Revision B1 B2 B3 Go to B1 Go to B2 Go to B3

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 chromosome Egg 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

DiseaseWhat it affectsType of allele cystic fibrosis the lungs – sticky mucus – difficulty in breathing recessive haemophyliathe blood can’t clot recessive Huntington’s disease the nervous system – uncontrollable movements dominant sickle cell anaemiathe bloods ability to pick up oxygen co-dominant These are the key ones to remember

inherited Characteristics depend on environment both eg eye coloureg 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.

Go to HigherContinue with Foundation

Spend 10 min writing down everything you can remember about B1

a gene recessive chromosomes

John Reshma Kate Lucy

46 XY

Go to B1 Go to B2 Go to B3

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 Ff Jane must be a carrier because her mother Kate has the condition. ffFf ff

Go to B1 Go to B2 Go to B3

B2 - Keeping Healthy

coldflu virusesbacteria 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 you LDL (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 Risk of heart attack Shoe size Reading age 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 animation ADH levels increased ADH levels decreased danger water level in the blood 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

BDC

x x x

5 x 5000

x x x

x x x

A C B

x x x

CA D

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

Go to B1 Go to B2 Go to B3

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

A C B 1

CA D b

x x x

x x x

x x x

x x x

x x x x

x x x x

x x x x

Go to B1 Go to B2 Go to B3

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 cycle Carbon 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 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 selection Variation: 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-celled Then 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 evolution The branches in the diagram show divergence All 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 scientific It 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 cauliflowerbroccolibrussel sprouts Selective breeding (“human” selection as opposed to natural selection)

How to get sweet tomatoes 1. Grow some normal non sweet tomatoes 2. 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

ADEADE BCFBCF F

B D A F

F

BEFBEF ACDACD D F

Go to B1 Go to B2 Go to B3

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

BEFBEF ACDACD D H

H

H

H

H