food chains and food webs
The fundamental source of energy, allowing any organism to survive, grow and reproduce is sunlight, travelling 149,600,000 km to Earth to kick-start the vast webs of feeding organisms. By converting this light energy into chemical energy by photosynthesis, energy can be passed on as food between organisms. These organisms can be divided into 3 key groups, determined by how they obtain this vital chemical energy and other nutrients. These are:
6CO2 + 6H2O + energy (light) --> C6H12O6 + 6O2
Consumers are organisms that feed on other organisms for their source of energy. Animals are consumers and are classed in 3 different ways:
When organisms of these 3 key groups develop a feeding relationship we call this a food chain. Each stage in a food chain is called a trophic level, and usually there are no more than 4 or 5 trophic levels in a food chain. This is simply down to the lack of energy being passed on to any further organisms.
- Producers
- Consumers
- Decomposers
6CO2 + 6H2O + energy (light) --> C6H12O6 + 6O2
Consumers are organisms that feed on other organisms for their source of energy. Animals are consumers and are classed in 3 different ways:
- Primary consumers – feed on producers
- Secondary consumers – feed on primary consumers
- Tertiary consumers – feed on secondary consumers
When organisms of these 3 key groups develop a feeding relationship we call this a food chain. Each stage in a food chain is called a trophic level, and usually there are no more than 4 or 5 trophic levels in a food chain. This is simply down to the lack of energy being passed on to any further organisms.
Ultimately, nearly all animals do not rely on just one food source for all their energy needs. Within a single habitat, multiple food chains are linked together to form a vast food web. These provide a better representation of the feeding relationships within an environment, as a producer or consumer is likely to be eaten by more than 1 other organism. Below is an example of a food web with 5 possible food chains: