revision exam questions and hints. exam hints use your reading time to look at the whole exam, and...

Revision exam questions and hints

Exam hints

Use your reading time to look at the whole exam, and do the questions that you know first.

If you don’t know an answer, move on to the next question, and come back to it – that way you’re less likely to run out of time.

Read the questions carefully.Read your answer and check you have answered the question that was

asked.Don’t rewrite the question – it wastes time.Look at the marks allowed for each question – the more marks, the

more information needed (generally 1 mark = 1 point).Don’t waffle – it makes it harder for marks to be given for the correct

information you’ve provided if it is hidden in pages of unnecessary information.

For the extended answers – tick the box of the number of the question you are answering, so the marker knows which one you’ve done.

Do all the multiple choice questions – they’re worth 2 marks each and there is no penalty for a wrong answer – so if you don’t know the right answer guess, you may pick up extra marks.

Biology 2001 WATP Q32The cell membrane plays an important part in the survival of the cell. The following diagram is one idea

about the structure of the cell membrane

a) i) the cell membrane is thought to be made from 2 types of compounds, labelled A & B in the diagram above.

What is A ______________ What is B __________________

ii) Membranes are said to be differentially or semi-permeable. What is meant by this

b) Why would a cell need two different types of molecules in its membrane? What does each part do?

Molecule AMolecule B

c) Substance can enter by passive processes, such as diffusion, and active processes, such as phagocytosis. Explain the difference between the terms ‘passive’ and ‘active’.

A

B

Biology 2001 WATP Q32The cell membrane plays an important part in the survival of the cell. The following diagram is one idea

about the structure of the cell membrane

a) i) the cell membrane is thought to be made from 2 types of compounds, labelled A & B in the diagram above.

What is A phospholipid What is B proteinii) Membranes are said to be differentially or semi-permeable. What is meant by thisAllows some substances through, but not others.b) Why would a cell need two different types of molecules in its membrane? What does each

part do?Molecule A waterproof, flexible layer, self repairing, that lets in small particlesMolecule B provides channels for larger particles (facilitated diffusion), acts as pumps or gates

(active transport), acts as receptor sitesc) Substance can enter by passive processes, such as diffusion, and active processes, such

as phagocytosis. Explain the difference between the terms ‘passive’ and ‘active’. Passive – no energy required, eg osmosis, diffusion, substances move along a concentration

gradient - from areas of high concentration, to areas of low concentration.Active – energy required, eg active transport, ion pumps, gates, endocytosis, exocytosis,

substances can move against a concentration gradient - from areas of low concentration, to areas of high concentration.

A B

i) What is the name of the process that has occurred to the onion cell?

ii) How can you explain these changes?

e) After 30 minutes the student placed the onion cell in distilled water. Describe what you would expect to happen to the cell, and explain why this occurs.

Biology 2001 WATP Q32

d) A student observed changes in an onion cell which was placed in salt water. His sketches are shown below.

i) What is the name of the process that has occurred to the onion cell? Plasmolysis (osmosis)ii) How can you explain these changes?Water concentration is higher inside the cell than outside the cellWater moves out by osmosisCytoplasm shrinks and moves away from cell wall

e) After 30 minutes the student placed the onion cell in distilled water. Describe what you would expect to happen to the cell, and explain why this occurs.

Water re-enters cellBy osmosis as water concentration is now higher outside the cellCell becomes turgid/cytoplasm refillsVacuoles reappear


d) A student observed changes in an onion cell which was placed in salt water. His sketches are shown below.

The above diagram represents a segment of DNA

a) i) what is the name given to the structural unit contained in the box X?

ii) What kinds of molecules are labelled A, B and c?

A

B

C

b) i) If A is adenine and G is guanine, what are M and N?

