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B1 B2 B3

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B1 – You and your Genes

Locating genes

Genes are located in chromosomes which are in the nucleus of cells

cell

nucleus

23 pairs = 46 chromosomes altogether

Sperm cells can have an X or Y sex chromosomeEgg cells can only have an X sex chromosome

Most characteristics are determined by genes called alleles

An allele can be dominant, recessive (or co-dominant)

Alleles mostly come in pairs

The alleles you inherit is called your genotype

Your phenotype is what you look like, your

characteristics

Punnett

square

If both the alleles you inherit are the

same you are homozygous for that

characteristic e.g. NN or nn

If you inherit different alleles you are heterozygous e.g Nn

Disease What it affects Type of allele

cystic fibrosisthe lungs – sticky mucus – difficulty in breathing

recessive

haemophylia the blood can’t clot

recessive

Huntington’s diseasethe nervous system – uncontrollable movements

dominant

sickle cell anaemia

the bloods ability to pick up oxygen

co-dominant

These are the key ones to remember

inherited

Characteristics depend on

environment

both

eg eye colour eg dyeing your hair

eg weight

Identical twins (formed when a fertilised egg starts to divide and splits to form 2 babies instead of one).

Natural clones

Asexual reproduction (eg bacteria)

Clones have got identical genes

Plant cuttings can be grown into clones of the original plant.

Stem cells are unspecialised cells

Shows stem cells being extracted from a blastocyst

early embryo

Making stem cells using the DNA from a patient means the cells wont be rejected when they are transplanted into the patient

This means that the patient’s immune system wont attack the transplanted stem cells

foreign cell with antigen

White blood cells recognise it as a foreign cell and make antibodies

The antibodies help to kill the

foreign cell

X

With this technique the white blood cells do not recognise the

transplanted stem cells as foreign and therefore don’t attack them

IVF – In Vitro Fertilisation

Embryos left over from IVF treatment can be used to obtain stem cells

The fertilised egg can now be implanted into the uterus of the mother

The fertilised egg can now be tested for genetic diseases if desired.

controversial

The right decision is the one which leads to the best outcome for the majority of people involved

Some things are considered to be unnatural or wrong

Opinion. Against cloning and against

using embryos.

Opinion. Seems to be against using stem cells. Points out possible risks. Uses exaggerated

language. No mention of embryos.

Seems to be for using stem cells. Hasn’t said anything

about using embryos.For using stem cells and using embryos.

These people could be biased.

Gordon is supposed to be impartial, ie he should give a balanced view.

The other people could have a vested interest, ie they could have a direct benefit or are campaigners for a cause.

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Spend 10 min writing down everything you can remember about B1

a gene

recessive

chromosomes

John

Reshma

Kate

Lucy

46

XY

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Higher material

understand that genes are instructions for a cell that describe how to make proteins, which may be structural or enzymes;

recall that the sex of a human embryo is determined by a gene on the Y chromosome;

understand the link between this gene and the development of sex organs into either ovaries or testes.understand the implications of testing embryos for embryo selection (pre-implantation genetic diagnosis);

understand the implications of the use of genetic testing by others,(for example for genetic screening programmes, by employers and insurance companies.);

in the context of use of genetic testing by others can:

• distinguish what can be done (technical feasibility), from what should be done (values);

• explain why different courses of action may be taken in different social and environmental contexts.

understand how clones of animals occur:

• naturally, when cells of an embryo separate (identical twins);

• artificially, when the nucleus from an adult body cell is

transferred to an empty unfertilised egg cell;

Spend 10 min writing down everything you can remember about B1

f

f

F fJane must be a carrier because her mother Kate has the condition.ffFf

Ff ff

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B2 - Keeping Healthy

cold flu

viruses

bacteria

antibiotics

Antibiotics are only effective against bacteria or fungi.

Symptoms of disease are caused by damage to cells and by toxins.

fungi

Warmth and moisture are good conditions for microorganisms to grow.

m i c r o o r g a n i s m s

foreign cell with antigen

White blood cells recognise it as a foreign cell and make antibodies

The antibodies help to kill the

foreign cell

X

Memory cells “remember” how to make these antibodies so if you are infected again your immune system can make the right antibodies quickly – you become immune to that particular form of microbe.

animation

a vaccine is a dead or weakened form of bacteria or virus.

When administered the vaccine causes an immune response and eventually antibodies are produced.You are now immune to that particular microbe so if you get infected with a real version you won’t get ill.

What is a vaccine ?

Why is it important for at least 95% of people in a society to take a vaccine against a a particularly harmful virus or bacteria ?

> to eradicate the virus or bacteria

Why do vaccines against influenza have to be developed regularly ?

