Population Dynamics Life Science Populations Change Population Dynamics

Population Dynamics Life Science

Populations Change! § Population Dynamics is the study of why populations change and what causes them to change

§ All living things need resources such as water, energy and living space. § Carrying Capacity- maximum number of individuals an ecosystem can support

Three stages of population change § Growth- population increases in size § Births > Deaths § Stability- the population does not increase or decrease, but stay the same § Births Deaths § Decline- the population decreases in size § Deaths > Births

Patterns of Growth § Rapid growth- very sharp increase in the numbers of individuals in a population

§ Gradual growth- Increases at a fairly steady rate

Darwin and his observations § All populations are able to grow rapidly § Populations tend to remain constant in size § There are limits to the natural resources § Within a given population there is genetic variation

4 Characteristics that define a population § Population size- the number of individuals in a population at a given time § This can be a result of a climate change, time of year, and availability of resources § Population density- the measure of the number of individuals living in a certain space

§ Low density

§ High Density

Population Spacing Clumped-gather around resources in groups Uniform-evenly space themselves compete for resources Random-no regard to individuals, or resources

Age Structure § Age determines the amount on how much a population can grow § Post reproductive- organisms that can no longer reproduce § Reproductive- organisms capable of reproduction § Pre-reproductive- not yet able to reproduce

How can scientists predict population change?

Populations Respond to Pressures 8 -2

Population Responding to Pressures § Population growth is limited § This is a result of many factors § Birth- numbers of births in a population § Death- numbers of deaths in a population § Immigration- movement of individuals into a given area § Emigration- movement of individuals out of a population

Population Change § Population Change = (birth + immigration) (death + emigration)

Limiting Factors § Prevents the continuing growth of a population § Density – Dependent Factors § Density – Independent Factors

Density Dependent Factor § § Competition Disease Parasitism Predation

Density Independent Factors § § § Drought Hurricanes Tornados Fires Floods

Survival Strategies § Opportunists- species that reproduce rapidly and have a short life span

§ Competitors- species with adaptations that allow them to remain near their carrying capacity for long periods of time