GCSE Biology Revision
2006-2007
Life Processes
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Movement
Respiration
Sensitivity
Growth
Reproduction
Excretion
Nutrition
Mrs Gren – or –many
naughty rabbits eat green
rhubarb stems
Plant and Animal Cells
(cellulose)
mitochondria
Cell specialisation
Cell organisation
system
organism
Transport In and Out of Cells
• Diffusion – from a high to a low
concentration until they are evenly spread
• Osmosis – from a region of high water
concentration to a region of low (weak to a
strong solution) through a semi permeable
membrane
• Active transport – from a low to a high
concentration across a cell membrane
Digestion
Balanced Diets
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Carbohydrates
Protein
Lipids / Fats
Vitamins
Minerals
Fibre
Water
The Duodenum
Amylase
Starch
Protease
Proteins
Amino acids
and
polypeptide
s
Fats
Fatty acids
and
Glycerol
Lipase
Maltose
The Ileum
Maltase
Maltose
Glucose
Sucrase
Sucrose
Lactase
Lactose
Peptidase
Polypeptides
Glucose and
Fructose
Glucose and
Galactose
Amino acids
Lipase
Fat
Fatty acids and
Glycerol
Absorption and Assimilation
Glucose and amino
acids are absorbed
into the blood
Fatty acids and
glycerol are
absorbed into the
lacteal
Assimilation
• All digested glucose and amino acids pass
into the liver in the Hepatic Portal Vein.
• Fats enter the lymphatic system which
enters the blood and returns them to the
liver.
• The food is used for growth, repair,
respiration.
• Excess food is mostly stored as fat.
Food Testing
• Starch – add iodine – turns black
• Glucose or reducing sugar – add
Benedict's solution and boil – turns brick
red
• Protein – Biuret test – add NaOH or KOH
and then 1% copper sulphate – a violet
colouration
Aerobic Respiration
• With oxygen
• C6H12O6 + 6O2
6H2O + 6CO2 + energy
Anaerobic Respiration
• Animals
Glucose
• Plants
Glucose
Lactic acid
Ethanol and carbon dioxide
Oxygen debt – the amount of oxygen
needed to breakdown the lactic acid
accumulated
Structure of Thorax
The Thorax
Breathing in
• Is controlled by the intercostal muscles
and the diaphragm.
• When we breathe in the intercostal
muscles contract and the ribs move up
and out. The diaphragm contracts and
moves down.
• This increases the space inside the chest
and air rushes into the lungs.
Breathing out
• The intercostal muscles and the
diaphragm relax.
• The ribcage drops down and the
diaphragm moves upwards.
• This reduces the space inside the chest
and pushes air out of the lungs.
Breathing Rate and Depth
• Rate - how many breaths per minute
• Depth – how much air is being taken in,
normally ½ litre per breath
• Measured with a spirometer
% of different gases in inhaled and
exhaled air
Gas
Inhaled air
(%)
Exhaled
air (%)
Oxygen
20
16
Carbon
dioxide
0.04
4
Nitrogen
79
79
Water
vapour
Variable
level
100%
saturated
Gaseous exchange
What makes the lung good at
gaseous exchange?
• Large surface area – greater volume of
gases exchanged
• Good blood supply – O2 and CO2
exchanged more quickly
• Thin membranes – allows diffusion
• Moist lining – for the gases to dissolve
Keeping the Lungs Clean
• Dust, bacteria and other particles stick to
the mucus secreted by cells lining the
airways
• Cilia attached to these cells waft the
mucus and dirt out of the lungs and it is
swallowed.
• Acid in the stomach kills the bacteria
Effects of Smoking
•Tar causes
cancer
•Nicotine is
addictive
•Smoking
removes the hairs
that keep the
lungs clean
Photosynthesis
light
carbon dioxide+water
glucose+oxygen
chlorophyll
6H2O + 6CO2
C6H12O6 + 6O2
Leaf Structure
• The leaf has a waxy cuticle to stop it losing
water.
• The epidermis is a protective layer of cells and
contains no chloroplasts.
• The palisade layer contains the most
chloroplasts as it is near the top of the leaf. The
chloroplasts contain the pigment chlorophyll. It is
here that photosynthesis takes place.
• The palisade cells are arranged upright. This
means the light has to pass through the cell
lengthways and so increases the amount of light
absorbed.
