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B1 Revision

Diet and metabolic rate
Carbohydrates release energy
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Protein is needs for growth, cell repair and cell replacement
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Small amounts of vitamins mineral ions are needed to keep blood, bones, skin healthy
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These reactions are
called your metabolism
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Different people have different metabolic rates
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Bigger people need more energy than a smaller person because they need more energy as
they have more cells
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Regular exercise increases the metabolic rate of a person as it creates more muscle
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Factors affecting health
People who don’t have the right amount of nutrients are called malnourished
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A poor diet and lack of exercise can also lead to obesity
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Too much salt can lead to high blood pressure and heart problems
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A lack of Vitamin C can cause scurvy which is a problem with skin, joints and gums
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Exercise increase the amount of energy used by the body, therefore it isn’t stored as fat
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Your health can be affected by inherited factors as well
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Cholesterol is a fatty substance which is needed for good health
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Evaluating slimming chains
Questions to ask:
Is the report a scientific study?
Was it written by a qualified person (not associated with the company)?
Have there been other studies with similar results?
To lose weight, you need to just take in less energy than you use
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Bacteria cause you to feel ill because they produce toxins and damage your cells
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They replicate themselves by invading your cells and using the cells’ machinery to produce
duplicates of themselves
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The damage done to cells is what makes you feel ill
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To prevent microorganisms getting in through cuts, the skin seals the wounds by clotting the
blood
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❖Producing antibodies
Every foreign cell has unique molecules on its surface (Antigens)
When the white blood cells find these antigens, they start producing proteins called antibodies
to lock on and kill the invading cells
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If the person is infected again with he same pathogen, the white blood cells will rapidly produce
the antibodies to kill it, this person is now naturally immune to that pathogen
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Vaccinations
A vaccine contains a small amount of the microorganism which are either dead or inactive
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This then causes your body to produce antibodies to attack the antigens
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Some vaccinations wear off over time, therefore people need to get the vaccine again
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Epidemics can be prevented if large numbers of people are vaccinated
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Against vaccinations:
Vaccines don’t always work
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Antibiotics are different though
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Different antibiotics ill different bacterium, therefore the right one must be used
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This is because viruses are located within body
cells, therefore it is difficult to find medicines to cure these viruses because body cells would be
affected
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When an infection is treated, only the non-resistant strains of the bacteria would be killed
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The resistant bacteria could cause a serious infection that it currently not treatable by any
antibiotics
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To slow down the rate of resistant bacteria developing, doctors must ensure that they don’t
overprescribe antibiotics
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Microorganisms are grown in agar jelly which contains the proteins, carbohydrates, minerals and
vitamins that the microbes need
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Paper discs are soaked into the different types of antibiotics and then paced on the agar jelly
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The Petri dish has to be closed with a lid so microorganisms from the air don’t get in
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The inoculating loops are sterilised be putting it through a flame
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Semmelweis was a doctor who worked in Vienna general hospital during the 1840s
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He told doctors to use antiseptic solutions, this cut death rated from 12% to 2%
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Therefore, Semmelweis was unable to explain why his method worked
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All 5 sense organs contain different receptors
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Stimulus
Receptor
Sensory neurone
Relay neurone
Motor neuron
Effector
Response
Example:
Receptors in skin detect stimulus
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Relay neurons send impulses to the motor neurons
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The effector causes the reaction
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The electrical impulses diffuse through the synapse to get to the other neuron
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They can reduce the risk of getting injured
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Reflex arc
The neurons in reflex arcs go through the spinal cord
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Hormones
Hormones are chemical messages sent in the blood
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Hormones control things in organs and cells that need constant adjustment
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They have quite long lasting affects
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Nerves:
Very fast message
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Act on a precise areas
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Act for a long time
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Menstrual cycle
The definition is the monthly release of an egg from a women’s ovaries and the
build up/breakdown of the protective lining in the uterus (womb)
Stage 1
Day 1
Bleeding begins
Lining of uterus breaks down for about 4 days
Stage 2
Day 4-14
Lining of uterus build up into thick spongy layer full of blood vessels reedy to receive fertilised
egg
Stage 3
Day 14
An egg is developed and then released from the ovary
Stage 4
Day 14-28
Wall is maintained, if no fertilised egg comes to the uterus, the spongy lining starts to break
down again and the cycle begins again
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FSH
Produced by pituitary gland
Causes an egg to mature in one of the ovaries
Stimulates the ovaries to produce oestrogen
Oestrogen
Produced in the ovaries
Causes pituitary to produce LH
Inhibits the further release of FSH
LH
Produces by pituitary gland
Stimulates the growth of an egg at around the middle of the cycle
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Naturally, oestrogen helps stimulate the release of eggs, but if it is taken daily, it stops the
production of FSH, after while, egg development and production are stopped
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The pill is an oral contraceptive
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A common side affect of this was blood clots
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Pros:
Cons:
99% effective
Not 100% effective, can lead to pregnancy
Reduces risk of some cancers
Side affects: Headaches, nausea
Doesn’t prevent STDs
Some females have very low levels of FSH, therefore their eggs cannot mature
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Pros:
Cons:
Helps women to get pregnant
Expensive – Doesn't always work
Too many eggs could be stimulated, could lead
to multiple births

