Concept 1 · free preview
Ecosystems
Understand
All the living things of an area (biotic components) together with their physical surroundings (abiotic components) form an ecosystem — a pond, a forest, a grassland.
| Component | Examples | Role |
|---|---|---|
| Abiotic | sunlight, water, air, soil, temperature | physical conditions for life |
| Producers | green plants, algae | make food by photosynthesis |
| Consumers | herbivores (deer), carnivores (lion), omnivores (humans) | depend on others for food |
| Decomposers | bacteria, fungi | break down dead matter and return nutrients to the soil |
Rule
Food chain: grass → grasshopper → frog → snake → eagle; each link is a trophic level
Many interlinked food chains form a food web
10% law (Lindeman): only about 10% of energy passes from one trophic level to the next; the rest is used up or lost as heat — so chains usually have 3–4 levels
Energy flows one way (sun → producers → consumers); nutrients cycle
The pyramid of energy is always upright; pyramids of numbers (many insects on one tree) and biomass (ponds) can be inverted
Example
Grass traps 10,000 J → grasshopper about 1,000 J → frog 100 J → snake 10 J. Very little energy is left by the fourth level.
Remember
'Which pyramid is always upright?' — the pyramid of energy.
Common mistake
Calling fungi or earthworms abiotic — they are living, i.e. biotic components.
Check yourself
What role do bacteria and fungi play in an ecosystem?