Edexcel A Level Biology B Paper 2: Advanced Physiology, Evolution and Ecology November 2020 question paper 9BI0/02

1h 45m 90 marks

9 questions

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A karyotype shows the chromosomes found in the cells of an individual.

The photograph shows a karyotype from a child with a genetic condition.

(Source: © Dept. of Clinical Cytogenetics, Addenbrookes Hospital / Science Photo Library)

(a)(i)

Which of the following identifies the genetic condition shown in the photograph?

$Question 1, shown as an image$

(1)

Answer

(a)(ii)

Which process would have caused the genetic condition shown by this karyotype?

$Question 1, shown as an image$

(1)

Answer

(b)

The photograph shows cells in different stages of mitosis.

(Source: © STEVE GSCHMEISSNER / Science Photo Library)

(b)(i)

Which of the following correctly identifies the stages shown in the photograph?

(1)

Answer

(b)(ii)

Colchicine is a chemical that inhibits mitosis.

A student investigated the effect of colchicine on mitosis.

Two sets of genetically identical cells were grown in culture. Colchicine was added to one culture of cells but not to the other culture of cells.

Six hours after treatment, the mean percentages of cells in each stage of mitosis were determined.

The results are shown in the table.

Mitosis	Mean percentage of cells in stage ± Standard Deviation
stage	cells cultured without colchicine	cells cultured with colchicine
interphase	84.8 ± 4.2	82.8 ± 3.2
prophase	10.2 ± 2.2	16.3 ± 3.1
metaphase	1.8 ± 0.4	0.8 ± 0.2
anaphase	1.8 ± 0.2	0.7 ± 0.1
telophase	1.4 ± 0.3	0.4 ± 0.1

Analyse the data to comment on how colchicine affects mitosis.

(4)

Answer

Acetylcholine is a neurotransmitter produced by the parasympathetic nervous system.

(a)

Describe the process by which acetylcholine is released from a synapse.

(4)

Answer

(b)

Some chemical pesticides, such as diisopropyl fluorophosphate (DFP), affect the activity of synapses.

This pesticide acts by binding irreversibly to the R group of an amino acid in the active site of acetylcholinesterase.

(b)(i)

Explain why DFP inhibits the activity of acetylcholinesterase.

(2)

Answer

(b)(ii)

Explain why a person poisoned with DFP has a slower heart rate.

(3)

Answer

(a)

The diagram shows a cell from the proximal convoluted tubule of the nephron.

Explain how the features shown in the diagram enable this cell to carry out its function.

(4)

Answer

(b)(i)

Which of the following statements about facilitated diffusion are correct?

1. substances move through membrane proteins

2. substances move against a concentration gradient

3. substances move down a concentration gradient

4. substances move between phospholipids

$Question 3, shown as an image$

(1)

Answer

(b)(ii)

(1)

Answer

In cats, the gene for fur length is not located on the X chromosome. The allele for short fur (F) is dominant to the allele for long fur (f).

The pedigree diagram shows the inheritance of fur length in a family of cats.

(a)

Explain how one piece of evidence from the diagram shows that the allele for short fur is dominant to the allele for long fur.

(2)

Answer

(b)

A gene for fur colour in cats is located on the X chromosome.

The alleles for black fur (X^B) and orange fur (X^o) are codominant.

Tortoiseshell cats have areas of black and orange fur.

(b)(i)

Give all the possible genotypes of a male, black cat with short fur.

(1)

Answer

(b)(ii)

Explain why all tortoiseshell cats are female.

(2)

Answer

(b)(iii)

In a genetic cross, a tortoiseshell cat with long fur was mated with an orange male cat, heterozygous for fur length.

Deduce the probability of producing a tortoiseshell cat with long fur from this cross.

Use a genetic diagram to support your answer.

(4)

Answer

Palm plants and cocoa plants are used to produce lipids for the food industry.

Palm oil is produced from palm plants. Cocoa butter is produced from cocoa plants.

(a)

(2)

Answer

(b)

The fatty acid compositions of palm oil and cocoa butter are shown in the table.

