Feeding Relationships
Problem — How do living beings in an environment feed, and how are they connected by food chains?
- Understand that living beings need matter and energy to live.
- Identify the main diets of animals.
- Build and read a food chain.
- Understand that food chains in an environment can be linked together.
- Understand that a change in the environment can affect several living beings.
Part 1: Living beings need to feed
Feeding means taking matter from the environment to grow, function, repair, and obtain the energy necessary for life.
All living beings need matter and energy to live. This matter allows them to grow, move, breathe, reproduce, or repair their bodies.
Animals must consume other living beings or parts of living beings to feed. Green plants, on the other hand, make their own matter from mineral matter using light. This process of making matter using light is called photosynthesis.
A primary producer is a living being, such as a green plant or an alga, capable of making its own matter thanks to light.
Grass makes its matter using light. A rabbit can eat this grass. A fox can eat the rabbit. These living beings are therefore connected by their feeding.
In a natural environment, no living being is completely isolated. Each living being depends on its environment and often on other living beings to feed.
All living beings need matter and energy to live. Green plants make their own matter: they are primary producers. Animals feed on other living beings or parts of living beings. Feeding thus creates relationships between living beings in the same environment.
Part 2: Different diets
Animals do not all eat the same thing. Some feed mostly on plants, others mostly on animals, and some consume both plants and animals.
An animal's diet corresponds to the set of foods it regularly consumes.
Main diets of animals
| Diet | What the animal eats | Examples |
|---|---|---|
| Herbivore | Mostly eats plants or parts of plants. | Rabbit, cow, snail, caterpillar. |
| Carnivore | Mostly eats other animals. | Fox, owl, frog, spider. |
| Omnivore | Eats plants and animals. | Wild boar, human, blackbird, hedgehog. |
The caterpillar is an herbivore because it eats leaves. The titmouse can eat caterpillars: it is then a carnivore. The wild boar is an omnivore because it can eat acorns, roots, insects, and sometimes small animals.
The role of decomposers
In an environment, some living beings feed on dead organic matter, such as dead leaves, animal remains, or plant debris. They contribute to the decomposition of this matter.
Decomposers are living beings, such as certain bacteria and fungi, that transform dead organic matter and participate in matter recycling.
Fungi and bacteria participate in the decomposition of dead leaves. Earthworms also fragment and mix organic matter in the soil.
Observing clues to identify a diet
Sometimes we can know an animal’s diet by observing its behavior, meal remains, or certain parts of its body.
- Sharp teeth help catch or cut meat.
- Flat teeth help grind plants.
- A thin beak can help catch insects.
- Chewed leaves can show that an herbivore has passed by.
The diet indicates what an animal usually eats. A herbivore mostly eats plants, a carnivore mostly eats other animals, and an omnivore consumes both plants and animals. Decomposers, like some fungi and bacteria, transform dead organic matter and play an important role in living environments.
Part 3: Food chains
In an environment, some living beings serve as food for others. These relationships can be represented by a food chain.
A food chain is a sequence of living beings where each living being is eaten by the next one.
In a food chain, the arrow means "is eaten by". It goes from the eaten living being to the living being that eats it.
Grass → rabbit → fox reads as: the grass is eaten by the rabbit, and then the rabbit is eaten by the fox.
Links in a food chain
Each living being in a food chain is called a link. The first link is often a primary producer, like a green plant or an alga.
| Position in the chain | Role | Example |
|---|---|---|
| First link | Primary producer. | Grass, leaves, algae. |
| Second link | Consumer that eats the primary producer. | Rabbit, caterpillar, snail. |
| Third link | Consumer that eats another animal. | Fox, titmouse, frog. |
Several examples of food chains
- Leaf → caterpillar → titmouse
- Grass → grasshopper → frog → snake
- Algae → small crustacean → fish → heron
- Seed → mouse → owl
A food chain should not be read just as a simple list. It shows a transfer of matter between living beings. Part of the energy contained in this matter is used by living beings to function.
A food chain represents a sequence of living beings where each link is eaten by the next one. The arrow means "is eaten by". A food chain usually starts with a primary producer, then continues with one or more consumers. It shows how matter circulates among living beings in an environment.
Part 4: Food webs in an environment
In nature, feeding relationships are often more complex than a single chain. The same animal may eat several different foods and may also be eaten by multiple predators.
A food web is a set of interconnected food chains within the same environment.
For example, a caterpillar can be eaten by a titmouse, a spider, or a frog. A titmouse can itself be eaten by a sparrowhawk. This forms several linked food chains.
In a hedge, leaves can be eaten by caterpillars and snails. Caterpillars can be eaten by titmice. Snails can be eaten by hedgehogs. The hedge therefore shelters several food chains that form a food web.
A disturbance can have consequences
Because living beings are linked, the disappearance or sharp decrease of a species can change the balance of the environment.
If insects become much fewer, animals that eat them, such as certain frogs, bats, or birds, may lack food. This can then affect other living beings in the food web.
| Change in environment | Possible consequence | Example |
|---|---|---|
| Decrease in wildflowers | Less food for certain insects. | Fewer bees, butterflies, or other pollinators. |
| Decrease in insects | Less food for insectivorous animals. | Less food for swallows or bats. |
| Disappearance of a predator | Possible increase in some prey. | More rodents if their predators decrease. |
Food webs therefore show that living beings in an ecosystem are interdependent. Changing an element of the web can have effects on other living beings.
In a natural environment, food chains are linked together and form a food web. A living being can belong to several food chains. Since species are linked by their feeding, changing a population can affect other living beings in the environment.
Living beings need matter and energy to live. Green plants, such as plants and algae, are primary producers because they make their own matter using light. Animals feed on other living beings or parts of living beings: they can be herbivores, carnivores, or omnivores. A food chain is a sequence of living beings where each link is eaten by the next; the arrow means "is eaten by". In nature, several food chains are linked and form a food web. Feeding relationships show that living beings in the same environment depend on each other.