Biology Unit 1 (B1)

Front 1

What is a healthy diet?

Back 1

A healthy diet is balanced and contains the right amount of each of the food groups to match the body's needs. The food groups are:

• carbohydrates
• fats
• proteins
• mineral ions and vitamins

Front 2

Why are carbohydrates needed and where are they sourced?

Back 2

Carbohydrates are needed for energy and are sourced from bread, pasta, rice, and sugary foods.

Front 3

Why are fats needed and where are they sourced?

Back 3

Fats are also used for energy and they can be sourced in butter, cheese, and fried foods.

Front 4

Why are proteins needed and where are they sourced?

Back 4

Proteins are used to build and repair tissue in the body. They can be sourced in meat, fish, cheese, and nuts.

Front 5

Why are mineral ions and vitamins needed and where are they sourced?

Back 5

Mineral ions and vitamins are needed in small amounts to keep the body healthy and they are found in fruit and vegetables.

Front 6

What is malnourishment?

Back 6

Malnourishment happens if a persons diet is unbalanced. An effect of malnourishment might be that the body lacks some food groups, such as vitamins or minerals. This can lead to deficiency diseases, such as rickets which is caused by a lack of vitamin D.

Front 7

What are the two types of malnourishment?

Back 7

There are two types of malnourishment:

• underweight: where people do not eat enough and exercise too much. Their diet has little food or energy, and they lose body mass.
• overweight: where people eat too much and do little exercise. Their diet contains too much energy and food for their needs. They gain body mass.

Front 8

What are overweight people at risk of?

Back 8

Overweight people are at risk of type 2 diabetes, obesity, and a high level of cholesterol. Cholesterol can block blood vessels which can lead to heart problems or strokes. Although, some inherited genes can also affect the cholesterol levels.

Front 9

What is metabolic rate and metabolism?

Back 9

Metabolism is the cells in your body carrying out chemical reactions. The rate at which these occur is called the metabolic rate.

Front 10

What are the factors that affect the metabolic rate?

Back 10

• Exercise: the more you exercise, the more the reactions, such as respiration, occur in the cells, so the metabolic rate is higher. More exercise increase the amount of energy used by the body. Glucose from the diet is respired to release energy for the muscles to contract. Exercise make people healthier.
• Proportion of muscle to fat: more muscle and less body fat will increase the metabolic rate, because the reactions occur in the muscle.The more muscle, the more reactions, which means the rate is higher.

Front 11

​What is a balanced diet?

Back 11

The correct balance of foods and energy.

Front 12

Explain why too much cholesterol is bad for your health.

Back 12

Cholesterol blocks blood vessels. This leads to heart attack and strokes.

Front 13

What is a pathogen?

Back 13

A pathogen is a microorganism that causes an infectious disease. They include some bacteria and viruses.

Front 14

What is bacteria?

Back 14

Not all bacteria are pathogens. When bacteria infect our body, they reproduce rapidly, and may produce poisons, called toxins. They are many different types of pathogenic bacteria, and they will cause different diseases. There are even millions of bacteria on our skin.

Front 15

What are viruses?

Back 15

Viruses are much smaller than bacteria. When viruses infect our body, they need to get into our cells. There they will reproduce rapidly and damage our cells, bursting out an causes cells to release toxins, which make us ill.

Front 16

Which doctor realised that washing hands was good for hygiene?

Back 16

Before biologists discovered microorganisms, a Hungarian doctor, Ignaz Semmelwiess, recognised that washing hands was important. In his hospital he showed that if doctors washed their hands between patients, the numbers of deaths from infectious diseases decreased. Today washing hands is common practice.

Front 17

Why is it important to grow microorganisms in labs?

Back 17

It is important for biologists to grow microorganisms in labs so that they can test treatments, such as antibiotics for disease, or to investigate how effective disinfectants might be at killing bacteria.

Front 18

What are the difference between painkillers and antibiotics?

Back 18

Painkillers:

• These are taken to relieve the symptoms of an infection.
• They do nothing to the pathogens.
• They include aspirin, codeine, and paracetamol.

Antibiotics:

• These are drugs that kill bacteria.
• They disrupt the chemical reactions in the life processes of the bacteria.
• By killing the bacteria in our body, they help to make us well.
• Specific antibiotics work on different bacteria.

Front 19

Why do some bacteria become resistant to antibiotics?

