Ecosystems: Antarctica, rainforests and hot deserts

Last time

Before we start: last time, in Coasts, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.

Living in extremes

Penguins survive the Antarctic cold, while cacti survive desert heat. Every ecosystem has plants and animals adapted to its climate. This lesson covers the Antarctic, tropical rainforests and hot deserts.

What an ecosystem is

An ecosystem is a community of plants and animals and the non-living environment they depend on: climate, soil and water. Energy flows through food chains, from producers to consumers. Nutrients cycle between living things, soil and dead matter.

Antarctica

Antarctica is covered by a thick ice sheet, with extremely low temperatures, strong winds, and very little precipitation: it is a cold desert. Few plants survive, mainly mosses and lichens on bare rock. Life is concentrated in the sea. Krill, small shrimp-like animals, are the base of the food chain for fish, penguins, seals and whales.

Antarctic adaptations and threats

Animals have thick fat, called blubber, and dense feathers or fur. Penguins huddle together for warmth. Threats: climate change melting ice, over-fishing of krill, and pollution from tourism and research stations. The Antarctic Treaty protects the continent for peaceful science and bans mining.

Tropical rainforests

Rainforests grow near the equator, with high temperatures and heavy rain all year. They have layers: the emergents, the canopy, the under-canopy, and the shrub layer near the dark forest floor. Trees have buttress roots for support, and drip-tip leaves to shed heavy rain.

Hot deserts

Hot deserts receive very little rain, often less than 250 millimetres a year, and it is unreliable. Days are very hot, but nights can be cold, because clear skies let heat escape. They are found mainly along the tropics, such as the Sahara and the Thar.

Desert plants

Cacti store water in thick, fleshy stems, and have spines instead of leaves to reduce water loss. Some plants have very long roots to reach groundwater, or wide shallow roots to catch rain quickly. Others have waxy leaves, or seeds that wait years for rain, then grow and flower quickly.

Desert animals and people

Animals are often nocturnal, active at night when it is cooler. Camels store fat in their humps and can go days without water. People live by nomadic herding, oases, and irrigation. Threats: desertification from over-grazing and climate change, and pressure on water.

Three ecosystems compared

The three ecosystems compared.

Mistakes that lose marks

Mistake one: describing an adaptation without explaining how it helps. Mistake two: saying Antarctica has heavy snowfall. It is very dry. Mistake three: using statistics when told not to. The fix: feature, then how it helps survival.

The full-marks tip

The full-marks tip: for every adaptation, say what it is and how it helps the plant or animal survive. Read the question: some say do not use statistics.

On one card

So, on one card: ecosystems. Keep it for revision.