Name: Form:

Teaching Group:

2

REVISION TIPS To be successful in your exams you must be well prepared. This

involves hard work both in and outside the classroom.

Listen carefully during the lesson and try not to be distracted.

To learn something you must understand it. So read through your work after each

lesson and ask for help if you are unsure of anything.

Set yourself a realistic time frame for revision. Work with small chunks of

time over a longer time span rather than hours on end at the last moment.

Get up and walk about whilst trying to learn something.

Avoid last a minute rush.

When you are revising have a copy of the syllabus, your notes, paper and

coloured pencils/highlighters. Check off the topic when you have fully

understood and learnt it.

In the exam, read the question carefully and make sure you answer the question being

asked. Some key question words are:

STATE means write the facts for the answer in a short concise way

EXPLAIN means to make known in detail or give the reason for something.

DESCRIBE means to state what the form or function of something is using words

or diagrams. For a graph it means to state what the graph shows or what pattern is

shown by the results. An explanation may be required eg if you are asked to

describe a process.

SUMMARISE means to give a brief statement of.

LIST means write facts one after the other

DISTINGUISH BETWEEN state the important differences between two things.

Remember to be precise and say which you are describing.

= revision tip

3

BIOLOGY – topic check list 1. ADAPTATION AND COMPETITION

Why and how should organisms be classified?

Which organisms live here and how are they affected by others?

What features enable organisms to survive here?

What affects the numbers of organisms here?

Does pollution affect where organisms live?

2. VARIATION

Are all individuals in a species the same?

What causes variation?

What causes genes to alter?

What are the risks in the environment?

3. EVOLUTION

Do species change over time?

What is natural selection?

How does evolution work?

Is evolution still going on?

4. INHERITANCE

What are chromosomes made of and what is DNA?

What are genes and how do they affect cells?

What effect does cell division have on the genetic composition of cells?

What causes offspring to be male or female?

Are other features inherited in the same way?

How was the mechanism worked out?

Can some conditions be passed on in families?

5. GENE TECHNOLOGY

Why should anyone need genetically identical individuals?

Can genes be transferred between organisms artificially?

Why is this gene transfer carried out?

Are there any ethical issues surrounding this technology?

Is there a planning or control process surrounding the use of this technology?

6. HOMEOSTASIS

Why is the core temperature of the body always around 37 degrees?

How does the body keep the temperature constant? Structure of the skin.

Why should the level of glucose in the blood vary and how is it kept constant?

What happens when the control mechanism fails to work efficiently?

7. NERVOUS SYSTEM

How does the body check on its surroundings?

Why are some reactions very fast?

What is a reflex arc?

8. HEALTH

What is health?

What causes ill health?

How can ill health be treated? Production and trialling of medicines

Are there ethical issues involved with these treatments and how should decisions be

made

4

1. ADAPTATION AND COMPETITION

Why and how should organisms be classified? Which organisms live here and how are they affected by others? What features enable organisms to survive here? What affects the numbers of organisms here? Does pollution? Candidates should: (a) know that organisms that have similar features and characteristics can be classified together in a logical way. Understand the need for a scientific system for identification and scientific as opposed to 'common' names. (b) use local first and/or second hand data/ICT simulation: to compare the variety of organisms which live in particular habitats; investigate how the organisms in an area are affected by other organisms. (w(i)a) (c) explore information about the morphological adaptations shown by organisms which enable them to survive in their environment. (d) know that individuals have a basic need for energy and resources from their environment the size of a population of individuals may be affected by competition, for food, space, light; predation, disease, pollution, availability of minerals. (e) examine how indicator species, changes in pH and oxygen levels may be used as signs of pollution in a stream examination of lichens as indicators of air pollution. (w(i)a)

During revision:

Highlight any topic that you have covered in lessons and have fully understood and learnt

Add any extra notes or „aides de memoir‟ below

5 1. Adaptation and competition

Key words

a) There are many visible differences between living things. Scientists use these

differences to „classify‟ or put living things into groups that have features in common.

With the advance in technology, the DNA of living things is also being used to make

classification more precise.

Carolus Linnaeus (1707-78) first introduced an organised system to classify living things

and it forms the basis of today‟s system. In his system living things are put into the

following groups.

o Kingdom

o Phylum (Division)

o Class

o Order

o Family

o Genus

o Species

Make up a mnemonic to help you remember the order, for example:

King Prawns Can Only Fill Giant‟s Stomachs

At species level, only members of the same species can mate to produce fertile offspring.

Every living thing is given two names (Latin) and so the system is called the ‘binomial’

system.

The FIRST NAME (written with a capital at the start) is the organism‟s GENUS The

second name (written with no capital) is the species name.

Canis familiaris = domestic dog, Homo sapiens = human

In text the binomial or scientific name is usually written in italics or is underlined

As we move down the groups,

there are more similarities and

fewer differences between the

members of the group.

• Environment

• Habitat

• Population

• Community

• Adaptation

• Competition

• Living things and physical features

• Place where plants and animals live

• Number of one type of living thing in a habitat

• Number of populations in a habitat

• Special feature that helps living thing survive

• When a number of living things fight for the same resource

6

b) ADAPTATION – special features which make an organism particularly well suited to

where they live.

Even in our own back garden we see

adaptations. The blue tit can hold

itself on the edge of the feeder with

long claws and flexible legs. The

blackbird cannot do this but feeds in

an upright position on the table. What

other adaptations do they have?