M

N

ii) What messenger RNA bases pair with adenine and guanine

With adenine

With guanine


A

B

C

XM

NG

The above diagram represents a segment of DNAa) i) what is the name given to the structural unit contained in the box X?nucleotide ii) What kinds of molecules are labelled A, B and c?A base/nitrogenous baseB sugar/ribose sugarC phosphateb) i) If A is adenine and G is guanine, what are M and N?M thymineN cytosineii) What messenger RNA bases pair with adenine and guanineWith adenine uracilWith guanine cytosine


A

B

C

XM

NG

c) Name and describe two events that result in every gamete containing a different combination of maternal and paternal DNA

d) Explain how comparative studies of DNA support the concept of evolution

e) Describe how the occurrence of a favourable DNA mutation might affect the process of speciation in an isolated population of birds


c) Name and describe two events that result in every gamete containing a different combination of maternal and paternal DNA

Crossing over/chiasmata

- Exchange of DNA between chromatids

Independent assortmen/segregation

- Each homologous pair separates independently & randomly to the others

d) Explain how comparative studies of DNA support the concept of evolution

DNA compared by hybridisation

All organisms have DNA which is similar

Differences exist due to mutations

The least differences are seen in the most closely related species

Number of mutations correlate with time

Basic similarities in DNA suggest common ancestor

e) Describe how the occurrence of a favourable DNA mutation might affect the process of speciation in an isolated population of birds (remember VOSSSIC)

Isolated population has different conditions to original population

Mutation may give adaptive advantage

More likely to survive or breed More offspring More offspring have mutation Gene frequency changes Over a long time speciation occurs – the new population is no longer able to breed with the original

population


a) What is the mode of inheritance for this condition? (2 marks)

b) Outline the evidence in the pedigree that provides definite support for your answer in part (a) above. (3

marks)

c) What is the chance that another child of individuals 5 and 6 will be affected? Show some working.

(2 marks)

d) Despite a clear understanding of how this condition is inherited, it continues to appear in populations and families. Give a reason for its continued appearance. (1mark)

Human Biology Q43

The pedigree drawn below represents the inheritance of a rare genetic condition that affects normal liver functions. Individuals who inherit this condition experience no symptoms until they become middle-aged (40-55 years). At this point in their life, affected individuals will present with severe digestive and blood composition problems.

a) What is the mode of inheritance for this condition? (2 marks) Autosomal recessiveb) Outline the evidence in the pedigree that provides definite support for your

answer in part (a) above. (3 marks) Recessive – individuals 5 & 6 don’t have it but individual 11 doesAutosomal – individual 1 has it, but her son 4, doesn’t - individual 11 has it and her father 6 doesn’t

Human Biology Q43


c) What is the chance that another child of individuals 5 and 6 will be affected? Show some working. (2 marks)

N n 1/4N NN Nnn Nn nn

d) Despite a clear understanding of how this condition is inherited, it continues to appear in populations and families. Give a reason for its continued appearance. (1mark)

It can skip generations as it is recessiveIt doesn’t appear until later in life – often after the affected individual has had offspring (and

passed on the gene)

Human Biology Q43


e) What is the chance that Jane is a carrier?

(1 mark)

f) What is the chance that Jane will have an affected daughter?

(1 mark)

g) What is the chance that Jane will have an affected child?

(1 mark)

Human Biology Q43

A family with a history of haemophilia (X-linked recessive) has the following pedigree:

e) What is the chance that Jane is a carrier? (1 mark) ½ (mother is carrier)f) What is the chance that Jane will have an affected daughter? (1 mark)

0 – her husband is unaffected

g) What is the chance that Jane will have an affected child? (1 mark)

If she is a carrier, she has ¼ chance of affected childShe has ½ chance of being a carrierHer chance = ¼ x ½ = 1/8

Human Biology Q43

A family with a history of haemophilia (X-linked recessive) has the following pedigree:

Normal = XH Haemophilia = Xh

XH

XH

Xh

Y

XH XH

XH

XH Xh

XhY Y

Carrier female

Normal male

a) What is the probability that individual III-4 is heterozygous? Show your working. (2 marks)

b) List all the individuals for whom genotype is uncertain. (2 marks)

c) If individual III-2 married and had children with an affected person, what is the chance that their child will have the condition? Show your working. (2 marks)

d) A second student examined this pedigree and made the statement: "There is evidence on the pedigree that this condition could also be inherited as a sex linked recessive

condition". Is this statement correct or incorrect? Use evidence from the pedigree to support your answer.

(2 marks)

Human Biology Q46The pedigree shown below represents the inheritance of a genetic condition that affects normal vision. A student examined this pedigree and concluded that the condition must be inherited in an autosomal fashion. On the basis of this information, answer the questions below. In your analysis, use the letters N or n.

a) What is the probability that individual III-4 is heterozygous? Show your working. (2 marks)

100% - she doesn’t show the condition so must have N, and mother has the condition, so must have given her a n

b) List all the individuals for whom genotype is uncertain. (2 marks)II4, II5, II7, III2


N = normal, n = disease

If individual III-2 married and had children with an affected person, what is the chance that their child will have the condition? Show your working. (2 marks)

His parents are both Nn, so he has 2/3 chance of being NnIf he is Nn his children have ½ chance of being nn, as their mother is nn

d) A second student examined this pedigree and made the statement: "There is evidence on the pedigree that this condition could also be inherited as a sex linked recessive

condition". Is this statement correct or incorrect? Use evidence from the pedigree to support your answer.

