody receptors.
• Endocytosis of neutrophil membrane → phagocytic vacuole.
Lysosomes attach to phagocytic vacuole → pathogen digested by proteases
Objective: Distinguish between natural and artificial immunity
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Active immunity
Lymphocytes are activated by antigens on the surface of pathogens
Natural active immunity - acquired due to infection
Artificial active immunity – vaccination
Takes time for enough B and T cells to be produced to mount an effective
response.
Passive immunity
B and T cells are not activated and plasma cells have not produced antibodies.
The antigen doesn’t have to be encountered for the body to make the antibodies.
Antibodies appear immediately in blood but protection is only temporary.
Artificial passive immunity
Used when a very rapid immune response is needed e.g. after infection with
tetanus.
Human antibodies are injected. In the case of tetanus, these are antitoxin
antibodies.
Antibodies come from blood donors who have recently had the tetanus
vaccination.
Only provides short-term protection as abs destroyed by phagocytes in spleen
and liver.
● Natural passive immunity
● A mother’s antibodies pass across the placenta to the foetus and remain for
several months, so immunity is temporary
● Memory cells do not cross the placenta, so immunity is temporary.
Objective:Describe the function of the lymphatic system in the circulation of body
fluids and the production of lymphocytes
● The lymphatic system circulates and returns tissue fluid around the body and
back to the circulatory system
● This prevents oedema
● Lymph nodes are the major site of lymphocyte production
● The lymphatic system also transports fats, fatty acids and glycerol from the
lacteals to the circulation
TOPIC: RESPIRATION
Define respiration as the release of energy from food substance in all living cells
SUB – TOPIC: AEROBIC RESPIRATION
Define aerobic respiration as the release of a relatively large amount of energy
from the breakdown of glucose, in the presence of oxygen
Objective: State the balanced equation for aerobic respiration (using words and
symbols)
Glucose + Oxygen → Carbon Dioxide + Water+ Energy
C6H12O6 + 6CO2 = 6CO2 + 6H2O + 38ATP
Objective:Name and describe the uses of energy in the body of humans
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Energy is muscle contraction
It is also needed for nerve impulse transmission
Production and release of neurotransmitter substances use energy
Energy is needed for the heart to beat to be able to circulate blood
Energy is used for the synthesis of new materials for growth, e.g. protein
synthesis
It is needed for the regulation of body temperature
Removal of waste substances uses energy
It is used to obtain and digest food
It is also used for the absorption of digested food by active transport
Energy propels sperm cells forward
Define anaerobic respiration as the release of a relatively small amount of energy,
by the breakdown of glucose in the absence of oxygen
Objective: State the balanced equation for anaerobic respiration using words and
symbols in muscles (glucose=lactic acid and C 6H12O6=2C3H6O3) and yeast
(glucose =alcohol +carbon dioxide and C6H12O6=2C2H50H+2C02)
In muscles: glucose = lactic acid + energy
C6H12O6 = 2C3H6O3+ 2ATP
In yeast: glucose = alcohol + carbon dioxide + energy
C6H12O6 = 2C2H50H + 2C02 + 2ATP
Objective: Describe the role of anaerobic respiration in brewing and breadmaking
● Yeast, a single cell fungus, respire anaerobically, It releases energy from glucose
● In wine making, yeast break down the sugars from grapes and change them into
alcohol
● In breads making, the carbon dioxide produced by yeast causes the dough to
rise, while the alcohol produced evaporates during baking
Objective: Describe the production of lactic acid in muscles during exercise
● A build - up of lactic acid (which is poisonous) produces musclefatigue.
● Muscle fatigue makes muscles ache and contract less powerfully.
● A recovery period is needed. During this time, more oxygen is taken in to
convert the lactic acid back into pyruvic acid again.
● The volume of oxygen needed is called the oxygendebt.
Objective: Compare aerobic respiration and anaerobic respiration in terms of
relative amounts of energy released
● Aerobic respiration, a lot of energy is released whereas anaerobic less energy is
released
SUB – TOPIC: RESPIRATORY SYSTEM IN HUMANS
Objective:Distinguish between breathing and gaseous exchange
● Breathing is a mechanism of inhalation and exhalation whereby air moves in and
out of the lungs
● Gaseous exchange is the diffusion of oxygen from blood into the cells, and the
diffusion of carbon dioxide from the cells into the blood
Objective: State the differences in composition between inspired and expired air
Oxygen%
Carbon dioxide %
Nitrogen %
Temperature
Moisture
Inspiredair
21
0.04
79
Variable
Variable
Expiredair
16
4
79
28-34˚C
Very moist
Objective: Describe the gross structure of organs associated with gaseous
exchange: trachea, lungs, bronchi, bronchioles, alveoli, diaphragm and
intercostal musclesand the diaphragm in the ventilation of the lung
Trachea with cartilage ring
Bronchi (bronchus)
Bronchioles
Alveoli (alveolus)
Diaphragm
● The thorax is an air-tight chamber formed by ribcage and the intercostal muscles,
with the dome shaped diaphragm muscle forming the floor
● The diaphragm muscle is attached to the body wall at the base of the ribcage,
separating the thorax from the abdomen
● Air enters through the nasal cavity and the mouth
● From there the air passes through the pharynx at the back of the mouth
● The pharynx leads to the trachea (windpipe) and air passes through the larynx
● The trachea is supported by incomplete rings of cartilage (C-shaped cartilage
rings) to prevent it from collapsing under pressure
● Above the larynx is a flap, the epiglottis, which prevents food from going into the
trachea
● The trachea runs down towards the lungs and divides into two bronchi, one
bronchus going to each lung
● Each lung is covered by two thin membranes called pleural membranes, which
secretes and maintains a fluid called the pleural fluid
● The pleural fluid fills the space between the two membranes, and protects the
lungs from friction during breathing movement
● Within the lungs, each bronchus divides into smaller bronchioles
● The bronchi and larger bronchiole are also supported by small O-shaped
cartilage rings to prevent them from collapsing
● The bulk of the lung tissue consists of tiny air sacs called alveoli
● The alveoli are arranged into clusters served by a bronchiole
● Each cluster of alveoli is wrapped in a vast capillary system
Objective: discuss the role of the ribs, the internal and external intercostal
muscles and the diaphragm in the ventilation of the lungs
● The muscles involved in the breathing are the diaphragm, intercostal and
abdominal
● In inhalation, the diaphragm contracts and becomes less dome-shaped
(flattened while moving downwards)
● Abdominal muscles relax
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External intercostal muscles contract
Ribs and sternum move upwards and outwards
Thoracic cavity increases in volume
Internal pressure decreases
Elastic lungs expand
Oxygen-laden air flows into the lungs-lungs inflate
In exhalation, diaphragm relaxes and becomes more dome-shaped while
moving upwards
Abdominal muscles contract forcing abdominal contents against diaphragm
Internal intercostal muscles contract
Ribs and sternum move downwards and inwards to a resting position
Thoracic cavity decreases in volume
Internal pressure increases
Elastic lungs are compressed
Air filled with carbon dioxide is forced out of the lungs – lungs deflate
Objective: List the feature of gaseous exchange surfaces
● provide large surface area for gas exchange
● surface must be thin for efficient exchange of gases by diffusion
● Elastin in alveoli walls causes the walls to be elastic – this allows alveoli to
expand and increase in volume and to recoil during breathing. Elasticity also
prevents bursting of alveoli
● A gaseous exchange surface must have an efficient transport system for oxygen
and carbon dioxide – all alveoli are surround by a network of capillaries
● The gaseous exchange surface must always moist
● There must always be a concentration gradient between air in the alveoli and the
blood
Objective: Describe a test for carbon dioxide (with limewater)
● When CO2 is bubbled through clear lime water, the lime water turns milky.
● This change from clear to milky indicates the presence of CO 2
Objective: Describe the effects of physical activity on rate and depth of breathing
● When, excising, the demand for energy increase
● The rate of breathing increase to supply extra energy
● Oxygen can be increase in the body by increase the breathing rate and the depth
of breathing (lung volume)
Objective: Describe the effects of tobacco smoke and its major toxic components
on the respiratory system (e.g. nicotine, tar and carbon monoxide)
● Smoking causes serious damage to the respiratory system
● Tobacco contains tar, nicotine and carbon monoxide
Tar
● Tar is absorbed by some cells in the lungs, especially the ones lining the bronchi
and bronchioles
● Tar contains cancer causing chemical known as carcinogens which makes the
cells divide, and build up into a thicker layer
Nicotine
● Nicotine affects the brains, it stimulate and make you feel more alert and active
● It makes heart rate and blood pressure increase and very addictive
● It increases the stickiness of platelets and this increases the risk of blood clots
(thrombosis)
Carbon monoxide
● Carbon monoxide Combines with haemoglobin inside the red blood cells. This
means there will be less haemoglobin available to carry oxygen
Objective: Discuss the effects of air pollution and allergic reactions such as hay
fever, on structures associated with gaseous exchange in humans
● Tobacco smoke, air pollution and allergic reactions, such as hayfever, can affect
the structure of the gaseous exchange surface.
● This can lead to disease of the lungs, such as lung cancer, and other respiratory
diseases
TOPIC: EXCRETION IN HUMANS
Define excretion as the removal of waste products of metabolism (some of which
are toxic and substances in excess of requirement) from the body
Objective: Describe the formation of urea and the breakdown of alcohol, drugs
and hormones in the liver
● Alcohol is broken down by the liver into water and carbon dioxide – this is known
as detoxification
● Drugs such as tranquillizers, painkillers and illegal drugs are broken down by the
liver to less harmful substances
● Hormones are continually produced by the endocrine glands and are constantly
broken down by the liver to prevent accumulation in the tissues
● Excess amino acids are broken down in the liver. During this process urea is
formed
● Part of amino acid is converted into carbohydrates and the part containing
nitrogen is converted into a waste substances called urea in a process called
deamination
Breakdown of alcohol, drugs and hormones in the liver
● Alcohol: is broken down into carbon dioxide and water
● Drugs: broken down by the liver to prevent build up in the tissue
● Hormones: broken down by the liver to prevent build up in the tissue
Objective: Describe the function of the kidney simply in terms of the removal of
urea and excess water and the re-absorption of glucose and some salts (details
of kidney structure and nephron are not required)
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Kidney filter out waste products and unwanted products from the blood
The kidneys also control the amount of water in the body
For ultrafiltration
Kidneys regulate salt concentrations of the body fluids by excreting excess salts
or reabsorbing water and salts
● They regulate the pH of body fluids and blood
● They reabsorb useful substances like glucose, amino acids and vitamins
Objective: Describe the relative positions of ureter, bladder and urethra in the
body
Objective: Outline dialysis and discuss its application in kidney machines
● Dialysis is the term to describe the diffusion of a solute through a partially
permeable membrane
● Kidney machine or artificial kidney or dialysis machine does the work of a kidney
The kidney machines: how it works
● Artery in the patient’s arm is connected to a kidney machine by a tube
● Blood flow from the person’s artery to the kidney machine and another tube is
connected to vein which allow blood to flow back into a vein in person’s arm
● Inside the kidney is a unit called a dialyzer, which contains a dialysis fluid
● Dialysis fluid contains water, glucose, amino acids and salt in the same
concentrations the blood plasma
● A partially permeable membrane separates the dialysis fluid, so urea in the blood
diffuses through the membrane into the dialysis fluid
● No concentration gradient for glucose and amino acids, between the blood and
dialysis fluid, no loss or gain these substance
● Excess salt will diffuse down the their concentration gradient out of the blood
● Kidney machines remove urea and excess salt from blood through a process
called dialysis
Objective: Discuss the advantages and disadvantages of kidney transplants
compared to dialysis
● Advantages of kidneytransplant:
– person can lead a normal life
– one is not dependent on machines
– continuous filtration of blood occurs after a transplant
– cheaper than dialysis
– patient has a better quality of life and a longer life expectancy
● Disadvantages of kidney transplant:
– There may be no kidney available
– Person’s immune may reject the donated kidney
– The operation is very costly
– Tissue type and blood group of donor and recipient must be closely
matched
● Advantages of kidney machines:
– person is kept alive and can lead a normal life and
– Dialysis may be carried home.
