GCSE Biology Revision

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GCSE Biology Revision

• 2006-2007

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Life Processes

• Movement
• Respiration
• Sensitivity
• Growth
• Reproduction
• Excretion
• Nutrition

Mrs Gren or many naughty rabbits eat green
rhubarb stems
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Plant and Animal Cells
(cellulose)
mitochondria
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Cell specialisation
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Cell organisation
system
organism
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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

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Digestion
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Balanced Diets

• Carbohydrates
• Protein
• Lipids / Fats
• Vitamins
• Minerals
• Fibre
• Water

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The Duodenum
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The Ileum
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Absorption and Assimilation
Glucose and amino acids are absorbed into the
blood Fatty acids and glycerol are absorbed into
the lacteal
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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.

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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

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Aerobic Respiration

• With oxygen
• C6H12O6 6O2 6H2O 6CO2 energy

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Anaerobic Respiration

• Animals
• Glucose Lactic acid
• Plants
• Glucose Ethanol and carbon dioxide
• Oxygen debt the amount of oxygen needed to
  breakdown the lactic accumulated

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Structure of Thorax
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The Thorax
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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.

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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.

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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

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of different gases in inhaled and exhaled air
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Gaseous exchange
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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

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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

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Effects of Smoking

• Tar causes cancer
• Nicotine is addictive
• Smoking removes the hairs that keep the lungs
  clean

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Photosynthesis

• lightcarbon dioxidewater
  glucoseoxygen chlorophyll
• 6H2O 6CO2 C6H12O6
  6O2

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Leaf Structure
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• 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.

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Stomata
Guard cells
stoma
Water moves into the guard cells by osmosis and
the stoma opens
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Day
During the daytime the rate of photosynthesis is
greater than the rate of respiration
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Night
During both the day and night respiration occurs
in plants.
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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.

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• 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.

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• If you plot the rate of photosynthesis against
  the levels of these three limiting factors you
  get graphs like the ones below.

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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.

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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

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Mineral Requirements
Magnesium for chlorophyll Nitrogen for
growth Phosphorus for cell membranes and DNA
Remember how to test leaves for starch
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The Heart
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The Heart

• Pumps blood around the body
• Pumps blood to the lungs
• To pick up oxygen
• Remove carbon dioxide

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Double Circulation
Heart Lungs Heart Body Heart
Greater pressure, better oxygenation, faster flow
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Arteries Veins and Capillaries
Thin walls, deoxygenated blood, to the heart,
valves
Thick walls, oxygenated blood, away from heart
Link arteries to veins, site of exchange of
metabolites and waste
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Blood
Red blood cells, transport oxygen, biconcave, no
nucleus,
White blood cells, defence, engulf bacteria,
produce antibodies
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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

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Blood Cells
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Tissue exchange
Glucose
Waste
PLASMA
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The lymphatic system

• Transports excess fluid from the tissues
• Transports digested fat
• Contains white blood cells that fight infection

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William Harvey

• 1578-1657
• Observed blood flow around the body
• Noticed existence of valves in veins
• Concluded blood pumped via veins round body
• Major medical breakthrough!

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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

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Transport in Plants
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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.
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• Xylem consists of dead cells with no end walls,
  which contain lignin to form stiff tubes. They
  are impermeable.

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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.
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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.
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Transpiration

• Temperature
• Humidity
• Air movement
• Light

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Ecology Competition and Adaptation
Keeping cool
Keeping warm
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Plant adaptations
Not being eaten Reducing water loss
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Predators, Prey and Co-operation
Snowshoe hare
Arctic fox
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Food Chains
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Woodland Food Web
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Pyramid of Numbers
Remember not always pyramid shape
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Pyramid of biomass
fox
rabbit
grass
Biomass is dry weight water has been removed
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Decomposition
Decomposers are bacteria and fungi
Organic matter- ammonium compounds-nitrite-nitrate
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The Carbon Cycle
Plants and animals die and decay
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Nitrogen Cycle
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Food Production and farming methods

• Monoculture
• Hedgerow removal
• Biological pest control
• Pesticides and herbicides and insecticides

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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

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Global Warming and Acid Rain
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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
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The Nervous System
Stimulus
Response
Receptor
Effector
Sensory Neuron
Motor neuron
Central nervous system
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Motor neuron
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The Eye
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Accommodation
Long distance lens long and thin, ciliary
muscle relaxed, suspensory ligaments taut Near
lens short and fat ciliary muscle contacted,
suspensory ligaments loose
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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
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The CNS and Reflex Actions
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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

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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.

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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

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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

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Plant responses and Auxins
Hormone rooting powder causes roots to grow from
cut stems Seedless fruits grapes, cucumbers,
bananas. (parthenocarpy) Selective weedkillers
2-4-D causes weeds to grow too fast and results
in death, grass doesnt take it up well
Q 3,4,5 page 102 for Wednesday
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Homeostasis

• Temperature Control
• Water Control
• Salt Balance
• Sugar control
• Carbon Dioxide Control
• Urea

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Temperature Control

• Thermoregulation keeps the body at constant
  temperature (37oC).
• Enzymes work best.
• Temperature is regulated by the hypothalamus.

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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.

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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.

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Keeping Warm

• Vasoconstriction - less blood flows to the skins
  surface, keeping heat in. You may look pale!!
• Decrease in sweat.
• Shivering generates heat (respiration).
• Hairs stand up and trap insulating air.

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Carbon dioxide

• Excess carbon dioxide results in a drop in the
  bodys pH (acidic).
• Breathing out removes this excess.
• The rate and depth of breathing will alter to
  suit the amount of CO2.

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The Kidney
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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 !!

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The kidney
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• 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

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Kidneys how they work
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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.

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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

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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.

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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.

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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!!

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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.

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Cell Division - Mitosis
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DNA
DNA structure discovered by Crick and Watson
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Genetic and Environmental causes of Variation

• Variation is inherited
• Genetic skin colour
• Environmental hair length
• Both height, weight, intelligence

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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

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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

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Harmful mutations

• Downs 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

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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

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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

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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
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Genetic Crosses
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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

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Darwin

• Evidence for evolution
• Fossils
• Homologous structures bats wing, forearm,
  horses leg.

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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