In ecology we study ecosystems, habitats and communities, in which every organism has its own niche - Leaving Cert Biology - Question 10 - 20101

A habitat is the natural environment in which a particular species of organism lives. It provides the essential conditions for survival, including food, shelter, and breeding sites. Each habitat is characterized by specific physical features and organism interactions.

A niche refers to the functional role or occupation of an organism within its ecosystem. It encompasses how the organism interacts with biotic and abiotic factors, including its food sources, habitat requirements, and its contribution to energy flow and nutrient cycling in the ecosystem.

One ecosystem I studied is a freshwater pond.

Simple Food Chain:

1. Phytoplankton (Producers)
2. Zooplankton (Primary Consumers)
3. Small fish (Secondary Consumers)
4. Larger fish (Tertiary Consumers)

A trophic level refers to the position an organism occupies in a food chain. It indicates how energy and nutrients flow through an ecosystem, with producers at the first level and successive levels occupied by primary consumers, secondary consumers, and so forth. Each level represents a step in the energy transfer.

In the pyramid of numbers:

• C: Producers (e.g. plants)
• B: Primary Consumers (e.g. herbivores)
• A: Secondary Consumers (e.g. carnivores)

If all the organisms at C (Producers) were removed, the organisms at B (Primary Consumers) would likely experience a decline in population due to the lack of food sources. This would disrupt the balance of the ecosystem and could lead to a decrease in the organisms at A (Secondary Consumers) as well, due to reduced availability of prey.