Population Ecology Chapter 14

Population Ecology Population – group of one species Based on density Interact and interbreed with each other Based on density Number of individ. In a given area Can vary depending on dispersion Uniform – evenly spaced Random – position independent of others Clumped – end to aggregate in patches

Population Dispersion

Population Growth Changes in populations Based on how many organisms are added and how many are taken away Growth rate- change in population size can be positive, negative or zero

Population Growth Under ideal conditions population will grow More organisms are born than die Exponential growth – the larger a population is, the faster it grows Will not last forever- will slow down Zero growth – population stays the same

Limits to Population Growth Eventually nutrients run out Carry Capacity – average number of individuals an area can support Based on density dependent factors Limit large, dense populations Energy, shelter, predators, soil nutrients, water, competition, etc. Density – Independent Factors Kill off organisms no matter how large the population is Examples: weather, natural disasters, human activities

Density Dependent Limiting Factors Competition – When individuals compete for resources (ie food, energy, etc) More individuals in an area limits the amount of certain resources available Helps determine the carrying capacity of an environment

Density Dependent Limiting Factors Predation When one species eats another. Tend to live in balance with each other As one population goes up, so does the other and vise versa Increase in prey, leads to an increase in predator Decrease in predator, leads to an increase in prey

Density Dependent Limiting Factors Parasitism An organism that takes nourishment from its host Live at the expense of the host Parasite populations grow only if host population is dense Easier to spread

Density Dependent Limiting Factors Crowding and Stress Most animals need a certain amount of space. Higher the population, the less space available. Also weaken immune system

Demography Study of population growth and other stats Life Tables – age specific summary of birth and death rates Determines survivorship curve Types Type I – many live to adulthood, then rapid die off Type II – equal chance of dying at any age Type III – lots of young, but not many make it to reproductive age