Life on Earth - PROBLEMS with Fertilisers and Pesticides

Question 1

What does the term ‘leaching’ refer to?
Why is it bad?

Answer 1

• Refers to the process of fertilisers being washed by the rain from soil into rivers or lakes.
• Bad because it adds unwanted nitrates to the water.

Question 2

How can additional nitrates affect plants?

Answer 2

They will increase the rate of plant growth

Question 3

Explain the timeline of leaching and its long term affects

Answer 3

1. Leaching occurs, stimulating algae growth and increases algal populations, causing an algal bloom
2. Algal bloom present? → Light levels are reduced → Aquatic plants lower down in the river/pond/lake are killed
3. Dead plants and algae become food for bacteria, so bacteria populations increase
4. The bacteria use up a lot of oxygen during respiration, reducing oxygen avaliablity for other organisms

Question 4

Why are algal blooms bad?

Answer 4

They reduce the biodiversity of aquatic habitats

Question 5

Name one method of reducing fertiliser use

Answer 5

GM crops

Question 6

Name two ways in which pesticides are harmful

Answer 6

• Toxic to unintended species
• Can cause bioaccumulation

Question 7

Define the term ‘bioaccumulation’

Answer 7

the accumulation of toxic substances in the bodies of organisms over time

Question 8

Explain the process of ‘Biomagnification’

Answer 8

• bioaccumulation taken place in prey species = feeding interactions pass them along food chains.
• Each predator consumes many prey = toxicity level increases at each level of the food chain.
• At higher levels of the food chain, the toxicity can become lethal

Question 9

Name two ways that pesticide use can be reduced

Answer 9

GM crops, biological control

Question 10

Define biological control

Answer 10

pest population is reduced by introducing its natural enemy or predator on purpose