Stomata
Guard
cells
Water moves into
the guard cells by
osmosis and the
stoma opens
stoma
Day
During the daytime the rate of photosynthesis is greater
than the rate of respiration
Night
During both the day and night respiration occurs in plants.
Limiting Factors
• Photosynthesis is a chemical reaction, its
rate depends upon temperature, how
much CO2 is available, light intensity,
amount of chlorophyll or water.
• Without enough light a plant cannot
photosynthesise very fast, even if there is
plenty of water and carbon dioxide.
Increasing the light intensity will make
photosynthesis faster.
• Sometimes photosynthesis is limited by the
level of carbon dioxide. Even if there is
plenty of light a plant cannot
photosynthesise if it has run out of carbon
dioxide.
• Temperature can be a limiting factor too. If
it gets too cold the rate of photosynthesis
will slow right down; equally, plants cease to
be able to photosynthesise if it gets too hot.
• If you plot the rate of photosynthesis against
the levels of these three limiting factors you get
graphs like the ones below.
Maximising growth
• Understanding the factors that limit photosynthesis
enables greenhouse farmers to maximise the
conditions for plant growth. They often use paraffin
lamps inside the greenhouse because burning
paraffin produces carbon dioxide as well as heat,
and so makes photosynthesis proceed faster.
They may also use artificial light to enable
photosynthesis to continue beyond daylight hours.
Uses of Glucose
• Turned into starch for storage
• Converted into lipid/fat for storage –
energy rich
• Nitrogen can be added and turned into
protein
• Stored in fruit
• Used in respiration
Mineral Requirements
Magnesium for
chlorophyll
Nitrogen for growth
Phosphorus for cell
membranes and DNA
Remember how to test leaves for starch
The Heart
The Heart
• Pumps blood
around the body
• Pumps blood to the
lungs
• To pick up oxygen
• Remove carbon
dioxide
Double Circulation
Heart
Lungs
Greater
pressure,
Heart
better
oxygenation,
Body
faster flow
Heart
Arteries Veins and Capillaries
Thick walls,
oxygenated blood,
away from heart
Thin walls, deoxygenated
blood, to the heart, valves
Link arteries to veins,
site of exchange of
metabolites and waste
Blood
Red blood cells,
transport
oxygen,
biconcave, no
nucleus,
White blood cells,
defence, engulf
bacteria, produce
antibodies
Platelets
• Used in the clotting of blood
• Damage cause them to clump and they
begin the conversion of soluble fibrinogen
(blood protein) into insoluble fibrin which
meshes over the wound and traps red
cells. They dry and form a scab
Blood Cells
Tissue exchange
Glucose
Waste
PLASMA
The lymphatic system
• Transports excess fluid from the tissues
• Transports digested fat
• Contains white blood cells that fight
infection
William Harvey
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1578-1657
Observed blood flow around the body
Noticed existence of valves in veins
Concluded blood pumped via veins round
body
• Major medical breakthrough!
Galen
• Lived 1,000 years before Harvey
• Did not use the scientific method
– Observation and experimentation
• Thought blood went from side to side
• Did not realise transport existed round
body through capillaries
Transport in Plants
The Plant Transport System
A plant's transport system is made up of two types
of tubes - strong, thick pipes called xylem
vessels, and thinner tubes called phloem
vessels. The cells of these vessels are modified to
make them suited to performing their special
functions
Together xylem and phloem form the vascular
tissue, often also referred to as the vascular
bundle.
Xylem consists of
dead cells with no
end walls, which
contain lignin to
form stiff tubes.
They are
impermeable.
Phloem consists of
living cells lined with
cytoplasm, with walls
made of cellulose
and perforated end
walls. They are
permeable, and are
surrounded by
companion cells.
Water is taken up the plant from the roots to the leaves (for
photosynthesis and transpiration) - in xylem vessels .
Minerals dissolved in the water are taken up the plant to the shoots
and leaves - in xylem vessels.
Food (the product of photosynthesis) is taken from the leaves and
moved up and down the plant to any part which needs it (for growth
or for storage) - in phloem vessels.