Notes (a) CLASSIFICATON

Notes (b) ADAPTATIONS

7

c) Examples of adaptation

• PHYSICAL (morphological) eg webbed feet of a frog, camouflage

• SEASONAL – overwintering organ eg bulb, migration, hibernation

• BEHAVIOURAL – huddling, nocturnal, crepuscular

DESERT – hot + dry

o Small body – larger surface area

o large ears increases heat loss

o stay in burrow in day – avoid predators, keep cool

o nocturnal – avoids high daytime temperatures

o large eyes – see in the dark

POLAR – cold, little food and water

o large body – smaller surface to lose heat

o thick fur – reduces heat loss

o thick fat layer under skin – reduces heat loss

o small ears – lose less heat

Eg Fennec fox

Eg polar bear

How is a camel adapted to

survive in its environment?

Remember to name or

describe the adaptation

and say HOW it helps the

living thing to survive.

Notes (c) EXAMPLES OF ADAPTATION in animals

8

Plants have adaptations to live in hot or dry conditions. Water is mainly lost from the

underside of the leaf by transpiration.

The adaptations include:

o thick waxy layer - to reduce water loss

o formation of spines - leaf surface area reduced

o extensive superficial and deep root system - to maximise water uptake

o fleshy tissue eg in stem of cactus - water storage

o leaves curled in - to protect lower surface and so reduce water loss

CACTUS CONIFER

Notes (c) EXAMPLES OF ADAPTATION in plants

MARRAM GRASS

9

d) living things have basic needs to stay alive

Living things may fight or compete for these basic essentials for life.

• Animals compete with one another for: shelter, food, water and a MATE

• Plants compete for light, water and nutrients

The size of a population may be affected by the availability of the essentials above

together with other factors including: predators, disease, pollution.

Eg male Robins will fight for the

Territory in the garden

LIVING THINGS

• COMPETITION WITHIN A SPECIES

• Plants compete for space light, water +

nutrients

• Animals may compete for a mate,

nesting spot, food

• The strongest will survive

• COMPETITION BETWEEN DIFFERENT

SPECIES

• The resources competed for can be the

same as competition within a species

• Often living things occupy slightly

different parts of a habitat or have a

varied diet

Think of some examples

that you know to help

you remember these

Eg different garden birds eat different

food and so can all survive in the garden

10

PREY

• Are hunted and eaten by predators

• Most have eyes at the side of their head

• Alert and easily startled

• May crowd and live in groups

• Often have acute hearing and a good sense

of smell

• May have armour, spines or method to deter

predator

• Well camouflaged

• Many are nocturnal

Think of a predator

and a prey that you

know to help you

remember the

features of each

• PREDATORS

• Catch + kill prey

• Eyes point forward

• Good eyesight

• Excellent sense of smell

• Sharp claws, beaks or teeth

• Often camouflaged or good at hunting

by stealth

Notes (d) competition + populations

11

e) POLLUTION INDICATORS

Certain living things can tolerate pollution better than others. Which living things are

present can be used to indicate or show how much pollution is present.

Air pollution indicator species are lichens. Lichens are a fungus and an algae living

together. Lichens are sensitive to the amount of sulphur dioxide present in the air.

Generally speaking in high levels of sulphur dioxide, there will be no lichens. The less

pollution, the bigger the lichens.

Water pollution indicator species are sensitive to the amount of oxygen present in the

water. Some examples are shown below.

These animals are found in clean water: Mayfly Nymph (6mm)

Stone fly nymph (14mm)

Salmon trout (40cm)

These animals are found in slightly polluted water:

Freshwater shrimp(4mm)

Caddis fly larvae (10mm)

Snail (20mm)

These animals are found in very dirty water:

Water louse (12mm)

Blood worm (16mm)

Rat-tailed maggot (10mm)

High air pollution Low air pollution

12

Notes: (e) POLLUTION INDICATORS

13 2. VARIATION

Are all individuals in a species the same? What causes variation? What causes genes to alter? What are the risks in the environment? Candidates should: (a) examine the variation in height/length in individuals of the same species by collecting and analysing data and know that variation may be due to environmental or genetic causes. (w(i)a) (b) know that sexual reproduction leads to offspring that are genetically different from the parents unlike asexual reproduction where genetically identical offspring called clones are produced from a single parent. Sexual reproduction therefore gives rise to increased variation. (c) understand that new genes result from changes, mutations, in existing genes and that mutations occur naturally at random. Mutations may be beneficial or harmful and are increased by exposure to radiation and some toxic chemicals. (d) variation is the basis of evolution.

a) Variation is slight differences between living things. It is important to help a

species survive. This is because it will be more likely that at least a few of the species

will survive if conditions become difficult.

There are 2 types of variation:

CONTINUOUS – this is when the data has a continuous sequence of values eg, height,

weight

DISCONTINUOUS – this is when the data has discrete values eg right or left handed,

pierced ears, blood groups – the values are one or the other

We are all humans but we are all different!

We get all our characteristics or features in one of three ways

• INHERITED from our parents

• ENVIRONMENTAL or picked up from the environment

• A MIXTURE of inheritance and the environment

14

c) MUTATIONS

Mutations are changes in the structure of the DNA molecule. This can result in a change

in a gene, the arrangements of the genes on a chromosome, or the number of

chromosomes in a cell. They can be passed on to daughter cells through cell division.

