Food Chains and Food Webs: Exploring the Flow of Energy 

 

What are Food Chains?

A food chain shows the transfer of energy from one organism to another, starting with a producer (a plant or algae).

• All the enrgy in the food chain comes from the sun, in the form of light energy
• Energy is transferred in food chains by eating/consuming substances in the trophic level below and so on.
• When looking at a food chain the arrows show the direction of energy transfer

Key Features of a Food Chain:

1. Producer: The first organism in a food chain. It makes its own food using sunlight (e.g., grass).
2. Consumers: Organisms that eat other organisms to get energy.
   • Primary Consumers: Eat producers (e.g., a grasshopper).
   • Secondary Consumers: Eat primary consumers (e.g., a frog).
   • Tertiary Consumers: Eat secondary consumers (e.g., a snake).
3. Decomposers: Break down dead organisms and recycle nutrients (e.g., fungi, bacteria).

Example of a Simple Food Chain: $$\text{Grass} \to \text{Grasshopper} \to \text{Frog} \to \text{Snake} \to \text{Hawk}$$

 

 

What are Food Webs?

A food web is a network of interconnected food chains.

• They show how energy flows through an entire ecosystem.
• Organisms often have multiple food sources, which makes food webs more realistic.
• Food webs are useful as they show how interconnected and dependent different animal populations are and how a change in one population can affect various others.

Example of a Food Web:

• Grass is eaten by both rabbits and grasshoppers.
• Frogs eat grasshoppers, while foxes eat rabbits and frogs.

 

Types of Organisms in Food Chains and Webs

Term	Definition	Examples
Producer	Makes its own food using sunlight (photosynthesis).	Grass, algae
Herbivore	Eats only plants.	Rabbit, grasshopper
Carnivore	Eats other animals.	Lion, snake
Omnivore	Eats both plants and animals.	Bear, human
Decomposer	Breaks down dead or waste materials to recycle nutrients.	Fungi, bacteria

 

Trophic Levels: Positions in the Food Chain

Trophic Level	Role	Example
1st (Producer)	Converts sunlight to energy	Grass
2nd (Primary Consumer)	Herbivore eating the producer	Grasshopper
3rd (Secondary Consumer)	Carnivore eating the herbivore	Frog
4th (Tertiary Consumer)	Carnivore eating secondary consumers	Snake

 

Why Energy Decreases Across Trophic Levels

Energy transfer between trophic levels is inefficient:

• Only $10\%$ of energy is passed to the next level.
• Reasons for Energy Loss:
  • Energy used for life processes (e.g., movement, growth).
  • Energy lost as heat.
  • Energy left in undigested materials.

 

 

Human Impact on Food Chains and Webs

Humans can disrupt food chains and webs through:

1. Overharvesting: Reducing the population of key species (e.g., overfishing).
2. Introducing Foreign Species: Non-native species can outcompete or prey on native species, disrupting the balance.