Transpiration
•Temperature
•Humidity
•Air movement
•Light
Ecology – Competition and
Adaptation
Keeping warm
Keeping cool
Plant adaptations
Not being eaten
Reducing water
loss
Predators, Prey and Co-operation
Snowshoe hare
Arctic fox
Food Chains
Woodland Food Web
Pyramid of Numbers
Remember not
always pyramid
shape
Pyramid of biomass
fox
rabbit
grass
Biomass is dry weight – water has
been removed
Decomposition
Decomposers
are bacteria and
fungi
Organic matter- ammonium compoundsnitrite-nitrate
The Carbon Cycle
Plants and animals die and
decay
Nitrogen Cycle
Food Production and farming
methods
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Monoculture
Hedgerow removal
Biological pest control
Pesticides and herbicides and insecticides
Energy and Waste
• Burning fossil fuels such as coal, oil or gas
• Greenhouse effect
• Sulphur dioxide and nitrous oxides are
formed which dissolve in water to form
acid rain
• Reduce the demand for energy so it
reaches a sustainable level- will not use
up the resources or pollute the planet
Global Warming and Acid Rain
Conservation
To prevent habitats and
organisms from
disappearing
Limit or ban hunting. Gene banks of frozen eggs,
sperm or embryos. Zoos and captive breeding
programmes. Preserve habitats
The Nervous System
Stimulus
Response
Receptor
Effector
Sensory
Neuron
Motor neuron
Central
nervous
system
Motor neuron
The Eye
Accommodation
Long distance – lens
long and thin, ciliary
muscle relaxed,
suspensory ligaments
taut
Near – lens short and
fat ciliary muscle
contacted, suspensory
ligaments loose
Nerves Synapses and Drugs
Some drugs stimulate synapses
like a neurotransmitter, LSD
and nicotine
Others block the enzyme that
normally breaks down the
neurotransmitter
Alcohol depresses synaptic
activity in the brain and acts as
a depressant. So do solvents
The CNS and Reflex Actions
Hormones
• Proteins that are chemical messengers in
the body
• Carried in the blood to target cells
• Response is slower
• May last for hours
• Can stimulate more than one target
Controlling glucose,
• After eating a lot of carbohydrate blood sugar
level rises.
• Islets of Langerhans in the pancreas release
insulin, the glucose is stored as glycogen in the
liver.
• The blood sugar level drops .
• When blood sugar levels are low the insulin
production stops.
• Glucagon is produced by the pancreas allowing
glucose release from the liver and muscles.
Uses of Hormones
• Controlling fertility – the contraceptive pill,
may contain oestrogen and progesterone
and controls the release of pituitary
hormones and ovulation
• Mini pill, progesterone allows ovulation but
makes the vagina and uterus unsuitable
for sperm
• Anabolic steroids build muscle – reduce
the production of testosterone
Uses of plant hormones
• Auxins allow plants to respond to the
environment – tropic responses
• Auxin (IAA) causes • They stimulate shoots to grow rapidly
• Stops side shoots growing
• Stimulates growth of roots from the base
of stems or leaves
• Auxin from seeds cause fruit to swell
Plant responses and Auxins
Hormone rooting powder causes
roots to grow from cut stems
Seedless fruits –grapes,
cucumbers, bananas.
(parthenocarpy)
Q 3,4,5 page
102 for
Wednesday
Selective weedkillers 2-4-D
causes weeds to grow too fast and
results in death, grass doesn’t take
it up well
Homeostasis
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Temperature Control
Water Control
Salt Balance
Sugar control
Carbon Dioxide Control
Urea
Temperature Control
•Thermoregulation
keeps the body at
constant temperature
(37oC).
•Enzymes work best.
•Temperature is
regulated by the
hypothalamus.
Temperature Control
•Heat is made in most
cells but in particular
muscle and liver.
•Heat is lost by
convection, conduction
and radiation.
•Evaporation of water
from a surface removes
heat.
Keeping Cool
•Vasodilation, more
blood flows nearer the
skin and heat is lost.
•Sweating, evaporation
causes heat loss.
•Hairs lie flat allowing
more heat out.
Keeping Warm
•Vasoconstriction - less
blood flows to the skin’s
surface, keeping heat
in. You may look pale!!
•Decrease in sweat.
•Shivering generates
heat (respiration).
•Hairs stand up and trap
insulating air.
Carbon dioxide
• Excess carbon dioxide results in a drop in
the body’s pH (acidic).
• Breathing out removes this excess.
• The rate and depth of breathing will alter
to suit the amount of CO2.