Mutations can be caused by:

- Ionising radiation (UV, X-rays , cosmic rays)

- Radioactive substances (in Earth‟s crust)

- Certain chemicals

b) REPRODUCTION

There are two forms of reproduction:

• ASEXUAL REPRODUCTION – there is no fusion or joining of cells and only ONE

parent is needed. All the offspring are identical or CLONES

• SEXUAL REPRODUCTION – involves the fusion or joining of special sex cells

called GAMETES. The offspring are a mixture of genetic information from 2

parents and so are all different or show VARIATION

INHERITED

Shape of nose, eye colour,

blood group, gender

MIXTURE

Height, weight, health,

ENVIRONMENTAL

Language spoken, scars,

piercings, tattoos

Think of things you have

inherited from your

parents, have picked up in

life or a mixture of each

Hair colour from mum

Make up a table of differences between sexual and asexual

reproduction

15

Effects:

- Mostly harmful

- Causes death or abnormality in reproductive cells

- Causes cancer in body cells

- Some CAN be neutral or even beneficial (e.g. the peppered moth)

The differences in an individual caused by a mutation leads to VARIATION. This can be

the raw material in natural selection

Notes: MUTATIONS

16

3. EVOLUTION

Do species change over time? What is natural selection? How does evolution work? Is evolution still going on? Candidates should: (a) examine evidence and interpret data about how organisms and species have changed over time. Suggest reasons why species may become extinct. (w(i)a,b) (b) consider how individuals with characteristics adapted to their environment are more likely to survive and breed successfully. Consider the uses and limitations of modelling to illustrate the effect of camouflage colouring in prey and predator relationships. (c) know that the genes which have enabled these better adapted individuals to survive are then passed on to the next generation. This is natural selection. (w(i)c) (d) consider the process of data collection, creative interpretation and deduction that lead Charles Darwin to propose the theory of evolution. Discuss the controversy surrounding the acceptance of the theory. Discuss evidence that evolution is ongoing such as data on Warfarin resistance in rats.

a) Charles Darwin (1809-1882)

Darwin travelled to the Galapogos Islands in the HMS

Beagle and observed the plants and animals there. His key

observations:

1) All living things produce more offspring than survive to

adulthood

2) In spite of this, population sizes remain roughly constant

3) Variation exists among species

4) Characteristics can be passed on from one generation to the next.

b) Living things that have features that are best suited to their habitat are more

likely to survive. This is clearly seen in species that are camouflaged. The

peppered moth is a well known example. The moth has two forms, one dark the

other light. The dark dominate in areas where the background is darkened due to

pollution, and the lighter version in the less polluted lighter backgrounds.

Dark moth stands

out on the lighter

background and is

more likely to be

eaten

Lighter moth stands

out on the darker

background and is

more likely to be

eaten

17

c) This idea can be modelled in a laboratory. This method has limitations and care

must be taken because in the natural situation the following factors play a part.

The size of the population is a significant factor. It must be large enough for the

results to be valid

Living things of reproductive age may not successfully produce offspring

Immigration or emigration may take place

Random mutations may occur

Colour may not only effect predation rates. For example a darker shell may absorb

more heat from the sun and so affect the chance of survivial.

C ) Natural Selection.

This was first suggested by Darwin but now has a more detailed scientific basis.

It can explain selection of simple features that have appeared by mutation, for example

colour, but cannot explain how complex features, for example, an eye, has appeared. For

this to have appeared, many mutations would have to occur all at once to form the eye

that works

Modern day examples of natural selection in action include antibiotic resistance and

warfarin resistance in rats

(NB. The idea of evolution as described by Darwin, the controversy around it and

alternative ideas are on the Higher paper)

The four main stages in natural selection are outlined below:

a) Variation – some strains of bacteria are resistant and some aren‟t.

b) Competition – The non-resistant bacteria are killed by the penicillin

c) Survival of the fittest – the resistant bacteria survive.

d) Passing on of genes – the resistant bacteria reproduce and pass on

their adaptations to their offspring.

The main evidence for this is from fossil records.

• There is no record of the origins of life on Earth, it is a puzzle that can never be

completely solved.

• Scientists must try to keep an open mind and make judgements based on fact and

not belief. Scientists must not try to make facts fit their ideas !!

• One source of information is fossils. These are the remains of plants and animals

that were around in the past !

Resistant bacteria Non resistant bacteria

18

• The fossil record is not complete and can only provide a small piece of evidence.

Some of the aging techniques are also unreliable.

• The theory of evolution tells us that all species of living things alive today have

evolved from the first simple life forms that existed on the earth.

• There are a number of different ideas about how life has become what we see

today. None can be proven scientifically.

• The 4 main ideas are: Darwin, Lamarck , Intelligent Design and Creation

EXTINCTION is the permanent loss of all the members of a species from the face of

the Earth. Causes of extinction:

