Ecology: Unit 2 EEn.2.7.2 Objectives: Explain the characteristics used to describe a population. What factors affect population size? What are exponential and logistical growths How is diversity tie into genetic variation, population, and the ecosystem?

Characteristics of a population 3 Important characteristics of a population are: a. Geographic Distribution – area inhibited by the population. b. Population Density – the # of individuals in an area. c. Growth Rate - # of organisms can grow rapidly or decrease in # as well. This depends on whether they are being protected of preyed upon.

Factors that affects population size Number of births – population will grow if more individuals born than die. Number of deaths – if death rate is greater than birth rate, then population will shrink. - If birth rate = death rate, population will stay the same

Factors that affects population size c. Number of individuals that enter or leave the population. 1. Immigration – population grows as individuals move in. 2. Emmigration – population decrease as individual move out of an area.

Exponential Growth Occurs when the individuals in a population reproduce at a constant rate. Initially, the population will increase slowly, and then over time it becomes larger and larger until it approaches an infinitely large size

Logistic Growth As resource becomes less available, the growth of a population slows or stops. This does not man the size of the population has dropped, it is still growing, but at a much slower rate. J - Curve S - Curve

Carrying Capacity The largest/maximum number of individuals that an environment can support. Limiting factors – determine an area’s carrying capacity by limiting population size.

Limits to Growth Limiting factors – is a factor such as insufficient nutrient/food) that causes population growth to decrease/reach its carrying capacity. Density dependent factorsof organisms (based on the # of organisms) - food availability, space, water, harsh winter, & competition.

Limits to Growth Density independent factors (the # of organisms does not matter) – It affects all populations, regardless of the population size. Unusual weather, fire, flood, & earthquake.

Genetic Variations in Population Genetic variation describes naturally occurring genetic differences among individuals of the same species. This variation permits flexibility and survival of a population in the face of changing environmental circumstances.

Genetic Variations in Population Consequently, genetic variation is often considered an advantage, as it is a form of preparation for the unexpected. But how does genetic variation increase or decrease? And what effect do fluctuations in genetic variation have on populations over time?

Genetic Variations in Population http://www.nature.com/scitable/topicpage/the- genetic-variation-in-a-population-is-6526354 Why are mating patterns important, and explain nonrandom mating, inbreeding, and outbreeding. What role does genetic drift plays in genetic variation? What is a population bottleneck? How does the physical distribution of individual affects a population? What occurs during mating?