The Kidney
Urea
• Urea is produced when proteins and
amino acids are broken down in the liver.
• It is poisonous.
• The kidneys remove it but so does
sweating !!
The kidney
The kidneys have four functions:
• Regulation of blood water levels
• Reabsorption of useful substances into
the blood
• Adjustment of the levels of salts and
ions in the blood
• Excretion of urea and other metabolic
wastes
Kidneys: how they work
Kidney transplant
• This is when the diseased kidney is
surgically removed and replaced by a fully
functioning kidney from a deceased or a
live donor.
• It is only possible after a satisfactory
tissue-match. Even after a successful
tissue-match the recipient's immune
system has to be drugged or suppressed
to stop it from rejecting the new kidney.
Kidney failure
• In the event of kidney failure due to infection or
disease, the kidney can no longer remove
metabolic waste products from the body.
Excretion of metabolic waste is a vital function
and their accumulation will result in eventual
death.
• There are two solutions to the problem of kidney
malfunction or failure:
• Kidney transplant
• Kidney dialysis
Kidney dialysis
• In the absence of a suitable donor kidney, the
alternative solution is for the patient to be
hooked-up to a dialysis machine every 2 - 3
days.
• A dialysis machine mimics the functioning of the
kidney. Blood from an artery in the patient's arm
is pumped into the kidney machine which
removes urea and excess salts from it.
• The blood is checked for air bubbles before
being returned to a vein in the arm.
Osmoregulation
•Is keeping the water
and salt levels constant
in the blood.
•They are regulated by
the hypothalamus.
•Water moves into the
cells by osmosis and
could cause them to
burst.
Blood concentration too high
•The hypothalamus
senses too little water in
the blood.
•A message is sent to
the pituitary gland to
release anti-diuretic
hormone.
•This stops the kidneys
removing water and
going to the loo!!
Blood concentration too low.
•Too much water in the blood stops the
hypothalamus signalling the pituitary.
•Water is removed by the kidneys.
•Large amounts of dilute urine produced.
Cell Division - Mitosis
DNA
DNA structure
discovered by
Crick and
Watson
Genetic and Environmental causes
of Variation
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Variation is inherited
Genetic – skin colour
Environmental – hair length
Both – height, weight, intelligence
Asexual reproduction
• Produces identical copies called clones –
onions, strawberries, potatoes, greenfly
• This type of cell division is mitosis
• Cuttings and grafting in plants
• Micropropogation used by growers
Mutations
• Change in the DNA of an organism
caused by an error when it is copied
• Radiation and certain chemicals such as
cigarette smoke can cause mutations
• Most are harmful and leads to illness or
death
• Useful ones are rare but have a dramatic
impact on a species and its evolution
Harmful mutations
• Down’s syndrome – an extra chromosome
number 21
• Cystic fibrosis is caused by a mutation in
the DNA. It is a recessive allele which
affects 1 in 2000 children.
• It causes sticky mucus which blocks the
lungs and pancreas
Genetic Engineering
• Is the ability to alter DNA
• A gene from one organism can be
transferred into the DNA of a completely
different organism
• In some cases the all the DNA is removed
from a cell and replaced with the DNA
from another organism
• Dolly the sheep was the first example of
genetic cloning
Selective Breeding
• In animals – dogs, cows, sheep, cats and
so on. To produce certain traits
• In plants for taste, texture, shelf life
• Is done by choosing parents with the
required traits. These are then bred to
produce offspring.
• Sexual reproduction will ensure variation
Mendel
Studied peas and
concluded that
characteristics were
passed on from one
generation to another.
Law of segregation – the 2 alleles separate when
gametes are formed, one allele into one gamete
and the other into another
Law of independent assortment – any gamete of
the father can fertilise any gamete of the mother
Genetic Crosses
Evolution
• Most organisms overproduce
• Population numbers remain constant
• Sexual reproduction ensures that all
offspring exhibit variation
• These variations are inherited from the
parents
• From these Darwin produced his theory of
evolution
Darwin
Evidence for evolution
•Fossils
•Homologous structures –
bat’s wing, forearm, horse’s
leg.
New Species – Survival of the
Fittest
• The peppered moth
• Pale ones no longer camouflaged during
the Industrial Revolution – were no longer
camouflaged
• Darker ones survived to reproduce and
some of their offspring were even darker
• This is survival of the fittest