Chapter 9Chapter 9

Population EcologyPopulation Ecology

They were over-They were over-hunted to the hunted to the brink of extinction brink of extinction by the early by the early 1900’s and are 1900’s and are now making a now making a comeback.comeback.

Core Case Study: Core Case Study: Southern Sea Otters: Are They Back Southern Sea Otters: Are They Back

from the Brink of Extinction?from the Brink of Extinction?

Figure 8-1Figure 8-1

Core Case Study: Core Case Study: Southern Sea Otters: Are They Back Southern Sea Otters: Are They Back

from the Brink of Extinction?from the Brink of Extinction?

Sea otters are an Sea otters are an important important keystone species keystone species for sea urchins for sea urchins and other kelp-and other kelp-eating organisms.eating organisms.

Figure 8-1Figure 8-1

POPULATION DYNAMICS AND POPULATION DYNAMICS AND CARRYING CAPACITYCARRYING CAPACITY

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

Do humans live in clumps?Do humans live in clumps? Figure 8-2Figure 8-2

Populations change in size density and age Populations change in size density and age distribution distribution Most members of populations live together in Most members of populations live together in groups or clumps. Why?groups or clumps. Why?

Availability of resources varies from place to Availability of resources varies from place to placeplace

Living in groups offers better protection from Living in groups offers better protection from predatorspredators

Some predators live in packs to hunt more Some predators live in packs to hunt more efficientlyefficiently

Temporary groups may form for matting and Temporary groups may form for matting and carrying for youngcarrying for young

Four variables influence/ govern population Four variables influence/ govern population sizesize

Births aka natalityBirths aka natality Deaths aka mortalityDeaths aka mortality ImmigrationImmigration Emigration Emigration

Which ones increase population size?Which ones increase population size?

Age Structure: Young Populations Age Structure: Young Populations Can Grow FastCan Grow Fast

How fast a population grows or declines How fast a population grows or declines depends on its age structure.depends on its age structure. Prereproductive agePrereproductive age: not mature enough to : not mature enough to

reproduce.reproduce. Reproductive ageReproductive age: those capable of : those capable of

reproduction.reproduction. Postreproductive agePostreproductive age: those too old to : those too old to

reproduce.reproduce.

Limits on Population Growth: Limits on Population Growth: Biotic Potential vs. Environmental Biotic Potential vs. Environmental

ResistanceResistance

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

which a population would grow if it had unlimited which a population would grow if it had unlimited resources.resources.

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

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

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

Figure 8-4Figure 8-4

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

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

Figure 8-4Figure 8-4

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

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

Figure 8-6Figure 8-6

What four factors have the greatest influence What four factors have the greatest influence on limiting populations?on limiting populations?

LightLight WaterWater NutrientsNutrients Competition or predationCompetition or predation

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

Over time species may increase their Over time species may increase their carrying capacity by developing adaptations.carrying capacity by developing adaptations.

Some species maintain their carrying Some species maintain their carrying capacity by migrating to other areas.capacity by migrating to other areas.

So far, technological, social, and other So far, technological, social, and other cultural changes have extended the earth’s cultural changes have extended the earth’s carrying capacity for humans.carrying capacity for humans.

Types of Population Change Types of Population Change Curves in NatureCurves in Nature

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

Figure 8-7Figure 8-7

Carrying capacity is the ________.Carrying capacity is the ________.

a.a. Maximum population size that a given Maximum population size that a given environment can sustainenvironment can sustain

b.b. Greatest number of different niches Greatest number of different niches possible in a given areapossible in a given area

c.c. Potential growth in the number of species in Potential growth in the number of species in a given areaa given area

d.d. Limitation on numbers of species in a Limitation on numbers of species in a communitycommunity

e.e. Average number of offspring carried to term Average number of offspring carried to term by a speciesby a species

Unregulated populations tend to increase by Unregulated populations tend to increase by ______.______.

a.a. Linear growthLinear growth

b.b. Exponential growthExponential growth

c.c. Pyramidal growthPyramidal growth

d.d. EmigrationEmigration

e.e. ImmigrationImmigration

A logistic growth curve depicting a population A logistic growth curve depicting a population that is limited by a definite carrying capacity that is limited by a definite carrying capacity is shaped like the letter ___.is shaped like the letter ___.

