Energy and Ecosystems - Exampro

Question 1

When starfish feed on mussels they leave behind the empty shell. Explain how quadrats could be used to determine the % of mussels that had been eaten by starfish on a rocky shore. (3 marks)

Answer 1

• Use of random numbers
• Large numbers of quadrats
• Count number of dead and live mussels in unit area

Question 2

The percentage of barnacles in the diet is much higher than the percentage of energy they provide. Suggest one explanation for this difference. (1 mark)

Answer 2

• Different size organisms

- Not all eaten

Question 3

The gross productivity of the plants in the field was highest in July.
Use the data in the table to explain why. (2 marks)

Answer 3

• High temperatures allows enzymes to work faster = more e-s complexes formed
• PHS reactions are faster

Question 4

Give the equation that links gross productivity and net productivity. (1 mark)

Answer 4

NPP = GPP - R

Question 5

The net productivity of the plants in the field was higher in August than in July. Use the equation ‘NPP = GPP - R’ and your knowledge of PHS and respiration to suggest why. (2 marks)

Answer 5

• Respiration is slower = less
• LDR less affected by temperature increase
• Energy loss is lower

Question 6

A horse was kept in the field from March to October. During the summer months, the horse was able to eat more than it needed to meet its minimum daily requirements.
Suggest how the horse used the extra nutrients absorbed. (2 marks)

Answer 6

• Stored as fat

- Used for growth

Question 7

The horse’s mean energy expenditure was higher in March than it was in August. Use information in the table to suggest why. (2 marks)

Answer 7

• More heat is lost in March as it is colder
• Maintain body temperature = more heat generated
• By respiration

Question 8

Keeping cattle indoors, in barns, leads to a higher efficiency of energy transfer. Explain why (1 mark)

Answer 8

• Less energy lost as heat/ movement

Question 9

In the investigation, the scientists used pigs of the same breed, with similar genotypes.
Explain why. ( 2 marks)

Answer 9

• Same breed so similar alleles

- Only temperature affects results

Question 10

The pigs were allowed to eat as much food as they wanted. How could this have decreased the reliability of any conclusions drawn from the investigation/ (2 marks)

Answer 10

• Different growth rates

- Not due to temperature