– Recipient cannot reject the dialysis machine
● Disadvantages of kidney machines:
– dialysis can take several hours, and a person should go to the hospital for
three to four days a week
– there can be shortage of machines
– one needs to be close to the hospital
– it is very expensive
– no continuous filtration of blood
– the process can cause the loss of some minerals like calcium and iron
– diet and fluid intake must be controlled
– a person cannot do sport
TOPIC: COORDINATION AND RESPONSE
SUB-TOPIC: CO-ORDINATION IN PLANTS
Define the plant growth substances as chemicals that affect the
activities of particular cells organs
Objective: Describe the chemical control of plant growth by auxins
a) Plant cells can produce hormones: which are chemical messengers that travel
throughout the plant causing other cells called target cells to respond.
b) In plants, hormones control:
1. Plant growth & development
2. Plant responses to environment
● When trees to drop their leaves.
● When to start new growth.
● When to cause fruit to ripen.
● When to cause flowers to bloom.
● When to cause seeds to sprout.
● Auxins are plant hormones that are made in the cells all the time and cause
differential growth. differential growth means one side behaves differently from
the other side
● In roots, auxins slow down the growth of cells and in shoots, auxins increase the
rate of growth.
Objective: Describe the use of plant growth substances in food production
(ethane and auxins)
● Plant hormones can be made artificially and used to control and regulate plant
growth.
● Synthetic plant hormones are designed to imitate the effects of the natural plant
growth substances, such as auxins.
● Synthetic hormones are used on commercial basis as they are cheaper to
produce and are not broken down by the plant’s enzymes.
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Ethylene (ethene)
Ethylene or ethene is a colourless gaseous hydrocarbon, C 2H4, which occurs
naturally in plants and acts as a growth substance in a variety of physiological
roles
Ethene is not required for normal growth, but produced in response to stresses,
such as water shortage, or when the concentration of auxins is elevated.
It effects include fruit ripening, e.g. in bananas, apples, and avocados, natural
produce ethylene gas during the later stages of ripening
In some plants , ethylene suppresses flowing
Seed germination, bud opening, and root initiation may also be promoted by
ethylene
NB: farmers can control when their fruits ripens by using ethene gas which stimulates
ripening. E.g. citrus fruits and tomatoes can be picked and transported to the market
while they are still green and unripe. When they reach the market, they can be exposed
to ethene gas to ripen before they are sold. Fruits produce ethane gas when they ripen.
Bananas produce a lot of ethene gas. That is why other fruits ripen quickly when they
are mixed with bananas
Synthetic auxins can be :
● Added to some plants to induce the production of seedless fruits, for example
seedless tomatoes, squashes and grapes, added hormones can also increase
the size of grapes before harvest
● Used to prevent potatoes from sprouting and growing new shoots
● Used to slow down the ripening of grapefruit so that they are ripened at different
times and can be sold when prizes are higher
● Used for rooting of cuttings and nicropropagation (propagation of plants by
cloning )in plants
Objective: Describe the effects of synthetic plant growth substances used as
weed killers
● Weed are plants that do grow when they are not wanted
● Weedkillers containing synthetic plant hormones such as auxins, can be sprayed
onto the weeds to encourage rapid, uncontrolled growth that causes the weed to
die
Objective: Define and distinguish between geotropism and phototropism
□ Geotropism: is the growth response of a part of a plant to the stimulus of
gravity
□ Phototropism is the growth response of a part of a plant to the stimulus of
light
Tropism: the way a plant grows in response to stimuli in the environment.
− Phototropism: growth response to light, plants bend towards light
− Geotropism: growth response to gravity, plant roots grow down with gravity;
shoots (stems) grow up against gravity and out of the soil.
Objective: Describe geotropism and phototropism in terms of auxins regulating
differential growth
● Auxin in roots slow down the growth of cells
● Auxin collects on the lower side of roots and slows down growth of cell at the
lower side.
● Auxin causes the shoots and stem and leaves to grow towards light
Geotropism PhototropismPhototropism
SUB – TOPIC: COORDINATION IN HUMANS
TOPIC: HORMONES
Define hormones as chemicals, produced by glands and carries by
the blood, which alter the activity of target cells in one or more
specific organs
Objective: Describe the chemical control of metabolic activity by adrenaline,
insulin and glucagon
● Your cells also need an exact level of glucose in the blood.
● Excess glucose gets turned into glycogen in the liver
● This is regulated by 2 hormones (chemicals) from the pancreas called:
1. Insulin
2. Glucagon
● If there is too much glucose in the blood, insulin converts some of it to glycogen
● If there is not enough glucose in the blood, glucagon converts some glycogen
into glucose.
● Glycogen can be stored in the liver and muscles
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Adrenaline
WHEN EXCITED OR FRIGHTENED THE BRAIN SEND MESSAGE ALONG A
NERVE TO YOUR ADRENAL GLANDS.
The adrenal gland secrete a hormone which is adrenaline, into the blood
Adrenaline causes the liver to break down stored glycogen and to release
glucose into the bloodstream
Adrenaline prepares the body for action
It is called the “fight or flight” hormone
SUB – TOPIC: NERVOUS CONTROL IN HUMANS
Objective: Describe the human nervous system in terms of the central nervous
system (brain and spinal cord ass areas of coordination) and the peripheral
nervous system
Nervous system consists of brain, spinal cord, nerves and sense organs
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•
•
Nervous system is made up of two main parts:
➢ The central nervous system
➢ The peripheral nervous system
The central nervous system (or CNS for short) is made up of the brain and the
spinal cord.
The peripheral nervous system is made up of the nerves ( neurons), the cranial
nerves, which connect brain and carry message from and to the brain, and
spinal nerves which connect to the spinal cord and carry message from receptors
to spinal cord and brain
Main Function of the nervous system:
This communication system controls and coordinates functions throughout the
body and responds to internal and external stimuli
Objective: Identify motor and sensory neurons from diagrams
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Sensory neurons- carry impulses from receptor to central nervous system
Motor neurons-carry impulses from the central nervous system to receptor
A nerve is an organ containing a bundle of nerve cells called neurons.
Neurons carry electrical messages called impulses throughout the body.
Objective: Describe effectors in terms of muscles and glands
● Receptor cells detect (respond) stimuli and the send information to the CNS as
nerves impulses
● The brain or spinal cord receive message and decide which effectors need to
react to the stimulus
● Brain or spinal cord then send message on, along the appropriate nerve fibres, to
the appropriate effect, which is usually a muscle or gland.
● Muscles contract and relax to cause the correct movement, while glands will
secrete the correct hormones
Objective: Describe a synapse as a small gap between neurons or nerves and
muscles where transmitter substances transmit a nervous impulse
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•
•
When a nerve ending meets up with another nerve ending/the point where the
ends of two neurons meet, we get a microscopic space. This space is called a
synapse
The electrical message travelling along a nerve has to cross the synapse as a
chemical message
When the chemical (neurotransmitter) reaches the other nerve ending it causes
an electrical impulse to travel along the next nerve cell
Objective: Distinguish between voluntary and involuntary actions
Voluntary actions
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An action which can be controlled (by will)
Involves a decision or thought process
Not automatic
Actions are made deliberately
Actions are made consciously
Involuntary actions
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An action which cannot be controlled
Is automatic
No thought process is required
Same stimulus always lead to same reaction – fixed response
Includes reflex actions like blinking, coughing, breathing and sneezing
Objective: Describe the action of voluntary antagonistic muscles in terms of the
bicep and triceps and the associated bones (radius, ulna, humorous)
Antagonistic muscles- these are muscles that work against each other, when one relax,
the other contract
● To bend your arm, biceps muscles contract. Biceps is attached to shoulder
blade (the scapula) at the end, and to the radius bone in the lower arm at the
end. When biceps contract, arm bends, and arm is pulled upwards.
● To straighten your arm, triceps muscles contracts. One end of triceps is
attached to your shoulder blade and humerus bone in your upper arm, and the
other end is attached to the ulna bone in your lower arm. As the triceps contract,
it pulls your arm down
Objective: Describe a simple reflex arc in terms of sensory, relay and motor
neurons and a reflex action as a means of integrating and coordinating stimuli
with responses
Sometimes a stimulus requires an immediate response, this is called a reflex
action. It is an involuntary response and we do it without thinking. These
automatic responses do not have to be learned. They can be very important in
preventing injury to ourselves.
NB: a reflex action is rapid, an automatic response to stimulus and an inborn response.
A reflex arc: The nerve pathway taken in a reflex action is called a reflex arc. The
nervous message goes to the spinal cord, and then a message passes from the spinal
cord directly to effectors to give an immediate response.
Define sense organs as groups of receptor cells responding to
specific stimuli: light, sound, touch, temperature and chemicals
Objective: Describe the structure
accommodation and pupil reflex
and
function
of
the
eye,
including
● eyelids, eyebrows and eyelashes helps to stop dirt from landing on the surface of
your eyes
● Conjunctiva is a thin, transparent membrane that covers the front of the eye and
protects the cornea. When you blink, your eyelid washes fluid from the tear
glands over the conjunctive and kept it moist. This fluid kills any bacteria on the
surface of the eye.
● Sclera is the tough outer layer of the eye that protects the eye against injury
● The cornea and aqueous humour bend the light rays that enter the eye through
the pupil which is the hole in the iris
● The transparent lens and jelly-like vitreous humour Bend light rays even more
and focus them onto the retina at the back of the eye
● The retina is a layer of light-sensitive receptor cells. Light is focused on the retina
and the optic nerve carries the impulses from the retina to the brain.