Controlling fertility continued
IVF:
Collect eggs from ovaries and mix with sperm in a lab
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Once the embryos are tiny balls of cells, 1 or 2 of them are put in the womb
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Pros:
Can give infertile couple children
Cons:
Some women have strong reaction to hormones eg Abdominal pain, vomiting
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Multiple births can happen if more than one embryo grows into a baby
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Expensive

Plant hormones
Auxin is a plant hormone that controls growth near the tips of shoots and roots
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Auxin is produced in the tips and moves backwards to stimulate the enlargement process which
occurs in the cells just behind the tips
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Shoots grow towards light
When a shoot tip is exposed to light, more auxin accumalates on the side that’s in the shade
than the side that’s in the light
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Shoots grow away from gravity
When a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip,
with more Auxin on the lower side
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Roots grow towards gravity
A root growing sideways will have more auxin on its lower side
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This means the cells on top grow faster and
roots bend downwards
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This stops the growth on that the side, causing the root to bend in the direction of the moisture
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Selective weed killers are made of plant growth hormones – they only affect the broad
leaved plants
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If you add rooting powder, which contains the plant
hormone auxin, they will produce roots rapidly and start growing new plants
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Homeostasis
It is al the functions you body carries out to maintain a internal environment
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If the food contains too much of any ion, the excess needs to be removed
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The kidneys remove the res of he excess ions from the blood, which then leaves in the urine
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The normal metabolism of cells removes glucose from the blood
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A hormone called insulin helps to maintain the right levels of glucose in your blood, so your cells
get a constant supply of energy

Homeostasis continued
Water is lost from the body in various ways:
Through the skin as sweat
Via the lungs through breathing
Via the kidneys as urine
On a cold day or when you are not doing exercise, you do not sweat much
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On a hot day or when you are doing lots of exercise, you sweat a lot
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Body temperature is controlled by the brain
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Therefore, your body tries to
maintain this temperature
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It receives messages from the skin which provide
information about the temperature
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Medicinal drugs are used for medical purposes
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Recreational drugs are used for fun
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Performance enhancing drugs improves someone's performance during sporting activities
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There are various types eg: Anabolic – Increase muscle, Stimulants – Increase heart rate
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For using PED:
Athletes have the right to make their own decision whether its worth risking
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It makes it fairer
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Health risks may not be known
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There is evidence which shows that they lower blood cholesterol and reduce risk of heart
disease in diabetic people
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One was given Statins whilst the other wasn't
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Cannabis
It is an illegal drug
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Drug testing
There are 3 main stages
Stage 1:
Drugs are tested on human cells and tissues in a lab
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This is to find out if the drug works and how harmful it is and which dosage should be used
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First, the drug is tested on healthy volunteers
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If the results from the test on the healthy volunteers are good, the drugs are then tested on
people with the illness
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The group of sufferers are put into two groups
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The other group is given a placebo
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The trial is called a double blind trial whereby the patients will not know which one they are
getting and the doctor will not know which patient is getting the new drug
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However, research conducted
later showed that Thalidomide was effective in reducing morning sickness in pregnant women
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Recently, Thalidomide has been used to treat people with leprosy
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The illegal drugs are usually classes as either hard or soft
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Why do people use recreational drugs?
Enjoyable, stress reliever
Cannabis is seen as a gateway drug because most users of heroin and ecstasy first used
cannabis
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Nicotine is the drug found it cigarettes which is extremely addictive
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It can lead to impaired judgement, poor coordination and unconsciousness
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Adaptations
Desert animals:
Large surface to volume ratio to lose more body in order to stay cool
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Don’t sweat much to reduce water loss
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Desert plants:
Cacti has spines instead of leaves to reduce water loss
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Extensive root system to reduce water loss
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Thick layer of fur to keep warm
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Plant and animal adaptations to deter predators:
Some plants and animals have some sort of armour (Eg tortoise has a shell)
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Some have warning colours (Eg wasps)
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Salty lakes
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No/Little light on sea bed
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This would happen if the number of prey decreased
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This would happen if the number of prey increased
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Measuring environmental change
Some living indicators can be used to measure environmental change:
Air pollution can be measured by looking at the number of lichen
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The more lichen there is, the better the air quality
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Mayfly larvae are very sensitive to the oxygen levels
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Satellites are used to measure the temperature of the sea surface and the amount of snow and
ice coverage in the arctic and Antarctica
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Rainfall is measured using rain gauges to find out the average rainfall
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Biomass is lost at each trophic level through various things including:
Faeces
Respiration
Movement
Maintaining body temperature
Some of the material is inedible (Eg bones)

