A2 Unit 3.5 Population size & ecosystems

Key Terms

Ecology - The study of living things and their interaction with each other & the environment

Ecosystem - A community of interdependent organisms (biotic factors) interacting with the abiotic components of their habitat

Community - All the members of every species in a habitat

Habitat - The physical place where an organism lives

Population - All of the organisms in one species that can interbreed in a habitat

Biotic factors - All of the living parts of an ecosystem (can influence population)

Abiotic factors - All of the non-living parts of an ecosystem (can influence population)

Niche - The role of an organism in an ecosystem (generally a feeding role)

Examples & Key Questions

Population Sizes + Formula

Graphs showing population growth - Lag phase & Log phase

Graphs showing population growth - Stationary phase & Death phase

Growth curve for a bacterial population & questions

Density Dependent & Independent factors - Log scales for growth curves

Calculating rate of growth example

Sampling Techniques: Quadrats

Random sampling using quadrats & Transect sampling

Key terms - Species/ plant density, Species % frequency & Species % cover