Population Dynamics 4.1

Remember populations? Population Biosphere- most broad level Biome Ecosystem Biological Community (Or just community) Population Organism –most basic level Population- several organisms of the same species that share the same geographic location. Ex: you are one of 500 Teenagers at Sweetwater High school.

Population dynamics There are a lot of different things to take into consideration when talking about a population of organisms. Population density Population dispersion/ distribution Population ranges

Population Density Population density- number of organisms per unit area. (how many of a certain type of organism can fit in one area) Ex: My 8th period class has 9 students. Therefore, there is a population density of 9 students per one classroom during 8th period.

Population Distribution/Dispersion Population distribution- the pattern of spacing of a population within an area. Ex: there are 3 per every 2 square feet of this classroom.

Density v. Dispersion American bison have a density of about 4 bison per km^2 White-tailed deer have a density of 10 deer per km^2. American Bison have a dispersion method of grouping together in groups called herds. White-tailed deer are randomly dispersed throughout appropriate habitats.

Population ranges Certain populations cannot live in certain areas of the biosphere. Ex: Humans cannot live in the arctic circle without special equipment. Therefore, the population range of humans does not include the arctic circle.

Other things about Populations Population limiting factors are things that keep a population from growing exponentially. Density-independent factors Density-dependent factors Population growth rate Reproductive patterns

Independent v Dependent Density Independent factors Density Dependent factors These are limiting factors that influence the population size that DO NOT depend on the density of the population. These are usually abiotic factors like weather. Ex: A population can decrease and become less dense after a hurricane wipes out a village. These are limiting factors that influence the population size and DO depend on the density of the population. These things are disease, competition, and predation. Ex: In Holocaust concentration camps, disease killed many people due to the massive amount of people in a small area.

Population Growth Rate Another factor that limits the size of a population is the growth rate. This is the rate at which the population reproduces. Ex: If there was only one female in a population, that population would grow very slowly due to there only being one female to reproduce with.

Population growth rate Two factors that are included with the growth rate are Emigration and Immigration. Emigration- the amount of individuals that move away from a population. Ex: 10 people move away from Sweetwater over a month’s time. Immigration- the amount of individuals that move into a population. Ex: 5 people move into Sweetwater over a month’s time.

Carrying capacity Exponential Growth model- describes population growth as never ending. Logistic Growth model- describes population growth as having a limit. Carrying capacity is the set numbers of individuals an ecosystem can support before it breaks down.

Carrying Capacity Carrying capacity is influenced by water, oxygen, and nutrients that are available at any given time.

Reproductive patterns There are two different ways that populations can reproduce. R- Strategy and K-Strategy.

R R-Strategy- organisms who use this strategy to reproduce will have a lot of offspring in a short period of time. They typically won’t put a lot of energy into raising these offspring, as there are so many. These organisms typically have short life spans, remember this as RUNTY offspring. They are also usually very small and mature quickly. Ex: Flies.

K K-Strategy- This type of reproduction includes only reproducing a few offspring at a time and putting A LOT of energy into raising them. Gestation will often be longer and offspring will often be larger. Remember this as KINGLY reproduction. Ex: Humans use this strategy.

Key Points There are a lot of factors that influence how big a population can get. Closer- how do the summer fox population correlate with the fall mice population?