Populations & resources
A population changes through births, deaths, immigration and emigration. Food, space and other conditions limit growth. Carrying capacity depends on those conditions and can vary. As density rises, competition for resources can reduce growth per individual.
Where this sits
- Comes after
- Food webs
Exercises from this rung
Generated by the app, from easiest to hardest
190 gulls live in an island of 10 hectares. What is the population density, in gulls per hectare?
Answer 19
Why 190 ÷ 10 = 19 per hectare. Density is what matters for competition: 190 gulls spread over 100 hectares would live comfortably, and the same number on a single one would run out of food. That is why counts are always given per area.
easierWhich group is an ecological population?
- A rabbit, a pine and a fungus with no spatial connection
- All living things and soil on the planet
- Rabbits of the same species living in one valley
Why A population groups individuals of the same species in a defined area and period. Interacting populations form a community. An ecosystem also includes the physical environment and exchanges of matter and energy.
in betweenAs seedling density in a pot rises, each grows less because light is limited. What mechanism does this illustrate?
- Density-dependent competition
- No interaction between individuals
- Unlimited creation of resources
Why When individuals share a limited resource, more individuals can reduce what each receives. This competition can slow population growth. Not every limitation depends on density: a frost, for example, can affect even a sparse population.
harder