Fatty acid	Chemical formula of fatty acid	Palm oil	Percentage of fatty acid found in palm oil and cocoa butter (%) Cocoa butter
palmitic acid	C₁₆H₃₂O₂	45	27
oleic acid	C₁₈H₃₄O₂	40	31
linoleic acid	C₁₈H₃₂O₂	10	3
myristic acid	C₁₄H₂₈O₂	1	1
stearic acid	C₁₈H₃₆O₂	4	38

(b)(i)

How many of the named fatty acids shown in the table are saturated?

$Question 5, shown as an image$

(1)

Answer

(b)(ii)

The percentage solid fat content (% SFC) is a measure of how much of a lipid is solid at different temperatures.

The graph shows the effect of temperature on the % SFC for palm oil and for cocoa butter.

Comment on the effect of temperature on the % SFC of palm oil and of cocoa butter.

(4)

Answer

(c)

Some forests in Borneo have been cleared to grow these plants.

Orangutans used to live in forests throughout this island but now they are found in small areas of forest.

The map shows the distribution of orangutans in parts of Borneo.

(c)(i)

Explain why in areas with low populations of orangutans, many of the orangutans have deformities and health problems.

(2)

Answer

(c)(ii)

The Malaysian government is paying local people to create and maintain ‘land-bridges’ of forest to link areas of forest together.

Explain why these payments will help to develop palm oil production and support conservation of orangutans.

(3)

Answer

(c)(iii)

State how treaties such as CITES help conserve orangutans.

(1)

Answer

The speed of a nerve impulse along a neurone depends on the diameter and the presence or absence of myelin.

(a)

The graph shows an action potential in a neurone.

When are voltage-gated sodium channels open?

$Question 6, shown as an image$

(1)

Answer

(b)

The graph shows the relationship between the diameter of the neurone and the speed of nerve impulses along myelinated and non-myelinated motor neurones.

(b)(i)

Compare and contrast the effect of diameter on the speed of an impulse in myelinated and non-myelinated motor neurones.

(4)

Answer

(b)(ii)

Determine the speed of a nerve impulse along a myelinated motor neurone with a diameter of 5 μm.

The equation for a linear relationship is y = mx + c

(3)

Answer

(b)(iii)

Multiple sclerosis (MS) is a disease that results in the loss of myelin around motor neurones.

Explain why the speed of nerve impulses along axons is slower in people with MS.

(3)

Answer

The primary productivity of plants depends on their ability to synthesise carbohydrates and transport solutes to cells.

(a)

The diagram shows the movement of water across a root.

What is the name of the water movement pathway shown in the diagram?

$Question 7, shown as an image$

(1)

Answer

(b)

Explain how the mass-flow hypothesis accounts for the movement of sugars from leaves to roots.

(4)

Answer

(c)

(6)

Answer

(a)(i)

Calculate the volume of oxygen bound to haemoglobin at a partial pressure of oxygen of 6 kPa in 100 cm³ blood.

The concentration of haemoglobin is 15 g per dm³ blood.

When fully saturated, there is 1.36 cm³ oxygen per g of haemoglobin.

(3)

Answer

(a)(ii)

Explain why the oxygen dissociation curves for haemoglobin and myoglobin are different.

(4)

Answer

(b)

(4)

Answer

(c)

Tibetan populations have a recessive allele that helps them to survive at high altitude.

In a village in Tibet, 1950 people out of a population of 2500 people carry two copies of this allele.

(c)(i)

Calculate the number of heterozygous people in the village.

Use the Hardy-Weinberg equation

(3)

Answer

(c)(ii)

This allele is currently found only in human populations in Tibet.

The allele has also been found in the fossil bones of an extinct form of modern humans called the Denisovans.

Fossils of Denisovans have been found in Tibet.

Explain why scientists think that the Denisovans belonged to the same species as modern humans.

(2)

Answer

The diagram shows the structure of a rod cell.

(a)(i)

How many of the labelled organelles have a double membrane?

$Question 9, shown as an image$

(1)

Answer

(a)(ii)

Which of the following statements about the effect of light on rod cells are correct?

1. rhodopsin breaks down into opsin and trans-retinal

2. voltage-gated sodium channels open in the membrane

3. more neurotransmitter is released from the presynaptic terminal

$Question 9, shown as an image$

(1)

Answer

(b)

(6)

Answer

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Edexcel 9BI0 · Paper 2

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