Habitats

A habitat is any part of the environment in which a community of organisms is found. A habitat must provide food, water, air (oxygen for respiration in all living things and carbon dioxide for photosynthesis in plants), warmth/shelter, light and a place to reproduce.

A habitat may be as small as a single leaf or as large as the ocean, depending on the organisms that live within it. There may be competition between the organisms in a habitat for the limited resources, but also some interdependence of the species that live there.

Ecosystems

In an ecosystem everything is interconnected, with each living thing relying on others to for survival. Some animals rely on plants for food, whilst other animals hunt other animals. Everything is finely balanced, removing one organism can have a big impact on another.

Biotic factors are the living components and refer to all living organisms found in an ecosystem such as animals, plants, fungi and microbes.

Abiotic factors are the non-living components of ecosystems, such as the climate and soil.

The abiotic and biotic factors of an ecosystem interact constantly. Rainfall affects the type of vegetation which can grow. Plants capture sunlight and can also influence rainfall. Herbivores feed on plants, carnivores feed on other animals, and the decomposers, such as fungi, recycle nutrients back into the soil.

The particular role of an organism and the resources it uses in a particular ecosystem is called its niche.

Food Chains

A food chain describes the flow of energy from one organism to the next and the specific interdependence of living organisms on each other for food. The flow of energy can be represented by arrows in a diagram. The arrows should point towards the animal doing to eating, as it shows the flow of energy. Children often wrongly draw the arrows pointing the other way.

Every food chain consists of a producer plus consumers. Producers are (usually) plants that make their own food through photosynthesis; consumers are animals that obtain energy by eating plants or other animals that have eaten plants.

Green plants are able to convert energy from sunlight into food stores by the process of photosynthesis. They do this using a chemical called chlorophyll. Plants turn water and carbon dioxide into sugar and oxygen.

Animals gain energy by consuming these plants or other animals that eat plants.

Each food chain shows the relationship between a producer, the primary consumer that eats the producer, the secondary consumer that eats the primary consumer, and so on. When any organism dies, decomposers break down and return minerals and energy to the soil, to be recycled by other organisms.

Organisms can belong to more than one food chain. In reality, within an ecosystem, many food chains combine to create a more complicated relationship known as a food web. Removal or reduction in the population numbers of a particular organism in a food web can have a significant impact on all the other dependent organisms. For example, an animal may not be able to survive if they lose a significant part of their diet. In turn, other animals may depend on that animal, so the effect can be significant across an entire food web.

Predators and Prey

Primary consumers only eat producers (plants) and are called herbivores. Secondary and tertiary consumers eat other animals that are eat plants, or animals that have eat plants. Secondary consumers can either be either omnivores, which eat a diet of both plants and other animals, or carnivores, which only eat meat. Tertiary consumers are usually at the top of the food chain, which means they are not eaten by any other animals. When organisms die, they are broken down by decomposers and minerals are returned to the soil to be reused by plants.

An animal that hunts other animals for food is known as a predator, whilst the animal it hunts is called its prey.

Glossary

Habitat: A place where a particular organism lives, providing all the basic needs for survival and reproduction.

Environment: All the conditions and surroundings that affect living things, their survival, growth and evolution.

Niche: A role taken by a type of organism within its habitat.

Producer: An organism that is capable of making its own food. Producers form the start of every food chain. Often a green plant, but some bacteria can also play the role of producers in some food chains.

Predator: An animal that catches and eats other animals (prey).

Prey: An animal that is eaten by another animal (a predator).

Food chain: A food chain is a means of describing the ways that animals gain energy and food from other organisms.

Consumer: An organism in a food chain that gets its energy from eating another organism.  Consumers include all animals.

Primary consumers: Consumers that eat producers. Usually herbivores that eat plants.

Secondary consumers: Animals which prey on other animals. Usually carnivores but can also be omnivores.

Tertiary consumers: Animals which feed on both primary and secondary consumers. These are often at the top of the food chain.

Photosynthesis: The process by which green plants convert the Sun’s energy into food. Light energy from the Sun is captured by chlorophyll and used to change carbon dioxide and water into oxygen and food (sugar).