Build food webs, calculate how much energy reaches each trophic level, read predator–prey graphs, and explain how niches — including the time of day an animal is active — reduce competition.
A food chain shows one feeding path: grass → kob antelope → lion. A food web joins many chains, because most animals eat more than one food and are eaten by more than one predator. Arrows point in the direction energy flows — from the food to the feeder.
Each feeding level is a trophic level. Only about 10% of the energy at one level becomes biomass in the next; the rest is used in respiration and lost as heat, or lost in faeces and uneaten parts.
This explains why food chains are short, why there are few apex predators, and why ecological pyramids of energy are always upright.
Predator and prey populations often cycle. When prey increase, predators have more food and increase after a delay. More predators reduce the prey; with less food, predator numbers then fall, and the cycle repeats. The predator peak always comes after the prey peak.
An organism’s niche is its role in the ecosystem: where it lives, what it eats, when it is active and how it interacts with other species.
Two species cannot share exactly the same niche for long (competitive exclusion). Species coexist by using resources differently — resource partitioning. Plants with roots at different depths, or animals feeding at different times of day, avoid direct competition.
Human activity can push animals into new niches. Where people and livestock are active by day, some prey species become more nocturnal. This increases their temporal overlap with nocturnal predators such as lions, so predation on those prey rises. Prey numbers fall, which can destabilise the predator population too.