Our Environment Cheat Sheet

Definitions

Environment

The surroundings of an organism, made up of biotic and abiotic components.

Ecosystem

All the interacting organisms of an area together with the non-living components of their environment.

Biotic components

The living parts of an ecosystem, such as plants, animals and microorganisms.

Abiotic components

The non-living parts of an ecosystem, such as air, water, soil and sunlight.

Producers

Organisms that make their own food, mainly green plants, using sunlight.

Consumers

Organisms that depend on other organisms for food; they may be primary, secondary or tertiary.

Decomposers

Microorganisms such as bacteria and fungi that break down dead matter and return nutrients to the soil.

Food chain

A series of organisms through which food and energy pass from one level to the next.

Food web

A network of interconnected food chains in an ecosystem.

Trophic level

Each step or level in a food chain at which food and energy are transferred.

Biomagnification

The increase in the concentration of harmful chemicals at each successive trophic level.

Biodegradable waste

Waste that can be broken down by microorganisms; e.g. food waste, paper.

Non-biodegradable waste

Waste that cannot be broken down by microorganisms; e.g. plastics, glass, metals.

Ozone layer

A layer of ozone (O₃) in the upper atmosphere that absorbs harmful ultraviolet rays from the Sun.

Ozone depletion

The thinning of the ozone layer caused mainly by chlorofluorocarbons (CFCs).

Key Points

• An ecosystem has biotic components (producers, consumers, decomposers) and abiotic components; a pond is a good example.
• A food chain shows the transfer of food and energy: producers → primary consumers → secondary consumers → tertiary consumers.
• Energy flows in one direction through a food chain, and only about 10% of the energy is passed from one trophic level to the next.
• Because energy is lost at every step, food chains usually have only three or four trophic levels.
• Harmful chemicals such as pesticides become more concentrated at higher trophic levels through biomagnification.
• Human activities such as the use of CFCs have damaged the ozone layer, allowing more ultraviolet radiation to reach the Earth.
• Waste is classified as biodegradable (broken down by microorganisms) and non-biodegradable (not broken down).
• Garbage should be segregated so that biodegradable waste can be composted and non-biodegradable waste can be recycled.