Back 19

Some bacteria can develop a mutation that gives them resistance to an antibiotic. They will survive by natural selection and form a resistant strain of bacteria. Gradually overtime the entire population of the bacteria will become resistant, and this means that scientists need to develop a new antibiotic.

Front 20

How does the body prevent microorganisms from entering the body?

Back 20

These include:

• Skin - this acts as a barrier
• blood clots - this seals cuts
• digestive system - stomach acid kills bacteria
• respiratory system - mucus traps bacteria

Front 21

What happens to a pathogen once it enters the body?

Back 21

When a pathogen enters, the immune system comes to the rescue. It uses two types of white blood cell.

• Lymphocyte
• Phagocyte

Front 22

​What is a phagocyte and what does it do?

Back 22

A phagocyte is a white blood cell.

A phagocyte locate the pathogen, and then engulfs the pathogen, and then ingests it.

Front 23

What is a lymphocyte and what does it do?

Back 23

A lymphocyte is white blood cell.

• It locates the pathogen
• reacts to antigens on specific pathogen
• massively increases in number
• produces antibodies
• antibodies are proteins and are specific to the antigens on the particular pathogen
• antibodies destroy the specific pathogen
• lymphocytes can also produce antitoxins specific to a toxin released by the pathogen.

Front 24

What does immunity mean?

Back 24

Immunity means the ability to resist an infection. This can be acquired in two ways:

• Natural immunity
• Artificial immunity

Front 25

​What is natural immunity?

Back 25

This happens when we are infected and some of the lymphocytes that produce the antibiotics are retained to deal withe future infections.

Front 26

What is artificial immunity?

Back 26

These are given by vaccines, which contain dead or inactive pathogens. This triggers an immune response. The lymphocytes are retained, and will respond rapidly if a future infection by the pathogen occurs. For example the MMR vaccine protects us against future infections of measles, mumps, and rubella.

Front 27

What is a change in the environment called and what does it mean?

(Coordination/nerves)

Back 27

A change in the environment is called a stimulus. Animals need to respond to these changes by changing their behavior. Selecting the appropriate behavior for the stimulus is called Coordination.

Front 28

Which two systems in the body help coordination?

Back 28

The nervous system

and

The hormone system

Front 29

What is the nervous system made up of?

Back 29

The nervous system is made up of nerve cells called neurones.

It is divided into two parts:

• the central nervous system (CNS) - the brain and spinal cord.
• the peripheral nervous system - the nerves taking messages to and from the CNS.

Front 30

How does the nervous system work?

Back 30

The nervous system acts by detecting the stimulus in receptors called sense organs. These send an electrical message called an impulse along nerves to the CNS. The CNS then coordinates an appropriate response, then sends an impulse out to an effector. This brings a response, by either contracting a muscle or releasing a chemical substance from a gland.

Front 31

What are the body's receptors and what do they do?

Back 31

We have different receptors for different stimuli.

Sense - Receptor - Stimulus

• Sight - eyes - light
• hearing - ears - sound
• balance - ears - change in position
• smell - nose - chemicals
• taste - tongue - chemicals
• touch - skin - pressure, pain, temperature

Front 32

What are the body's neurones and what do they do?

Back 32

There are three types of neurone:

• Sensory neurone - take impulses from receptors into the CNS
• Relay neurone - takes impulses from the sensory neurone to the correct motor neurone inside the CNS
• Motor neurone - takes impulses from the CNS to the effector.

The junction between the two neurones is called a synapse.

Front 33

What are the reflexes in the body?

(not the pathway of the reflex action)

Back 33

The reflexes in the body are rapid, protective, and automatic. The pathway taken by the impulses is called to reflex arc (see following flashcard). An example would be, pulling your hand away from a sharp pin is a reflex arc.

Front 34

What is the pathway of the reflex arc?

Back 34

• Stimulus
• Receptor
• Sensory neurone
• Relay neurone
• Motor neurone
• Synapses
• Effector
• Response

Front 35

What part does the hormonal control play in the control systems of the body?

Back 35

The hormonal control system plays a role in controlling the balance of our internal systems. It works by releasing hormones into the blood stream. A hormone is a chemical messenger released in one gland and having its effect on a target organ elsewhere in the body. The effect is generally slower but longer lasting than nerve reflexes.

Front 36

What are the internal conditions of the body that are controlled?

