principles of population ecology population ecologists ask: 1) how many are in the population? 2)...

Principles of Population Ecology

Population ecologists ask:

1) How many are in the population?

2) Are its numbers increasing / decreasing?

3) What is its pattern of reproduction?

4) What is its pattern of mortality?Significance of understanding this?1.Manage domestic and wild populations2.Manage pests3. Save Endangered Species4.Understand our own population changes

Principles of Population Ecology

How Do Populations Change in Size?

On a global scale (closed system):

Principles of Population Ecology

How Do Populations Change in Size?

On a local scale (open system):

Principles of Population Ecology

How Do Populations Change in Size?

Global scale:

r = b – d

Growth rate

Birth rate

Death rate

Principles of Population Ecology

How Do Populations Change in Size?

Local scale:

r = (b – d) + (i – e)

Growth rate

Birth rate

Death rate

Immigration rate

Emigration rate

Rule of 70: 70/Growth Rate% = Doubling Time

Biotic Potential

Maximum Population Growth-

under ideal conditions = intrinsic rate of increase

J-shaped curve (exponential growth)

Carrying Capacity

Environmental Resistance-

Exponential growth cannot occur forever.

What factors prevent it from doing so?

S-shaped curve (logistic growth)

Principles of Population Ecology

Overshooting the carrying capacity can lead to a population crash.

Positive & NegativeFeedback Loops

Population Crash

Population 1910= 26 / 1935= 2K / crash / 1945=8

Reproductive Strategies

Life History Strategies

r-selected K-selectedvs.

high growth rate slow growth rate

small body size large body size

early maturity late maturity

short life span long life span

large broods small broods

little / no parental care high parental care

Which are we? How do we apply this knowledge?

Survivorship & Reproduction

Density Dependent Factors

• Factors that influence population growth when its density is high.

• Predation, competition, disease, parasites, food availability.

Locust

Lemmings

Factors that Affect Population Size

Density-Dependence and Boom-or-Bust Population Cycles

Predator birth timing?

Predatory Prey Dynamics

Wolves Established 1949 - Moose 1900 approx. 1980’s parvovirous hits wolves1995 & 96 harsh winters and overgrazingTick numbers increase with warm spring & fallIsle Royal southern limit of Moose

Ticks

Density-Independent Factors:

• Regardless of population density, influences population growth.

• Weather, fire, earthquakes, etc…