All living things need energy to survive. Living things get their energy from different places. Eating food is how animals get energy. This food provides the organism with calories which they would otherwise not survive without. 

There are 4 categories of organisms in the food chain:

• Producers
• Consumers
• Predator
• Prey

Plants are known as producers, this means they make their own food through the process of photosynthesis. Animals are known as consumers, this means that they get their nutrition by eating other living things such as other animals or plants. Plants also create their own food using the suns energy through the process of photosynthesis.

An animal that eats another animal is called a predator. The animal they eat is called the prey. So predators eat prey. An example is a lion that eats a deer. The lion is the predator and the deer is the prey. 

What is a food chain?

A food chain is a sequence that shows us how plants and animals depend on each other for food in an ecosystem. The food chain shows how energy is transferred between the different organisms. Food chains usually begin with plants and end with a large animals. Food chains are represented as diagrams. 

Organisms eat different things in order to get energy. Some animals eat plants, some eat meat, and others eat plants and meat.

• Animals that eat plants are called herbivores. An example of a herbivore is a sheep.
• Animals that eat meat are called carnivores. An example of a carnivore is a lion.
• Animals that eat both plants and animals are called omnivores. An example of an omnivore is a bear. 

All organisms have different features which allow them to eat different types of food. Some animals have teeth that allow them to eat specific types of food. All animals have different digestive tracts that are specialised according to the food it eats. 

A food chain shows the trophic levels of animals.

What are trophic levels? 

Trophic levels are hierarchal levels in an ecosystem. Each trophic level refers to the position in a food chain that animals occupy. These include:

• Producer
• Primary consumer
• Secondary consumer
• Tertiary consumer
• Quaternary consumer

Decomposers are also an important part of food chains that sustain ecosystems. They break down decaying organic matter in order to create soil. The process then begins again as plants absorb nutrients from the soil. 

First, a food chain begins with a producer. The primary consumers are the animals that eat the plants. The secondary consumers are the animals that eats the primary consumers. The tertiary consumers are the animals that eat the secondary consumers. When all living things die, decomposers feed on them. Some examples of decomposers are bacteria, fungi, beetles, etc.

Example of a food chain

Producer  ➜  Primary consumer  ➜  Secondary consumer  ➜  Tertiary consumer

Grass  ➜  Rabbit  ➜  Fox  ➜  Lion

The rabbit eats the plants, the fox eats the rabbit, and the lion eats the fox. The plants are the producers, the rabbit is the primary consumer, the fox is the secondary consumer, and the lion is the tertiary consumer.

Example of a food chain

Producer  ➜  Primary consumer  ➜  Secondary consumer  ➜ Tertiary consumer  ➜  Quaternary consumer 

Algae  ➜  Small fish  ➜  Bigger fish  ➜ Sea lion  ➜  Sharks 

The small fish eats the algae, the bigger fish eats the small fish, the sea lion eats the bigger fish, and the shark eats the sea lion. Algae is the producer, the small fish is the primary consumer, the big fish is the secondary consumers, the sea lion is the tertiary consumers, the shark is the quaternary consumer.