Back 36

• Water content - All the cells in the body need to be bathed in water. Water enters the body by food and drink and is released during respiration. It leaves by the lungs when we breathe out, by the skin in sweat, and by the kidneys by urine.
• Ion content - ions are needed to keep the nerves and muscles healthy. Ions are taken in from the diet and lost in sweat and urine.
• Temperature - the body needs to maintain a stable temperature for its enzymes to function.
• Blood sugar levels - sugar is needed as a source of energy for cells, but too much will lead to circulatory problems. Hormones regulate the level of blood sugar.

Front 37

How do hormones control the menstrual cycle?

Back 37

Hormones control the exact timings that the release of an egg, and the preparation of the womb for pregnancy.

• The cycle begins with the rlease of follicide stimulating hormone (FSH) form the pituitary gland.
• This stimulates the egg to mature in the ovary.
• FSH also stimulates to ovary to produce a hormone called oestrogen, which causes the wall of the womb to thicken.
• The high levels of oestrogen stimulate the release of the second pituitary hormone called luteinising hormone (LH) and stops the production of FSH.
• On day 14 of the cycle the LH level peaks and causes a mature egg to be released, this is called ovulation.
• The ovary bow produces a mix of oestrogen and progesterone.
• These hormones continue to thicken the wall of the womb, which can now receive a fertilised egg if the woman is pregnant.
• With high oestrogen and progesterone no FSH is produces, and no eggs mature.
• If the woman does not become pregnant oestrogen and progesterone levels fall, and the wall of the womb is shed, together with some blood as the menstrual flow, or period.
• The cycle then starts again.

(See page 28 of the AQA Biology Student book for diagram and more information)

Front 38

How can fertility be controlled by contraceptive treatments?

Back 38

• Contraceptive treatments - contraceptives drugs are used to prevent pregnancy. These make use of the fact that the hormones oestrogen and progesterone will inhibit the production of FSH, and so stop eggs maturing.

Front 39

How can fertility be controlled by fertility treatments?

Back 39

Hormones can also be used to help women become pregnant. Some women have trouble with becoming pregnant because of low levels of FSH and LH. In such cases women can take a fertility drug. This results in eggs being matured and released.

Front 40

What is the process of In Vitro Fertilisation (IVF)

Back 40

• The woman is given a treatment of fertility dugs.
• Several eggs mature and are released; they are collected by the doctor.
• These eggs are mixed with the fathers sperm.
• The fertilised eggs develop into small balls of cells, called embryos.
• One or two embryos are inserted back into the mother's womb.
• The embryos develop into a baby in the womb.

Front 41

What are the benefits and problems of IVF?

Back 41

Benefits - families can control when they will start a family, and how many children they will have. IVF allows infertile couples to have children, and embryos can be screened for disorders.

Problems - some people have ethical concerns about controlling fertility and disposing of unwanted embryos. IVF is expensive. There are side effects of the pill, and some women stay on the pill for too long.

Front 42

What stimuli do plants respond to?

Back 42

Plants responses are in the form of growth movements called tropism.

Stimulus - Response of shoot - Response of root - tropism

• light - grows towards the light - grows away from light - phototropism
• gravity - grows away from gravity (up) - grows towards gravity - gravitropism
• moisture - grows toward moisture - grows away from moisture - hydrotropism

Front 43

What does the hormone auxin do in plants?

Back 43

Auxin brings about the growth movement in phototropism and gravitropism. The auxin is produced in the shoot and root tips.

Front 44

What are the uses of plant hormones?

Back 44

• Weedkillers - here auxins cause the shoots of broad-leafed weeds to grow rapidly, but not the roots, so they will no be able to absorb enough water to survive.

• Rooting hormones - here cuttings are dipped in rooting hormones containing auxins, which encourage the formation of new roots.

Front 45

What is a drug and what does it do?

Back 45

A drug is a chemical that affects our body chemistry. Drugs are used to treat illness but are also abused by some people.

Front 46

What are the uses of medical drugs and what example are there?

Back 46

There are many drugs developed for medical use to treat symptoms and causes of illness. Drugs such as antibiotics, painkillers, and statins.

Front 47

What are statins used for?

Back 47

Statins are used to reduce blood cholesterol level. These drugs can reduce the risk of cardiovascular diseases such as heart attacks.

Front 48

What are the trials and rules associated with drug testing?

Back 48

Clinical trials -

• large numbers of patients give more reliable results
• start with a low dose to check the drug is safe
• Increase dose to find the optimum dose
• Some patients are given a placebo pill to act as a control with which compare the experimental group.

