Population Ecology

Population Number of Individuals of the same species that live together in one area or place

What dynamics might be involved in predicting population growth? Population size Population growth rate Carrying Capacity Limiting Factors

Population Size Number of individuals in a population Growth occurs when the birthrate is greater than the death rate.

Population Growth Curves Exponential growth: Population increases by a constant proportion per unit of time At this growth rate the population exhibits a J-shaped curve

Population Growth Curves Logistic growth: Population increases rapidly for a period of time, its growth begins to slow, and ultimately, growth stops (can decrease as well) At this growth rate the population exhibits an S-shaped curve. K (carrying capacity) = maximum population size that an environment can support K

Factors That Control Population Growth Populations don’t grow indefinitely because of limiting factors. Limiting Factors Include: Competition Predation Parasitism Crowding Stress Disease

Competition Primary sources of Competition: Food Water Space Mates Situation in which two or more organisms attempt to use the same scarce resource (this could be a food source, a good location for capturing sunlight by plants, a particular nutrient, etc…)

Predation A relationship between two organisms in which one organism (predator) kills and devours another organism (prey). Affects population size of both predator and the prey.

Parasitism: The relationship between two organisms where one organism benefits (parasite) and the other is harmed (host). Example: Tapeworm You are harmed because it lives off your intestinal fluids Segments break off to form a new worm!

Biodiversity The number of species living within an ecosystem.

How Populations Evolve Hardy-Weinberg Principle The frequencies of alleles in a population do not change unless evolutionary forces act on the population. p2 + 2pq + q2 = 1

How Biodiversity Impacts Population Growth 6 forces that cause populations to evolve: Mutation – ultimate source of all variation Migration – movement of organisms from one population to another, creates gene flow. Nonrandom mating – when individuals prefer to mate with others of their own genotype, inbreeding is an example. Genetic drift – random change in response to their environment. Natural selection –survival of the fittest. Extinction- species that have disappeared permanently.