CLS Ecosystems - Key Concepts

Explain how quadrats can be used to estimate the population size of an organism in two different areas.

• Quadrats are placed randomly in each area, the number of organisms in each quadrat is counted, and the average is calculated. This average is then multiplied by the total area to estimate the population size in each area.

• Quadrats are placed only in the area with the most organisms, and the total number found is used as the estimate for both areas.

• Quadrats are used to trap organisms, and the number of trapped organisms is doubled to estimate the population size in each area.

• Quadrats are placed in a line along the edge of each area, and only the organisms touching the quadrat edges are counted for the estimate.

Explain the transfer of substances and of energy along a food chain.

• Energy and substances are transferred only through the air and not by eating.

• Energy and substances are transferred from one organism to another when one organism eats another. Only a small percentage of energy is passed on at each trophic level; the rest is lost as heat, waste, or used for life processes.

• All energy is passed on completely from one organism to the next without any loss.

• Substances and energy are only transferred at the producer level and do not move up the food chain.

Why is only about 10% of energy transferred from one trophic level to the next?

• Because energy is only needed by producers, not by consumers.

• Because energy is created at each trophic level and accumulates.

• Because all organisms at each level store all the energy they consume.

• Because most energy is lost as heat, waste, or used for life processes such as movement and respiration.

Define the following term: Animals that eat other plants or animals.

• Producers

• Consumers

• Decomposers

• Herbivores

Define the following term: Organisms which decay dead material and help recycle nutrients.

• Decomposers

• Producers

• Consumers

• Predators

Define the following term: A self-supporting system of organisms interacting with each other and with a physical environment.

• Ecosystem

• Habitat

• Population

• Community

All the non-living or non-biological components of an ecosystem i.e. physical factors such as soil, moisture, range of temperature, and availability of light.

• Producers

• Biotic factors

• Abiotic factors

• Consumers

The ecological area that is inhabited by a particular organism. It is made up of the environment (physical factors) as well as living factors such as the availability of food and the presence of predators.

• Population

• Niche

• Biome

• Habitat

All individuals of a particular species found in an ecosystem at any one time.

• Habitat

• Community

• Population

• Ecosystem

All individuals of all species found in an ecosystem at any one time.

• Community

• Population

• Habitat

• Biome