• Double blind trial - These are used so there are no biased results. Neither the patient or doctor know who has been given the placebo or the real drug.

Front 49

How are new drugs tested?

Back 49

1. A new drug is developed by scientists to treat a disease
2. Lab trials on cells, tissues, and animals. This will check toxicity, and whether the drug works
3. Clinical trials - here the drug is tested on human volunteers
4. If successful, the drug is marketed

Front 50

What was thalidomide and what was the problem with it?

Back 50

Thalidomide was a drug developed as a sleeping pill in the 1950s. It also helped treat morning sickness in pregnant women. The drug was not throughly tested, and it had terrible side-effects. The babies born from the mothers who were using thalidomide had severe limb abnormalities. as a result the drug was banned.

Thalidomide is now used to treat leprosy.

Front 51

What is drug abuse and how does it affect some people?

Back 51

Some drugs are illegal and some are legal. Some are more harmful than others.

Drug abuse - where people take drugs for no medical reason. Drugs act by changing the chemical processes in the body, particularly the brain. Some people develop an addiction, and may become dependent on them. This means that they need drugs to maintaining a functioning lifestyle. If these people try and give up the drug, the will get withdrawal symptoms as the body's chemical reactions fail to function fully.

Front 52

What affect does alcohol have on the body?

Back 52

Alcohol is a common legal drug. It relaxes people and would not be considered drug abuse. However, high doses of alcohol can impair judgement and lead to reckless behavior, which might affect society as a whole.

Long use of alcohol may lead to serious damage of the liver and other organs. Other legal recreational drugs include caffeine and nicotine.

Front 53

Name two illegal recreational drugs and their effects.

Back 53

There are many types of recreational drugs. For example:

• Cannabis - the smoke contains chemicals that give the feeling of well being. This can lead the user onto more powerful drugs. In some people it may lead to serious mental health problems. Although it can be used to treat chronic painful illnesses such as MS.
• Steroids - these are perfomance enhancing drugs and are usually used by athletes. This can give an unfair advantage, so are banned in sport. they can cause side-effects such as interfering with reproductive cycle and heart problems.

Front 54

What do adaptations do?

Back 54

Adaptations allow plants to survive in environments or changing environments.

Such as trees, the bigger the leaves means that more sunlight can be absorbed.

Front 55

Name two adaptations for a polar bear in the arctic and state how it aids survival.

Back 55

Small ears - this reduces surface area which reduces heat loss.

Thickness of insulating coat - the thick fur coat insulates the body against the cold.

Amount of body fat - the polar bear has a thick layer of fat which insulates against heat loss, and can be used in respiration to generate heat.

Camouflage - the white fur means that the animal blends in with the environment.

Front 56

Name two adaptations for a camel in the desert and state how it aids survival.

Back 56

Long legs - to lift the body high above the hot sand.

Thickness of insulating coat - the thin fur in the coat traps less insulating air.

Amount of body fat - the thin layer of body fat reduces heat retention. There is a store of fat in the hump that can be used to release energy and water.

Camouflage - sandy coloured fur blends in with the background.

Front 57

Name two adaptations for a cactus in a desert and state how it aids it survival.

Back 57

Surface area of the - the leaves are spines, which reduces surface area. This in turn reduces water loss.

Water storage tissues - stems are swollen to store water.

Extensive root system - the roots of the cactus are often shallow but they cover a large area, which allows greater absorption of water when it does rain.

Front 58

Name an extremophile and state how its adaptation aids it survival.

Back 58

Whales - They are able to live in great depths of the ocean and withstand the pressure. They have small lungs, which makes them less buoyant, reducing the energy needed to dive.

Bacteria - It is able to live in very high temperatures, such as volcanic areas. They are adapted by having enzymes which can still work at high temperatures.

Front 59

What is a population?

(in terms of organisms)

Back 59

A population is the amount of individual species in one area.

Front 60

What is the distribution?

(in terms of organisms)

Back 60

The distribution of the population is the range and extent of the area in which the organisms live.

Front 61

What factors affect distribution?

Back 61

• Competition with other organisms
• effective adaptation to the environment
• change in the environment
• pollution

Front 62

What resources do plants compete for?

Back 62

Plants compete for:

• Space - for roots and canopy so they can get get enough light and water
• Light - needed for photosynthesis
• Water - plants cannot survive without water
• Minerals - if the soil is low on minerals, they do not grow well
• Carbon dioxide - the more carbon dioxide means the better the plant will grow

Front 63

What resources do animals compete for?

