Population Ecology Biology 1-2

Population Ecology Population ecology studies changes in population size and the factors control their size over time. Population ecology studies changes in population size and the factors control their size over time. Population-a group of individuals of the same species in a defined area. Population-a group of individuals of the same species in a defined area.

Population Growth The size of a population is based on two sets of opposing factors. The size of a population is based on two sets of opposing factors. Growth factors-factors that cause a population to grow. Growth factors-factors that cause a population to grow. Lots of food or living space, good climate, little competition or predation. Lots of food or living space, good climate, little competition or predation. Limiting factors-factors that cause a population to shrink. Limiting factors-factors that cause a population to shrink. Little food or living space, poor climate, lots of competition/predation, disease. Little food or living space, poor climate, lots of competition/predation, disease.

Exponential Growth If given unlimited space and resources, a population can grow exponentially. If given unlimited space and resources, a population can grow exponentially. No environment can support exponential growth forever. No environment can support exponential growth forever. Resources are limited. Resources are limited.

Carrying Capacity Growth and limiting factors work against each other to create an upper limit to a population. Growth and limiting factors work against each other to create an upper limit to a population. Carrying capacity-maximum number of individuals an area can support indefinitely. Carrying capacity-maximum number of individuals an area can support indefinitely.

Carrying Capacity cont’d Growth factors cause the population to increase. Growth factors cause the population to increase. Limiting factors slow the growth rate. Limiting factors slow the growth rate. At the carrying capacity, the growth rate is zero. At the carrying capacity, the growth rate is zero.

Life Histories The life history of an organism is all the events from birth to death. Includes: The life history of an organism is all the events from birth to death. Includes: When it reproduces. When it reproduces. How often it reproduces. How often it reproduces. Number of offspring. Number of offspring. Amount of care. Amount of care.

Life Histories cont’d Organisms can be put into two groups, based on their life histories. Organisms can be put into two groups, based on their life histories. r-selected species r-selected species K-selected species K-selected species

r-Selected Species r-selected species use most of their energy for their offspring. r-selected species use most of their energy for their offspring. Produce lots of offspring. Produce lots of offspring. Provide little or no care for the young. Provide little or no care for the young. Tend to be smaller and shorter lived organisms. Tend to be smaller and shorter lived organisms. Have low survival rates. Have low survival rates. If they make it past infancy they live to an old age. If they make it past infancy they live to an old age. Allows them to succeed in unstable environments. Allows them to succeed in unstable environments.

r-Selected Species cont’d r-selected populations reproduce rapidly and easily overshoot the carrying capacity. r-selected populations reproduce rapidly and easily overshoot the carrying capacity. They grow rapidly and use up resources. They grow rapidly and use up resources. Limiting factors increase and their numbers drop off. Limiting factors increase and their numbers drop off. Too many predators, not enough food. Too many predators, not enough food. When the population is low enough they recover. When the population is low enough they recover. Less predation, more food. Less predation, more food. Swing back and forth around the carrying capacity. Swing back and forth around the carrying capacity.

K-Selected Species K-selected species are organisms that put their energy into raising their young. K-selected species are organisms that put their energy into raising their young. Have fewer offspring. Have fewer offspring. Provide lots of care for the young. Provide lots of care for the young. Higher infant survival rates. Higher infant survival rates. Tend to be larger and longer lived. Tend to be larger and longer lived.

K-Selected Species cont’d K-selected populations grow much more slowly. K-selected populations grow much more slowly. Level off as they near the carrying capacity. Level off as they near the carrying capacity. Reproduce so slowly they cannot handle change very well. Reproduce so slowly they cannot handle change very well. Work to ensure the survival of their young. Work to ensure the survival of their young.