Population Ecology Chapter 9, Miller 14th Edition

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Population Ecology Chapter 9, Miller 14th Edition

• AP Environmental Science
• A.C. Mosley
• Mrs. Dow

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Case Study Sea Otters Are They Back From the
Brink of Extinction
(a) Southern sea otter
(c) Kelp bed
(b) Sea Urchin
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Population Dynamics Outline

• Characteristics of a Population
• Population Dynamics and Carrying Capacity
• Reproductive Strategies
• Conservation Biology
• Human Impacts
• Working with Nature

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9-1 Characteristics of a Population

• Population - individuals inhabiting the same area
  at the same time
• Population Dynamics Population change due to
• Population Size - number of individuals
• Population Density - population size in a certain
  space at a given time
• Population Dispersion - spatial pattern in
  habitat
• Age distribution - proportion of individuals in
  each age group in population

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Population Size

• Natality
• Number of individuals added through reproduction
• Crude Birth Rate - Births per 1000
• Total Fertility Rate Average number of children
  born alive per woman in her lifetime
• Mortality
• Number of individuals removed through death
• Crude Death Rate Deaths per 1000

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Population Density

• Population Density (or ecological population
  density) is the amount of individuals in a
  population per unit habitat area
• Some species exist in high densities - Mice
• Some species exist in low densities - Mountain
  lions
• Density depends upon
• social/population structure
• mating relationships
• time of year

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Population Dispersion
Population dispersion is the spatial pattern of
distribution There are three main
classifications Clumped individuals are lumped
into groups ex. Flocking birds or herbivore
herds due to resources that are clumped or
social interactions most common
http//www.johndarm.clara.net/galleryphots/
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Population Dispersion
http//www.calflora.net/bloomingplants/creosotebus
h2.html
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Age Structure

• The age structure of a population is usually
  shown graphically
• The population is usually divided up into
  prereproductives, reproductives and
  postreproductives
• The age structure of a population dictates
  whether is will grow, shrink, or stay the same
  size

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Age Structure Diagrams
Positive Growth Zero Growth
Negative Growth (ZPG) Pyramid
Shape Vertical Edges Inverted
Pyramid
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• Four variables influencing growth
• Births
• Deaths
• Immigration
• Emigration
• Increase ? by birth immigration
• Decrease ? death emigration
• Population change (Birth Immigration)-
• 
  (DeathEmigration)

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Population Dynamics Outline

• Characteristics of a Population
• Population Dynamics and Carrying Capacity
• Reproductive Strategies
• Conservation Biology
• Human Impacts
• Working with Nature

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Biotic Potential

• The biotic potential is the populations capacity
  for growth
• The intrinsic rate of increase (r) is the rate of
  population growth with unlimited resources.
• Abiotic Contributing Factors
• Favorable light
• Favorable Temperatures
• Favorable chemical environment - nutrients
• Biotic Contributing Factors
• Reproductive rate
• Generalized niche
• Ability to migrate or disperse
• Adequate defense mechanisms
• Ability to cope with adverse conditions

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• Rapidly growing populations have four
  characteristics
• Reproduction early in life
• Short periods between generations
• Long reproductive lives
• Multiple offspring each time they reproduce
• A single house fly could
• total 5.6 trillion house flies
• within 13 months

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Environmental Resistance

• Consists of all factors that act to limit the
  growth of a population
• Abiotic Contributing Factors
• Unfavorable light
• Unfavorable Temperatures
• Unfavorable chemical environment - nutrients
• Biotic Contributing Factors
• Low reproductive rate
• Specialized niche
• Inability to migrate or disperse
• Inadequate defense mechanisms
• Inability to cope with adverse conditions

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• Biotic Potential
• factors allow a population to increase under
  ideal conditions, potentially leading to
  exponential growth
• Environmental Resistance
• affect the young more than the elderly in a
  population, thereby affecting recruitment
  (survival to reproductive age)

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Population Growth

• Population growth depends upon
• birth rates
• death rates
• immigration rates (into area)
• emigration rates (exit area)
• Pop Pop0 (b i) - (d e)
• ZPG
• (b i) (d e)

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• Limits on population growth
• Carrying capacity K determined by biotic
  potential environmental resistance
• This is the of a species individuals that can
  be sustained indefinitely in a specific space
• As a population reaches its carrying capacity,
  its growth rate will decrease because resources
  become more scarce.