Decay
Microorganisms work best in warm and moist conditions
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The process of decay allows nutrients to be put back into the soil which provides plants and
trees with the nutrients needed for photosynthesis
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Plants release some carbon back into the atmosphere during respiration
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When microorganisms decay animal and plant remains, they release carbon when they respire
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Variation
There are two types of variation, environmental and genetic
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Genes are passes through the gametes which the offspring develop from
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The offspring of most animals and some plants are not clones because they get genes from
both parents
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Examples of things which are affected by genes and the environment are:
❖Height
❖Weight
❖Hair colour
❖Skin colour

Genes, Chromosomes and DNA
The majority of cells contain a nucleus
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The human nucleus has 23 pairs of chromosomes
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Each gene controls the development of somehtign different
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A gene is a short section of the chromosome
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Sexual reproduction
This is when genetic information from the mother and father is combined to provide the genes
of the offspring
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Each gamete contains 23 chromosomes each
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The offspring are clones of the parent
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Method:
Chromosomes have identical halves
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This forms 2 identical sets of ‘half chromosomes’
A membrane forms around each set
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Some organisms also produce the offspring via this process
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This process is quite quick and cheap
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The cells
grow into new plants which are clones
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Animal cloning using embryo transplants:
Sperm cells are taken from a bull and egg cells are taken from a cow
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The embryo splits many times before any of the cells become specialised
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These grow into calves which are identical
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A complete set of chromosomes from an adult body cell is placed into the egg cell
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When the embryo develops into a ball of cells, its implanted into an adult female
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Cloning continued
Issues surrounding cloning:
Reduces genes available, therefore if a disease breaks, very few will be resistant to it
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Cloning can preserve endangered species
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Useful genes are copied from one organism’s chromosomes to the cell of another
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Human insulin is inserted into bacteria which then replicates
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Genetic engineering continued
Genetically modified crops are crops which have had their genes altered so that they are
resistant to viruses, insects and herbicides
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Scientists are trying to treat these disorders by
inserting working genes to sufferers
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But some people believe that genetic engineering could cause problems which could be passed
on to the next generations
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People in developing countries lack
nutrients, crops can be modified to contain
these nutrients
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Reduces farmland biodiversity
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Transferred genes may be passed onto other
crops that people don't want to be resistant
to certain things
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Charles Darwin came up with the theory of natural selection
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For example some rabbits have big ears whilst the others have small ears
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Evolution can occur due to mutation
A mutation is a change which occurs in an organism’s DNA
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The characteristics can then be passed onto future generation though natural selection
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Darwin was unable to explain why and how these characteristics appeared
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There wasn't enough evidence
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Eg if a rabbit ran a
lot, its offspring would get long legs

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