GOOD MORNING!!!
(APES Review, 3/7/12, CAPT Week)
 Our Plan for This Wednesday Morning…
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1) EAT! EAT! EAT!
2) Lab Activity: Estimating Population Size
3) Lecture: Introduce Population Biology
4) Activity: Population Growth Activity
5) Calculation Practice – Growth Rate
6) Lecture: Human Population Dynamics
7) Activity (Computers): Age Structure Diagram
HW:
• prb.org activity
• Quiz/Test, TBD
POPULATION BIOLOGY
Chapter 6
HUMAN POPULATION
DYNAMICS
(Chapter 7 – See other PPOINT)
What Limits the Growth of Populations?
 Intrinsic factors - Operate within or between
individual organisms in the same species.
 Extrinsic factors - Imposed from outside the
population.
 Biotic factors - Caused by living organisms.
 Abiotic factors - Caused by non-living
environmental components.
Populations Have Certain
Characteristics (2)
 Why Do Population Sizes Change?
• Temperature
• Presence of disease organisms or harmful
chemicals
• Resource availability
• Arrival or disappearance of competing species
Populations Can Grow, Shrink, or
Remain Stable (1)
 Population size governed by
•
•
•
•
Births
Deaths
Immigration
Emigration
 Population change =
(births + immigration) – (deaths + emigration)
Fig. 5-B, p. 110
Population size
Environmental
resistance
Carrying capacity (K)
Population stabilizes
Exponential
growth
Biotic
potential
Time (t)
Fig. 5-11, p. 111
No population can continue to increase in size indefinitely. Exponential growth (left half
of the curve) occurs when resources are not limiting and a population can grow at its
intrinsic rate of increase (r) or biotic potential. Such exponential growth is converted to
logistic growth, in which the growth rate decreases as the population becomes larger
and faces environmental resistance. Over time, the population size stabilizes at or near
the carrying capacity (K) of its environment, which results in a sigmoid (S-shaped)
population growth curve. Depending on resource availability, the size of a population
often fluctuates around its carrying capacity, although a population may temporarily
exceed its carrying capacity and then suffer a sharp decline or crash in its numbers..
Question: What is an example of environmental resistance that humans have not been
able to overcome?
Boom and Bust Cycles
r-Adapted Species

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Short life
Rapid growth
Early maturity
Many small
offspring
 Little parental care
 Little investment in
individual offspring.
 Adapted to
unstable
environment.
 Pioneers,
colonizers
 Niche generalists
 Prey
 Regulated mainly
by extrinsic factors.
 Low trophic level
K-Adapted Species


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Long life
Slower growth
Late maturity
Fewer large
offspring
 High parental care
and protection.
 High investment in
individual offspring.
 Adapted to stable
environment.
 Later stages of
succession.
 Niche specialists
 Predators
 Regulated mainly
by intrinsic factors.
 High trophic level
Number of sheep (millions)
2.0
1.5
1.0
Population
overshoots
carrying
capacity
Carrying capacity
Population recovers
and stabilizes
Population
Exponential runs out of
resources
growth
and crashes
.5
1800
1825
1850
1875
Year
1900
1925
Fig. 5-12, p. 111
Population
overshoots
carrying
capacity
Number of reindeer
2,000
1,500
Population
crashes
1,000
500
Carrying
capacity
0
1910
1920
1930
Year
1940
1950
Fig. 5-13, p. 112
Number of individuals
Carrying capacity
K
K species;
experience
K selection
r species;
experience
r selection
Time
Fig. 5-14, p. 112
Fig. 5-15, p. 114
No Population Can Grow Indefinitely:
J-Curves and S-Curves (1)
 Biotic potential
• Low
• High
 Intrinsic rate of increase (r)
 Individuals in populations with high r
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•
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Reproduce early in life
Have short generation times
Can reproduce many times
Have many offspring each time they reproduce
No Population Can Grow Indefinitely:
J-Curves and S-Curves (2)
 Size of populations limited by
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•
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Light
Water
Space
Nutrients
Exposure to too many competitors, predators or
infectious diseases
Density Dependent Factors
 Higher proportion of population is affected as
population density increases.
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•
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Predation
Parasitism
Infectious disease
Competition for resources
 Tend to reduce population size by decreasing
natality or increasing mortality.