Change in climate

• Meteorites

• New predator

• New disease

• Competition

One fossil record – the horse

Modern horse

Equus 1.6m

Pliohippus 5 million

years ago

1.0m

Merychippus 25 million

years ago

1.0m

Mesohipus 37 million

yers ago

0.6m

Hyracotherium 55 million

years ago

0.4m

19

4. INHERITANCE

What are chromosomes made of and what is DNA? What are genes and how do they affect cells? What effect does cell division have on the genetic composition of cells? What causes offspring to be male or female? Are other features inherited in the same way? How was the mechanism worked out? Can some conditions be passed on in families? Candidates should: (a) know that chromosomes are strands of DNA. DNA contains coded information that determines how cells function due to the types of proteins coded for. DNA can be extracted from cells, such as Kiwi fruit. (b) know that DNA can be analysed by 'genetic fingerprinting' which can be used to show the similarity between two DNA samples, for instance in criminal and paternity cases. (w(iv)a) (c) assess the issues surrounding 'gene ownership' as a result of DNA analysis and consider whether the ethical issues involved are a matter for society and beyond the scope of science to solve. (w(i)d;(iv)a,b) (d) understand the significance of mitosis and meiosis. (e) know that genes are sections of DNA molecules that determine inherited characteristics and are in pairs. Genes have different forms, called alleles. (f) know that in human body cells, one of the pairs of chromosomes carries the genes which determine sex, XX or XY. These separate and combine randomly at fertilisation. (g) consider the scientific process of experimentation, observation and deduction that led Gregor Mendel to propose the mechanism of inheritance. Discuss why the significance of the work was not recognised and validated by scientists for many years. (w(i)a,b;(iv)c) (h) be able to complete Punnet squares and explain the outcomes of monohybrid crosses. (i) understand that some mutations cause conditions which may be passed on in families, as shown by the mechanism of inheritance of cystic fibrosis, and be able to interpret family trees

Notes: evolution

Note the main points for

each idea. Note the

strengths and weakness of

each idea.

20

The DNA molecule looks like a spiral staircase

Pairs of „bases‟ form the steps

of the staircase

DNA is made up of ‘nucleotides‟

a) + e)

A gene can have different forms

these are called ALLELES

The gene for eye colour has alleles for brown, blue, green etc.

Our chromosomes hold all the information we inherit. Different living things have

different numbers of chromosomes

We have 46 chromosomes made up of 23 pairs. .One of each pair has come from our

mother and the other from our father

Kiwi fruit, like other living things, contains DNA. It can be used to extract DNA which

can than be studied. Other living material can also be used!

Proteins are made up of amino acids.

The order of the amino acids determine which protein it is.

3 bases „code‟ for one amino acid. So the order of the bases

determines the order of the amino acids

This is called „protein synthesis‟.

cell membrane

cytoplasm

Nucleus with chromosomes A chromosome

A section of a chromosome = a gene

The bases always match

up in the same pairs: A

with T and C with G

The sequence of the

bases will determine

the protein that is

made.

21

T C A A A C T G G T C A

RIBOSOME

b) Our DNA is unique to us!! It can make us stand out in a crowd. This can be good for

some of us but bad for the „baddies‟!! Genetic fingerprinting can be used to identify a

criminal or a dead body. Only a small amount of blood, saliva, hair or semen is needed.

Our DNA is very similar to our parents.

Genetic fingerprinting can be used to determine who is the father, or mother, of a child.

d) In a recent murder hunt, the police obtained blood samples from more than 5,000

people for genetic fingerprinting. The Home Office is considering creating a data

base which will contain everyone‟s genetic prints.

Do you think that this would be a good idea?

• Give reasons for your answer.

d) When we grow or have to repair damage done to our body, new cells have to be made.

These cells must be the same as the ones they are replacing. However, when our sex cells

(gametes) are made, the number of chromosomes has to be halved. Each gamete is

slightly different to all the others that are made by the same person.

= amino acid

Make up a list of uses for DNA or „genetic

fingerprinting‟. For each give a reason why it

is right and why it might be wrong to use it

22

There are two ways that cells can divide: mitosis and meiosis. Each type of cell division is

outlined below:

f) In humans there are 23 pairs of chromosomes. One of these pairs are called the sex

chromosomes because they carry the genes that will determine if we are male or female.

This pair will separate by meiosis during the formation of the gametes (sex cells) and

then combine randomly at fertilisation. The sex chromosomes are named „X‟ and „Y‟.

A female is „XX‟ and a male is „XY‟.

All our body cells have 23 pairs, or a total of 46 chromosomes

Our sex cells (gametes), the egg (ovum) and sperm have only 1 set of chromosomes – 23 in total

mum dad

fertilisation

46 chromosomes

The number of chromosomes is halved to make the gametes

Mitosis:

• Used for growth and repair of cells

• Used in asexual reproduction

• Cells with identical number of

chromosomes and genetic information

are produced

Meiosis:

• Used to produce gametes for

sexual reproduction

• Each daughter cell has half the

number of chromosomes of the

parent

• One copy of each chromosome is

in each daughter cell. They are

all GENETICALLY different.

This brings in VARIATION

between individuals

Makes ‘ME’

‘MY TOES IS’ made this

way!

23

This can also be shown in a Punnett square

gametes X Y

X XX XY

X XX XY

The Punnett square was first used in 1905 by R C Punnett who used it to predict genetic

crosses. The male alleles go across the top, and the female down the side.

Key words:

chromosome Strands of DNA

DNA DeoxyriboNucleic Acid

gene Section of DNA (chromosome) that determine inherited

characteristics

allele Alternative form of a gene eg blue or brown alleles of

the gene for eye colour

gamete Sex cell – egg(ovum) or sperm

zygote Formed when an egg is fertilised by a sperm

Male is XY Female is XX

MOTHER = XX FATHER = XY

meiosis meiosis

fertilisation

female female male male 50% chance of a boy

50% chance of a girl

gametes

24

dominant If present, this allele will be expressed

recessive The characteristic of this allele will only be seen if no

dominant gene is present

homozygous The two alleles present are the same

heterozygous The two alleles present are different

phenotype Physical appearance of an individual

genotype Genetic make up of an individual

Gregor Mendel is the father of modern genetics because of the

work he did on pea plants in 1865.

He chose pea plants because they had characteristics that were

easy to see and they were easy to grow.

Two plants were taken, one which is pure-bred for tallness and one

pure-bred for shortness, and Mendel crossed them:

All the plants produced were tall.

