Paper 2: Advanced Physiology, Evolution and Ecology

Explain why fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin, and why this is important.

Describe the events of the cardiac cycle, including the role of the valves.

Describe the clotting cascade.

Describe the evidence used to support the three-domain system of classification.

Explain why the biological species concept is difficult to apply to extinct organisms and to bacteria.

DNA sequencing shows that species X and Y differ at 12 bases in a gene, X and Z at 30 bases, and Y and Z at 31 bases. Explain which two species are most closely related and why DNA evidence is more reliable than physical features.

Calculate the heterozygosity index for a population in which 18 of 60 individuals sampled were heterozygous at a gene locus, and explain what a low value suggests.

Evaluate the role of zoos and seed banks in conservation.

Explain how a frameshift mutation affects a protein.

In a population of snails, 36% have the recessive phenotype (pink shell). Calculate the frequency of the dominant allele and the percentage of heterozygous snails.

Explain how sympatric speciation can occur.

Explain why genes that are close together on a chromosome are usually inherited together.

Explain how the body responds to a rise in core body temperature.

Describe ultrafiltration in the glomerulus.

Explain how a nerve impulse is propagated along a myelinated axon.

Describe how light causes a generator potential in a rod cell.

Explain how phytochrome controls flowering in a long-day plant.

Explain how auxin causes a shoot to bend towards light.

Grass has NPP of 12 000 kJ m⁻² year⁻¹. Rabbits eat 2 400 kJ m⁻² year⁻¹ of it and their production is 240 kJ m⁻² year⁻¹. Calculate the efficiency of energy transfer from grass to rabbit production and give two reasons why it is so low.

Describe secondary succession on abandoned farmland.

Describe the roles of bacteria in the nitrogen cycle.

A scientist claims that rising CO₂ concentrations are causing earlier leaf opening in trees. Evaluate the evidence that would be needed to support this claim.

Describe how fMRI and CT scans are used to investigate brain structure and function, and give one limitation of each.

Explain how a drug that inhibits the breakdown of a neurotransmitter could affect synaptic transmission.

Discuss the effects of large-scale deforestation on ecosystems and on the global carbon cycle.

Explain how the structure of the alveoli and the control of breathing allow gas exchange to keep pace with demand during exercise.