Habitat and ecosystem

Ecosystems may be terrestrial, like forests and grasslands, or aquatic, like ponds and seas. Within them, producers (plants) make food, consumers (animals) eat others, and decomposers (bacteria, fungi) break down dead matter.

In real life: A pond is an ecosystem where fish, plants, insects and microbes interact with the water, mud and sunlight around them.

Worked example 1

Question. In grass to grasshopper to frog to snake, name the producer and a consumer.

Answer: Grass is the producer; the grasshopper, frog and snake are consumers.

Food webs, trophic levels and symbiosis

In mutualism both partners benefit, in commensalism one benefits while the other is unaffected, and in parasitism one benefits while the other is harmed. Healthy ecosystems give us clean air, water, food and medicine.

In real life: A bee and a flower share mutualism: the bee gets nectar and the flower gets pollinated, so both gain.

Worked example 2

Question. A bee feeds on nectar and pollinates the flower. What relationship is this?

Answer: It is mutualism, because both the bee and the flower benefit.

Worked example 3

Question. What happens to energy as it passes up the trophic levels?

Answer: Energy decreases at each higher trophic level, so top predators are few.