New News Biology #66

Food Chains

A food chain shows what gets eaten by what in an ecosystem. It is a simplified version of a food web, as it only shows one chain.

Organization of a food chain:

They start with a producer (a photosynthetic organism) like grass. Photosynthetic just means an organism that can produce glucose by photosynthesis

Primary consumer eats the producer. An example is mice. In a food chain, only one primary producer is shown, although there may be many.

The secondary consumer feeds on the primary consumer - secondary consumers are always some type of predator. Take an owl as an example.

Tertiary consumer eats the secondary consumer.

Some food chains have even more levels after this, however, some don’t even have this many levels.

An important fact to remember in food chains is that most of the energy gets lost as it passes through the food chain. For example, if there were 1000 joules of energy produced by the producer, maybe roughly 100 joules would be passed on to the primary consumer, and maybe 10 joules to the secondary consumer.

Predator prey cycle - the graph shows that the population of both prey and predator cycle up and down.

Observing the graph, we can see that the population of the predator (owls) lags behind the population of prey (field mice), which is known as out of phase.

At the beginning of the graph, we can see that the population of the field mice increases while the population of the owls stays low, because not enough predators are limiting the population of field mice.

Then we can see that there are lots of field mice, as well as more owls, because there is an abundance of food for the predators and making them thrive.

But when the predator population peaks, it starts causing a decline in prey population.

However, with fewer mice to feed on, the owl population decreases as well, and we end up where we started, and the cycle repeats.