Two of these plants were crossed and 3 out of every 4 plants were tall.

Learn these well.

They will help you to understand the

questions and so be able to answer it.

Cross 1

Cross 2

X

25

I‟‟m 1 in 2,000

This led Mendel to hypothesise that “for every characteristic there must be two

determiners”. He labelled one „dominant‟ and the other as „recessive‟.

The significance of Mendel‟s work was not recognised until the early 1900‟s because no

one had seen a chromosome.

Mendel‟s unit of inheritance was named a „gene‟ in 1910.

Punnett squares can be used to show Mendel‟s experimental crosses with peas.

Cross 1: Pure bred (homozygous) tall plant x pure bred (homozygous) short plant

Let T = tall (dominant), t = short (recessive)

Parents: TT x tt

gametes T T

t Tt Tt

t Tt Tt

Cross 2: Now if two of the F1 plants are crossed: Parents: Tt x Tt

gametes T t

T T T T t

t Tt tt

The ratio is 3 tall : 1 short

If the genotype of an individual is not known, a test cross is done. In this the unknown

individual is crossed with a known homozygous recessive.

i) Family trees or „pedigrees‟ have been used to trace characteristics through family

trees for hundreds of years

Cystic fibrosis is a genetic disorder. It cannot be caught like other illnesses, it can only

be inherited.

Cystic fibrosis causes the airways to produce a thick

sticky mucus that prevents the respiratory system

working properly. A sufferer has to have physiotherapy

to remove this mucus. It also effects how the pancreas works.

The person has to take certain digestive enzymes as tablets before

eating.

Cystic fibrosis is caused by a faulty recessive allele.

This means that both parents must be carriers (heterozygous) for

the condition if a child is to be born with cystic fibrosis. This is shown in

the Punnett square below.

All the offspring (F1) are

heterozygous tall

The offspring (F1) are:

1 homozygous tall

2 heterozygous tall

1 homozygous short

26

Always give the letter of the

dominant allele as the capital and

then the recessive allele as the

lower case of the SAME letter

Let the normal allele = N and the allele for cystic fibrosis = n

Both parents must be carriers (heterozygous):

Nn x Nn

There is a 25% or 1 in 4 chance of a child having cystic fibrosis

A family tree is often used to show how a genetic condition is passed on to successive

generations

gametes N n

N NN Nn

n Nn nn

The offspring (F1) are:

1 homozygous normal

2 heterozygous normal

1 homozygous cystic fibrosis

Children have CF even

though parents do not.

The gene for CF must

therefore be recessive and

the parents are carriers

Notes: Inheritance

There‟s quite a lot to learn in this section.

Learn the jargon and this will help you

understand what is being asked. Work through

a number of examples using a Punnett square

27

5. GENE TECHNOLOGY

Why should anyone need genetically identical individuals? Can genes be transferred between organisms artificially? Why is this done? Are there any ethical issues surrounding this technology? Is there a planning or control process surrounding the use of this technology? Candidates should: (a) know the commercial applications of clones of plants and animals. (w(iv)a) (b) know that genes can be transferred artificially from one organism to another, and understand that the introduction of genes from resistant plants into Soya bean plants, so increasing their resistance to herbicides, may increase the crop yield. (w(iv)a) (c) critically assess the issues surrounding this GM crop technology and how decisions are made, including the need to plan scientifically valid, suitable trials to assess the possible effects in order to inform the debate: for the scientific community, government policy departments, wider public opinion. (w(i)a;(iv)b,c)

a) When we grow or replace damaged and worn out cells, our cells can divide to produce

new, identical cells. This is called cell division (mitosis).

Some living things can reproduce a whole organism without making sex cells. These are

mainly plants. We can use this when we grow plants from cuttings. All the resulting

plants are identical to the parents and are called CLONES. This can be done on a

commercial scale.

Micro propagation or tissue culture.

This is a technique used in plants.

A stem from a desirable plant is cut into many pieces, each

piece has a bud. Each piece is sterilised to remove pathogens.

It is then put into a pot with growth medium and rooting

hormones. A plantlet grows which can then be potted up,

grown and sold. This method is fast and needs little space.

The plants are all genetically identical, disease free and can be

grown all the year round.

Cloning in animals is much more controversial.

Embryo transplants/cloning. Eggs are taken from the

best cows and fertilised with sperm from the best bull

in a petri dish. This is called in vitro fertilisation. The

fertilised egg divides to make a ball of cells. These

cells can be separated and each one is grown into a new

embryo. Each embryo will grow into an individual that

will be genetically identical - they will be clones. The

embryos are put into less desirable 'host' or

'surrogate' cows, which will free up the best cows for

further egg production.

28

Sheep A

Sheep B

Adult udder

cell

Mature

ovum

Nucleus

removed

Empty ovum

Nucleus removed

Mild

electric

shock

Nucleus +

ovum fuse

Embryo implanted

in sheep C

Lamb is a clone of Sheep A

ADULT CELL

CLONING

You must be able to describe how

animals are cloned and which type

of reproduction is involved

Notes: Cloning

29

b) Genes can be taken from one organism and transferred to another. This is called

‘genetic engineering’. It can be used to produce certain proteins that can then be

collected and used by humans. One example of this is the production of insulin (the

function of insulin is in section 6 homeostasis)

This technology can also be used to put in a herbicide resistant gene into crops such as

soya. This may increase the yield and so produce more food for humans and other

animals. These are called „genetically modified‟ or „GM‟ crops.

