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Population Ecology

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Population Ecology. Chapter Overview Questions. What are the major characteristics of populations? How do populations respond to changes in environmental conditions? How do species differ in their reproductive patterns?. POPULATION DYNAMICS AND CARRYING CAPACITY. - PowerPoint PPT Presentation

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Page 1: Population Ecology

Population Ecology

Page 2: Population Ecology

Chapter Overview Questions

What are the major characteristics of populations?

How do populations respond to changes in environmental conditions?

How do species differ in their reproductive patterns?

Page 3: Population Ecology

POPULATION DYNAMICS AND CARRYING CAPACITY

Most populations live in clumps although other patterns occur based on resource distribution.

Figure 8-2

Page 4: Population Ecology

Fig. 8-2a, p. 162(a) Clumped (elephants)

Page 5: Population Ecology

Fig. 8-2b, p. 162(b) Uniform (creosote bush)

Page 6: Population Ecology

Fig. 8-2c, p. 162(c) Random (dandelions)

Page 7: Population Ecology

Changes in Population Size: Entrances and Exits

Populations increase through births and immigration

Populations decrease through deaths and emigration

Page 8: Population Ecology

Limits on Population Growth: Biotic Potential vs. Environmental

Resistance

No population can increase its size indefinitely. The intrinsic rate of increase (r) is the rate at

which a population would grow if it had unlimited resources.

Carrying capacity (K): the maximum population of a given species that a particular habitat can sustain indefinitely without degrading the habitat.

Page 9: Population Ecology

Exponential and Logistic Population Growth: J-Curves and S-Curves

Populations grow rapidly with ample resources, but as resources become limited, its growth rate slows and levels off.

Figure 8-4

Page 10: Population Ecology

Fig. 8-3, p. 163

EnvironmentalResistance

Time (t)

Po

pu

lat i

on

si z

e (N)

Carrying capacity (K)

ExponentialGrowth

BioticPotential

Page 11: Population Ecology

Exponential and Logistic Population Growth: J-Curves and S-Curves

As a population levels off, it often fluctuates slightly above and below the carrying capacity.

Figure 8-4

Page 12: Population Ecology

Fig. 8-4, p. 164

Carrying capacity

Year

Nu

mb

er o

f sh

eep

(m

illi

on

s)Overshoot

Page 13: Population Ecology

Exceeding Carrying Capacity: Move, Switch Habits, or Decline in Size

Members of populations which exceed their resources will die unless they adapt or move to an area with more resources.

Figure 8-6

Page 14: Population Ecology

Fig. 8-6, p. 165

Nu

mb

er o

f re

ind

eer

Populationovershootscarryingcapacity

Carryingcapacity

Year

PopulationCrashes

Page 15: Population Ecology

Population Density and Population Change: Effects of Crowding

Population density: the number of individuals in a population found in a particular area or volume. A population’s density can affect how rapidly it

can grow or decline.• e.g. biotic factors like disease

Some population control factors are not affected by population density.• e.g. abiotic factors like weather

Page 16: Population Ecology

Types of Population Change Curves in Nature

Population sizes may stay the same, increase, decrease, vary in regular cycles, or change erratically. Stable: fluctuates slightly above and below carrying

capacity. Irruptive: populations explode and then crash to a

more stable level. Cyclic: populations fluctuate and regular cyclic or

boom-and-bust cycles. Irregular: erratic changes possibly due to chaos or

drastic change.

Page 17: Population Ecology

Types of Population Change Curves in Nature

Population sizes often vary in regular cycles when the predator and prey populations are controlled by the scarcity of resources.

Figure 8-7

Page 18: Population Ecology

Fig. 8-7, p. 166

Po

pu

lati

on

siz

e (t

ho

usa

nd

s)

Year

LynxHare

Page 19: Population Ecology

Case Study: Exploding White-Tailed Deer Populations in the United States

Since the 1930s the white-tailed deer population has exploded in the United States. Nearly extinct prior to their protection in 1920’s.

Today 25-30 million white-tailed deer in U.S. pose human interaction problems. Deer-vehicle collisions (1.5 million per year). Transmit disease (Lyme disease in deer ticks).

Page 20: Population Ecology

Reproductive Patterns:Opportunists and Competitors

Large number of smaller offspring with little parental care (r-selected species).

Fewer, larger offspring with higher invested parental care (K-selected species).

Figure 8-9

Page 21: Population Ecology

Fig. 8-9, p. 168

r species;experiencer selection

Time

Nu

mb

er o

f in

div

idu

als

KCarrying capacity

K species;experienceK selection

Page 22: Population Ecology

Reproductive Patterns

r-selected species tend to be opportunists while K-selected species tend to be competitors.

Figure 8-10

Page 23: Population Ecology

Fig. 8-10a, p. 168

Many small offspring

Little or no parental care and protection of offspring

Early reproductive age

Most offspring die before reaching reproductive age

Small adults

Adapted to unstable climate and environmental conditions

High population growth rate (r)

Population size fluctuates wildly above and below carrying capacity (K)

Generalist niche

Low ability to compete

Early successional species

r-Selected SpeciesCockroach

Dandelion

Page 24: Population Ecology

Fig. 8-10b, p. 168

Fewer, larger offspring

High parental care and protection of offspring

Later reproductive age

Most offspring survive to reproductive age

Larger adults

Adapted to stable climate and environmental conditions

Lower population growth rate (r)

Population size fairly stable and usually close to carrying capacity (K)

Specialist niche

High ability to compete

Late successional species

K-Selected Species

SaguaroElephant

Page 25: Population Ecology
Page 26: Population Ecology

Survivorship Curves: Short to Long Lives

The populations of different species vary in how long individual members typically live.

Figure 8-11

Page 27: Population Ecology

Fig. 8-11, p. 169

Per

cen

tag

e su

rviv

ing

(lo

g s

cale

)

Age

Early loss

Late loss

Constant loss

Page 28: Population Ecology

Animation: Life History Patterns

PLAYANIMATION