Species interactions and food webs

≈ 48 min

Species interactions and food webs

Food webs represent feeding relationships and the movement of matter and energy through an ecosystem. Producers capture energy; consumers obtain it by feeding; decomposers recycle nutrients from dead material. Predation, competition, mutualism and parasitism affect population sizes. Removing one species can create indirect effects, so a food-web prediction should trace more than one connection and state uncertainty.

Work it through

If a predator declines, its prey may increase. Greater prey numbers can reduce the plants they eat. However, disease, migration and another predator may also affect the outcome, so the web supports a hypothesis rather than a guaranteed result.

Mastery target

Use arrows correctly to trace energy transfer, then predict a direct and an indirect consequence of a change.

In a food web, an arrow normally points from

The organism being eaten to the organism that eats it

Predator to sunlight only

Consumer to its own waste only

Plant to soil without a relationship

Name the key biological term from Species interactions and food webs: enter the term that best fits the explanation and visual model.

If insects decline sharply, what is a plausible indirect effect on insect-eating birds?

Their food supply may decrease, lowering survival or reproduction.

Their cells become chloroplasts.

All plants immediately disappear.

Energy is created.

Which statement corrects a common misunderstanding in Species interactions and food webs?

Correct: Energy is not recycled in a food web; it eventually leaves as heat. Matter such as carbon can cycle.

A single observation is enough to prove every biological claim.

Scientific terms are interchangeable whenever they sound similar.

A process always has exactly the same result in every environment.