B7 Page 11 Flashcards
Explain what happens when farmers give plants extra nutrients.
The use of fertilisers can cause eutrophication:
- Nitrates from the fertilised fields can be washed into rivers and lakes by rain. The nitrates can cause lots of algae to grow at the surface of the water which prevents light form reaching plants below. Eventually these organisms die because they can’t photosynthesise. Bacteria decompose the dead material ad use up oxygen. This oxygen isn’t replaced because photosynthesis is only taking place at the surface. Animals that need’d oxygen from the water suffocate.
How do human actions damage ecosystems?
Human activities can unbalance natural ecosystems by changing inputs and outputs.
Explain how ecosystems are damaged when humans take biomass out for their own use.
- Over fishing removes food source for some organisms in the food chain
- Unsustainable timber harvesting removes habitats and food sources for some organisms.
Explain how the clearing of vegetation can cause major problems for ecosystems.
- they reduce the biodiversity of an ecosystem
- they can increase soil erosion. Increased soil erosion can lead to silting of rivers, were soil is washed into rivers- making them more likely to flood.
- can cause desertification- where land becomes infertile so it cannot support vegetation.
What problems are caused when humans create non-recyclable waste?
Bioaccumulation- if metal is released into waters it can be eaten by small organisms and stored in their tissues in small amounts. Lots of those small organisms are eaten by a predator-so a much larger amount of heavy metal will be stored in the predator’s tissues which could kill it.
Why are human systems not closed loop systems?
1) Human systems create non-recyclable waste
2) many humans use fossil fuels:
- using fossil fuels produces waste emissions that aren’t used again
- fossil fuels take millions of years to form form the decay of dead organisms, but only seconds to use.