Gene for insulin

is „cut‟ out using

an enzyme

Bacterial DNA, in the

form of a circular

„plasmid‟ is removed.

Chromosome with insulin gene

Plasmid cut open using an enzyme

Insulin gene put into bacterial

plasmid using an enzyme The bacterial plasmid is put back into the

bacteria. The bacteria is then put in a

large container with plenty of food and

oxygen and multiplies rapidly.

The bacteria produce the insulin along with their own proteins. This can

then be collected, purified and used by diabetics.

30

b) The growth and use of GM crops is very controversial. Any trials must be

done scientifically with suitable controlled trials. This evidence could then

be used to inform the debate between scientists, government and the public.

For GM crops Against GM crops

Could be an answer to global

hunger. Crops with resistance to

drought and frost could increase

the areas of food production

Resistance to herbicides in GM

crops could pass out into the „wild‟

population and form „super weeds‟

which would be difficult to control

Introduced genes are not harmful

because they are digested as

other food materials into harmless

sub units.

The effect of „foreign‟ genes

outside the initial population has

not been fully researched nor is it

fully understood

Less use of artificial chemicals in

farming and less fertilizers if

genes to increase nitrate uptake

are introduced

GM crops will probably lead to

„super‟ farms and so destroy many

habitats and reduce biodiversity.

Many ethical issues arise from this new technology.

Who owns the new or „recombinant‟ DNA?

Should imperfect genes be replaced in an embryo or an embryo discarded if an

undesirable gene is found?

Be prepared to put forward

arguments for and against

such questions.

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6. HOMEOSTASIS

Why is the temperature of the body always around 37 degrees? How does the body keep it constant? Why should the level of glucose in the blood vary and so needs to be kept constant? What happens when the control mechanism fails to work efficiently? Candidates should: (a) understand that animals need to regulate the conditions inside their bodies to keep them relatively constant and protected from harmful effects. (b) recognise and label a simplified given diagram of a vertical section through the skin and understand its role in temperature regulation (c) use data to draw conclusions about the relationship between glucose and insulin levels in the blood and understand that glucose levels need to be kept within a constant range. (w(i)a) (d) know that diabetes is a condition in which a person's blood glucose may rise to a fatally high level because the body does not produce enough insulin. It can be diagnosed by the presence of glucose in the urine. (e) plan and carry out testing of artificial urine samples for glucose.

a) Homeostasis is the regulation of the conditions inside our body. Hundreds of chemical

reactions take place in our body and in our cells. For these to work correctly certain

conditions such as temperature, water content, pH and glucose levels must be kept within

a certain range. If this changes then our chemical reactions do not take place as they

should and so our body doesn‟t function as it should. This can result in illness and even

death if not corrected.

b) Our body temperature must stay at 37oC.

Our internal body temperature is detected by the thermoregulatory centre in the brain.

Our skin is the main organ that regulates our body temperature.

Normal 37o C

Too high and the chemical

reactions will go too fast and

the enzymes that control them

may be denatured or destroyed.

Too low will result in the

chemical reactions going too

slow to keep our body

working properly and alive

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Too hot Too cold

Sweat glands release sweat onto the

surface of the skin. This cools the

body down by heat loss during

evaporation of the sweat

Sweat glands do not release sweat

Blood capillaries dilate and blood flow

near the surface increases. Heat is

lost by radiation from the skin.

Blood capillaries constrict so blood flow

near surface is reduced. Heat loss is

also reduced

Hairs lay flat against the skin Hairs pulled upright by erector

muscles. This traps a layer of air and

so reduced heat loss.

No shivering Involuntary contractions of the

muscles (shivering) generates heat

energy.

c) The glucose level in the blood is detected by the pancreas.

Blood glucose levels will

increase when food is eaten.

How quickly this happens

depends on the type of food

eaten.

Glucose is used in energy

production by respiration and

so its levels will fall during

exercise.

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Too much glucose in circulation can lead to health problems including blindness and poor

circulation. The pancreas releases 2 hormones (chemical messengers) to control the level

of glucose – insulin and glucagon.

Glucose cannot be stored but can be changed into glycogen which can be stored. The flow

chart above shows how this takes place.

d) Excess glucose will pass out in the urine and this, together with excessive thirst and

the increase need to go to pass urine are sign of a diabetic. Diabetes has a number of

causes: Juvenile diabetes (type 1)– either insulin is not produced or is not detected.

Diagnosed early in life. This is also known as type 1 diabetes and is controlled by

insulin injections. It is thought to be an auto immune condition.

• Maturity onset diabetes (type 2)– confined to overweight, older people. Too little

insulin produced to meet demands of the body. This is also known as type 2

diabetes and can usually be controlled by diet.

• Stress diabetes – may occur during pregnancy or when under other physical or

mental stress. This is usually temporary and can be controlled by diet.

GLUCOSE

GLYCOGEN

glucagon insulin

When the glucose is „‟igh‟ (i)

Insulin is released

When the ’gluc has gone’

(low glucose levels)

„gluc-a-gon’ is released!!

Notes: Homeostasis

34 7. NERVOUS SYSTEM

How does the body check on its surroundings? Why are some reactions very fast? What is a reflex arc? Candidates should: (a) know that sense organs are groups of receptor cells, which respond to specific stimuli: light, sound, touch, temperature, chemicals, and then relay this information as electrical signals, called nerve impulses, to the brain. (b) know that some responses in animals are reflex actions. These reactions are fast, automatic and some are protective, as exemplified by the withdrawal reflex. (c) know that a reflex arc involves stimulus � receptor � coordinator � effector. Recognise and label a given diagram of a reflex arc to show: receptor, sensory nerve cell, connecting nerve cell in spinal cord, motor nerve cell, effector, synapses. (d) plan and carry out practical work on sensitivity and reaction times.

a) The nervous system enables us to react to our surroundings and coordinate our

behaviour.

