Topic 12 Introduction to Population Ecology

Populations are affected by interactions with environment

Ecological Consequences

1. distribution

2. demographics

3. population Size

4. population growth

Ecological Consequences

1. change in genetic/phenotypic frequencies in a population

2. adaptations

3. macroevolution

Ecology

study of organisms and their interactions with their environment

Population Ecology

study of populations and their interaction with the environment

Properties of Population Ecology

1. density

2. dispersion

3. demographics

4. life history

Density

Dispersion

pattern of spacing of individuals in population

Clumped

individuals aggravated into patches (most common)

Uniform

individuals are evenly spaced

Random

spaced randomly (least common)

Demographics

study of vital statistics, ex: death, and birth rate, age class structure, and sex ratio

Life table

summary of survival and reproductive rates for each age cohort in a population

Cohort

a group born at the same time (of the same age)

Survivorship curves

plots number of individuals (or proportion of individuals alive at each age)

no curve is better

in each the population size can increase

natural selections has selected for which best fits the environment.

Type 1 (survivorship curve)

low mortality of juveniles

high mortality in oldest individuals

casual factors: relatively small number of offspring, parental care

Type 2 (survivorship curve)

uniform death rate across age classes

casual factors: age-independent predation/parasitism.

Type 3 (survivorship curve)

mortality high for juveniles

low mortality for older age classes

casual factors: many, relatively small offspring produced - little to no parental care.

Life History Traits

physiological, behavioral feature that affect reproduction, growth, and survival.

ex: age of sexual maturity, size of adult, fecundity, number of reproductive cycles, parental care, longevity.

Principle of Allocation

energy invested (used) in one life history trait/characteristic can’t be used for another. results in trade-offs.

Life History Strategies

semelparity

iteroparity

Semelparity

produce many offspring once in life

-high fecundity

-low survivorship

Iteroparity

produce few offspring many times in life

-low fecundity

-high survivorship