20.Human influences on Ecosystems

Question 1

Describe the effects of :

a) Untreated sewage on aquatic ecosystems

Answer 1

1. Provides a good source of food for bacteria and they reproduce rapidly
2. Bacteria respire aerobically and deplete oxygen
3. Aquatic organisms such as fish die of suffocation-Eutrophication

Question 2

b) Fertilisers on aquatic ecosystems

Answer 2

1. Causes rapid growth of algae which then die
2. Decomposing bacteria feed on algae
3. Oxygen is depleted and aquatic organisms die-Eutrophication

Question 3

c)Heavy metals

Answer 3

Heavy metals do not break down and so bioaccumulate in food chains
This cause food poisoning to top carnivores.