Resources and environment, Year 7: more practice

Producers

提示They are always at the start of the chain.

为什么Green plants and algae are producers. Everything else in a food chain depends on them for energy.

Break down dead material and return nutrients to the soil

提示Think about what happens to a fallen leaf.

为什么Without decomposers, dead plants and animals would pile up and nutrients would stay locked away.

The rabbit

提示The grass is the producer; this is the first consumer.

为什么A primary consumer eats a producer. The fox is a secondary consumer because it eats the rabbit.

It increases

提示What no longer eats the rabbits?

为什么With no predators, rabbits breed and survive in greater numbers, until they may eat so much grass that food runs short.

Chemical weathering

提示The rock itself changes or dissolves.

为什么Limestone is especially affected by acid rain. Chemical weathering changes the make-up of the rock.

Biological weathering

提示A living thing is doing the damage.

为什么Roots, burrowing animals and lichens can all help break down rock.

Weathering breaks rock down where it is; erosion wears it away and carries it off

提示One happens in place; the other involves movement.

为什么Erosion needs a moving agent such as a river, glacier, wave or wind. Weathering has no such agent.

It takes millions of years to form, far slower than we use it

提示Compare the speed of formation with the speed of use.

为什么A renewable resource is replaced within a human lifetime. Coal forms over millions of years.

Only if trees are replanted as fast as they are cut

提示Think about whether new growth keeps pace with felling.

为什么Forests regrow, but if they are cut faster than they grow, the resource is used up.

Sand

提示Beaches are covered in it.

为什么Glass is made by melting sand with other materials such as soda ash and limestone.