1. The Abundance and Distribution of Populations
Chapter 6: Module 18
The Abundance and Distribution of Populations

2. Nature exists at several levels of complexity.
Individual  Population Community  Ecosystem  Biosphere
Individual – a single organism
Population – the individuals that belong to the same species and live in a given area at a particular time.
- the unit of evolution
Community – incorporates all of the populations of organisms within a given area.

3. Ecosystem – consists of all the biotic and abiotic components in a particular location.
Biosphere – incorporates all of Earth’s ecosystems.

5. Populations have distinctive characteristics
Population ecology – is the study of factors that cause populations to increase or decrease.
Characteristics of Populations
Population size (N) = the total number of individuals within a define area at a given time
1987 – only 22 American condors are left in the wild.
Captive breeding program increased the number of condors to 437 by 2014.

6. Population density = is the number of individuals per unit area (or volume, in the case of aquatic organisms) at a given time.
Significance:
a. Population density and size can help scientists estimate whether a species is rare or abundant.
coyotes – 1/km2 (in some parts of Texas)
- 12/km2 (in other parts of TX)

7. To determine whether a population in a particular location is so dense that it might outstrip its food supply.
Can be particularly useful measure for wildlife managers who must set hunting or fishing limits on a species.
ex: more hunting or fishing permits for zones with high-density populations.

8. Population distribution = is a description of how individuals are distributed with respect to one another.
3 types:
a. Random
b. Uniform
c. Clumped
Significance: essential to conservation and management of pest species.

12. Population Sex Ratio = ratio of males to females
Significance: helps scientists estimate the number of offspring a population will produce in the next generation.

13. Population Age Structure = describes how many individuals fit into particular age categories.
Significance: helps ecologists predict how rapidly a population can grow.

14. Population size is affected by density-dependent and density-independent factors.
Density-dependent factors
= a factor that influences an individual’s probability of survival and reproduction in a manner that depends on the size of the population.
ex: limiting resource
- food, water, nutrients (P,K), nest sites

15. Carrying capacity (K)= the limit of how many individuals in a population the environment can sustain.
It is the maximum
number of individuals that a particular ecosystem can support.

16. Density-independent factors
= a factor that has the same effect on an individual’s probability of survival and the amount of reproduction at any population size.
ex: tornado, hurricanes, floods, fires, volcanic eruption and other climatic events