Human Impact on Biodiversity Flashcards
All 6 cards in this deck
What is meant by biodiversity?
The variety (number) of different species living in an ecosystem, or on Earth as a whole.
What are the steps of eutrophication?
e.g. fertiliser washed off a field into a lake
- Run-off / leaching of fertiliser causes a build-up of nitrates (and phosphates) in the water.
- This causes an overgrowth of algae, which blocks sunlight from plants in the water, so they cannot photosynthesise and die.
- Decomposers (microorganisms) respire as they break down the dead plants, so oxygen concentration falls and fish and other animals die.
Give two ways fish farming can reduce biodiversity in the surrounding water.
Waste and uneaten food cause eutrophication; parasites and disease spread from the farm to wild fish.
Give one positive impact of fish farming on biodiversity.
It reduces pressure on wild fish stocks, so wild populations can recover.
How can introducing a non-indigenous species reduce biodiversity?
e.g. signal crayfish introduced into English rivers
It outcompetes native species for food and habitat, preys on them, and brings disease they have no resistance to — so native species' numbers fall. e.g. white-clawed crayfish numbers decrease.
What is a non-indigenous species?
A species that does not naturally live in an area but has been brought there by humans, either on purpose (e.g. for food) or by accident (e.g. carried on ships).