Populations How much is too much?

What defines a population? A group of individuals - within the same species - living within the same area - during a specific time Levels of Organization review: organisms -> populations -> communities -> ecosystems -> biome -> biosphere

Population characteristics Sex ratio (males:females) Age distribution Population density Spatial distribution Size

What changes the size of a population? Natality (birth rate) Immigration Mortality (death rate) Emigration

Factors that influence population growth rates Density-independent/extrinsic limiting factors - Chance Density-dependent/intrinsic limiting factors - Availability of raw materials - Availability of energy - Accumulation of waste products - Interactions among organisms

Population Growth Models

Reproductive Strategies Populations of K-strategists - long lifespan - few offspring - care for offspring - reaches carrying capacity Populations of r-strategists - short lifespan - many offspring - little to no care for offspring - does not reach carrying capacity