AP Biology Barron's Chapter 15--Ecology

Terms in this set (76)

1. Size
--Total number of individuals in a population and is represented by N

2. Density
--Number of individuals per unit area of volume. Counting the number of organisms inhabiting a certain area is often very difficult, if not impossible. Instead of counting each organism scientists use sampling techniques to estimate the number of organisms living in one area. One technique that is used is called mark and recapture which is when organisms are captured, tagged, and then released. Some time later, the same process is repeated and the following formula is used for the collected data:
N= Number marked in first catch x total number in second catch/ number of recaptures in second catch

3. Dispersion
--The pattern of spacing of individuals within the area the population inhabits. The most common pattern of this is CLUMPED. Some populations are spread in a UNIFORM pattern. RANDOM spacing occurs in the absence of any special attractions or repulsions.

4. Survivorship/ Mortality Curves
--Show the size and composition of a population
>Three types:
1. Type I curves show organisms with low death rates in young and middle age and high mortality rates in old age. There is a great deal of parenting, which accounts for the high survival rates of the young. This is characteristic of humans.
2. Type II curves describe a species with a death rate that is constant over the life span. This describes the hydra, reptiles, and rodents.
3. Type 3 curves show a very high death rate among the young but then shows that death rates decline for those few individuals that have survived to a certain age. This is characteristic of fish and invertebrates that release thousands of eggs, have external fertilization, and have no parenting.

5. Age Structure Diagrams--Show the relative numbers of individuals at each age.

Developing countries have a pyramid shaped graph (India) and developed countries have zero population growth where the number of people at each age group is about the same and the birth rates and the death rates are about equal (USA).