● The blind spot is where the optic nerve leaves the eye
● Rods work in dim light and cannot distinguish colour
● Cones work in bright light and can distinguish colour
● Cones and rood are mainly in the centre of the retina, particularly the Fovea
● Fovea is the part of the retina directly in line with the centre of the lens and the
cornea
Accommodation is process by which the focal length of the lens of the eye
is changed so the clear images of the objects at a range of distances are
displayed on the retina
● Retina – receives the image
● Full of light receptors which are sensitive to:
➢ Colour
➢ Light levels
➢ Massive blood supply is also needed
● Fovea is the main focal point and has greatest density of light receptors
Focusing on objects
● The lens and cornea focus the light on the retina
Bending light
● Light is refracted and bent to focus it as it passes through the lens
● Lens thickness can be changed so the amount of bending is changed
Near vision
● to bend the light more to focus it
● Fat lens needed
Distance vision
● Rays enter the eye closer together
● Need less bending
● Thinner lens needed
Changing lens thickness
● The lens is slightly elastic; its relaxed state is short and fat.
● Ciliary muscles are attached to the lens, when contracted they pull the lens thin
Controlling light levels
● Your eye is very sensitive and can be damaged by harsh light.
● Your iris controls light allowed into the eye by changing the size of the pupil
Pupil reflex
● In high light intensity, greater number of impulses pass along sensory neurons to
the brain
● Brain sends impulses to the iris of the eye
● Circular muscles of the iris relax
● Iris becomes larger and the pupil constricts (decreases in size)
● This stops too much light from entering into the eye and damaging the retina
● In dim light fewer impulses pass along sensory neurons to the bain
● The brain sends impulses to the iris of the eye
● Circular muscles of the iris relax
● Radial muscles of the iris contract
● Iris becomes smaller and the pupil dilates (increases in size)
● This lets more light into the eye for better vision
Objective: Distinguish between rods and cones, in terms of function and
distribution of structure (no detail required)
Retina receptors
● the rods and cones are light sensitive cells
● cones work in bright light and can distinguish colour (red, green and blue light)
and are mainly in the centre of retina, particularly in the fovea
● more sensitive to light
● rods work in dim light and cannot distinguish colour, are mainly at the edge of
the retina
Objective: Compare nervous and hormonal control systems
Nervous system
Endocrine/hormonal system
1. Message carried as electrical impulses Message carried as a chemical
2. Message carried along nerves
Message carried in blood
3. Message travel to specific effectors
Message travels throughout the body
4. Localised response
Widespread response
5. Rapid, short lived response
Slower, long-term response
6. Hormones carried in blood
Impulse transmitted by neurons (nerve
cells)
SUB – TOPIC: DRUGS
Objective: Describe the effects of alcohol, cannabis (dagga), nicotine and heroin,
and the dangers of their misuse
● cannabis (dagga) is made from the leaves and resin of the Indian hemp and it is
illegal and users tend to see, feel, hear confusingly
● cannabis can cause a state of relaxation and causes euphoria
● using cannabis in very large doses can cause hallucinations
● it can also cause memory loss
● heroin is an addictive drug
● usage of heroin can lead to constipation, arthritis, infection of heart valves,
nausea and vomiting and lack of appetite
● when heroin is injected into the same veins over a long time, the veins can
collapse
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nicotine is stimulant, it make you feel alert
use of nicotine reduces appetite and raises metabolism
it increases the stickiness of blood platelets and increases the risk of blood clots
it enhance the risk of cancer
emphysema in lungs can be a result of smoking
Objective: Describe the personal and social problems that arise (arising) from
drug abuse, with (by) reference e to alcohol, cannabis (dagga) , nicotine and
heroin
● drug abuse, such as the abuse of alcohol, dagga (cannabis), nicotine and heroin,
can cause personal and social problems, such as loss of employment, the
breakdown of relationships within family and friends, and criminal activities to pay
for drugs
● poor work performance
● antisocial behavior like violence, crimes, etc.
● child neglect and abuse
● abuse of spouses
● neglect of personal appearances
● inability to study or write exams or drop out of school
● prevents people from making sensible decisions
TOPIC: HOMEOSTASIS
Define homeostasis as the maintenance of a constant
internal environment around cells
Objective: Discuss the general role of negative feedback on homeostasis
● Negative feedback is when the body take corrective action. e.g. when you get
hot, special temperature receptors detect the change in your body temperature
and correct the change.
● Body responds by lowering the temperature.
● The corrective change is the opposite of the change it is responding to
● This is known as negative feedback – getting the body back to an ideal balance
Objective: distinguish between ectothermic and endothermic animals
● All fish, amphibians and reptiles are ectothermic.
● Ectothermic are animals that rely mainly on an external source for body heat
● all birds and mammals are endothermic, animals whose body source is internal
Objective: list ways of temperature regulation in ectothermic and endothermic
animals
● The hypothalamus acts as a thermostat and receives nerve impulses from heat
and cold thermo receptors in the skin.
● There are also receptors in the hypothalamus- called central thermoreceptor
● These detect changes in blood temperature.
Mechanisms that control body temperature in endotherms
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vasoconstriction
vasodilation
hairs in low and high temperatures
sweat glands in low and high temperatures
shivering in low temperatures
exercise
Objective: describe temperature regulation; explain the effects of sweating,
vasodilation and vasoconstriction only
● in endotherms, heat can be generated within the body
● this is done through cell respiration, high metabolism and by muscular
contractions
● they maintain a constant body temperature irrespective of the external
environmental temperature
● this is important because of optimum temperature for enzyme activity
Sweating
● when temperatures are high, the arterioles which supply blood to the sweat
glands dilate
● this causes more blood to flow to the sweat glands
● more sweat is produced
● more evaporation of sweat from the skin surface occurs
● more heat is lost though evaporation
● when temperatures are low, the arterioles with blood constrict
● less blood flows to the sweat glands
● less sweat is therefore produced and secreted
● less evaporation of sweat from the skin
● less heat is therefore lost through evaporation
Vasodilation
● when the external temperature is very high and your body temperature rises too
much above 37oC, the muscles around the arterioles in the skin relax
● arterioles dilate and increase in diameter
● this leads to an increase in heat loss through radiation and convection from the
skin
Vasoconstriction
● when the external temperature is low and the body temperature falls below 37 oC,
the muscles around the arterioles contract
● arterioles constrict and reduce in diameter
● less blood now flows in the skin capillaries
● less heat is lost through radiation from the skin
Objective: describe the control of the glucose content of the blood by the liver,
and by insulin and glucagon from the pancreases
● blood sugar level are controlled by insulin and glucagon
● insulin convert glucose to glycogen and reduces blood sugar level
● glucagon convert glycogen to glucose and increase sugar levels
SECTION III – DEVELOPMENT OF THE ORGANISM AND THE CONTINUITY OF
LIFE
CELL DIVISION
THERE ARE TWO TYPES OF CELL DIVISION
1. Mitosis
2. Meiosis
THE PROCESS OF MITOSIS
Objective: Describe the importance or significance of mitosis
1. Mitosis is responsible for all form of asexual reproductionin plant and animals: produce new organisms which are identical to parents and each other such as:
propagation in plants &binary fusion in bacteria and protozoa.
2. Mitosis is responsible for the cell replacement: repair and healing of damage or
worn out cell or tissue for maintenance of multicellular organisms.
3. Mitosis is responsible for the growth of an organism: - allow organisms to
grow a the cells splits, their numbers increase leading to growth.
4. 4. Genetic stability: daughter cells are genetically identical to parent cell.
5. 5. Regeneration: missing parts such as legs of crustacean can grow back.
CLONING
Cloning
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Is a process of producing genetically identical organisms.
It’s a result of mitosis.
A clone: is a genetically identical copy of another organism.
Cloning occur in both plants and animals.
Outline the principles and social implications of cloning
Principles of cloning involves:
1. Taking a diploid cell from the body of organism(donor) e.g. a skin or udder cell.
2. Removing the nucleus from this donor cell by means of a micro-pipette.
3. Remove an egg cell(ovum) from the ovary of an organism and enucleate it by
removing the nucleus the nucleus with a fine glass needle. Dispose of this
nucleus
4. Nucleus from the donor cell is inserted or placed into the enucleated egg cell
using an electric shock.
5. The fused cell then starts to divide by mitosis to form an embryo.
6.
This embryo is placed into the uterus of foster mother(surrogated)mother and left to
develop.
7.
Thecloneis formed: the new individual is genetically identical to the individual from
which the diploid nucleus was taken.
SOCIAL IMPLICATION OF CLONING
o Clones may have cloning related health problems.
o The application of the technique to clone humans would be open to serious moral
issues.
o Theoretically any number of genetically identical copies of the same person(e.g
Einstein or Nelson Mandela)might be made.
o People view cloning unethical and immoral as it destroy some cell in order to
obtain other organ for the sake of transplant.
o Creating twins or triplets through cloning creates a spirit of direct ownership in
the donor of adult DNA cloning.
o Cloning some plants desirable crops might be of great advantage.
o Cloning desirable animals might be advantage i.e. in farming.
Describe the production of gametes by meiosis simply in terms of halving of
chromosome number leading to variation
✓ Is a type of cell division by which fourhaploid cells genetically different from
each other are produced from a diploid cell.
✓ Occur in the gamete-producing cells of plants and animals.
✓ Lead to formations of gametes i.e. egg (ova) or sperms, and pollen grains.
✓ Meiosis produce FOUR cells with half number of chromosome and with
different combination of genes described as haploid = n.
✓ Diploid number of chromosomes = 2n are restored during fertilization.
Describe the significance or importance of meiosis
1. Meiosis is needed for sexual reproduction: -for production of gametes(sex
cells).
2. Meiosis promote genetic variation, because of the combination of genetic
information during meiosis process.
3. Reduction division which reduces the diploid chromosome number to a haploid
number.
COMPARE & CONTRAST BETWEEN MITOSIS & MEIOSIS
TOPIC: REPRODUCTION
SUB – TOPIC: ASEXUAL AND SEXUAL REPRODUCTION
Define asexual reproduction as reproduction which does not
involved fusion of gametes
Asexual reproduction in bacteria
Binary Fission - occurs in one-celled organisms such as the ameba and paramecium.
The nucleus divides by mitosis and the cytoplasm divides, forming 2 new daughter cells
of equal size.
Asexual reproduction in Fungi
Sporulation - occurs in molds, mosses, etc
Spores are produced in large numbers by mitosis.
Spores are surrounded by a tough coat to help them survive harsh environmental
conditions
➢ fungi are organisms that grow on living or dead plants and animal matters
➢ majority of fungi reproduce by spores
➢ spores are cells that are able to develop into a plant
➢ fungi (mould)reproduce by forming tiny white threads called HYPHAE that grow
into the bread. Some of the hyphae grow up from the bread and produce
structures called sporangia. Millions of identical spores are produced inside the
sporangia. When the sporangium is ripe and burst, the spores are released into
the air. If a spore lands in a suitable place it will develop into a new fungus
➢ many HYPHAE, one HYHPA: this se are threadlike filaments that make up the
fungal body
Tubers are underground food stores, which stores food over the winter and provides a
new plant with food until it can make its own. Examples: potato, artichoke, yam,
cassava, water chestnut, arrowroot. Food made by the new plant is sent to make new
tubers. Thereby reproducing by itself.
