On your packet write down three ideas under opener. Population Density What factors influence how a population changes over time? On your packet write down three ideas under opener.

Characteristics of Populations A group of individuals of the same species that live in the same area at the same time. These are the important characteristics of a population: 1. Geographic distribution 2. Density 3. Dispersion 4. Growth rate 5. Age structure

Geographic distribution is the range of the population. This term describes: the area that is inhabited by the population. The range can vary in ______. It may be just a few centimeters, such as the mold on a piece of bread. Or the range may be huge, such as the migration area of whales. size

Population Density Population density is: the number of individuals per unit area. Density is one of the main characteristics that describes a population. There is tremendous variation in density depending on the _________ and the _____________. Some populations have _____ densities, while other populations have ______ densities. species ecosystem low high

Calculating Population Density To calculate population density you divide the number of individuals by area. *Remember Area=Length x Width* 1mile 2mile Ex. What is the population density of 14 cats in a 1mile x 2mile area? Area= mile x mile= mile2 Pop. Density= cats÷ mile2 = cats/mile2 1 2 2 14 2 7

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Clumped Dispersion Random Dispersion Even Dispersion Dispersion is…. …. the spatial distribution of individuals within the population. The three types of dispersion are: Clumped Dispersion Random Dispersion Even Dispersion

Clumped Dispersion a) In clumped dispersion the individuals are clustered together. Clumped distributions often occur when resources such as food, water, or living spaces are clumped together. Clumped distributions may also occur because a species has a certain social behavior, such as herding animals, flocks of birds, schools of fish or hives of bees.

Even Dispersion a) In an even dispersion, individuals are: These penguins exhibit even dispersion because of aggressive interactions that occur between neighbors. a) In an even dispersion, individuals are: separated by a fairly even distance. Even distributions are usually the result of _____________________, but the interaction results in the individuals trying to get as far away from each other as possible. social interactions

Random Dispersion a) In random dispersion, the location of one individual is independent of the location of the other individuals. b) Random dispersal may result from seed dispersal: by the wind or animals. c) A forest or a field of wildflowers results from the random dispersal of seeds.

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Limits to Growth Limiting Factors: No population can undergo exponential growth forever. There are… …limits to how fast and how big a population can grow. Examples of limiting factors include: 1. Competition 2. Predation 3. Parasitism and disease 4. Drought and other climate extremes 5. Human disturbances Limiting Factors: A limiting factor is a factor that causes population growth to decrease.

Density-Dependent Factors 1. A limiting factor that depends on population size is called a density-dependent limiting factor. Density-Dependent Factors This means that the limiting factor only becomes “_________” when: the population density reaches a certain level. limiting

Density-dependent limiting factors include: competition predation parasitism and disease shortages of food shortage of territory/nesting sites. Competition for resources Predation Territory Parasitism Predator/Prey Interactions

Density-Independent Factors The density-independent factors affect: all populations in similar ways, regardless of the size of the population. Density-Independent Factors Examples of density-independent factors include: a) Unusual weather or natural disasters such as floods and fires. b) Certain human activities, such as the damning of a river, or clear-cutting a forest.

These factors would affect …. ….. any population of any size. In response to density-independent factors, populations may experience a “______” where the population is nearly _________. crash eliminated If one population is nearly decimated, it may also affect another population if the second population depends on the first as a food source.

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