a.a. JJ

b.b. LL

c.c. MM

d.d. SS

e.e. NN

In a population of field mice, an example of an In a population of field mice, an example of an adaptive trait that could help with adaptive trait that could help with reproduction and/or survival would be ____reproduction and/or survival would be ____

a.a. Being brightly colored so other mice can Being brightly colored so other mice can see yousee you

b.b. Having a higher metabolismHaving a higher metabolismc.c. Spending more time running around looking Spending more time running around looking

for better seedsfor better seedsd.d. Having a bit more fur to withstand colder Having a bit more fur to withstand colder

weatherweathere.e. Having shorter legs to be closer to the Having shorter legs to be closer to the

groundground

Which of the following types of species is least Which of the following types of species is least vulnerable to habitat fragmentation?vulnerable to habitat fragmentation?

a.a. GeneralistsGeneralists

b.b. SpecialistsSpecialists

c.c. Large predatorsLarge predators

d.d. Migratory speciesMigratory species

e.e. Keystone species Keystone species

Population Density and Population Population Density and Population Change: Effects of CrowdingChange: Effects of Crowding

Population density: the number of individuals Population density: the number of individuals in a population found in a particular area or in a population found in a particular area or volume.volume.

What is a density-dependent factor?What is a density-dependent factor?

What is a density-independent factor?What is a density-independent factor?

Types of Population Change Types of Population Change Curves in NatureCurves in Nature

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

capacity.capacity. IrruptiveIrruptive: populations explode and then crash to a : populations explode and then crash to a

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

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

drastic change. drastic change.

What is the hypothesis of bottom-up control?What is the hypothesis of bottom-up control?

What is the hypothesis of top-down control?What is the hypothesis of top-down control?

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

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

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

What are the 2 types of reproduction?What are the 2 types of reproduction? Asexual- each cell divides and results in an Asexual- each cell divides and results in an

identical clone of the original cell; no genetic identical clone of the original cell; no genetic recombinationrecombination

Sexual- gametes from each parent combine Sexual- gametes from each parent combine to produce offspring with a combination of to produce offspring with a combination of genetic traits from each parentgenetic traits from each parent

What are the 3 disadvantages to sexual What are the 3 disadvantages to sexual reproduction? reproduction?

1)1) Males do not give birth; Females have to Males do not give birth; Females have to produce twice the offspring to maintain produce twice the offspring to maintain population sizepopulation size

2)2) Chances of genetic errors/ defects increase Chances of genetic errors/ defects increase during splitting/ recombination.during splitting/ recombination.

3)3) Courtship & mating consumes energy and Courtship & mating consumes energy and time, transmit disease and inflict injury on time, transmit disease and inflict injury on males in some cases.males in some cases.

What are the two advantages of sexual What are the two advantages of sexual reproduction?reproduction?

1)1) Genetic diversity helps ensure survival of Genetic diversity helps ensure survival of species in the face of environmental species in the face of environmental changes.changes.

2)2) Males may help with food gathering and/or Males may help with food gathering and/or rearing of offspring. rearing of offspring.

Reproductive Patterns:Reproductive Patterns:Opportunists and CompetitorsOpportunists and Competitors

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

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

Figure 8-9Figure 8-9

Reproductive PatternsReproductive Patterns

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

Figure 8-10Figure 8-10

Survivorship Curves: Survivorship Curves: Short to Long LivesShort to Long Lives

The way to represent the age structure of a The way to represent the age structure of a population is with a population is with a survivorship curvesurvivorship curve.. Late loss populationLate loss population live to an old age. live to an old age. Constant loss populationConstant loss population die at all ages. die at all ages. Most members of Most members of early loss populationearly loss population, die at , die at

young ages.young ages.

Survivorship Curves: Survivorship Curves: Short to Long LivesShort to Long Lives

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

Figure 8-11Figure 8-11

What is a life table/ actuary table?What is a life table/ actuary table?

Variations in genetic diversity can affect the Variations in genetic diversity can affect the survival of small, isolated populations. survival of small, isolated populations. What is the founder effect?What is the founder effect?

