Characteristics Of Populations Lesson 8 September 3rd, 2010

Characteristics of Populations As populations grow the resources available to each individual gets smaller. When resources are decreased the number of births will decrease and the number of deaths will increase. Eventually the number of births will equal the number of deaths. This is called an equilibrium.

Biotic Potential The maximum number of offspring that a species could produce, if resources were unlimited.

4 Factors of biotic potential Birth Potential The maximum number of offspring per birth Survival Capacity The number of offspring that reach reproductive age. Procreation The number of times that a species reproduces a year. Length of reproductive life The age of sexual maturity and the number of years the individual can reproduce.

Limiting Factor Limiting Factor - Environmental factor that prevents an increase in the number of organisms in a population or prevents them from moving into new habitats.

Limiting Factor Abiotic Limiting Factors Biotic Limiting Factors Sunlight, water, soil, and air, natural disturbances such as storms, fires, droughts, and logging. Biotic Limiting Factors Competition among organisms for resources, presence of predators, reliance on other organisms for survival, and the presence of disease causing organisms.

Carrying capacity The maximum number individuals that an organism can support without reducing its ability to support future generations of the same species. Exceeding the carrying capacity hurts the environment.

Carrying Capacity The figure shows a rabbit population after it is was introduced to an ecosystem. At first the population grows quickly and then it slows down to the point where the number of births equals the number of deaths.

Limits of Tolerance Law of minimum Law of Tolerance The nutrient in least supply is the one that limits growth. Law of Tolerance An organism can survive within a certain range of an abiotic factor; above or below the limit it cannot survive.

Density Dependent Factors A population is said to be dense when there are a large number of organisms in a small area. Density-independent factors Affect members of a population regardless of population density Flood, fire, pesticides, change in climate, drought Affect the members of a population due to the density of the population. Food shortage, intraspecific competition, introduction of exotic species, increased predation.

Density Dependent Factors

Homework / MSIP Read Page 77 – 79 Page 79 # 1,2,4