Objective: discuss the advantages and disadvantages of asexual reproduction
● Offspring have no variation
● Offspring are genetically identical to one another
Define sexual reproduction which involves the fusion of two gametes to form a
zygote
Objective:discuss the advantages and disadvantages of sexual reproduction
● Offspring are not genetically identical to one another
● There is variation in the offspring
SUB – TOPIC: SEXUAL REPRODUCTION IN PLANTS
Objective:Describe the structure and function of the flower of a named
dicotyledonous plant
● Some plants produce asexually and some produce sexually.
● The reproductive part of those plant that reproduce sexually is called a FLOWER.
● The flower: is an sexual organ of sexual reproduction in flowering plants
(angiosperms).
● It is where the sex cells of the plants are produced and join to form seeds.
A FLOWER:Flowers can be either Unisexual flowers or Bisexual flower
Bisexual flower: has the stamen and carpels in the same flower
Unisexual Flowers: has Stamen (male organs) and Carpel (female organs) on
separate flower
Parts and functions of the flower
● Receptacle: the top of the flower stalk which is expanded and which bears the
parts of the flower.
● Stalk (peduncle):
✓ Holds the whole flower and connect it to the stem.
✓ Carries inorganic & organic nutrients to the flower.
● Calyx (Sepals):
✓ It consists of the green sepals, which protect the flower while it is developing in
the bud stage.
✓ Protect the flower while it is in developing in the bud stage.
● Petals: with bright colour and smell (scented) to attract insects for
pollination.
● Nectar gland/ nectary:
✓ A swelling found on the receptacle or other parts of some flowers which
produces nectar.
● Nectar: is a sweet sugary solution produced by nectaries. Insects and birds
feed on nectar and pollinate the flower.
⦿ Stamen: is the male reproductive structure or organs of the flower consist of an
anther and filament.
✓ Anther: produce pollen grains (the male gamete /sex cells).
✓ Filament: the thin stem that holds the anther in position expose it to agents of
pollination.
✓ Male gamete:the haploid sex cell which fuse with the female gamete during
fertilisation to form the diploid zygote.
The carpel
⦿ Carpel (pistil): -he female reproductive structure or organs of the flower consist
of a stigma, style, ovary and ovule.
✓ Stigma: -receptive tip of style that receive pollen from the anther during
pollination. It also produce nutritive materials for pollen to germinate
✓ Style: -the swollen part from the stigma to the bottom of the carpel (ovary) which
is the path through which the pollen tube grows on its way to the ovary for
fertilisation. It carries the stigma to be exposed to the agent of pollination.
✓ Ovary: -the base of the carpel that contain the female sex cells (the ovules)
and develop into the fruit after fertilization.
✓ Ovules: -located within the ovary that contain the female gametes and
develop into a seed after fertilisation.
✓ Female gamete: the haploid sex cell (ovum) which fuse with the male gamete
during fertilisation to form the diploid zygote.
Define pollination as the transfer of pollen from a mature antherto the
receptive stigma.
Objective:Name the agents of pollination
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Animals such as birds
Insects
Wind
Water.
Humans
Objective: Distinguish between self- pollination and cross-pollination
1. Self-Pollination: is the transfer of the pollen from the anther to the stigma within
the same flower or between flowers of the same plant.
2. Cross-Pollination: Is the transfer of pollen from the anther of one flower to the
stigma of flower of another plant same species.
Self pollination
Cross pollination
Objective: Compare the different structural adaptations of insect-pollinated and
wind- pollinated flowers
Insect pollination
▶ Insect pollination: is the transfer of pollen from the anther to the receptive
stigma by insects. The flowers are called insect-pollinated flower.
Adaptations of insect pollinated flower
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Have large, conspicuous petals, often with guidelines.
Anther inside the flower, where insect has to brush past them to get to nectar.
Have an attractive smell (scent).
Produce nectaries.
Sticky pollen to stick on animal body.
Reproductive organs(stamens and carpels) are enclosed within the flower.
Smaller Stigmaissticky, not feathery.
Smaller anthers, because less pollen needed to be produced
INSECT POLLINATED FLOWER
WIND POLLINATION
Adaptations of wind pollinated flower.
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Small and dull coloured.
Do not produce nectar.
Do not produce smell (no scent).
Reproductive organs (anther and stigma) protrude from the flower and are
projected outside the flower.
● Have large feathery anther to catch pollen grains from the air.
● Produce very large amount of pollen as most of it is lost in the wind.
● Smooth, small, light and dry pollen to be carried by the wind.
WIND POLLINATED FLOWER
Objective:Describe the growth of the pollen tube and the process of double
fertilisation
● A pollen grain lands on the stigma, and the stigma produce a sticky
nutritive fluid.
● The pollen grain absorbs this fluid and producing a pollen tube.
● The growth of the pollen tube is controlled by the pollen tube nucleus.
● The pollen tube emerges from the pollen grain and grows through the
stigma into the style and reaching the ovary.
● During the growth of the pollen tube, the haploid two generative
nuclei(male gametes)move down the pollen tube.
● The pollen tube grows towards the micropyle on the ovule and degenerate.
● The tip of the pollen tube ruptures and the two male gametes enter the ovule.
Double fertilization
● One male gamete fuses with the female gamete(egg cell)to form diploid
zygote,which then forms the embryo plant.
● The other one fuses with the two polar nuclei to form the endosperm nucleus
which is triploid.
NB after fertilization the petal,stamen , stigma and style dry out and fall off.
Objective:describe the formation of the fruit and seed
a) Formation of the fruit:
● The fruit develop from ovary
● Function of the fruit: to protect the seed inside it until they are ripe.
b) Formation of the seed:
● The seed develop from the ovule.
● The zygote divides by mitosis forming an embryo plant.
● The embryo plant consists of the radical (developing root) and plumule
(developing stem/shoot), between a single or two cotyledons (seed lobes).
● The triploid endosperm nucleus divides repeatedly by mitosis to form the
endosperm which is the food store.(in monocotyledonous plant)
● In the case dicotyledonous plant endosperm (food store) is held in the
cotyledons.
● The two layers that cover the ovule(integument) develop into a tough, hard
outer coat called a testa.
● The content of the testa (ovule) loses water, and the whole structure becomes a
seed.
Objective:Describe the structure of a non-endospermic seed
● The seed is covered by a hard tough protective seed coat called the testa. It
protects the seed from mechanical damage or the decomposition by fungi and
bacteria.
● The micropyle is a small hole in the testa through which water and oxygen enters
to enable germination.
● The hilum is the scar where the seed was attached to the fruit.
● The embryo plant is found between the two cotyledons.
● The embryo plant consists of the radical (developing root) and
plumule(developing stem with two tiny leaves).
● The cotyledons(seed lobes) are the food storage(starch, protein and lipids).
The internal structure of the non-endospermic seed.
Objective:Define dispersal of seeds and fruits
▶ DISPERSAL: is the spreading out of seeds and fruits as far as possible
from the parent plant.
▶ FRUITS: apart from protecting the seeds inside until they are ripe. They also help
to disperse the seeds.
Seeds and fruit can be dispersed through:
a) Wind dispersal
b) Animal dispersal
c) Water dispersal
d) Self-dispersal
Objective: describe adaptations of seeds and fruit dispersed by wind, water,
animals and self
ADAPTATION OF WIND DISPERSAL SEEDS AND FRUIT
● Very light in weight.
● Small in size with flattened wing-like structures to allow it to be carried (blown)
by wind.
● Some have feathery hair increasing surface are “flight” over long distances i.e.
dandelion seeds.
ADAPTATION OF WATER DISPERSAL SEEDS AND FRUIT
● Generally, light in weight and waterproof which allow them to float on the
surface of water to be carried to distant places..
● Have large surface area for floating on water.
ADAPTATION OF ANIMAL DISPERSAL SEEDS AND FRUIT
● Coloured, sweet and juicy to attract birds (animals) to eat them and be dropped
in faeces I far places. i.e. tomatoes, guava, and wild berries.
● Some have hooks to catch on the fur of mammals and be dropped far away.
● Succulent fruits i.e. marula and strawberry have seeds which can through the
digestive system of animals unharmed and are carried long distance before
deposited along with fertilizer on the ground.
ADAPTATION OF SELF -DISPERSAL SEEDS AND FRUIT
● Seeds are hidden inside pods which become heated by the sun, increasing the
pressure inside the pods. The pod eventually explodes releasing seeds.
TOPIC: HUMAN REPRODUCTIVE SYSTEM
SUB – TOPIC: SEXUAL REPRODUCTION IN HUMANS
Objective: describe the structure and function of human male and female
reproductive system (microscope structures/sex hormones are not required)
Scrotum
● The testes are inside a sac called the scrotum.
● It hangs outside the body, keeping the sperm cool.
● Sperms only develop properly in cool conditions.
Sperm duct/vas deferens
● Sperms are produced all the time.
● They are stored in small tubes outside the testes.
● Eventually they pass along a much bigger tube called the sperm tube.
Glands
● Glands add a fluid which keeps the sperms alive.
The sperms and the fluid are called semen
Penis
● The penis must be erect for the semen to pass out.
● This happens when blood is pumped into special spongy tissue in the penis.
Sperm
● During an ejaculation, semen is pumped out of the penis – due to a contraction of
the muscles around the sperm tubes.
● Each ejaculation makes about a teaspoon of semen but this can contain:: 500
million sperms.
Ovaries
● The ovaries are the female sex organs.
● They produce the eggs.
● They also make the female hormones oestrogen and progesterone (between 10
and 15 years).
Egg tube
● An egg is released about every 28 days.
● The egg passes out of the ovary and moves into the egg tube.
● This is called ovulation and is when an egg may become fertilized.
Uterus
● The egg slowly moves down towards the uterus (womb).
● If sperms are present in the egg tube the egg will be fertilised.
● If the egg is not fertilised it will dies after about a day.
Cervix
● The lower end of the uterus has a ring of muscle called the cervix.
● It leads to a muscular tube called the vagina that opens to the outside of the
body
Objective: describe the role of testosterone and oestrogen in the development
and regulation of secondary sexual characteristics at puberty
Testosterone in male
●
●
●
●
●
●
voice break and deepen
body muscle grow
hair grow on face, chest and armpits
pubic hair around sex organs
penis and testes enlarge
testes start to produce sperm
Oestrogen in female
●
●
●
●
●
●
●
●
more fats on hips, highs, buttocks and breast
the pelvis widens
hair grows on armpits
sex organs develop and increase in size
growth spurt, which is earlier but not as prolonged as in males
pubic hair
ovaries start to release ova
menstruation starts
Objective: describe the menstrual cycle
●
●
●
●
cycle begins in females at puberty (around age of 10 - 12)
cycle is controlled by female hormones
new cycle starts with menstruation
during menstruation female hormone levels are low
● after menstruation the oestrogen levels rise to just before ovulation
● by day 14 the uterus lining has thickened and ovulation occurs
● after ovulation the levels of progesterone rise to maintain the lining so that
implantation can occur between days 20 to 23
● if sexual intercourse takes place and there no fertilisation the cycle will start over
again
Objective: describe the sites of production and the role of oestrogen and
progesterone in the menstrual cycle and in pregnancy
● The pituitary gland controls the production of the hormones oestrogen and
progesterone by the ovaries
● The oestrogen levels rises just before ovulation.