• Interspecific Interactions
• Predator-Prey oscillations
• Intraspecific Interactions
• Territoriality
• Stress and Crowding
• Stress-related diseases
Density Independent Factors
 Constant proportion of the population is affected
regardless of population density.
 Tend to be abiotic components.
 Do not directly regulate population size.
 EXAMPLES:
Sample Problem: A population of birds was measured to be 1500 birds. Over the
course of a year, there were 300 births and 200 deaths. 100 birds entered the
population by migration, 50 birds left population by emigration.
How to Calculate Change in Population Size
How to Calculate Growth Rate of a Population:
Calculating R from CBR and CDR
How to Calculate Doubling Time of a Population:
No Population Can Grow Indefinitely:
J-Curves and S-Curves (3)
 Environmental resistance
 Carrying capacity (K)
 Exponential growth
 Logistic growth
Genetic Diversity Can Affect the Size
of Small Populations
 Founder effect
 Demographic bottleneck
 Genetic drift
 Inbreeding
 Minimum viable population size
Under Some Circumstances Population
Density Affects Population Size
 Density-dependent population controls
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Predation
Parasitism
Infectious disease
Competition for resources
Several Different Types of Population
Change Occur in Nature
 Stable
 Irruptive
 Cyclic fluctuations, boom-and-bust cycles
• Top-down population regulation
• Bottom-up population regulation
 Irregular
Survivorship Curves
Humans Are Not Exempt from Nature’s
Population Controls
 Ireland
• Potato crop in 1845
 Bubonic plague
• Fourteenth century
 AIDS
• Global epidemic
Case Study: Exploding White-Tailed Deer
Population in the U.S.
 1900: deer habitat destruction and uncontrolled
hunting
 1920s–1930s: laws to protect the deer
 Current population explosion for deer
• Lyme disease
• Deer-vehicle accidents
• Eating garden plants and shrubs
 Ways to control the deer population
Core Case Study: Southern Sea Otters: Are
They Back from the Brink of Extinction?
 Habitat
 Hunted: early 1900s
 Partial recovery
 Why care about sea otters?
• Ethics
• Keystone species
• Tourism dollars
LOOK NO FURTHER…
 ALL OF THE INFORMATION ON the SLIDES
FOLLOWING THIS ONE WILL NOT BE ON THE
POPULATION TEST!
5-1 How Do Species Interact?
 Concept 5-1 Five types of species
interactions—competition, predation, parasitism,
mutualism, and commensalism—affect the
resource use and population sizes of the
species in an ecosystem.
Species Interact in Five Major Ways
 Interspecific Competition
 Predation
 Parasitism
 Mutualism
 Commensalism
Most Species Compete with One Another
for Certain Resources
 Competition
 Competitive exclusion principle
Most Consumer Species Feed on Live
Organisms of Other Species (1)
 Predators may capture prey by
• Walking
• Swimming
• Flying
• Pursuit and ambush
• Camouflage
• Chemical warfare
Most Consumer Species Feed on Live
Organisms of Other Species (2)
 Prey may avoid capture by
• Camouflage
• Chemical warfare
• Warning coloration
• Mimicry
• Deceptive looks
• Deceptive behavior
Science Focus: Why Should We Care
about Kelp Forests?
 Kelp forests: biologically diverse marine habitat
 Major threats to kelp forests
• Sea urchins
• Pollution from water run-off
• Global warming
Predator and Prey Species Can Drive
Each Other’s Evolution
 Intense natural selection pressures between
predator and prey populations
 Coevolution
Some Species Feed off Other Species by
Living on or in Them
 Parasitism
 Parasite-host interaction may lead to coevolution
In Some Interactions, Both Species
Benefit
 Mutualism
 Nutrition and protection relationship
 Gut inhabitant mutualism
In Some Interactions, One Species
Benefits and the Other Is Not Harmed
 Commensalism
 Epiphytes
 Birds nesting in trees
5-2 How Can Natural Selection Reduce
Competition between Species?
 Concept 5-2 Some species develop
adaptations that allow them to reduce or avoid
competition with other species for resources.
Some Species Evolve Ways to Share
Resources
 Resource partitioning
 Reduce niche overlap
 Use shared resources at different
• Times
• Places
• Ways