(2 marks)

No – II6 has it and her father doesn’t - II6 has it and her son doesn’t


Extended answers

When choosing the extended answers look for the ones you can put the most information about – you want at least 10 points

Diagrams are a useful way of getting marks – draw one if it is relevant. Remember to put on labels

Tables are acceptable & help you organise the information you want to get over

Be explicit – even if it looks obvious (eg in an osmotic regulation question write down which has the most water & salt which way the water will move)

Provide examples (eg arid adaptations of plants include rolled leaves eg marram grass, water storage eg cactus, boab) – there are often marks attached

Read the questions carefully – make sure you are answering the question they want


a) Mitosis and meiosis are important processes in cells and both contribute in some way to reproduction. Discuss the purpose of mitosis and meiosis and in what ways these processes are different.

b) The transport of water from the soil to the leaves of plants is essential for the survival of all plants. Flowering plants have many structural and physiological adaptations for transporting water and other nutrients. Discuss some of the adaptations of the roots, stems and leaves which allow water and other nutrients to be transported throughout the plant.

c) DNA carries the genetic information to manufacture enzymes. Discuss the structure of DNA and how this code is translated into proteins such as enzymes.

d) Scientists are concerned about large scale changes in the global ecosystem, such as deterioration of the ozone layer, desertification and the greenhouse effect (global warming), arising from the activities of humans. Explain the terms ‘deterioration of the ozone layer’ and ‘the greenhouse effect ‘ and discuss the causes and consequences of each of these problems.


a) Mitosis and meiosis are important processes in cells and both contribute in some way to reproduction. Discuss the purpose of mitosis and meiosis and in what ways these processes are different.

Key questions to answer – purpose of mitosis (ie asexual reproduction, growth & repair)purpose of meiosis (ie sexual reproduction/production of gametes)differences between the 2 – consider table for your answer

mitosis meiosisLocation all cells gonads/sex organsNumber of divisions 1 2Number of cells produced 2 4Amount of variation none lotsChromosome number diploid haploid


b) The transport of water from the soil to the leaves of plants is essential for the survival of all plants. Flowering plants have many structural and physiological adaptations for transporting water and other nutrients. Discuss some of the adaptations of the roots, stems and leaves which allow water and other nutrients to be transported throughout the plant.

Key questions to answer – Structures for water, salt & sugar transport in plantsYou should use diagrams for this oneRoots – root hairs inc SA, use of active transport to inc salt concentration in roots (pulls in water by osmosis), size & distribution of roots (eg deep taproots, shallow roots)

Stems – Xylem for water & salts – dead cells, lignin for strengthening, thin tubes (capillary action)Phloem for sugars – living cells with sieve plates & companion cells, active transport of sugar into and out of phloem (translocation)

Leaves – stomata & guard cells, water loss through stomata creates transpiration stream, turgor pressure opens guard cells


DNA carries the genetic information to manufacture enzymes. Discuss the structure of DNA and how this code is translated into proteins such as enzymes.

Key questions to answer – Structure of DNAYou should use diagrams for this oneDouble helixNucleotides – Sugar, phosphate and base4 nucleotides – thymine, adenine, guanine, cytosineBase pairing rule A- T, C - G

How code proteins Codon – 3 nucleotides amino acidRibosomes make the proteinsmRNA takes code to ribosome sequence of amino acidsUracil replaces thymine, other nucleotides the sametRNA carries amino acid to ribosomeAnti-codon on tRNA complements mRNA (A-U, C-G)

Biology 2001 WATP Q36Scientists are concerned about large scale changes in the global ecosystem,

such as deterioration of the ozone layer, desertification and the greenhouse effect (global warming), arising from the activities of humans. Explain the terms ‘deterioration of the ozone layer’ and ‘the greenhouse effect ‘ and discuss the causes and consequences of each of these problems.

