Chapter 53: Introduction to Population Ecology

Organism: 1 Species
Population: A group of Organisms
Community: Multiple organisms

Dispersion Patterns:
Clumped Aggregated: Occurs when resources aren’t evenly distributed.
Uniform: Occurs when individuals are spread into territories/ scare resources.
Random: Positions don’t correlate with other individuals. Truly random.

Natality (B) : How much an individual adds to population.
Mortality (D): How much a population loses to death.

r= B- D

Immigration (i) : Individuals entering a population.
Emigration (e) : Individuals leaving a population.

r= (B-d) + (i-e)

Factors affecting r- max:
Reproductive Life span, number of reproductive cycles, number of offspring per reproductive cycle, age of reproductive maturity.

Density Dependent Factors: Regulate population sizes, greater effects as population sizes increase. Increase in d, decrease in b. (Predation, Disease, Competition)

Density Independent Factors: Limit population size, not affected by the size of the population, will happen whether large or small, generally abiotic or environmental. (Wild Fire, floods, drought)

Life History: Semelparous and Iteroparous
Semelparous: Reproduce 1 and the die. Example: Salmon
Iteroparous: Reproduce multiple times before death. Example: Humans.

Fecundity vs Fitness
Fecundity: Is the potential capacity to produce offspring.
Fitness: Is the ability of an individual to pass on its genetic information- the ability to reproduce successfully.
An individual with high fecundity can gave low fitness if they do not reproduce or do not reproduce much. Some also consider fitness to be lower if the off spring do not survive to reproduce themselves.

R-Selected Species: High Birth rate, large number of offspring but little to no parental care. Generally small in size. Short lifespan- early reproductive maturity. Includes organisms that reproduce asexually.

K-Selected Species: Low Birth rate, fewer offspring, but greater parental care. Larger in size, longer lifespan- longer time to reproductive maturity.

The power of population is indefinitely greater than the power in the earth to produce subsistence for man.

Abiotic: Not Living (Water, Temp, Air)
Biotic: Living (Animals, Plants, Bacteria)