Resources and environment, Year 8: more practice：全部卡片

The emergent layer

提示Think of the trees that stand clear above everything else.

为什么Emergent trees can reach 40 to 50 metres or more. They get full sunshine and strong wind.

The forest floor

提示Little sunlight reaches it.

为什么Very little sunlight reaches the floor. Fallen leaves rot quickly there.

To shed heavy rain quickly

提示It helps with the water that falls every day.

为什么Rainforests have rain almost daily. Quick run-off keeps the leaves clear of fungi and algae.

In the leaf litter and the living plants, not deep in the soil

提示Heavy rain washes nutrients out of the ground.

为什么Dead leaves rot fast in the heat and are absorbed by roots almost at once, so nutrients move quickly in a loop.

Soy (soya)

提示It feeds farm animals around the world.

为什么Large soy farms and cattle ranches are the main drivers of clearance in the Amazon basin.

Indonesia and Malaysia

提示Both are on or near Borneo and Sumatra.

为什么Palm oil is used in food, cosmetics and fuel. Most of it comes from these two countries.

Trees store carbon, which is released when they are burnt or rot, and fewer trees remain to absorb carbon dioxide

提示Think about what gas plants take in from the air.

为什么Forests are a carbon store and a carbon sink. Clearing them reduces absorption and releases stored carbon.

Coal

提示Natural gas is the cleaner of the two.

为什么Coal releases much more carbon dioxide than natural gas for the same energy.

It only produces power when the sun is shining

提示Think about the weather and the night.

为什么Gas can run whenever it is needed, whereas solar output varies with cloud and daylight.

It sits on a plate boundary, so hot rock lies close to the surface

提示Think about volcanoes and the Earth's crust.

为什么Iceland lies on the Mid-Atlantic Ridge. Heat from underground heats water, giving steam that turns turbines.