● Lining of the uterus thickens with blood vessels and mucous tissue to prepare for
implantation
● Just after ovulation the ovaries produce progesterone,
● Progesterone stimulates the uterus walls to thicken
● If no fertilisation took place, then the progesterone production slow down and this
causes the thick lining of the uterus to break down and gradually blood is lost
through the vagina. This is called menstruation
Objective: describe sexual intercourse, fertilisation and implantation
● Sexual intercourse: process by which spermatozoa from a male are deposited in
the body of a female during through the vagina. Penis enter the female vagina
● Fertilisation: fusion of male and female sex cells
● Implantation; the embryo sinks into the soft lining of the uterus
Objective: indicate the functions of the amniotic sac and amniotic fluid
● amniotic sac: contains amniotic fluid which cushion the development fetus so
that mechanical shock is lessened and the fetus lives in a space that is free from
the effects of gravity and pressure
Objective:describe the development of the foetus in terms of placenta, maternal
and foetal blood supplies and exchange of materials
●
●
●
●
placenta is thickened lining of the uterus where the embryo embeds itself
two arteries carry blood from the foetus to the placenta
one vein carries blood from the placenta to the foetus
blood of the mother and that of the foetus never mixes but is in close contact
Objective:describe ante-natal care in terms of dietary requirements and
maintaining good health
● Antenatal describes the period of gestation before the birth of the baby.
● Health women will have a healthy baby. Calcium and iron are needed in a
pregnant women’s diet
● Exercise is very important to keep the lungs, heart and muscles fit
Objective:describe the process of birth
●
●
●
●
Birth occurs 280 days after fertilisation. 9 months
Few weeks before birth, fetus moves its position. The head is next to the cervix
Contraction of uterus push the fetus towards the cervix
After hours of pushing, the amnion ruptures and releases the amniotic fluid,
‘’breaking of water’’
● Uterus contracts more forcefully and more frequently, this pushes the head of the
fetus out of the cervix and into the vagina. Once the head has appeared , the rest
of the birth continue quite quickly
● After the baby is born, the drop in temperatures stimulates the baby to breath,
and placenta is expelled soon after this and the umbilical cord is cut and clamped
● Cut of the umbilical cord forms the navel
Objective: describe the advantage of breast-feeding compared with bottle-feeding
Breast-milk
Always the correct temperature
Bottle-milk
Needs to be heated or cooled to correct
temperature
Contains protective antibodies
Contains no antibodies
More convenient and is always available Sometimes not available in shops
Free of charge
Very expensive
Digested more easily
More difficulty to digest
Free of harmful pathogens
Can contain harmful pathogens
Baby feels safe and develops sense of Baby feels less safe and does not develop
security
sense of security
SUB –TOPIC: METHODS OF BIRTH CONTROL AND INCREASING FERTILITY
Objective: name and describe the following methods of birth control: natural,
chemical, mechanical and surgical
Four methods of birth control
●
●
●
●
natural: rhythm method
chemical; contraceptive pill;, morning after pill
mechanical or barrier methods: condom and cap; IUD
Surgical: sterilization.
Oral Contraceptive or the pills
●
●
●
●
Contains female hormones, mostly progesterone which prevent ovulation
It is reliable if no days are missed
Pills do not protect against STDs
Pills can cause side effects such as heart diseases, high blood pressure,
nausea, weight gain, depression and tiredness
Spermicides
● Are chemicals creams or foams that kill sperm
● Placed in the vagina before sexual intercourse, or smeared round the edge of a
cap or condom
● Not reliable , bur reduce the chance of pregnancy when used with barrier
methods
● Do not protect against STDs
Condom
● For man, which is fitted on an erect penis
● Very reliable and protect against STDs
The Cap or diaphragm
● Fitted over the cervix like a cap and held in place by rubber
● More efficient if used with spermicides
● First fitted by doctor , making sure it is of correct size, after a women can be
putting it before sexual intercourse
● Cap does not protect against STDs
The intra-uterine device (IUD)
● Sometimes referred as coil or loop
● IUD is a piece of mental or rubber fitted by a trained person into a female’s
uterus
● Common in women previously gave birth
● IUD prevent implantation
● Very reliable and convenient
● May increase chances of uterine infection
● Some women may find it very uncomfortable
Sterilization
● Operation of tying or cutting the vas deferens in man
● Operation of permanently blocking , tying or cutting the fallopian tube by means
of clips in women
● Sterilisation in man is called vasectomy
● Sterilization in women is called laparotomy
● Both operations only produce sterility
● No effect on sexual performance or enjoyment
● Does not protect against STDs
Contraceptive injection
● Contains hormones progesterone only and they work by thickening the mucous
produced by the cervix and so making it harder for sperm to penetrate
● They also prevent ovulation
● Injection is administered once every two or three months, depending on the type
used
● Does not protect against sexual transmitted diseases
Withdrawal
● Man pulls out his penis out of the women’s vagina just before the sperm are
released at ejaculation
● Nor reliable as the sperm might link into the vagina before ejaculation
● Demand a lot of control and a man may wait too long before withdrawing
● Does not protect against STDs
The rhythm method
● Avoiding sexual intercourse near the time of ovulation
● Good for women who know their menstrual cycle very well
● Very unreliable and not recommended
● Does not protect against STDs
Objective:describe the hormonal control of ovulation and the role of the
contraceptive pill
● ovulation is the release of an egg cell from the ovary
● the oestrogen level rises just before ovulation
● the pill contains chemicals which have the same effect on the body as the
hormones oestrogen and progesterone, this (progesterone) suppresses ovulation
Objective: discuss the social aspects of artificial insemination and the use of
hormones in fertility drugs
● artificialinsemination: delivering sufficient semen of good quality into a female’s
vagina at about the time she is due to ovulate
● sperm can be from the husband or from any men
● if from another man, the couples are encouraged to have sex immediately, this is
because there is a chance that the husband ‘s sperm may fertilize the egg
Social implication of artificial insemination
●
●
●
●
Who is the legal father, donor or husband, and who has the paternity rights?
Should the child be told that their father is not their biological father?
Does the child have any claim on the donor’s estate after the death of the donor?
Semen from donor can be stored for years, even after death of the donor. Now
who owns the sperm and whether it should be used after the donor’s death
Fertilitydrugs: hormones treatment to stimulate their ovaries to produce ova
SUB-TOPIC: SEXUALLY TRANSMITTED DISEASES
Objective: describe the symptoms, signs, effects and treatment of gonorrhoea
and syphilis
Gonorrhoea
● caused by a bacteria called, Neisseria gonorrhoea, and transmitted only by
sexual intercourse
Signs and symptoms
● in men: sore on penis and yellow discharge or pus from penis, burning
sensation when urinating
● in women: thick discharge from vagina, burning feeling when passing urine
Effects
● in men: testes became infected, sperm duct blocked leading to infertility
● in women: oviducts become infected and blocked leading to infertility
Treatment
● can be treated by antibiotics (penicillin) in the early stage
Syphilis
● caused by a bacteria, Treponema pallidum, spread during sexual intercourse
● syphilis develops in three stages
Signs and symptoms of syphilis in men and women
● first stage: 10-20days after intercourse, a small swelling appears on the penis,
vagina or cervix, which may turn into an ulcer, and then disappears
● second stage: a few months later, sores and ulcers appear on other parts of the
body, also fever, skin rash and flu-like symptoms
● third stage; 10-20 years later, the bacteria have spread to other parts of the
body, damage to bones, blood vessels, the liver and the nervous system has
taken place. Syphilis can lead to serious brain damage, insanity and finally death.
Treatment
● can be treated by antibiotics (penicillin) in the early stage
Objective: describes the methods of transmission of the human immunedeficiency virus (HIV) and the ways in which it can be prevented from spreading
● HIV can be transmitted during sexual intercourse with an infected person, by
using contaminated needles, during blood transfusions, during birth and during
breast-feeding
● HIV lives in body fluids such as semen, blood and saliva and can be prevented
by using condoms, abstinence etc.
Objective: discuss the increased vulnerability of Namibians to other illness due to
the increased prevalence of HIV and AIDS
● HIV weakens the immune system, and less able to fight against infections
Objective: outline the social-economic consequences of the HIV and AIDS
pandemic for Namibia
● claims the lives of economically productive people
● Increased number of orphans
TOPIC: GROWTH AND DEVELOPMENT
Define growth in terms of increased in dry mass
● dry mass is the mass of a living organism, once all water has been removed from
it
Define development in terms of increased in complexity
● development is the complex process of growth and maturation that occurs in
living organisms
Objective: describe the environmental conditions that affect germination
● Germination takes place where there is water, oxygen and a suitable
temperature
● Water breaks dormancy and allows the cotyledon to swell and split the testa
● Oxygen needed for respiration , to provide energy
● Suitable temperature provides optimum conditions for enzyme action to catalyse
reactions
Objective: describe methods of measuring growth in a herbaceous plants and a
mammal
● Increase in dry mass of an organism is the most accurate ways of determining if
the organism has grown. However, the organism has to be killed and heated.
measure growth in length, mass, volume or area
Objective:discuss the advantages of different methods of measuring growth
method
advantages
disadvantages
Suitable
organisms
Height or length
Quick, easy; does not Only measures growth Small
plants;
damage organism;, can in one dimension
most animals
be used in the field
Length of one part of As above
Only measure growth Many animals,
body
of one part of body
such as small
mammals and
birds
Wet mass
Gives more accurate Plants
must
be Most animals,
measure of overall size uprooted, and roots small plants
than height or length; cleared of soil; difficult
fairly quick for small for
large
animals
animals
without
specific
equipment;, fluctuations
in water content may
affect results
Dry mass
Gives
the
bestTime-consuming; kills Plants;
small
measurement of the individual , so large animals such as
amount of living material numbers are needed insects
in an organism
TOPIC: INHERITANCE
SUB – TOPIC: DNA AND CHROMOSOMES
Objective: state the DNA in the hereditary material and that it is contained in the
chromosomes
● Chromosomes are made of deoxyribonucleic acid, known as DNA, and protein.
DNA is set of instruction for the cell. DNA is defined as the hereditary material
contained in the chromosomes
● A section of DNA molecule which gives instructions for making any one kind of
protein is called gene
Objective: define the terms chromosomes, homologous chromosomes, haploid
and diploid nuclei
● Chromosomes: a thread-like structure several to many found in the nucleus of
plants and animal cells.
● Chromosomes are the rod-shaped, filamentous bodies present in the nucleus,
which become visible during cell division.
● They are the carriers of the gene or unit of heredity.
● Chromosomes are not visible in active nucleus due to their high water content,
but are clearly seen during cell division.
● homologous chromosomes: chromosomes having the same structural features
● haploid nuclei: describing a nucleus, with a single set of unpaired chromosomes
● diploid nucleus: describing a nucleus with twice the haploid number of
chromosomes characteristic of the species.