Back 63

Animals compete for:

• Space and territory - the more crowded the area, the less food available
• Food - areas with little food will not support animal life
• Water - animals cannot survive without water
• Mates - animals need partners in order to reproduce

Front 64

What factors affect an organism's environment , which means it needs to adapt?

Back 64

Factors that affect if an organism needs to adapt are:

• Arrival of competitors
• Changes in the physical features of the environment, such as temperature or rainfall.

Front 65

How do pollutants affect survival and distribution of organisms?

Back 65

• Some species can survive well in high levels of pollution. Their presence indicates to biologists that there is high level of pollution.
• Other species can only survive in clean areas. Their presence indicates to biologists that there is no pollution in that area.

Front 66

What are indicators of air pollution?

Back 66

• Lichens are very good indicators of pollution.
• Some species are particularly sensitive to sulphur dioxide. Which is released form burning fossil fuels.
• These lichens do not grow in industrial areas.

Front 67

What are indicators of water pollution?

Back 67

• Polluted water contains high levels of microorganisms, which reduces the level of oxygen in the water.
• Invertebrates like the rat tailed maggot are able to survive in well polluted water that have low oxygen levels.
• This is because they have straw-like tail that can obtain oxygen from the air.
• The presence of these maggots indicates the water is polluted.

Front 68

How are pollution levels measured, other than using indicator species?

Back 68

Biologists can use a range of sensors that can measure the physical and chemical levels in the environment. Theses include:

• Maximum-minimum thermometers
• Oxygen meters
• Rainfall gauges

Front 69

What does a food chain show?

Back 69

• It shows the flow of energy and food (biomass) from one organisms to the next.
• Each link in the chain is given a name.
• The links are joined by an arrow.

Front 70

What is biomass and how can it be calculated?

Back 70

Biomass is the mass of living material. The biomass of each link in the food chain can be calculated by multiplying the number of individuals in that link by the dry mass of one individual.

This can then plot a pyramid of biomass.

Front 71

How do you plot a pyramid of biomass?

Back 71

There are rules when plotting a pyramid of biomass:

• The producer is always at the base
• Each bar represents the biomass of each trophic level
• Each bar must be drawn to the same scale

Front 72

What is natural recycling?

Back 72

Natural recycling is:

• When an organism dies, the body decays
• Which then returns the elements to the non-living world, like the soil and air
• They then become available for other organisms, such as plants to absorb.

Front 73

What is decay and what are the two principal groups of organisms involved?

Back 73

Decay is the breakdown of the waste or the body of an organism.

The two principal groups are:

• Detritivores - including earthworms, which eat bits of dead body as dead leaves, and digest them, releasing their waste, which contains the elements and can broken down further by decomposers.
• Decomposers - including bacteria and fungi. These microorganisms digest the waste and bodies by releasing enzyme to break down the materials.

Front 74

What is the carbon cycle and what does it do?

Back 74

• During the carbon cycle, the element carbon is constantly being cycled between living and non-living world.
• While the elements cycles, energy goes through the cycle.
• When carbon dioxide is built into carbohydrates and fats in plants. they take in and store the Sun's energy in these compounds.
• As the compounds move through the cycle, the energy either passes from one step to the next, or is released back into the atmosphere.

Front 75

What is variation and what is it caused by?

Back 75

Variation is the differences between individuals. This can also be different species.

Variation can be caused by:

• Genes - these are inherited from our parents. Example of characteristics that are controlled by genes are eye colour, earlobe shape, and flower colour.
• Environment - this is where the conditions in our surroundings influence a feature. Example of environmental characteristics are scars, and the number of flowers produced.
• Combination - both genes and the environment interact to determine a feature. Examples of characteristics controlled by a combination of height and body mass.

Front 76

What are genes?

Back 76

Genes are major contributors to variation in organisms.

• Genes are found in the nucleus of the cell.
• Genes are molecular codes that control the manufacture of proteins.
• These proteins influence the development of characteristics.
• For example, genes code for the pigments that colour the eyes. Different genes for different characteristics.

Front 77

How are genes passed on?

Back 77

Genes are passed on in gametes, the egg and sperm cells. The two gametes join to form the baby.

Front 78

What is reproduction and what are the two types?

Back 78

Reproduction is the production of new individuals of the same species.

