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 PresentationTRANSCRIPT
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
Most populations live in clumps although other patterns occur based on resource distribution.
Figure 8-2
Fig. 8-2a, p. 162(a) Clumped (elephants)
Fig. 8-2b, p. 162(b) Uniform (creosote bush)
Fig. 8-2c, p. 162(c) Random (dandelions)
Changes in Population Size: Entrances and Exits
Populations increase through births and immigration
Populations decrease through deaths and emigration
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.
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
Fig. 8-3, p. 163
EnvironmentalResistance
Time (t)
Po
pu
lat i
on
si z
e (N)
Carrying capacity (K)
ExponentialGrowth
BioticPotential
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
Fig. 8-4, p. 164
Carrying capacity
Year
Nu
mb
er o
f sh
eep
(m
illi
on
s)Overshoot
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
Fig. 8-6, p. 165
Nu
mb
er o
f re
ind
eer
Populationovershootscarryingcapacity
Carryingcapacity
Year
PopulationCrashes
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
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.
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
Fig. 8-7, p. 166
Po
pu
lati
on
siz
e (t
ho
usa
nd
s)
Year
LynxHare
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).
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
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
Reproductive Patterns
r-selected species tend to be opportunists while K-selected species tend to be competitors.
Figure 8-10
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
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
Survivorship Curves: Short to Long Lives
The populations of different species vary in how long individual members typically live.
Figure 8-11
Fig. 8-11, p. 169
Per
cen
tag
e su
rviv
ing
(lo
g s
cale
)
Age
Early loss
Late loss
Constant loss
Animation: Life History Patterns
PLAYANIMATION