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Flashcards · Biology · Human Impact on Ecosystems

Fish Farming, Introduced Species and Eutrophication

20 cards

  1. What is biodiversity?

    The variety of different species in an ecosystem or on Earth.

  2. What is fish farming?

    Rearing fish in cages, tanks or ponds and feeding them until they are harvested.

  3. Give two positive effects of fish farming.

    A reliable supply of protein, and less overfishing of wild fish.

  4. Give two negative effects of fish farming.

    Pollution from waste and spread of parasites and disease to wild fish.

  5. Why can escaped farmed fish harm wild fish?

    They compete with them and breed with them, which can reduce the wild population's genetic variation.

  6. What is a non-indigenous species?

    A species introduced to an area where it does not naturally live.

  7. Give two ways a non-indigenous species can be introduced.

    Deliberately (such as crops or pets) or accidentally (such as in cargo or ship ballast water).

  8. How can a non-indigenous species reduce biodiversity?

    It can outcompete, eat or spread disease to native species.

  9. Why can an introduced species multiply so quickly?

    It may have no natural predators or diseases in its new home.

  10. Why are grey squirrels a threat to red squirrels?

    They compete for food and carry squirrelpox, which kills red squirrels.

  11. Give one benefit of a non-indigenous species.

    Examples: crops such as potatoes feed people, or biological control reduces pests.

  12. Why was the cane toad harmful in Australia?

    It is poisonous, so native animals that ate it died, and it did not control the beetle.

  13. What is eutrophication?

    Excess mineral ions in water leading to an algal bloom, low oxygen and death of aquatic life.

  14. Which two minerals in fertiliser cause eutrophication?

    Nitrates and phosphates.

  15. Why do plants under an algal bloom die?

    The algae block the light, so they cannot photosynthesise.

  16. Why does the oxygen level fall in eutrophication?

    Bacteria decompose the dead plants and algae and use up the oxygen in respiration.

  17. Why do fish die in a eutrophic pond?

    There is not enough oxygen for them to respire.

  18. Give one way to reduce eutrophication.

    Use less fertiliser, avoid spreading it before rain, or leave a vegetation strip beside the field.

  19. A pond with a green layer of algae, dead plants and dead fish, with numbered markers and no labels. Describe the sequence of events in the diagram, in order. The same pond with the five stages of eutrophication written under it.

    1 Fertiliser is washed off the field into the pond. 2 Algae grow fast and form an algal bloom. 3 The algae block the light, so the plants die. 4 Bacteria decompose the dead matter and use up the oxygen. 5 Fish and other animals die from lack of oxygen.

  20. A fish farm cage in the sea, with feed, waste, an escaping fish and parasites, with no labels. Name the parts of the fish farm and explain two harmful effects. The same fish farm labelled Net cage, Fish feed, Uneaten food and faeces, Wild fish, Parasites and disease spread, and Escaped farmed fish.

    Net cage, fish feed, uneaten food and faeces, escaped farmed fish, wild fish. The waste pollutes the water and seabed (it can cause eutrophication). Parasites and disease spread to wild fish, and escaped farmed fish compete and breed with wild fish.