Edexcel A Level Biology B Paper 2: Advanced Physiology, Evolution and Ecology June 2017 question paper 9BI0/02

Chemical control in plants is brought about by plant growth substances such as auxins.

Auxins cause elongation of cells.

Auxins weaken the bonds between molecules found in cell walls. Molecules found in cell walls include cellulose and hemicellulose.

Which of the following statements about cellulose molecules is correct?

The following statements relate to calcium pectate:

1. found in the middle lamella

2. holds cell walls together

3. prevents the movement of water

Which of the following is correct for calcium pectate?

A scientist investigated apical dominance in plants.

In experiment 1, the shoot tips were cut off and the growth of lateral shoots assessed.

This was repeated in experiment 2, but auxin was placed over the cut end of the tips and the growth of lateral shoots was assessed.

The results are shown in the diagrams.

Explain how the interaction between auxins and cytokinins could have produced the results shown in the diagram.

The brain is involved in many homeostatic mechanisms.

The diagram shows a vertical section through a human brain.

Which row of the table correctly matches the regions X, Y and Z with their functions?

An action potential results from the depolarisation of the membrane of a neurone.

Which row of the table shows the correct state of the ion channels during this depolarisation?

The autonomic nervous system plays a role in regulating heart rate.

The diagram shows an ECG trace from a student before and during exercise.

Calculate the heart rate of this student during exercise.

Describe how exercise results in an increased heart rate.

In flowering plants, pollen grains grow pollen tubes that are involved in fertilisation, producing a zygote and endosperm.

Which row of the table shows the correct description for these nuclei?

The mean length of the pollen tubes in the control group was 7.5 mm.

Calculate the mean length of the pollen tubes after adding 0.010 μg cm^–3 of chemical A.

Analyse the data to comment on the effects of chemical A and chemical B on the roles of transcription and translation in pollen tube growth.

The retina is the light sensitive structure in the eye.

The diagram shows some of the cells in a human retina.

Which row in the table correctly identifies the cells W, X and Y ?

Draw an arrow on the diagram to show the direction of the light passing through the retina.

Explain why a higher light intensity is required to produce an action potential in cell Z than in cell W.

Explain how the diagram shows that red-green colour blindness is caused by a recessive allele.

Use a genetic diagram to determine the probability that the next child of individuals 6 and 7 is a male who is colour blind.

The diagram shows the structure of a synaptic junction between three neurones.

Neurone A releases the excitatory neurotransmitter acetylcholine.

Neurone B releases the inhibitory neurotransmitter glutamate.

Glutamate causes chloride ions to move into the postsynaptic neurone.

Describe the sequence of events that leads to an excitatory postsynaptic potential (EPSP) in the postsynaptic neurone after stimulation of neurone A.

Which of the following rows correctly describes the action of each substance on this postsynaptic neurone?

A scientist investigated the effect of the intensity of stimulation of neurones A and B on the production of an action potential in the postsynaptic neurone.

High intensity stimulation of neurones A and B causes a high frequency of impulses to arrive at the presynaptic terminals.

The results are shown in the table.

Explain the effect of the intensity of stimulation on the production of an action potential in the postsynaptic neurone.

Name organelle Q.

Calculate the maximum diameter of organelle Q.

Describe the role of the Golgi apparatus in producing secreted enzymes.

Calcium ions are needed for the secretion of enzymes from pancreatic cells.

The graph shows the effect of increasing calcium ion concentration on the uptake of calcium ions by pancreatic cells.

Explain the effects of calcium ion concentration on the rate of uptake of calcium ions through the pancreatic cell membrane.

The diagram shows four varieties of rabbit.

Fur colour in rabbits is controlled by four different alleles:

• the allele for brown fur, C, is dominant to all other alleles

• the allele for chinchilla fur, c^ch, is dominant to the alleles for Himalayan and albino

• the allele for Himalayan fur, c^h, is dominant to the allele for albino

• the allele for albino fur, c, is recessive to all other alleles

Describe how new combinations of alleles are produced in meiosis.

State all the possible genotypes of a rabbit with brown fur.

Two parent rabbits with brown fur were mated. Two of the F₁ offspring had chinchilla fur.

The F₁ rabbit offspring with chinchilla fur were mated.

The F₂ generation consisted of some rabbits with chinchilla fur and the rest having Himalayan fur.

Use genetic crosses to deduce the genotypes of the two parent rabbits with brown fur.

The fur colour of animals can be affected by natural selection.

Compare and contrast stabilising selection with disruptive selection.

The effects of light intensity and temperature on the net primary productivity (NPP) of young willow trees were investigated.

Young willow trees were grown in two greenhouses: one with high light intensity and one with low light intensity.

In each greenhouse, groups of these willow trees were kept at different temperatures for six months.

The results are shown in the graph.

State what is meant by the term net primary productivity.

Explain why temperature has different effects on NPP at these two light intensities.

*(b) In a further investigation, succession was monitored for fifty years in an abandoned field.

The field was originally used to grow crops.

After fifty years, large numbers of coniferous trees were growing in the field.

These coniferous trees do not shed many leaves.

When compared with younger trees, older coniferous trees have a much higher proportion of tree stem, branches and roots and a lower proportion of leaves.

The following factors were monitored:

• plant biomass

• NPP

• mineral ion content of soil

• index of diversity of animals

The line graphs show the trends that happened over fifty years for each of the factors.

mineral ion content of soil

Analyse the data to explain how succession is linked to the changes in this abandoned field.

Polyphenol oxidase is an enzyme found in many plant cells.

This enzyme catalyses the following reaction

This reaction causes cut fruit to turn brown when exposed to air.

A student carried out an investigation into the rate at which grape juice produced quinone.

The graph shows the results of this investigation.

Calculate the initial rate of this reaction.

Explain why adding citric acid to cut fruit reduces the rate at which the fruit turns brown.

The diagram shows the structures of monophenol and a molecule called tropolone.

Tropolone can be added to grape juice to slow the rate at which the juice turns brown.

Explain how tropolone affects the rate at which the grape juice turns brown.

Plant breeders have developed a grape variety that produces inactive polyphenol oxidase.

The bonding in this enzyme is changed and this prevents the juice from turning brown.

Which of the following bonds are used to form the tertiary structure of enzymes?

The base sequence of this polyphenol oxidase gene is different in this grape variety.

Explain how this leads to the production of inactive enzyme.

The Northern elephant seal is a mammal found in the Eastern Pacific Ocean.

In the nineteenth century, Northern elephant seals were hunted and this reduced the population to about 20 seals.

The seals were listed as an Appendix II species when CITES was established in the 1970s.

The population has now recovered to over 100 000 individuals.

The seals in this population have developed health problems, including a high mortality rate for newborn pups, deformities and weak immune systems.

Describe the role of treaties such as CITES in maintaining global biodiversity.

Explain why, although the population of seals has recovered, many of the seals have health problems.

Northern elephant seals have a high concentration of haemoglobin in their blood.

The graph shows the oxygen dissociation curves for myoglobin, adult haemoglobin and fetal haemoglobin.

Which of the rows correctly matches each curve with myoglobin, adult haemoglobin and fetal haemoglobin?

Northern elephant seals are able to dive to great depths and hold their breath for up to two hours.

The tables show data for four diving mammals.

Calculate the total mass of haemoglobin in a Northern elephant seal.

*(ii) Analyse the data to explain how marine mammals are adapted for diving.