C4.1 Populations and Communities

C4.1.1 Population

• A population is a group of individuals of the same species living in a specific area at the same time, where they can interact

• A community is all the population of different species living and interacting in the same area

• Species are a group of organisms that can potentially interbreed to produce fertile offspring

• Intraspecific competition is competition between individuals of the same species (within a population)

• Interspecific competition is competition between individuals of the different species (between populations).

Population density = no. of individuals / area

C4.1.2 Estimation of population size by random sampling

Quadrats work best for sessile or very slow moving organisms like plants. Mobile animals usually require a different approach

    Population density = total indivual counted in all quadrats/ total area sampled (sum of quadrat areas)

    Estimate population size = Population density x total habitat area

C4.1.3 Random quadrat sampling to estimate population size for sessile organisms