Key questions to answer – What is deterioration of the ozone layerWhat is the greenhouse effectYou should use diagrams for this

Causes of both Ozone – CFC (refrigeration), halons (industry)Greenhouse – carbon dioxide (combustion & industry), methane (ruminants, decaying rubbish), CFC

ConsequencesOzone – increased UV rays increased skin cancer, damage to phytoplankton loss of productivityGreenhouse – increased global temperature, climate change, sea level rise, increase in diseases carried by insects loss of productivity, etc


a) Marine fish face osmoregulatory problems (water and salt balance). Explain the nature of these problems, and ways in which these fish maintain salts and water in homeostatic balance.

b) Cells perform a large number of processes essential for their survival. Aquatic single-celled organisms face particular problems. Outline the roles of the cell nucleus and other organelles which provide energy, remove wastes, repackage organic substances or allow the aquatic cell to move about in its environment.

c) The concept and meaning of evolution has changed from Darwin’s time to our modern era. How have the ideas about evolution changed since they were first mooted as a scientific explanation of life on Earth? What evidence is used to support the concept of evolution?

d) Since European settlement, much of our natural bush has been cleared for farmland, housing or industry. The ecosystems initially present in bush areas have changed considerably, and productivity has changed accordingly. Compare natural and urban ecosystems in terms of productivity, stability, inputs and outputs, and predict what you think will happen to our environment as more bushland disappears due to human expansion and progress.


a) Marine fish face osmoregulatory problems (water and salt balance). Explain the nature of these problems, and ways in which these fish maintain salts and water in homeostatic balance.

Sad fish – happy fish – but ONLY for sea

Key questions to answerNature of problem – Marine environment has lower water and higher salt than the fishFish will lose water by osmosis and gain salt by diffusionUnregulated this leads to cells shrivelling up/ fish dehydrating

Ways fish solve problemDrink constantlyUrine is concentrated & only small amount producedSalt is excreted from gillsShark produces urea & keeps high concentration in blood, so blood is same osmotic concentration as sea water (osmoconformer)


Cells perform a large number of processes essential for their survival. Aquatic single-celled organisms face particular problems. Outline the roles of the cell nucleus and other organelles which provide energy, remove wastes, repackage organic substances or allow the aquatic cell to move about in its environment.

Key questions to answerCell structures & functionsDiagram may be useful

Nucleus – controls cell activity

Energy – mitochondria (aerobic respiration), [cytoplasm (anaerobic respiration)], chloroplast (photosynthesis)

Remove wastes – cell membrane (exchange), lysosomes (contain enzymes to destroy wastes), [contractile vacuole (removes excess water]

Repackage – Golgi body

Movement – cilia and flagella


The concept and meaning of evolution has changed from Darwin’s time to our modern era. How have the ideas about evolution changed since they were first mooted as a scientific explanation of life on Earth? What evidence is used to support the concept of evolution?

Key questions to answerKey points of evolution – remember VOSSSIC (natural selection)

1st theories Darwin (natural selection, but couldn’t explain inheritance as no genetics knowledge) & Lamarck (acquired characteristics can be passed on eg giraffes stretching their necks)

Modern theories useGenetics to explain inheritance (provided by Mendel)DNA, mutations & events of sexual reproduction as sources of variationEffects of random genetic drift

EvidenceFossils; biogeography; comparative anatomy, embryology or immunology; biochemistry – DNA or proteins; artificial selection or breeding

Biology 2001 WATP Q37d) Since European settlement, much of our natural bush has been cleared for

farmland, housing or industry. The ecosystems initially present in bush areas have changed considerably, and productivity has changed accordingly. Compare natural and urban ecosystems in terms of productivity, stability, inputs and outputs, and predict what you think will happen to our environment as more bushland disappears due to human expansion and progress.

Key questions to answerCompare natural and urban ecosystems in terms of productivity, stability, inputs and outputs – this is probably best as a table (if you can remember the diagram that might help too)

natural urbanProductivity high lowStability high lowInputs low – sun high – food, fuel, goodsOutputs low – some run-off high – pollution, wastes, sewage

Predict what you think will happen to our environment as more bushland disappearsExtinctions, loss of biodiversity, productivity & stabilityIncrease in environmental problems eg greenhouse, salinity, erosion

revision exam questions and hints. exam hints use your reading time to look at the whole exam, and...

Documents

cell membrane ai

onion cell

active processes

b protein

active energy

passive processes

molecule b c substance

areas of high concentration