There are 4 types of nerve cells:

RECEPTOR – an impulse starts in response to a stimulus

SENSORY NEURONE – carries the impulse from the receptor into the central nervous

system (CNS)

RELAY NEURONE – carries the impulse in the CNS (the brain + spinal cord)

MOTOR NEURONE – carries the impulse from the CNS to the effector

The EFFECTOR then causes a response.

The nervous system uses electrical

impulses that travel along our nerve

cells (neurones).

The neurones are found inside our

nerves, a bit like spaghetti in a packet.

Nerve cells can only carry an impulse in

one direction.

35

The sequence along the different neurones is shown below:

STIMULUS RECEPTOR SENSORY RELAY MOTOR EFFECTOR RESPONSE

CELL NEURONE NEURONE NEURONE MUSCLE

orGLAND

1) Receptors in the eye

detect the stimulus of

the moving ball

2) The impulse is

carried by SENSORY

NEURONES (in the

optic nerve) to the brain

3) The brain decides to

move away the hand

4) This impulse is sent by

MOTOR NEURONES to the arm

muscles (the effectors) via the

spinal cord…

6) Which then moves the

hand towards the moving ball

to catch it

This is a

VOLUNTARY

REACTION

EARS

sensitive

to sound

EARS sensitive to

sound +

changes in position

SKIN sensitive to

touch, pressure,

pain + temperature EYES sensitive

to light

NOSE + TONGUE

sensitive to

chemicals

The RECEPTOR CELLS

are found in sense organs

Make up a neumonic

36

The nerve cells are not joined up directly to the

next one. There are gaps called SYNAPSES. The

electrical impulse cannot jump the gap. A chemical is

released that crosses the gap to the next neurone

b) Automatic actions, that you do without thinking are called REFLEX ACTIONS. These

are faster than a voluntary reaction.

Reflexes are important because they help you avoid danger and control actions in your

body like breathing.

c) The reflex arc is the name given to the sequence that takes place in a reflex action.

The sequence is shown in the diagram below:

Stimulus Receptor (i.e. the thing that detects the stimulus)

Effector (i.e. the thing that will do the reaction)

Response (i.e. action taken)

Bright light Eye (iris) Iris (muscle) Muscles contract

so pupil gets

smaller

Sour taste tongue Muscles in mouth Spit it out

Losing balance ears Muscles in legs Put foot out to

keep balance

Sit on a

drawing pin

Skin on bottom Muscles in legs Stand up quickly

Notes: Nervous System

37 8. HEALTH What is health? What causes ill health? How can ill health be treated? Are there ethical issues involved with these treatments and how should decisions be made? Candidates should: (a) know that health is affected by a variety of factors and that science and technology may provide the answer to some health problems. (b) know that some conditions can be prevented and that some can be treated by drugs or by other therapies. (c) know that gene therapy has been tried but there are difficulties in targetting the appropriate cells. It has been used to alleviate symptoms in Cystic Fibrosis sufferers but is not a cure for the underlying genetic condition and there may be side effects. (w(iv)a) (d) discuss the implications of genetic counselling and the ethical problems posed by an individual's prior knowledge of a genetic trait. (w(iv)a,b) (e) discuss: • the ethical issues surrounding, and • how decisions are made about the use of animals for testing drugs (w(iv)a,b) (f) investigate experimentally the comparative energy content from burning food and understand that energy from food, which is in excess, is stored as fat by the body. (g) explore and discuss available data, e.g. from ICT searches and food labelling, about the energy and additives in highly processed and less processed foods and the implications, particularly for health. (w(i)a;(iv)a) (h) know that some conditions are due to lifestyle choices and use information/data to explore the effects that alcohol, nicotine and drug abuse have on the chemical processes in peoples' bodies. Discuss how the attitudes to smoking have changed over time as scientific evidence about its effects has accumulated. (w(iv)a,c)

a) Good health is not just the absence of illness or disease.

GOOD HEALTH

Physical fitness

contentment

Absence of illness

Positive living +

enjoyment mental fitness

Happiness

38

POOR HEALTH

Lack of exercise

discontentment

Illness

Poor living conditions

Smoking

Stress + worry

Excess alcohol Genetic disorder

Poor diet

Poor health can be due to our life style, environment of genetic make up

b) We cannot control all the factors that cause poor health. We can help reduce the

effect of ill health with:

1. Gene therapy and genetic screening

2. Drugs (medicines – legal drugs)

3. Life style choices.

c) Gene therapy is a new area of technology where a faulty or missing gene is replaced

by a healthy one.

The sequence of all our genes and their position on the chromosomes are known. This

is as a result of an international project known as the „Human Genome‟ project.

A persons chromosomes can be screened. This can be done in an adult or in an embryo.

Genetic disorders can be detected.

There are 3 main ways to add new healthy genes:

1. Use viruses to carry genes into cells

2. Healthy genes are put into an aerosol which is inhaled. It is hoped the healthy gene

will replace the defective gene. This is used in treating cystic fibrosis.

3. Genes are treated so that they can target certain cells. They are then injected

into the bloodstream and activate the target cells. This could be used in the

treatment of skin cancer.

