How populations grow and communities interact in nature
Ecology studies how organisms interact with each other and their environment. Organisms adapt to abiotic factors such as temperature, water, light and soil; they may regulate their internal conditions, conform, migrate or suspend activity. A population is a group of one species in an area, described by density, birth rate, death rate and age structure. Populations show exponential growth, dN/dt = rN, when resources are unlimited, and logistic growth when resources limit them to a carrying capacity K.
Species interact in many ways: predation, competition, parasitism, commensalism, where one gains and the other is unaffected, and mutualism, where both gain, as with lichens or flowers and pollinators. In ecosystems, energy flows from producers to consumers, and only about 10 percent passes to each higher trophic level, so pyramids of energy are always upright. Biodiversity exists at genetic, species and ecosystem levels. It is lost through habitat destruction, overexploitation, invasive species and co-extinction, and is conserved in situ in national parks and biosphere reserves and ex situ in zoos and seed banks.
Why it matters
Ecology guides how we manage fisheries, forests and wildlife, control pests without harming other species, and plan for growing human populations. It explains why removing a predator can upset a whole ecosystem and why biodiversity hotspots such as the Western Ghats deserve protection. These ideas inform climate and conservation decisions worldwide.
Key terms
- Carrying capacity
- The maximum population size an environment can support with its resources.
- Mutualism
- An interaction between two species in which both benefit.
- Trophic level
- A step in a food chain, such as producers or primary consumers.
- In situ conservation
- Protecting species in their natural habitats, such as national parks.