VII. Community; interacting populations that VII. Community; interacting populations that inhabit a common environment. A. Limiting factors; factors that limit the existence , numbers, reproduction, and/ or distribution of organisms. Ex. Sunlight, climate, temperature, water nutrition/ food, fire, soil chemistry, space, other organisms. B. Climax community; A stable, mature community. Succession slows down and becomes fairly stable (reaches equilibrium). There is little or no change in species, often for a long period of time.

C. Succession; orderly natural changes and C. Succession; orderly natural changes and species replacements that take place in the communities of an ecosystem. 1. Primary; colonization of barren land begins in an area where there is no living organism. a. Pioneer species become established in an area. Ex; lichen is able to grow on bare rock. b. Pioneer species make up the first stage of soil development, then eventually die.

c. Weedy plants, insects and other new c. Weedy plants, insects and other new organisms move in, and out of the community. Equilibrium is reached. 2. Secondary succession; occurs when a natural disaster destroys a community, then the community is slowly rebuilt. a. Soil has already been established and it doesn’t take as long to reach the climax community.

VIII. Population dynamics; populations tend to. grow exponentially VIII. Population dynamics; populations tend to grow exponentially. As the population gets larger, it grows at a faster rate. A. Limiting factors; availability of food, disease, predators, or lack of space will cause population growth to slow. B. Carrying capacity; the number of organisms of one species that the environment can support. 1. Affected by limiting factors.

C. Reproductive patterns; determines population growth. 1. rapid life-history; organisms have a small body size, mature rapidly, reproduce early and have a short life span. Mice have a lifespan (in the wild) of 9 – 12 months. They can reproduce by 12 weeks of age. They have a gestation period of 18 -24 days.

2. slow life-history; larger species,. reproduce more slowly, mature 2. slow life-history; larger species, reproduce more slowly, mature slowly, and live for a longer period of time. Usually maintain population at or near carrying capacity. Elephants have a lifespan of 60 – 70 years. They can reproduce by 15 – 17 years of age. Females have a gestation period of 22 mos. (645 days)

D. Density factors; organisms may be dispersed in D. Density factors; organisms may be dispersed in random, clumped, or uniform patterns. Density describes the number of individuals in a given area.

Competition within a species for limited resources lead to individuals living at specific distances from one another.

There is no pattern to the way individuals fill an area.

Individuals live in groups, and the groups may be close together. This facilitates mating, protection and access to food sources.

1. Density-dependant factors; include disease, competition, predators, parasites and food. a. Predator populations are limited by the amount of available prey. Prey populations are limited by being caught for food. b. It is easier for parasites and disease to spread through a dense population, quickly reducing its numbers.

2. Density-independent factors; These can limit population growth regardless of the density of the population. Mostly abiotic, include things like volcanic eruptions, climatic changes, chemical pesticides, and other major habitat disruption.