Resources and environment, Year 7: more practice

Producers

HintThey are always at the start of the chain.

The whyGreen 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

HintThink about what happens to a fallen leaf.

The whyWithout decomposers, dead plants and animals would pile up and nutrients would stay locked away.

The rabbit

HintThe grass is the producer; this is the first consumer.

The whyA primary consumer eats a producer. The fox is a secondary consumer because it eats the rabbit.

It increases

HintWhat no longer eats the rabbits?

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

Chemical weathering

HintThe rock itself changes or dissolves.

The whyLimestone is especially affected by acid rain. Chemical weathering changes the make-up of the rock.

Biological weathering

HintA living thing is doing the damage.

The whyRoots, 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

HintOne happens in place; the other involves movement.

The whyErosion 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

HintCompare the speed of formation with the speed of use.

The whyA 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

HintThink about whether new growth keeps pace with felling.

The whyForests regrow, but if they are cut faster than they grow, the resource is used up.

Sand

HintBeaches are covered in it.

The whyGlass is made by melting sand with other materials such as soda ash and limestone.