2.1.1 Ecosystems

What is an Ecosystem?

Food Chains and Food Webs

Nutrient Cycle

Components of an Ecosystem

• Tertiary Consumers: Top (apex) predators that feed on the animals below them in the food web and have no predators of their own.
• Secondary Consumers: Small carnivores that prey on primary consumers.
• Primary Consumers: Herbivores that eat producers.
• Producers: Plants in an ecosystem. They form the foundation of food webs. Without producers, the ecosystem cannot support any other fauna.
• Decomposers: Organisms that break down dead organic matter, helping return nutrients to the soil.

Components of an Ecosystem

Impact of Changes in an Ecosystem

Some parts of the ecosystem depend on the others, e.g., consumers depend on producers for a source of food, and some depend on them for a habitat. If one part changes, it affects all the other parts that depend on it.

Example of a linked ecosystem:

Component	Effect	Reason
Reduction in common oak trees	Leads to a decrease in the population of beetles and moth caterpillars	Beetles and moth caterpillars rely on oak trees for food
Decrease in beetles and moth caterpillars	Causes a decline in the number of woodpeckers	Woodpeckers feed on beetles and moth caterpillars
Decline in woodpecker population	Results in a reduction in the number of owls	Owls feed on woodpeckers and other small birds that eat caterpillars
Overall effect	Affects the entire food chain, leading to imbalances in the ecosystem	Each species is interconnected, and changes in one affect others