● Gametes normally contain only one set of chromosome – this number is called
Haploid
● Somatic cells usually contain two sets of chromosome - 2n : Diploid
Define genes as a length of DNA coding for a specific protein
Define alleles as alternative forms of the same gene which code for different
versions of the same characteristics
SUB TOPIC: MONOHYBRID INHERITANCE
Objective: define the terms genotype, phenotype, homozygous, heterozygous,
dominant and recessive
● genotype : the genetic composition of an organism., i.e. the combination of
alleles it possesses
● phenotype: the observable characteristics of an organism
● Homozygous: describing an organism or cell in which the alleles at a given locus
on homologous chromosomes are identical. ( they may be either dominant or
recessive)
● Heterozygous: describing an organism or cell in which the alleles at a given locus
on homologous chromosomes are different.
● Dominant: when one allele is expressed over another allele in a gene
● Recessive: a condition where no dominant allele present in the heterozygous trait
Objective: calculate and predict the results of monohybrid crosses involving 1:1
and 3:1 ratios
Let the allele for round seeds be:
Let the allele for wrinkled seeds be:
Parents
phenotype
Genotype
Gametes
R (dominant allele)
r (recessive allele)
round seeds x wrinkled seeds
RR
rr
R
R
r
r
F1 generation
gametes
gametes R
R
r
Rr
Rr
r
Rr
Rr
F1 phenotypes
100% plants producing round seeds
F1 genotypes
100% heterozygote Rr
Ration
1:1
----------------------------------------------------------------------------------------• F1 intercross
• Parents phenotype
Genotype
•
Gametes
F2 generation
round seeds x round seeds
RrRr
R
gametes
R
r
r
R
gametes
R
RR
Rr
r
r
Rr
rr
Phenotype75% plants producing round seeds
25% plants producing wrinkled seeds
Genotype
25% RR 50% Rr
25% rr
Ratio
3:1 Round seeds: wrinkled seeds
Objective: describe the inheritance of sex in humans (XX, XY)
● Genes are carried on the sex chromosomes (X or Y)
Father
Mother
XY
XX
X
XY
X
X
Y
XX
A cell contains 23 pairs of chromosomes. During meiosis (cell division), the pairs of
chromosomes are separated so that only one of each pairs in the sex cells. Each egg
and sperm cell then has only one of the sex chromosomes. By joining the egg and
sperm cells during fertilization, a zygote with two sex chromosomes is formed.
● If after fertilisation, the pair of sex chromosomes consists of two X chromosomes
then that zygote will develop into a baby girl.
● If the pair of sex chromosomes consists of one X and one Y chromosomes, the
zygote will develop into a baby boy
● Egg cell will always carry an X chromosomes whereas as a sperm cell carry
either X or the Y-chromosomes.
● Chances of a woman conceiving a baby boy or girl are equal
Objective: explain co- dominance and inheritance of A, B, AB and O blood
groups:
● co -dominance : the condition that arises when both alleles in a heterozygous
organism are dominant and are fully expressed in the phenotype. e.g. example,
the human blood group AB is the result of two alleles, A and B, both being
expressed. A is not dominant to B, nor vice versa
Co- dominance
Genotype
Phenotype
group)
(blood
Inheritance of blood
● Four human blood
groups: group A, B, AB and
O
● These blood groups
are controlled by a single
gene represented by the
letter I.
● These genes has
three alleles represented by
letters A fro blood group A,
IA IA or IAI º
A
IB IB, or IBIº
B
IAIB
AB
IºIº
O
SUB – TOPIC:VARIATION
Objective:Describe continuous variation as influenced by the environment and
genes asillustrated by height
● Variation is the differences, which exist between individuals belonging to the
same species.
● Continuous variation is a smooth gradation between individuals. Example
include human height, hair colour and intelligence
● Continuously variable characteristics are greatly influenced by the environment..
a person may inherit genes for tallness and yet not get enough food to grow tall.
A plant may have the genes for large fruits but not get enough water , minerals or
sunlight to produce fruits
● Continuous variation in human population, such as height, physique and
intelligence, are always the result of interaction between the genotype and the
environment
Objective: Describe discontinuous variation as influenced by genes as illustrated
by bloodgroups
● Discontinuous variation: clearly defined differences in a characteristic that can
be observed in a population or the variation under the control of a single pair of
alleles or a small number of genes
● E.g. a person can either male or female, there is no gradual change between the
two extremes; you are either one or the other.
● Discontinuous variation cannot be altered by the environment, it is caused
entirely by reshuffling of genes
Define mutation as a sudden random change in the genetic material of a cell
Objective: Outline the effects of radiation and chemicals on the rate of mutation
● Increases the rate of mutation
● Down’s syndrome
● Exposure can cause uncontrolled cell division, leading to the formation of
turmours (cancer)
● Exposure of gonads(testes and ovaries) to radiation can lead to sterility or to
damage to genes in sex cells that can be passed on to children
Objective:Describe mutation as a source of variation, as shown by Down’s
syndrome
● Down’s syndrome is caused by chromosome mutation during meiosis.
● During the development of the ovum, two chromosomes fail to separate so an
extra chromosome is present in the ovum.
● Instead of the ovum having 23 chromosomes, it has 24.
● At fertilisation, the zygote has 47 chromosomes.
● The presence of this extra chromosomes results in a baby with down’s syndrome
e.g. flat face, round head
Objective: Describe sickle cell anaemia, and explain its incidence in relation to
malaria
● Sickle cell anaemia is a medical condition in which a sufferer has abnormal
haemoglobin in their red blood cells, which causes the cells to have a distorted
shape.
● The increased need for oxygen will result nor enough haemoglobin to carry much
oxygen.
● The distorted cells get stuck inside capillaries and can cause great pain. If not
treated sensibly, sufferers from sickle-cell anaemia can die at a young age
● Sickle-cell anaemia is caused by a recessive allele, h of the gene for the
production of haemoglobin. Normal allele for haemoglobin is labelled H. only
people with a homozygous recessive hh suffer from sickle-cell anaemia
● Most sufferer may die before the start to reproduce, so the allele for sickle-cell
anaemia may have lost from the population
● In areas where Malaria is common, it is an advantage to possess at least one
sickle-cell allele
● Homozygous HH. People with normal haemoglobin and do not have sickle-cell
malaria but can catch malaria
● Heterozygous Hh, individuals do not have sickle-cell anaemia but are less likely
to catch malaria
● Homozygous hh, persons having sickle- cell anaemia but do not suffer from
malaria.
SUB – TOPIC: SELECTION AND EVOLUTION
Define natural selection as the selection of only the best adapted organisms for
survival and reproduction
Define evolution as a process of change over a period of time
Objective:Evaluate (outline) the importance of natural selection as a possible
mechanism for evolution
● Living organism produce more offspring than the environment can support
● There is variation in the characteristic(or genetic traits) in a population of
organism
● There is competition between organisms in a population.
● Organisms with adaptive/suitable features will survive
● The surviving organisms reproduce and the successful characteristics(genetic
traits) are passed on to the next generation
Objective: Describe the development of strains of antibiotic resistant bacteria as
an example of natural selection
● Overuse of antibiotics has acted as a means of selecting resistant strains of
bacteria
● Some bacteria not killed by antibiotics became resistance and multiply producing
even more resistant bacteria
Define artificial selection as the modification of species by selective breeding
Objective: Describe the role of artificial selection in the production of species by
selective breeding and plant with increased economic importance
●
●
●
●
●
climate adapted crops
disease-resistant crop
high- yielding crops
nutritious crop
Purpose- selection organisms, e.g. yeast for brewing, cattle resistance to disease
or produce milk yields
SECTION IV: RELATIONSHIP OF ORGANISMS WITH ONE ANOTHER AND WITH
ENVIRONMENT
Objective: State that the Sun is the principal source of energy input to biological
systems
●
●
●
●
Is the principal source by which energy gets into ecosystems.
The sun emits solar energy that reach's the ecosystems.
Plants then covert it into chemical energy during the process of photosynthesis.
Energy is then stored in food produced by plants as chemical energy.
Objective: Describe the non-cyclical nature of energy flow.
NON-CYCLICAL MEANS:
●
●
●
●
Energy flow only in one direction through the ecosystem.
Energy does not flow back/ return to the sun.
Energy is not recycled within the ecosystem.
So energy can neither be created nor destroyed only change from one form to
another (Thermodynamic law).
● but energy changes from one form of energy to another:
Light energy→ chemical energy→ kinetic energy→ heat energy.
Objective: Define the terms food chain, food web, producer, consumer, herbivore,
carnivore, decomposer, ecosystems and trophic levels
Food chain
● Is the flow of energy from one organism to another through the feeding process.
● Energy is passed along a food chain from the plants (producers) to other
organisms (consumers).
● The sequence is shown by the arrow that indicates the direction of energy flow.
The diagram below illustrate various food chains, trophic levels and the organisms
natural ecosytem
FOOD WEB
● Is made up of interlinked food chains involving organisms within the same
ecosystem.
● It shows the feeding relationships between living organisms.
● It shows that most animals have more than onefood source.
● It shows the flow of energy in an ecosystem.
● It also show how food chains can interconnect in a complex way.
FOOD CHAINS AND FOOD WEBS CONSIST OF:
● Producers
● Consumers
● Trophic levels
PRODUCERS
● Organisms that are able to produce their own food through photosynthesis using
light, carbon dioxide and water.
● Referred to as photosynthetic organism.
● They are autotrophic.
Examples:green plants, some protoctists and some bacteria.
CONSUMERS
● Refers to all organisms that directly or indirectlyfeed from the plants.
● They are unable to utilize light energy for the synthesis of food( do not
photosynthesize).
● They obtain energy from plants(producers) or other organisms.
HERBIVORES
● They directly feed on plants (plant eaters).
● They are referred to as primary consumers.
Examples of herbivores are:
Goats, cattle, donkeys, sheep, zebra, mice, giraffe, Oryx, horse etc.
CARNIVORES
● They feed on herbivores.
● They have powerful claws and dentition adapted to tearing flesh, so they hunt
and kill for meat. Referred to as predators.
● They are referred to as secondary, tertiary or quaternary consumers,
depending on the complexity of the food web.
Examples of carnivores are:
Lions, tigers, leopards, cheetahs, eagles etc.
DECOMPOSERS
● They are micro-organisms which break down the dead remains of animals and
plants and feed on them to obtain energy.
● They are saprophytic organism.
● They break down of dead remains release nutrients into the soil that are used by
plants (producers) for growth and to stay healthy.
Example of decomposers:
Fungi and putrifying (decomposition) bacteria.
TROPHIC LEVELS
● Refers to feeding steps or levels, positions occupied by an organism in the food
chain or food web or ecosystem. i.e. organisms obtain energy from another
organism in one level before its level.
● It’s the particular position which an organism occupies in an ecosystem where it
obtains its food.
● Energy is transferred from one tropic level to the next higher trophic level.
● The first and lowest trophic level is occupied by producers where the transfer of
energy starts.
● The 2ndtrophic level consists of primary consumers (herbivores)that feed
directly on the producers.
● The 3rdtrophic level consists of secondary consumers (carnivores).
● The 4th trophic level consists of tertiary consumers (carnivores).
● The 5thtrophic level is the highest consist of quaternary consumers, mostly
scavengers and omnivores.
