Past paper questions

Question 1

Farming cattle for humans to eat is less efficient than farming crops because of
energy transfer.
Explain why

Answer 1

• energy lost between trophic levels
• energy lost via respiration/ excretion/ feaces

Question 2

Using all the information, suggest how speciation happened to produce two species of lemur.
(the lemur populations are separated by a river)

Answer 2

• geographical isolation/ allopatric speciation
• reproductive isolation
• different selection pressures
• variation due to mutations
• different alleles passed on so changes in allele frequencies
• cannot breed to produce fertile offspring

Question 3

Explain temporal summation

Answer 3

several impulses in short time so enough sodium ions enter to reach threshold

Question 4

Suggest why a data logger may be used instead of a ruler

Answer 4

more accurate if the differences in lengths are small

Question 5

Haemoglobins are chemically similar molecules found in many different species.
Differences in the primary structure of haemoglobin molecules can provide evidence of phylogenetic (evolutionary) relationships between species.
Explain how.

Answer 5

• mutations change base sequence
• change in amino acid sequence
• mutations build up over time
• less differences in amino acid sequences between closely related species
• closely related species have recent common ancestor

Question 6

How does ethanol and acid affect the cell membrane?

Answer 6

• phospholipids dissolve in ethanol
• acid denatures membrane proteins

Question 7

Describe a method this student could use to prepare colour standards and use them to give data for the total anthocyanin extracted from blueberries

Answer 7

• use known concentration of blueberry juice
• prepare dilution series
• compare with colour standards to give concentration

Question 8

Explain why death of alveolar epithelium cells reduces gas exchange in human lungs

Answer 8

• reduced surface area
• increased diffusion distance
• reduced rate of gas exchange

Question 9

Where are introns positioned?

Answer 9

between genes

Question 10

Give two structural features of an aorta wall and explain how they are related to the function of an aorta

Answer 10

• muscle withstands high blood pressure
• elastic tissue stretches and recoils smooths blood flow
• endothelium reduces friction