Human effects on ecosystemsEdexcel A-Level Biology B: Subtopic test

1. 1
   A fisheries scientist monitors a stock of North Sea haddock. Over 25 years the number of boats and hours fished each year has increased, but the total annual catch has stayed about the same. The mean length of fish landed has fallen and a growing proportion of the catch is made up of immature fish.

   (a)

   Which observation is the best indicator that the haddock stock is being overfished?

   [1 mark]

   • AThe mean length of fish caught has increased
   • BThe catch per unit of fishing effort has fallen
   • CMore species are being caught in the nets
   • DThe sea temperature has risen

   (b)

   Which measure would most directly allow young haddock to survive to breeding age?

   [1 mark]

   • AAllowing fishing only during the spawning season
   • BIncreasing the number of boats licensed
   • CUsing nets with a smaller mesh size
   • DUsing nets with a larger mesh size

   (c)

   Explain how a fishing quota helps to make the fishery sustainable.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A species of tortoise is prized in the international pet trade. Its wild population has fallen sharply, and it has been listed in Appendix I of CITES. Despite this, customs officers continue to seize shipments of the animals hidden in luggage and cargo.

   (a)

   What is the main aim of CITES?

   [1 mark]

   • ATo ensure international trade in wild animals and plants does not threaten their survival
   • BTo protect all habitats inside national parks
   • CTo reduce carbon dioxide emissions worldwide
   • DTo ban all fishing in international waters

   (b)

   Which statement describes a limitation of CITES?

   [1 mark]

   • AIt applies only to marine species
   • BIt sets up protected habitats in every member country
   • CIt cannot stop illegal trade that evades border controls or habitat loss
   • DIt has no member countries

   (c)

   Suggest why listing the tortoise in Appendix I may not on its own lead to recovery of the wild population.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A long-term monitoring station in a UK woodland recorded atmospheric carbon dioxide at 317 ppm in 1960 and 418 ppm in 2022. Over the same period the mean annual temperature at the site rose from 8.9 °C to 10.1 °C, and the mean date of first leafing of oak trees became 14 days earlier.

   (a)

   Calculate the percentage increase in carbon dioxide concentration between 1960 and 2022, and explain how this increase may be linked to the rise in temperature.

   [3 marks]

   (b)

   Evaluate the extent to which these data show that human activity is responsible for the earlier leafing of oak trees.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A small island nation depends on commercial fishing for food and jobs. Its marine scientists report that stocks of the main food fish have fallen by 60% in 30 years. The government is considering quota cuts and a no-take zone. It is also being asked by other countries to cut greenhouse gas emissions by replacing its diesel power stations with wind and solar energy, which would cost jobs and raise electricity prices in the short term. A fishing association disputes the scientists' claim that warming seas are contributing to the fall in stocks.

   (a)

   Evaluate the strategies the government could use to sustain its fish stocks while meeting the needs of the fishing community.

   [6 marks]

   (b)

   Explain how journals, peer review and scientific conferences are used to validate evidence about climate change, and discuss how attempts to reduce its possible causes may conflict with human needs.

   [6 marks]

   Total for question 4: 12 marks

End of questions