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Unlock This CourseAn ecosystem is a community of living things and the non-living environment they depend on, all linked together. Remember, Antarctica is cold, dry and windy. That climate is a huge part of this ecosystem.
Key terms:
Most of the land is under ice, so life is found on bare rock and on the coasts. The producers are mosses and lichens, plus just two flowering plants: Antarctic hair grass and Antarctic pearlwort. There are no trees. The animals are small, such as mites and springtails. Seabirds and seals visit the shore.
The Southern Ocean is full of life. Cold water holds plenty of nutrients, and the producers are microscopic floating plants called phytoplankton. They feed huge numbers of animals, from tiny krill to fish, penguins, seals and whales.
So the land is almost empty, but the ocean around it is one of the richest on Earth.
A food chain shows who eats whom, in a line. A food web joins many food chains together, because most animals eat more than one thing. In the Southern Ocean, the web is built on two key groups.
| Level | Who | What it eats |
|---|---|---|
| Producer | Phytoplankton | Makes its own food from sunlight |
| Primary consumer | Krill | Phytoplankton |
| Secondary consumer | Adelie penguins, crabeater seals, fish, squid, baleen whales | Krill (and fish, squid) |
| Top consumer | Leopard seals, killer whales (orcas) | Penguins, seals and fish |
One food chain is: phytoplankton → krill → Adelie penguin → leopard seal. A blue whale takes a shortcut: it eats krill directly, and can eat several tonnes of krill in a day. Krill sit in the middle of the web, so a very large number of animals depend on them.
The living and non-living parts are interrelated, which means a change in one affects the others. Here is the yearly cycle in the Southern Ocean, step by step.
The key idea is that light, sea ice and nutrients control phytoplankton, and phytoplankton and krill support the whole web. If krill numbers fall, the animals that feed on them have less food. Why krill numbers might fall is taught in Threats to Antarctica and Their Impacts.
An adaptation is a feature that helps a living thing survive in its environment. Here are the main ones in Antarctica.
| Adaptation | Who has it | How it helps |
|---|---|---|
| Blubber | Seals, whales, penguins | A thick fat layer under the skin that insulates the body and stores energy. |
| Dense feathers | Penguins | Tightly packed, overlapping and waterproof, so they trap warm air and keep out cold water. |
| Huddling | Emperor penguins | Birds crowd close together in winter, which cuts heat loss and shelters them from wind. |
| Migration | Some whales and seabirds | They travel to warmer waters or places when winter makes feeding hard, then return to feed in summer. |
| Antifreeze proteins | Some Antarctic fish | Proteins in the blood stop ice crystals growing, so the fish do not freeze in water below 0°C. |
| Low-growing form | Mosses and lichens | They hug the ground, so they avoid strong winds and stay slightly warmer, and they can survive being frozen and dry. |
Question: explain how a seal is adapted to the cold. Step 1, name the adaptation: a thick layer of blubber. Step 2, say what it does: it insulates the body. Step 3, give the result: so the seal loses less heat to the icy water and survives. Always use the pattern adaptation, what it does, why that helps.
Saying "penguins have blubber to keep warm" without explaining how. Writing that animals "choose" to adapt. Adaptations are features that have developed over a very long time. Also, do not mix up biotic (living) and abiotic (non-living). Ice is abiotic, even though it is part of the habitat of living things.
Fig. 1.1 shows made-up data for one part of the Southern Ocean over a year.
| Month | Daylight (hours) | Phytoplankton (index) | Krill (index) |
|---|---|---|---|
| June | 4 | 1 | 3 |
| September | 11 | 2 | 2 |
| December | 22 | 9 | 6 |
| March | 12 | 5 | 8 |
(a) Define the term producer. [1]
(b) Describe the pattern of phytoplankton shown in Fig. 1.1. [2]
(c) Explain how emperor penguins are adapted to survive in Antarctica. [3]
(d) Explain how abiotic and biotic factors are linked in the Southern Ocean ecosystem. [6]
(a) A living thing that makes its own food from sunlight, such as phytoplankton (1).
(b) Phytoplankton are lowest in June, at 1 (1). They rise to a peak of 9 in December, then fall to 5 in March (1).
(c) Any three from: dense, overlapping, waterproof feathers trap warm air and keep out cold water (1); a layer of blubber insulates the body (1); huddling together in winter reduces heat loss (1).
(d) Levels: Level 1 (1-2 marks) gives simple statements about the ecosystem; Level 2 (3-4 marks) links some factors with some explanation; Level 3 (5-6 marks) gives a developed, linked explanation using both abiotic and biotic factors and Fig. 1.1.
Level 3 answer: in winter there are few hours of light and sea ice covers the sea, so phytoplankton grow slowly. In spring, light increases and sea ice melts, releasing nutrients and algae, so phytoplankton multiply. Krill eat phytoplankton, so they increase a little later, as Fig. 1.1 shows. Penguins, seals and whales then feed on the krill. So the abiotic factors of light, ice and nutrients control the producers, which support krill and the whole food web.
In (d), name at least one abiotic factor and one biotic factor, and link them with "so" or "because". Use the data in Fig. 1.1 in your answer to show the link.