> because the virus changes very quickly

Over a period of time, bacteria and fungi may become resistant to antibiotics.

How can we reduce antibiotic resistance ?> we should only use antibiotics when necessary and always complete the course

Developing drugs

• test them on cells and animals in a laboratory• test them on healthy volunteers for safety• test them on people with the illness

Why do heart muscle cells need their own blood supply ?> because the heart has thick muscular walls

Why do arteries have thick muscular walls ?

Why do veins have valves ?

> to control blood flow by contracting or dilating

> to prevent blood from flowing backwards

A healthy artery

A partly blocked artery

A common cause of heart attack

HDL (high density lipoprotein) cholesterol is good for youLDL (low density lipoprotein) cholesterol is bad for you

What is a peer review ?> a review by fellow scientists to check that a study was done properly

What increases the confidence in a scientific claim ?• if it has been peer reviewed

- fair test

• if it has been replicated by other scientists

- large enough sample

LDL cholesterol levels

Ris

k o

f h

eart

att

ack

Shoe size

Readin

g

ag

e

There is a correlation between shoe size and reading age.

But is there a causal link ?No

There is a correlation between LDL cholesterol levels and the risk of having a heart attack.

Correlation or cause ?

But is there a causal link ?Yes

Homeostasis is the maintenance of a constant internal environment.

Strenuous exercise, survival in hot or cold climates affects homeostasis (eg temperature and water balance).

The cold water convects a lot of heat away from the body.

The air gets thinner with less oxygen as you climb higher.

scuba diving

Control of water balance

Water is gained from drinks, food and respiration and is lost through sweating, breathing, faeces and the excretion of urine.

A balanced water level is important for maintaining the concentration of cell contents at the correct level for cell activity.

The kidney works by:

• filtering small molecules from the blood to form urine (water, salt and urea)

• excreting the remaining urine, which is stored in the bladder

• reabsorbing as much water as the body requires

• reabsorbing as much salt as the body requires

• reabsorbing all the sugar

The kidneys balance water levels by producing dilute or concentrated urine as a response to the concentration of blood plasma.

The concentration of urine is controlled by a hormone called ADH, which is released into the bloodstream by the pituitary gland.

The concentration of blood plasma varies with external temperature, exercise level, intake of fluids and salt.

Play animationADH levels increased

ADH levels decreased

danger

danger

wate

r le

vel in

the

blo

od

ADH secretion is controlled by negative feedback

time

Alcohol results in a greater volume of more dilute urine, due to ADH suppression, which can lead to dehydration.

The drug Ecstasy results in a smaller volume of less dilute urine, due to increased ADH production.

more dilute = less concentrated

less dilute = more concentrated

Continue with Foundation Go to Higher

B D C

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5 x 5000

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ADH

hypothalamus

pituitary

increases

{because more water ends up in the urine}

error on original paper has been corrected

Draw a straight line from the correct description to the correct explanation

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Why is it necessary to vaccinate a high percentage of a population ?to prevent epidemics

Can distinguish what can be done (technical feasibility) from what should be done (values).

Can explain why different courses of action may be taken in different social and economic contexts.

How can antibiotics become less effective ?

due to random changes (mutations) in the genes of microorganisms

What is a ‘blind’ trial ?one where the patient doesn’t know whether they have received the real treatment or a placebo

What is a double ‘blind’ trial ?one where the patient and the medical staff do not know whether the real treatment or a placebo is being used

Why are ‘blind’ and double ‘blind’ trials used ?

they reduce the influence of psychological factors and enable evaluations to be more objective

Why are placebos not commonly used in human trials ?

when not giving a real treatment could result in patient deaths etc or when patients could benefit from treatment

What is an open label trial?

Both the patient and the doctor know the treatment, no one is

given a placebo

Can use data to develop an argument that a factor does/does not increase the chance of an outcome.

Can identify the presence (or absence) of a plausible mechanism as significant for the acceptance (or rejection) of a claimed causal link.

Epidemiological studies are the study of diseases in

populations of humans or other animals, specifically how, when and

where they occur.

Genetic study studies the types of genes a person has to look for alleles

that increase the risk of disease

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B3 - Life on Earth

Adaptations• Species – similar organisms that are capable of breeding to

produce fertile offspring

Adaptations – features that

species have that help

them survive in their

environments

Extinction can occur

if a species can’t adapt to

• Increased competition

• New predators

• New diseases

Cactus – spines to

reduce water loss

deep, wide-

spreading roots to

obtain water

Fish – gills to take oxygen

Streamlined to move easily

Swim bladder to maintain position in water

Food chains and webs

Food chains (start with plants, the producers)

•Animals are dependent upon each other

and their environment for survival.

•Food webs – show how all food chains are inter-related and dependent on each

other (interdependence)

•Environmental changes can alter the

food web.