This is a new area of treatment and there may be side effects as well as the benefits

of alleviating the symptoms. However the underlying genetic cause of certain

conditions eg cystic fibrosis will still be present.

39

d) Knowing the position of genes on our chromosomes can now allow us to find

information about ourselves that we couldn‟t until recent times. For example we can

be screened for „markers‟ for certain conditions such as certain cancers, heart disease

and diabetes. This would then give us the opportunity to change our lifestyle or to

seek medical tests to prevent the disease affecting us.

However, many people are concerned about finding out this information for a number

of reasons.

1. If we knew that we were going to get cancer it would completely dominate

our lives and those around us.

2. Life and even travel insurance companies would want to be given this

information and this could affect how much we pay for these.

3. This information may even affect our chances of a job!

This is a new technology and great care needs to be taken as its use expands.

e) Drugs. Conventional drugs take many years to produce. Research to find a drug has to

take place. Then the new drug has to go through a number of stages before it can be

used on humans. One of these stages involves using animals to test the drugs on. This is

an area of concern for many who disagree with the use of animals in this way. Great care

has to be taken to treat the animals used humanely and minimise suffering.

The drug testing has to be completed on a large enough sample. It also has to be checked

by scientists who will not gain financially from its production.

There have sadly been examples of where a drug tested for one use has been used for

another purpose. An example of theis is the drug „thallidomide‟. It was given to pregnant

woment o combat morning sickness and hadn‟t been tested for this use. The result was

severe limb deformities in many children whose mothers had take n the drug.

40

Building larger

molecules from

smaller ones For muscles

to contract

Keeping our body

warm when cold

Active transport

of materials into

and out of cells

e) Life style choices.

Different foods contain different amounts of energy. The energy value is clearly put

onto food packets so we know how much energy it contains.

In a school laboratory the following apparatus can be used to find out how much

energy is in different foods.

The food sample needs to be dry so it burns well and the water content won‟t affect the

results. The tin can will reduce the amount of heat energy that is lost to the air around.

The same amount of water must be used and the starting temperature must be the same.

The amount of energy stored in the food can be calculated per gram of food. Energy is

measured in Joules or kilo Joules.

We need to have food to supply our body with energy. The energy in our food is

eventually released by respiration and is used in our body in the following ways:

We need a certain amount of energy to carry out our life processes and so stay alive. The

amount of energy we need will depend on our age, gender, weight and also our day to day

activities.

41

• TOO MUCH

• Overweight - fat

• Arthritis

• Diabetes

• High blood pressure

• Heart disease

• TOO LITTLE

• Underweight – thin

• Muscles waste away

• Immune system doesn‟t work very well

• Periods become irregular and may stop

If our energy input, through eating, is greater than the energy we use, during our day to

day activities, the excess energy will be stored in our body as fat. This will lead to a

person becoming overweight and obese.

• A balanced human diet contains:

• CARBOHYDRATES – needed to provide energy

• PROTEIN – needed for growth, repair and replacing cells

• FAT – needed for storage of energy and cell membranes

• VITAMINS AND MINERALS – needed in small amounts for the correct functioning

of our body

• FIBRE – adds bulk to our food and gives bowels something to push against – avoids

constipation

•

Our diet should be balanced, not containing too much or too little of any of the main food

groups.

Problem Linked with

Heart disease Too much fat in diet

Diabetes (type 2) Too much sugar

Tooth decay Too much sugar

High blood pressure Too much salt

Bowel cancer Too little fibre

Obesity Too much fat and carbohydrate

INPUT OUTPUT

GETTING THE BALANCE RIGHT

42

g) Additives and preservative are put into processed food. These can affect our

health and some food colours have been linked to a change in the behaviour of young

children and teeagers. Processed food loses a lot of its nutritional value, particulary

vitamins as these can be destroyed by heating.

h) Our lifestyle choices can affect our health. Lack of exercise has an effect on the

health of our heart and circulatory system. Other factors such as smoking, alcohol and

drug abuse also affect our short term and long term health.

SMOKING:

Attitudes to smoking has changed since it was first introduced.

It has gone from being a sign of wealth, to one of sophistication to one now of disgust.

This has been mainly due to scientific research that has revealed what a burning

cigarette releases into a person and what harm those chemicals can cause. Smoking

related illnesses cost the NHS millions every year. However, the Government makes

millions from the sale of cigarettes through taxes.

The main harmful chemicals are:

Nicotine – addictive and increases blood pressure

Tar – contais over 4000 different chemicals, about 60 of which are known to be cancer

causing (carcinogens). Tar also stops the lung cleaning system of cilia from working.

Carbon monoxide – reduces the ability of red blood cells from carrying oxygen.

As well as the effects in the diagram, smoking also causes: emphysema, bronchitiis,

problems in pregnancy – reduced birth weight, arterial and heart disease, lung and other

cancers

Feeling of sickness, vomiting,

happiness or depression

Increased respiration

Increased blood

pressure

Increased

stomach

secretions

Reduced blood flow

to extremities

Increased cholesterol

levels

Increased adrenaline

release

Trembling in

heavy smokers

Increased gut movement

43

ALCOHOL

Alcohol contains the chemical ethanol.

Alcohol is a depressant and it causes reactions to slow down.

Alcohol can lead to a lack of self control and if taken to an excess can lead to

unconsciousness, coma and even death.

Alcohol is a toxin to our body and is broken down by the liver.

Excess alcohol can lead to permanent liver damage.

Alcohol can become addictive and can cause brain damage.

OTHER DRUGS

NOTES: Drugs