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 ID: 276273
Download Presentation The PPT/PDF document "Population Ecology" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Population EcologySlide2
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?Slide3
POPULATION DYNAMICS AND CARRYING CAPACITY
Most populations live in clumps although other patterns occur based on resource distribution.
Figure 8-2Slide4
Fig. 8-2a, p. 162
(a) Clumped (elephants)Slide5
Fig. 8-2b, p. 162
(b) Uniform (creosote bush)Slide6
Fig. 8-2c, p. 162
(c) Random (dandelions)Slide7
Changes in Population Size:
Entrances and Exits
Populations increase through births and immigration
Populations decrease through deaths and emigrationSlide8
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.Slide9
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 8-4Slide10
Fig. 8-3, p. 163
Environmental
Resistance
Time
(t)
Population size
(N)
Carrying capacity
(K)
Exponential
Growth
Biotic
PotentialSlide11
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 8-4Slide12
Fig. 8-4, p. 164
Carrying capacity
Year
Number of sheep (millions)
OvershootSlide13
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 8-6Slide14
Fig. 8-6, p. 165
Number of reindeer
Population
overshoots
carrying
capacity
Carrying
capacity
Year
Population
CrashesSlide15
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 weatherSlide16
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. Slide17
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 8-7Slide18
Fig. 8-7, p. 166
Population size (thousands)
Year
Lynx
HareSlide19
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).Slide20
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 8-9Slide21
Fig. 8-9, p. 168
r
species;
experience
r
selection
Time
Number of individuals
K
Carrying capacity
K
species;
experience
K
selectionSlide22
Reproductive Patterns
r-selected species tend to be opportunists while K-selected species tend to be competitors.
Figure 8-10Slide23
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 Species
Cockroach
DandelionSlide24
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
Saguaro
ElephantSlide25Slide26
Survivorship Curves:
Short to Long Lives
The populations of different species vary in how long individual members typically live.
Figure 8-11Slide27
Fig. 8-11, p. 169
Percentage surviving (log scale)
Age
Early loss
Late loss
Constant lossSlide28
Animation: Life History Patterns
PLAY
ANIMATION