● Energy is lostfrom one trophic level to the next, therefore not all energy the
producer have is transferred to the consumer and not all energy the consumer
gain is transferred to its prey.
The diagram below illustrate various food chains, trophic levels and the organisms
natural ecosytem
FOOD WEB
▶ Is made up of interlinked food chains involving organisms
within the same ecosystem.
▶ It shows the feeding relationships between living
organisms.
▶ It shows that most animals have more than onefood source.
▶ It shows the flow of energy in an ecosystem.
▶ It also show how food chains can interconnect in a complex
way.
ENERGY LOSSES IN FOOD CHAINS OR FOOD WEDS IN RELATION TO ITS
LENGTH.
● Energy is lost along the way as it’s transferred from one trophic level to the
next.
1
on average only approximately one tenth (10
● ), 10% of energy transferred from one trophic level to the next.
Energy is lost through:
✓ Respiration.
✓ Excretion.
✓ Egestion (defecation).
● As energy is lost from one trophic level to the next it limit the length of the food
chain.
Advantages of short food chain instead of long one:
● If it is long, no or less energy will be left to the highest trophic level.
● Short food chain reduces the amount of energy lost from the ecosystem.
▶ For example primary consumers obtain more energy by feeding directly from the
producers compare to other consumers.
▶ In food webs organisms in the highest trophic levels obtain more energy as they
feed on different sources.
Objective: Describe and interpret pyramids of biomass, numbers and energy.
▶ Food chains and food webs show feeding relationships in a community, but they
do not show how many living organisms are involved.
▶ The trophic levels of any ecosystem can be arranged in a pyramid shape.
So information can be shown in:
✓ Pyramid of numbers.
✓ Pyramid of biomass.
✓ Pyramid of energy.
PYRAMID OF NUMBERS
● The area of each box in the pyramid shows roughly the number of individual
organisms at each trophic level.
● It is a diagrammatic representation of the number of different organismsat
each trophic level in an ecosystem.
● Occur in different shape depending on the ecosystem.
PYRAMID OF BIOMASS
● Biomass is the total mass of an organism.
● So the biomass pyramid shows the actual weight or mass of living things at each
tropic level.
● It is a diagrammatic representation of the biomass of all organisms at each tropic
level in an ecosystem.
● Biomass: number of individual organism of a certain mass of each organism.
● The length of the bars represents relative biomass of organisms.
PYRAMID OF ENERGY
● Is the best way to show the feeding relationships in the community.
● It shows the energy transferred from one trophic level to the next.
● It is a diagrammatic representation of the total energy available at each tropic
level in an ecosystem.
● The length of the bars is drawn in proportion to the total amount energy at each
trophic level.
● The bottom is occupies by producer with more energy.
● Energy is lost through the ecosystem, plant only absorb some (sunlight), plant
use it for growth and repair tissue, respiration, produce heat.
● Therefore only less energy is left for the primary consumers others lost through
other processes.
● And only 1of 10 of the energy gained will be transferred to the next trophic level
again.
● The shorter food chain reduces the amount of energy lost from the ecosystem.
Objective: Explain that there is an increased efficiency in supplying green plants
as human food and that there is relative inefficiency, in terms of energy loss, in
feeding crop plants to animals.
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90% energy is lost at each trophic level.
Only 10% is transferred at each trophic level.
Eating plants involves short food chains i.e. cabbage to human.
Eating animals means longer food chain so more energy is lost i.e. maize-cowhuman.
● Some parts of animals cannot be eaten, so lots of energy stays in the skin,
bones, hooves and horns.
● Therefore more energy can be conserved in short food chain so more food can
be produced. It is therefore more energy efficient to feed directly on plants
(vegetarian diet).
TOPIC: NUTRIENT CYCLES
Objective:Describe the water cycle
1. EVAPORATION
● From the stream, lakes and the sea.
● Water turns into a gas (liquid to gas) from bodies, seas, rivers and soil etc.
Energy from the sun heats large areas of water and warms the air cause wind. So solar
energy and warm wind cause water to evaporate as water vapour
2. TRANSPIRATION
● Is the loss of water as water vapour through the stomata and lenticels of plants.
● Is another process that add water vapour in the atmosphere.
3. RESPIRATION/ PERSPIRATION
● Animals drink water and eat other animals. They then together with plants
release water as water vapour into the atmosphere through evaporation,
breathing or transpiration.
4. CONDENSATION
● Water vapour rises into the cooler atmosphere where it change from gas form to
a liquid because of lower temperature.
● So water vapour changes into water.
● Water turns into small water droplets forming clouds.
5. PRECIPITATION
● Occur when clouds becoming too heavy and water falls to the ground in form of
rain, snow, hail or dew.
6. RUN-OFF
● After precipitation, water on the ground, soil surface flows into rivers, dams, sea
and oceans.
● Some of the surface water sinks into the ground during infiltration forming
undergroundwater.
7. ABSORPTION
● Underground water and surface water are taken up by the plant root through the
process of osmosis and transported to the leaves.
● Animals also drink surface water, used for their own functions and some
evaporates into the atmosphere through breathing and evaporation.
The cycle starts over again….
Objective: describe the carbon cycle
Processes that are involved in the circulation of carbon:
● Photosynthesis.
● Respiration.
● Combustions (burning).
● Decomposition (decay).
1.Photosynthesis
● The process whereby plant remove carbon from the air as carbon dioxide.
● Carbon atoms from carbon dioxide become part of organic compound such as
glucose and starch molecules in plants.
2. Respiration
● In both plants and animals.
● Glucose contains carbon atoms is broken down to produce carbon dioxide and
water.
● Carbondioxide is released into the atmosphere.
3. Combustion
● Some plants become fossil during fossilization to form coal and oil.
● The burning of fossil fuels such as petrol, paraffin, diesel, oil and natural gas,
releases carbon dioxide into the atmosphere.
4. Decomposition
Other processes that release carbon dioxide into the atmosphere from the
breakdown of dead plants and animals by decomposers such as fungi and
putrifying bacteria.
Objective: Discuss the effects of the combustion of fossil fuels and the cutting
down of forests on the balance between oxygen and carbon dioxide.
Effect of fossil fuel combustion and cutting down of trees on oxygen and carbon
dioxide concentration
Deforestation:
Cutting down of trees, reduce the amount of plant material which removes carbon
dioxide from the atmosphere.
Due to burning wood and other fossil fuels more carbon dioxide is released into the air
without enough to remove them. So the level of carbon dioxide in the air increases
causing the earth to become warmer.
● Carbon dioxide forms a blanket that stop heat loss from the surface of the earth
increase global warming.
● So increase in carbon dioxide contributes to: global warming and acid rain.
● All radiation is absorbed by land and oceans and heats up the earth.
● The heat energy is then radiated back, and this causes the atmosphere to
become warmer.
● The heat trapped and cannot escape once it has entered the atmosphere. This is
greenhouse effect.
● Less carbon dioxide available for plant to photosynthesis.
● The amount of oxygen decreases in the atmosphere as carbon, Sulphur, nitrogen
combine with oxygen to form oxide.
Objective: Describe the nitrogen cycle in terms of decomposition by microorganisms; nitrogen fixation in roots; the absorption of these nitrogen
compounds and their conversion to proteins; the role of microorganisms in
decay and the return of nitrogen to the soil or the atmosphere
THE NITROGEN CYCLE
● Nitrogen occurs as a nitrogen gas in the atmosphere, very unreactive and cannot
be used directly by animals and plants.
● It is changed into a more reactive form such as ammonia or nitrates. This
process is called nitrogen fixation
Importance of nitrogen:
● Is an essential component of all protein molecules, the building blocks of all living
organisms.
● Play a role in the synthesis of some compounds such as nucleic acids (DNA and
RNA), chlorophyll and vitamins.
Nitrogen cycle includes the following processes
● Nitrogen fixation by Lightning.
● Nitrogen fixation by Rhizobium bacteria.
● Nitrification.
● Dentrification.
Decomposition or Ammonification
LIGHTNING
● Cause nitrogen gas in the air to combine with oxygen, forming nitrogen oxide.
● The oxides dissolve with rain and washed into the soil, where they form nitrates.
Nitrogen fixation can be fixed in 3 ways:
● Biological fixation.
● Atmospheric fixation.
● Industrial fixation.
Biological fixation
● Nitrogen fixing bacteria(Rhizobium), live in the soil and root nodules of legume
plants such as peas, beans etc.
● Those bacteria convert unreactive nitrogen gas (N 2) into nitrates (N2O).
Atmospheric fixation
● Energy of lightning breaks nitrogen molecules and enables their atoms to
combine with oxygen in the air forming nitrogen oxides.
● Oxide dissolves in rain forming nitric and nitrous acids which combine with other
salts to form nitrate.
Industrial fixation.
● Under higher temperature, atmospheric nitrogen and hydrogen is combined to
form ammonia (NH3).
● Ammonia is then used directly as fertilizer.
● Ammonia is converted to urea and ammonium nitrate.
● So NPK fertilizer added to the soil contain nitrogen in a form of nitrate in the soil.
AMMONIFICATION
● Done by putrifying (ammonifying) bacteria and fungi during decomposition of
dead plants and animals bodies.
● The process of decay release ammonia compound into the soil. Referred to as
ammonification.
● Excretory products of animals contain nitrogenous waste such as ammonia, urea
and uric acid are decomposed to form ammonia and ammonium compounds.
● Faeces and animal manure are also decomposed into ammonia and ammonium
compounds.
NITRIFICATION
● Done by nitrifying bacteria.
● Nitrifying bacteria oxidize ammonia and ammoniumcompounds into nitrites and
then to nitrates.
● Nitrifying bacteria live in the soil and use ammonia and ammonium compounds
as an energy source.
DENITRIFICATION
● Done by denitrifying bacteria.
● Those bacteria obtain energy by breaking down nitrates into nitrogen gas which
escapes back into the atmosphere.
● This process occurs in anaerobic conditions (in absence of oxygen).
● Denitrifying bacteria reduces the level of nitrates in the soil.
● Dentrification reduces soil fertility.
Absorption of nitrogen containing substance and their conversion to protein
● Plant absorbs nitrate ions from the soil.
● They use nitrates to synthesize amino acids which combine during protein
synthesis to produce protein.
● Proteins are essential for plantgrowth, hormones and enzymes.
Define population as a group of organisms of a single species that live in a
given area.
Objective:State the factors affecting the rate of population growth for a range of
living organisms.
Those factors above are limiting factors of the population because they control the size
of the population; either speed up or slow down or reduce the size of the population
Objective:Describe the importance of food supply, predation and disease
(including AIDS) on population size.
FOOD SUPPLY
● Food and water are essential for the animals in a population to survive.
● An increase in number of organism in a population leads to competition for the
same source of food.
● Due to competition stronger and fitter organisms survive and the weaker die of
starvation.
● So the size of the population depends on the amount of food available.
● Lack of food the size of the population decrease.
● Sufficient food supply, the population increase.
Predation
● Size of the population is influenced by predation.
● Predation: referred to the feeding relationship between two organisms.
