Human Impact on Biodiversity Flashcards

All 6 cards in this deck

What adds the nitrates to a lake or pond that cause eutrophication?

Leaching or run-off of fertilisers from fields.
Sewage, dead organic matter or phosphates can also cause it.

What is the sequence of events in eutrophication?
e.g. fertiliser runs off a field into a lake

1. Nitrates cause an algal bloom (rapid, excessive growth of algae) at the surface.
2. Algae and water plants lower in the water are deprived of light, so they die and are decomposed.
3. Oxygen concentration in the water decreases (decomposition / less photosynthesis), so the fish die.

Give one way fish farming can reduce biodiversity in the surrounding water.

Waste food and fish faeces add nitrates to the water, causing eutrophication.

Give one way fish farming can have a positive impact on biodiversity.

It reduces overfishing of wild fish, so wild fish populations are conserved.

True or false? Introducing a non-indigenous species to an ecosystem always increases its biodiversity.

False. The new species may outcompete, eat or bring disease to native species, so native species numbers fall and biodiversity decreases.

True or false? A graph showing that fish numbers in a lake fall as nitrate concentration rises proves that the nitrates killed the fish.

False. It shows only a correlation; another factor could be responsible, so further evidence is needed.