Population Ecology

What is Ecology?

• Study of organisms, their environment and interactions

• Different types of ecology

• Not environmentalists!

What is Ecology?

• Abiotic factors:– Water– Sun– Temperature– Wind– Soil– Disturbance

What is Ecology?• Organismal responses:

– Physiological – acclimation– Anatomical– Behavioral

Population Ecology

• Characteristics of Populations

• Described by demographics

– Size

– Age structure

– Density

– Dispersion pattern

Dispersion – Clumped

• Common

• Patchy resources c

lumped

 

Dispersion – Random

• Uniform conditions

Dispersion – Uniform

• Harsh competition

Determining Population Size

• Direct counts

• Sampling

– Plants

– Mark and recapture

Changes in Population Size

• Adds:

– Births

– Immigration

• Subtract:

– Death

– emigration

Exponential Growth

Limits on Growth

• Environmental conditions

• Limiting factors: Predation, food

supply, etc.

Carrying Capacity (K)• Sustainable resource supply for a

population

Logistic Growth

• As size of the population increases, rate of reproduction decreases

• When the population reaches carrying capacity, population growth ceases

Density-Dependent Controls

• Disease,

predation,

competition,

toxicity of waste

Density-Independent Controls

• Natural disasters,

climate events

LE 18-20a

Decreasing birth rate with increasing density

LE 18-20b

Increasing death rate with increasing density

LE 18-22

Exponentialgrowth

Suddendecline

Human Population Growth

• 6 billion

• Average annual increase is 1.26%

• Increase exponentially

Human Population Growth

Future Growth

• 2 Million yrs for population to reach

1 billion

• Only 12 yrs to reach 5th billion

• 1.26% growth is not sustainable

Ecological Footprints

16

14

12

10

8

6

4

2

00 2 4 6 8 10 12 14 16

Available ecological capacity (ha per person)

Eco

log

ica

l fo

otp

rint

(ha

pe

r p

ers

on

)

Japan

UK

Spain

Germany

NetherlandsNorway

USA

World

ChinaIndia

Sweden

Canada

Australia

New Zealand

Figure 36.9B

Traffic in downtown Cairo, Egypt

Manhattan,New York City

Refugee camp in ZaireFigure 36.9C

Age Structure DiagramsShow age distribution of a population

Rapid Growth

Slow Growth

Zero Growth

Negative Growth

Resource Consumption

• U. S. has 4.7% world’s population

• India has 16%

• U.S. uses 25% of processed minerals and energy and produces 25% of global pollution

• India is mere 3%

Life History Patterns

• Patterns of survival and reproduction

Survivorship Curves

• Graph of age-specific survivorship

Type I – K selected

Type II

Type III – r selected

Table 18.2

Life Tables

• Population is divided into age

categories

• Birth rates and mortality risks are

calculated for each age category

Table 18.1

Life Tables

Question of the Day