GCSE · Geography · AQA · Spec 8035

Interdependence in cold environments

Picture frozen ground, bitter cold and hardly any rain or snow. Now warm it up. The ground thaws, plants spread, new animals move in. One change, and everything moves.

Build the web

What affects what in a cold environment?

Six parts of a cold environment are listed below. Pick one part, pick a part it affects, and add the link. Aim for at least five links, and think carefully about which way each arrow points. Then compare your web with the lesson's.

  1. Climate (very cold, very little precipitation)
  2. Water
  3. Soil (often frozen as permafrost)
  4. Plants
  5. Animals
  6. People
Add a link

No links yet.

Living or non-living?

Sort the parts of a cold ecosystem

Pick an item, then choose the group it belongs in.

Still to sort

Biotic (living) (0)

The living parts: plants, animals, bacteria, fungi and people.

Where the line is: It must be living. Something that came from living things but is now dead does not count.

Abiotic (non-living) (0)

The non-living parts: soil, climate, water, nutrients and sunlight.

Where the line is: Anything non-living goes here, including dead plant and animal matter.

10 of 10 still to sort.

Every part of an ecosystem is either biotic or abiotic. The test is simple: is it living?

Watch out: Careful with things that come from living things, or that living things need. Don't ask what it is connected to; ask only whether it is alive.

A cold-environment food chain

Work along the chain. At each level, ask: what does this depend on?

The tundra nutrient cycle

Rebuild the cycle, then break it

3 stages are missing. Use the rest of the loop to work out which goes where.

  1. Stage 1: Soil store

    Nutrients held in the soil.

  3. Stage 3: Biomass store

    Nutrients held in all the plants and animals. Every plant and animal is part of this cycle as well as the food web: reindeer lichen relies on the soil for nutrients, stabilises the soil through its roots, adds nutrients when it decomposes, and is food for animals.

  5. Stage 5: Litter store

    Dead leaves and other dead plant and animal matter.

…and stage 6 leads back to stage 1.

Guess first

Which store holds the most nutrients?

Put the three tundra nutrient stores in order of how many nutrients each one holds.

1 · Holds the most nutrients3 · Holds the fewest nutrients

  1. Biomass store (all the plants and animals)

  2. Litter store (dead plant and animal matter)

  3. Soil store

Watch out: Don't assume the living things hold most of the nutrients. In the tundra they don't.

Climate change

?

Reason it through

What happens to a tundra ecosystem when the climate gets warmer?

Link 1 of 4

First link · your turn

Temperatures rise. What happens to the frozen ground, and to the plants?

2
Locked — reveal the link above first
3
Locked — reveal the link above first
4
Locked — reveal the link above first

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Change one part of a cold ecosystem, and every other part feels it.

What you need to know

  • Interdependence means the parts of an ecosystem depend on or affect each other, so a change to one part affects the others.
  • Biotic components are living (plants, animals, bacteria, fungi, people); abiotic components are non-living (soil, climate, water, nutrients, sunlight).
  • Polar, tundra and alpine environments are cold environments, and each is a biome: a large-scale global ecosystem.
  • Food chains, food webs and nutrient cycles all show how the biotic and abiotic parts of a cold environment depend on each other.
  • The tundra nutrient cycle has three stores: soil, biomass and litter.

The big picture

In a cold environment, climate, water, soil, plants, animals and people all depend on or affect each other, so a change to one part changes the others. The cold limits plants, freezes the soil into permafrost and makes farming hard; fewer plants mean fewer animals; and plants even feed back on the climate through evapotranspiration. Food chains, food webs and the tundra nutrient cycle show these links, and the nutrient cycle holds a surprise: the soil is the biggest nutrient store, yet tundra soils are still poor. Warm the climate and the whole system shifts.

Key points

1Climate drives most links: the cold and the lack of precipitation limit plant growth, freeze the soil and make farming difficult.
2Permafrost stops deep-rooting plants growing, because their roots cannot reach nutrients in the frozen lower layers.
3Fewer plants means less food for herbivores, so fewer animals can survive.
4Plants affect the climate too: the amount of evapotranspiration leads to a greater or lesser amount of precipitation.
5Soil and litter are abiotic, because they are non-living.
6A food web shows only biotic components, and every plant and animal is part of the nutrient cycle as well.
7Tundra stores: soil holds the most nutrients, then biomass, then litter, but very few nutrients flow through the system overall.
8Littering is the most important process in the tundra nutrient cycle; runoff is small, but melting permafrost is making it more frequent.
9Warming thaws the permafrost, boosts plant growth, supports more animals and new species, and may make farming possible.

Worked example

Problem

Use the idea of interdependence to explain why the tundra supports only a small number of animals.

⚠ Watch out

Calling soil or litter biotic because they are part of the natural world. The test is whether something is living: soil and litter are non-living, so both are abiotic.

🧠

Memory hook

The tundra keeps its nutrients in the freezer: the soil is the biggest store, but the cupboard is still nearly bare.

✓

Check yourself

Cover the page. Sketch climate, water, soil, plants, animals and people, and draw five arrows between them. Which arrow points back towards the climate, and what does it mean?

Flashcards

(15)
What does interdependence mean in an ecosystem?
The components depend on or are affected by each other, so a change to one will impact the others.
Biotic vs abiotic?
Biotic = living (plants, animals, bacteria, fungi, people). Abiotic = non-living (soil, climate, water, nutrients, sunlight).
Why are soil and litter classed as abiotic?
Both are non-living. Litter is dead leaves and decomposing matter; soil itself is non-living.
Name three types of cold environment.
Polar, tundra and alpine. Each is a biome: a large-scale global ecosystem.
What is permafrost, and why does it matter to plants?
Permanently frozen soil. Deep-rooting plants can't grow, because their roots can't reach nutrients in the frozen lower layers.
Why can't people in polar and tundra areas usually farm crops?
The cold and low precipitation, and soil that is frozen or too scarce, stop crops growing.
How can vegetation affect the climate?
Through evapotranspiration, the transfer of water to the atmosphere by evaporation from surfaces and transpiration from plants. The amount of evapotranspiration leads to a greater or lesser amount of precipitation.
What are the levels of a food chain, in order?
Producers → primary consumers (herbivores) → secondary consumers (carnivores) → tertiary consumers (top predators), with decomposers breaking down dead matter.
What do decomposers depend on, and what do they give back?
They depend on dead organic matter, and they return nutrients to the soil for producers to reuse.
What does a food web leave out?
Abiotic components such as climate, soil and water. It shows biotic links only, even though every organism relies on abiotic ones.
Rank the tundra nutrient stores from most to fewest nutrients.
Soil, then biomass, then litter.
Why is the tundra biomass store so small?
Precipitation is extremely low and it is extremely cold, so few plants can survive.
Which process matters most in the tundra nutrient cycle, and which loss is growing?
Littering matters most. Runoff is small because of the lack of rain, but melting permafrost is making it more frequent.
How is reindeer lichen part of the food web AND the nutrient cycle?
It relies on the soil for nutrients, stabilises the soil through its roots, adds nutrients when it decomposes, and is food for animals.
Give three effects of a warmer climate on the tundra.
Permafrost thaws so plants reach deeper nutrients; plant growth increases and supports more animals and new species; farming may become possible.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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