The two types of reproduction are:

1. Sexual reproduction - Gametes are brought together and fuse to form offspring. We inherit half our genes form our father and half from our mother. This means that the characteristics mix.
2. Asexual reproduction - This doesn't involve the production of gametes, this means:

• only one parent is needed.
• there is no mixing of genetic information.
• all offspring are genetically identical. They are called clones.

Front 79

How do gardeners use asexual reproduction?

Back 79

Gardeners use an asexual technique to produce large numbers of plants. They take cuttings from a parent plant, which will grow into new plants. The advantages are that:

• the process is cheap
• the new plants are all genetically identical and so share the characteristics the gardeners want.

Front 80

How does embryo transplant work?

Back 80

• Parents are selected with the desired characteristics.
• Their eggs are collected and fertilised with sperm in a dish.
• The embryos are allowed to develop into a ball of unspecialised cells.
• The ball of cells is then split up into pairs of cells.
• Each pari continues to develop, and can be transplanted into host mothers called surrogates.
• They give birth to identical offspring with the desired characteristics.

Front 81

How does cloning work?

Back 81

An example of cloning is the zorse (this example still works for cloning, and is the exam question that comes up (Jan2012)):

• Skin cell from zorse
• unfertilised egg taken from horse
• removes the nucleus from egg cell
• take nucleus from skin cell
• put into empty egg cell
• electric shock
• causes egg cell to divide and the embryo formed
• Then place the embryo into womb

Front 82

What is GM?

Back 82

Genetically modified organisms are organisms that have had their genes from other organisms, including plants and animals. By adding new genes their genetic code is altered so that they develop with desired characteristics.

Front 83

What are the benefits of GM produce?

Back 83

GM produce means that plants characteristics improve their survival the therefore increasing yield. Also, it increases economic value.

Front 84

What are the characteristics transferred by GM?

Back 84

• Herbicide resistance in plants - Soya is herbicide resistant, so when grown in fields the herbicide can be used to kill competing plants and the soya survives.
• Longer shelf life - Tomatoes and melons do not ripen as fast, and will not then start to decay and go soft on supermarket shelves.
• Insect resistance - Corn and cotton have genes that kill insect pests, which stops the plants being destroyed.
• Increased vitamin content - Golden rice contains vitamin A in its grains, whereas white rice does not. This helps prevent blindness in children.

Front 85

Name 4 arguments for GM crops.

Back 85

For:

1. GM crops require fewer pesticides in order to grow, so this means there is less pollution in the environment.
2. GM crops have a higher yield and can feed a larger population.
3. Some crops have a higher nutritional value.
4. GM crops have been eaten in some countries for over 10 years with no ill effects noted.

Front 86

Name 4 arguments against GM crops.

Back 86

Against:

1. There are uncertainties about the effect of eating GM crops.
2. GM crops are expensive to develop and test.
3. GM crops require a lot of testing which can take years.
4. It can disrupt the food chain if insect resistant plants grow, killing the insects.

Front 87

What is classification?

Back 87

Classification is the similarities and differences between organisms.

Front 88

What are some ecological links between organisms?

Back 88

Organisms that share features because they live in the same environment. For example, butterflies and birds both have wings, but the wings are very different in structure.

Front 89

What was Darwin's theory?

Back 89

Darwin's theory suggested that species might have developed or evolved from simple life forms that first appeared billions of years ago.

His theory was called evolution by natural selection. Evolution is the gradual change of an organism over time. His idea suggests that gradually one type of organism, called an ancestor, might change over many generations into one or more species.

Front 90

Why was Darwin's theory only gradually accepted?

Back 90

• The theory disagreed with most religious ideas about how God created all life forms.
• There was not much evidence at the time to convince other scientists.
• Scientists did not know about genes and how they are inherited, and cause variation, until 50 years after the theory was published, and so could not explain a mechanism for ho evolution could work.

Front 91

What was an alternative theory to Darwin's?

(Hint: JL)

Back 91

Jean Lamarck

His theory was explained in the evolution of giraffes:

• He believe that giraffes wanted to feed off leaves high on a tree, he said they had an inner need to stretch their necks.
• The giraffes would stretch their necks, becoming more successful.
• They pass on their longer necks to their offspring.
• Lamarck's theory is still not accepted today. Living things cannot decide to alter their body to meet an inner need.
• An example used against his theory was that someone who works out at the gym and develops their muscles wouldn't pass on their muscles to their children.