•All living things ultimately get their energy from the sun

Energy transfer•Plants capture energy from sunlight to build organic compounds

(photosynthesis).

•The compounds can be broken down to release

energy (respiration).

•Animals are consumers and break down food

molecules in respiration to release energy, used

for e.g. growth, keeping warm etc

•Only about 10% of the energy at each stage of a

food chain gets passed to the next level. The rest

-Escapes as heat and used for movement

-Excreted or cannot be eaten and passes to decomposers (bacteria and fungi)

Energy flows into decomposers and detritivores (e.g.woodlice) as they

feed on dead organisms and waste material

The carbon cycleCarbon dioxide is taken out of the atmosphere by photosynthesis

and the glucose produced is broken down during respiration, this

releases carbon dioxide back into the atmosphere

Dead organisms are broken down by microorganisms (decomposition)

to release carbon and this becomes part of a new organism.

Carbon dioxide is also added to the atmosphere by combustion (burning)

Measuring environmental changeMeasuring environmental change

Carbon dioxide levels are

rising, this is thought to be

linked to rises in

global temperature.

Climate change can be measured by

looking at the impact on living organisms

like phytoplankton.

Many species are threatened with extinction

if conditions change beyond their ability to

adapt.

The Nitrogen cycle

Life on Earth started at least 3,500 million years ago.

How did this incredible variety of life evolve ?

complex

simple

Charles Darwin

Some of the finches on the Galapagos Islands

Natural Selection

The key ideas relating to natural selectionVariation:

All members of a particular species have variations in their characteristics.

Environmental pressure:

Changes in the environment whether due to climate or disease or other species can make it difficult or impossible for some members of a species to survive.

Survival of the fittest:

Members of a species which have the characteristics to survive in an environment will pass their successful characteristics on to the next generation by passing on their genes.

Those that do not have successful characteristics will tend to die out.

Population size:

Population size tends to increase which means more competition for resources.

The fossil record is evidence for evolution

Embryonic evidence

Early embryonic development among vertebrates is very similar.

common ancestry

Evolution takes a long time

“Hi, my name is Adam and this is my partner Eve”

For 3 billion years life on Earth was single celled organisms or very simple multi-celledThen for the next 600 million years …

Only joking !!

This cartoon is incorrect.

We didn’t evolve from apes.

X

We evolved from ape-like mammals.

common ancestor

Tattersal

Wood

Johanson

3 theories about human evolutionThe branches in the

diagram show divergenceAll of the species are extinct except one – us.

The evolution of a larger brain gave some early humans a better chance of survival.

Notice there are a lot of question marks

Clarence Darrow and William Jennings Bryan, lawyers in the famous 1925 Scopes trial in Tennessee, America.

Not everyone agreed with the idea of natural selection.

To this day, the idea of natural selection is still challenged.

Creationism

This kind of explanation is not scientificIt is not based on observable evidence and cannot be

tested.

If the conditions on Earth had, at any stage, been different from what they actually were, evolution by natural selection could have produced different results.

eg humans might not have evolved

cabbage

cauliflower

broccoli brussel sprouts

Selective breeding

(“human” selection as opposed to natural selection)

How to get sweet tomatoes

1. Grow some normal non sweet tomatoes2. Select seeds from the sweetest one and breed some more tomatoes

3. Keep doing step 2 until you have tomatoes with the desired sweetness

(basic idea)

What can cause a species to become extinct ?• the environmental conditions change;

• a new species that is a competitor, predator or disease organism of that species is introduced;

• another organism in its food web becomes extinct;

Human activity is the main cause of modern extinctions.

Directly:

The passenger pigeon – mainly due to hunting.

Indirectly: The dodo – destruction of habitat and the introduction of other animals (eg pigs) to the island (Mauritius) who ate the eggs

Maintaining biodiversity is an important part of using the environment in a sustainable

way.

Biodiversity may be important for the future development of food crops and

medicines.

Biodiversity means the variety of life that exists on Earth.

Sustainability means that the needs and requirements of

People are met without damaging the Earth for future

generations

Specimen paper questions on B3 - Foundation

Go to HigherContinue with Foundation

evolution

natural

F

R

E

the brain

F

A

D

E

B

C

F

F

B

D

A

F

F

B

E

F

A

C

D

D

F

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Higher material

• interpret data on changes in a species in terms of natural selection;

• recall that changes can occur in genes (mutations)

• understand that mutated genes in sex cells can be passed on to offspring and may occasionally produce new characteristics

• understand that the combined effect of mutations, environmental changes and natural selection can produce new species

Specimen paper questions on B3 - Higher

H

B

E

F

A

C

D

D H

H

H

H

H