Population Ecology

• Dynamics of species’ populations• Interaction of populations with

environment

Population Ecology

• Most species live in groups

Groups

• Probability that a species will persist

Population Viability

Population Viability

Increased (+)• Favorable environment

(light, temp, nutrients)• Few competitors• Suitable defense

mechanisms• Able to migrate• Resistance to disease• Sufficient food• Generalized niche• Satisfactory habitat

Decreased (-)• Unfavorable

environment• Many competitors• Unsuitable defenses• Cannot migrate• Not resistant• Insufficient• Specialized niche• Unsatisfactory

habitat

• Number of organisms that an environment can support

Carrying Capacity (K)

• Below K, population increases• Above K, population decreases

Carrying Capacity (K)

• Keep populations in balance with environment

• Density dependent

• Density independent

Limiting Factors

• Max rate at which a population can grow

– When?

• Influences:

Biotic Potential

• Exponential Growth

• Logistic Growth

Growth Patterns

http://www.allamericanpatriots.com/photos/salmonella-bacteria

Growth Patterns

• Adaptations– Maximize growth rate when lacking limiting

factors• r-strategists • r = growth rate (births-deaths)

– Maintain population size near K• K-strategists• K = carrying capacity

Reproductive Strategies

Reproductive Strategies

r-strategists • Mature rapidly• Short lived• Tend to be prey• Many offspring

(overproduction)• Low parental care• most pest species are

r-selected

K-strategies• Mature slowly• Long lived• Tend to be predators• Few offspring

• High parental care• Most endangered

species are K-species

Reproductive Strategies

r-strategists • Wide fluctuations in

population• Usually small• Limited by

independent factors

K-strategies• Stabilized population

• Larger• Limited by dependent

factors

• K or r?

Reproductive Strategies

• At what point during an organism’s life does it die?

• Curves show age distribution characteristics, reproductive strategies, and life history

• Curves represent balance between resource limitations and competition

Survivorship Curves

Survivorship Curves

Type Description

I. Late Loss Reproduction occurs fairly early in life. Low mortality at birth. High probability of surviving until old age

II. Constant Loss All ages have fairly uniform death rate. Death usually due to predation

III. Early Loss Large numbers of offspring. High death rate for young, declines with age.

Survivorship Curves