Populations

Review Remember a population is a group of individuals that belong to the same species and live in the same area

Population Density Population density refers to the number of organisms per unit area Spatial Distribution Dispersion is the pattern of spacing of a population. Clumped Random Uniformed/Spaced

Population Dynamics Factors that affect a population’s size: Natality Birth Rate Mortality Death Rate Immigration Movement of individuals INTO an area Emigration Movement of individuals OUT of an area

Population Growth Growth rate is determined by looking at the change in number of individuals over time Population Growth natality > mortality immigration > emigration Population Stability natality = mortality Immigration = emigration

Exponential Growth This occurs when members of a population reproduce at a constant rate. Unrestricted growth Result is a “J-shaped” curve Population would become infinitely larger until a limiting factor slows the growth

Logistic Growth As resources become less available, the growth of a population slows. Restricted Growth “S-shaped” curve A population will reach it’s carrying capacity

Comparison

Carrying Capacity The maximum number of individuals in a species that an environment can support for the long term Carrying capacity is limited by the energy, water, oxygen, nutrients available or other limiting factors

Limiting Factors Any condition of the environment that limits the size of a population 2 major groups Density-Dependent Density-Independent

Density-Dependent When a limiting factor depends on population size Density-dependent factors only become limiting when the population density reaches a certain level Competition for food, water, space, sunlight, etc. can happen between 2 individuals of the same or different species

Density-Independent Affect ALL populations (large and small) in similar ways. Caused by human disturbance, natural disasters, seasonal cycles, etc Some density-independent limiting factors could severely upset the growth of a population.

Review What are the 3 types of dispersion? Random, Clumped, Uniform/Spaced What is natality? What is emigration? Birth Rate. Movement OUT of an area. What are the 2 types of growth curves? J-shaped & S-shaped What is carrying capacity? The max number of individuals that can be sustained in an area.

Any Questions?