A few individuals move to a new location that A few individuals move to a new location that is isolated from the original population. There is isolated from the original population. There is limited genetic diversity. is limited genetic diversity. http://www.pbs.org/wgbh/evolution/library/06/http://www.pbs.org/wgbh/evolution/library/06/3/l_063_03.html3/l_063_03.html

What is a demographic bottleneck?What is a demographic bottleneck?

A few individuals survive a catastrophic event.A few individuals survive a catastrophic event.

What is a genetic drift?What is a genetic drift?

Random changes in gene frequencies in a Random changes in gene frequencies in a population.population.

Why does inbreeding effect a population's Why does inbreeding effect a population's viability?viability?

Increases the number of defective genes in a Increases the number of defective genes in a population.population.

Humans have directly affected changes on Humans have directly affected changes on about ___% of the earth’s land surface. about ___% of the earth’s land surface. What are 9 of the major ways humans have What are 9 of the major ways humans have altered nature to meet their own needs?altered nature to meet their own needs?

1)1) Destruction and degradation of habitats has Destruction and degradation of habitats has reduced biodiversity.reduced biodiversity.

2)2) Homogenization of natural ecosystems by Homogenization of natural ecosystems by clearing land and planting only one species clearing land and planting only one species (monoculture)(monoculture)

3)3) Destruction of the earth’s net primary Destruction of the earth’s net primary productivity.productivity.

4) Certain types of intervention have unintentionally 4) Certain types of intervention have unintentionally strengthened pest species and disease causing strengthened pest species and disease causing bacteria.bacteria.

5) Some predator species have been deliberately 5) Some predator species have been deliberately eliminated from ranching areas.eliminated from ranching areas.

6) Alterations have occurred due to the introduction of 6) Alterations have occurred due to the introduction of nonnative species.nonnative species.

7) Renewable resources have been over-harvested.7) Renewable resources have been over-harvested.

8)Some human activities interfere with normal 8)Some human activities interfere with normal chemical cycling and energy flows in the chemical cycling and energy flows in the environment.environment.

9) We are increasingly dependent on nonrenewable 9) We are increasingly dependent on nonrenewable energy that pollutes the environment.energy that pollutes the environment.

Which of the following is generally true of K-Which of the following is generally true of K-strategist species as compared to r-strategist species as compared to r-strategist species?strategist species?

a.a. They reach sexual maturity earlierThey reach sexual maturity earlier

b.b. They have more youngThey have more young

c.c. They are more likely to be invasive speciesThey are more likely to be invasive species

d.d. They have longer life spansThey have longer life spans

e.e. Their population cycle are more rapidTheir population cycle are more rapid

Density-dependent factors ________Density-dependent factors ________

a.a. Include the effects of a hard freeze on an Include the effects of a hard freeze on an entire communityentire community

b.b. Include the effects of a hard freeze on a Include the effects of a hard freeze on a single species within a communitysingle species within a community

c.c. Cause decreases in the number of species Cause decreases in the number of species in an ecosystemin an ecosystem

d.d. Include the effects of disease on an entire Include the effects of disease on an entire communitycommunity

e.e. Include the effects of disease on a single Include the effects of disease on a single species within a communityspecies within a community

One examply of artificial selection is ____One examply of artificial selection is ____

a.a. Gypsy moths as an invasive speciesGypsy moths as an invasive species

b.b. Pet dogs that have gone wild, are mating, Pet dogs that have gone wild, are mating, and live in packsand live in packs

c.c. A ligerA liger

d.d. PopcornPopcorn

e.e. Humans placing a gene for human insulin in Humans placing a gene for human insulin in a flowera flower

Groups of organisms with low biotic potential, Groups of organisms with low biotic potential, such as grey whales, are said to be such as grey whales, are said to be ______.______.

a.a. r-selectedr-selected

b.b. K-selectedK-selected

c.c. Density-independent organismsDensity-independent organisms

d.d. Density-dependent organismsDensity-dependent organisms

e.e. Because of their size, grey whales actually Because of their size, grey whales actually have high biotic potentialhave high biotic potential

Which of the following best describes the Which of the following best describes the survivorship curve you would expect to find survivorship curve you would expect to find for a fish?for a fish?

a.a. Late lossLate loss

b.b. Constant lossConstant loss

c.c. Early lossEarly loss

d.d. No lossNo loss

e.e. None of these answersNone of these answers