The more the prey, the predator will increase.
As the predators increase, they require more food so they reduce the number of prey.
● This lead to decrease in food supply to predators so the number of predators
decrease.
● The population keeps on fluctuating.
DISEASES
● As the population size increase, it is easier for disease to be spread from
organism to organism.
● More diseases emerge and spread: -reduce the population numbers.
Example:
Increase in human population: competition of mating pattern arises leading to the
transmission of HIV virus, so people will die of AIDS decreasing the human population.
Size of the ecosystem
● The large the size of an area, the larger the population can grow.
● Small ecosystems have small number of organisms in the population.
● The large area may support large population in terms of food and space and
diseases do not spread that fast compare to the small area.
Objective: Identify the phases of asigmoid curve of population growth resulting
from the action of a limiting factor.
Sigmoid curve of population growth
The growth of a population:
● Is measured as the increase in its size over a period of time.
● Population shows characteristics patterns of growth with time.
Two basic population growth forms:
● J-shape population growth form (Exponential growth curve): occur when there is
no limit to population size.
● S-shape population growth form (Sigmoid growth curve): show the effect of
limiting factor on the population size.
LAG PHASE
● Population just introduced to the environment.
● Population starts with very low number.
● Is the slow growing phase of the population.
● Organisms adapt and acclimatize (adjusting) to the environment.
● Organisms seek out food, mates (breeding partner) breeding area.
Log (Exponential) phase
● Period of rapid rise in population size due to availability of food and no
competition.
● There is absent of predators.
● All conditions are favourable.
● Organisms found breeding partners.
● The birth rate is higher than death rate and emigration.
Stationary phase
● Growth rate become stable.
● The population remains constant because food supply and other resources are
limited.
● The death rate and birth rate become equal.
● Due to increase in population disease spread faster lead to decrease in number
of organisms who can reproduce.
● Predators can hunt more: increase in prey lead to increase in predators.
● Resources become scares as population gets large lead to increase in
competition.
● Maximum population size than an environment can support: reach its carrying
capacity, so the population growth is zero.
● K: is the carrying capacity of the environment.
Objective:Describe the increase in population size in the absence of limiting
factors (human population growth) and the social implications of current human
survival rate).
HUMAN POPULATION GROWTH
● The world population grows daily.
● There are two main reasons for the recent growth:
✓ The reduction of disease.
✓ An increase in food supply or production.
REDUCTION OF DISEASES
Causes the human population to increase because of the following reasons:
● Improvement in water supply.
● Sewage treatment decrease disease like dysentery, cholera and diarrhea etc.
● Hygienic food handling andgeneral standard of cleanliness.
● Immunization against infectious diseasessuch as polio, meningitis, tetanus, and
chicken pox.
● Discovery of antibiotics to treat diseases caused by bacteria such as syphilis,
gonorrhea and TB.
INCREASED FOOD PRODUCTION AND SUPPLY
Increase human population due to the following reasons:
● More land available and brought under cultivation because of modern
machinery and equipment.
● Fertilizers increase crop yield.
● More efficient agriculture due to modern technology.
● Pesticides control disease and pests and fewer crop are being destroyed.
Factors affect human population
● Birth (natality) rate: the rate at which new individuals are added to a population
through reproduction.
● Death (mortality) rate: the rate at which new individuals are lost to a population
through death.
● Immigration:the rate at which new individuals join a population from somewhere
else.
● Emigration:the rate at which new individuals leave a population to go
somewhere else.
Social implication of current human population growth
● Birth rate exceed death rate so the population increase, unless people be
educated on the usage of contraceptives.
● More overcrowding and pollution will occur.
● More unemployment.
● Less land will be available for agriculture.
● Growth in the population has effect on global climate change (global warming).
● Increase in global demand for water for irrigation, household, and industrial use
is higher than supply.
Objective: interpret graphs and diagrams of human population growth.
● Data on human population growth is presented in different ways: such as graphs
and pyramids.
● This is done by counting the population over years or by measuring the
population birth rate and death rate.
● Numbers of individual are then grouped based on gender and age group yielding
population pyramids.
● Therefore the population pyramid is a graphical representation and give
information of the age and gender for a specific country.
● Population pyramids can have:
● A Classic pyramid shape: more young people broader base at bottom and
narrow at top (few old people), mostly developing countries
● A columnar shape: even spread ages, mostly developed countries.
● A stable shape: zero growth or negative population growth with the low level of
immigration, same mortality and natality rate as well as good medical care lead
to high life expectancy.
The shape of the population pyramid conveys more information about a country as it is
influenced by:
● Birth rate and death rate and life expectancy.
● Medical standard of the country.
● Rate of immigration and emigration.
● Educational status.
TOPIC: HUMAN INFLUENCE ON THE ECOSYSTEM
SUB-TOPIC: DAMAGE TO THE ENVIRONMENT AND CONSERVATION
Objective: discuss ways in which the use of modern technology has resulted in
increased food production (using suitable examples)
● food production can be increased by using fertilisers pesticides, machinery and
varieties of plants and animals
Objective: describe the undesirable effects of deforestation
● destruction of habitants
● increase in the level of carbon dioxide in the atmosphere
Objective: describe the overuse and dangers of fertilisers on the land (e.g.
nitrates)
● overuse of fertilisers can cause harm to living organisms in rivers, lakes and
dams and this can lead to eutrophication
Objective:discuss alternatives to the use of large amounts of individually
produced fertilisers
● use manure and other natural fertilisers
● practice crop rotation
Objective: discuss the effects of irrigation
● can supplement rain water, so crops can be grown in dry or low rainfall period
● over irrigation causes soil erosion
● very expensive
Objective:describe the undesirable effects of water pollution by sewage and
chemicals waste (pesticides and herbicides)
● Diseases: sewage discharge into drinking waters e.g. river, diseases may be
transmitted when are person swim or drink, or eat food cooked from
contaminated water. Diseases such as cholera, typhoid and dysentery are
spread in this way
● Eutrophication: untreated sewage causes eutrophication, similar to Nitratecontaining fertilisers problem causes by
● Pesticides: chemicals to kill pests and herbicides are chemical used to kill weeds,
and the concentration of this in the food chain (bio magnifications) can be severe.
e.g. DDT pesticides
Objective: describe air pollution by sulphur dioxide (acid rain) and pollution due
to pesticides and herbicides and nuclear fall-out
● Sulphur is produced whenever coal, gas or oil is burnt.
● Sulphur dioxide is dangerous pollutant of the atmosphere. Very harmful to plants
as it is taken by plant leaves through stomata
● Leaf cells are killed and the leaf may drop off
● Is also brings diseases to people, e.g. colds, bronchitis and asthma
● Nuclear fall-out: contains radioactive materials, which can cause radiation
sickness, mutations and cancer in living things.
Objective: discuss the causes and apparent effects on the environment of acid
rain, and the measures that might be taken to reduce its incidence
● when fossil fuels, such as coal and oil are burnt, sulphur dioxide, carbon dioxide
and nitrogen oxides are released, these gases dissolve in water and form a weak
acid
● Sulphur dioxide reacts with oxygen and water in the atmosphere to form
sulphuric acid
● Nitrogen oxides can also form acid. This happens high in atmosphere before it
falls as acid rain.
● Acid rain falls on forest or lakes, people suffers even from a different country
Effect of acid rain
● Attacks building and statues, especially those made of marble and limestone
● Corrodes metals and causes them to rust
● Reduces the productivity of farm land and forests
Ways to reduce acid rain
● Car to be fitted with catalytic converters
● Reduce the burning of fossil fuels
Objective: Assess the significance of non-biodegradable plastics and other
materials used in the manufacturing industry
● Non –biodegradable are substances that cannot be broken down by bacteria.
E.g. Plastic and can cause severe damage to the environment
SUB – TOPIC: CONSERVATION
Define conservation as maintaining the environment and natural resources in a
state that maintains biodiversity
Note: Conversation means all of the following:
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taking care of our environment
trying not to damage the environment
not destroying the habitants of animals
protecting wildlife
Objective:describe the need for conservation of species and their habitats and of
natural resources
● Habitats should be conserved because the destruction of habitats means
destruction of species. It is the fault of humans that some species are extinct and
it is the responsibility of humans to ensure the survival of endangered species
Objective:discuss the advantages and disadvantages of tourism for conservation
Advantages of tourism for conservation
● brings foreign currency
● creates employment
● government earns revenue from tourist who pay taxes and visa fees
Disadvantaged of tourist for conversation
● damage to some species and habitats by road networks, vehicle and camping
● noise and human movement can disturb wildlife
● pollution by non-biodegradable materials and chemicals may have undesirable
effects on wildlife
● criminals may take advantage of tourist and rob them
● illegal immigration, goods smuggling and drug trafficking may increase
Objective: describe the principle of recycling materials, including sewage (water),
plastic and paper
Principles of recycling water
● recycling materials such as paper and sewage , can help to conserve natural
resources
● water and raw sewage go into the sewage collecting and pumping area
● sewage inlet takes it to the screening area so that large, solid rubbish and
objects can be removed
● rest of the sewage then goes to the grit removal area where the grit is removed
and used as landfill
● sewage then goes to the primary sedimentation tanks where solid matter forms
sludge, which is allowed to settle and is then separated from the liquid effluent
● sludge is digested by anaerobic bacteria in the anaerobic digester
● this produces methane which can be burnt as a power source for the sewage
plant and the solid matter can be dried and used as garden fertilisers
● Liquid effluent is sprayed onto stones where aerobic bacteria and Protoctista
feed on it and remove harmful substances.
● This aerobic stage kills anaerobic bacteria
● Clear effluent is produced which can be pimped into a river, or withdrawn to be
purified and disinfected by chlorination to be used again as drinking water
Principles of recycling plastic
● Collection of used plastic is the first step
● Plastic waste is sorted according to different types
● Pre-treatment: After sorting process, different types of plastic are separately
shredded and washed, to remove contaminant substances such as paper labels,
glue and other residues.
● A process called agglomeration is used during the pre-treatment stage. It
consists of heating the plastic at just below its melting point to reduce size,
before cutting it into small pieces
● Extrusion is a process to treat the plastic pieces with heat.
● Plastic granules are melted
● Melted plastic is cooled in a water bath and is later turned into pellets, which are
easier to use when making new products
Principles of recycling paper
● Collection of used paper and cardboard boxes is the first is the first step
● Once the paper is collected, it is taken to the recycling plant where the waste
paper is sorted and separated into types and grades
● Then it is sent through a baler, which forms the material into easily transportable
bales
● Recovered paper bales are then delivered to ta paper mill
● At the mill, the paper is soaked to form a pulp
● In this process, large amounts of water is added to the waste paper to produce
pulp which is then passed through a series of screens to remove contaminants,
like staples, plastic film and glue
● Pulp is filtered again to remove impurities such as coatings, fillers and loose ink
particles
● Finally, ink is removed using chemicals and air bubbles
● At this point, chemical brighteners and decolourisers may be added
● The paper is then left to dry and is rolled up to be sent to factories or shops
● Whole recycling process for a newspaper takes around seven days