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Population Growth

• Populations show two types of growth
• With few resource limitations
• Exponential
• J-shaped curve
• Growth is independent of population density
• The growth rate levels off as population reaches
  carrying capacity
• Logistic
• S-shaped curve
• Growth is not independent of population density

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Exponential Growth

• As early as Darwin, scientists have realized that
  populations have the ability to grow
  exponentially
• All populations have this ability, although not
  all populations realized this type of growth
• Darwin pondered the question of exponential
  growth. He knew that all species had the
  potential to grow exponentially
• He used elephants as an example because elephants
  are one of the slowest breeders on the planet

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Exponential Growth

• One female will produce 6 young over her 100 year
  life span. In a population, this amounts to a
  growth rate of 2
• Darwin wondered, how many elephants could result
  from one male and one female in 750 years?
• 19,000,000 elephants!!!

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Exponential Growth Graph
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Population Dynamics and Carrying Capacity

• Basic Concept Over a long period of time,
  populations of species in an ecosystem are
  usually in a state of equilibrium (balance
  between births and deaths)
• There is a dynamic balance between biotic
  potential and environmental resistance

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Carrying Capacity (K)

• Exponential curve is not realistic due to
  carrying capacity of area
• Carrying capacity is maximum number of
  individuals a habitat can support over a given
  period of time due to environmental resistance
  (sustainability)

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Logistic Growth

• Because of Environmental Resistance, population
  growth decreases as density reaches carrying
  capacity
• Graph of individuals vs. time yields a sigmoid or
  S-curved growth curve
• Reproductive time lag causes population overshoot
• Population will not be steady curve due to
  resources (prey) and predators

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Exponential growth, overshoot, and population
crash of reindeer introduced to a small island
off of SW Alaska
Population overshoots carrying capacity
2,000
Populationcrashes
1,500
Number of reindeer
1,000
Carrying capacity
500
1910
1920
1930
1940
1950
Year
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• Population exceeds K
• Organisms die unless they move
• Changes in the physical environment can occur
• Reducing grass cover by overgrazing allows
  sagebrush to move in an reduces the number of
  cattle that the land can support
• Technology cultural changes have extended K on
  Earth (temporarily)

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Density of a population density

• Density-independent (affects population size
  regardless of its density)
• Floods, hurricanes, fire, pesticide spraying ,
  pollution)
• Density-dependent (greater effect as population
  density increases)
• Competition for resources, predation, parasitism,
  disease bubonic plague)

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Population fluctuations in nature

• Stable (varies slightly above and below carrying
  capacity,K)
• Irruptive (explode to a high level and then
  drastically drop - insects)
• Cyclic (over a regular time period lemmings
  populations rise and fall ever 3-4 years)
• Irregular behavior (no pattern)

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General types of simplified population changes
curves found in nature
(d) Irregular
(a) Stable
Number of individuals
(c) Cyclic
(b) Irruptive
Time
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160
Hare
140
Lynx
120
100
80
Population size (thousands)
60
40
20
0
1845
1855
1865
1875
1885
1895
1905
1915
1925
1935
Year

• Predator prey relationships
• Lynx-Hare Cycle
• Cyclic ever 10 years

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Dynamic Equilibrium

• Dynamic equilibrium defines a population that
  is in balance with the carrying capacity of
  the environment.
• Most populations in nature show characteristics
  of dynamic equilibrium-a balance.
• This does not mean that they dont go through
  exponential growth at some time or had diebacks.
  

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Population Dynamics Outline

• Characteristics of a Population
• Population Dynamics and Carrying Capacity
• Reproductive Strategies
• Conservation Biology
• Human Impacts
• Working with Nature

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Reproductive Patterns and Survival (9-2)

• Asexual reproduction
• Does not utilize sex
• Each cell divides produce to identical cells
  (replicas of cell)

Bacteria-Cell division
Hydra - budding
Shoal grass- rhizomes
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• Sexual reproduction- 97 of earth species use it
• Gametes from each parent combine to produce
  offspring w/traits from each parent
• Issues
• 1. Males cannot give birth -- females need to
  produce 2x the offspring to even population
• 2. Chance of genetic errors increase during
  recombination
• 3. Consume energy and time transmit disease can
  cause injury
• Why utilize?
• Great genetic diversity
• Can tolerate climate changes
• Males may help with food gathering

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Reproductive Strategies

• Goal of every species is to produce as many
  offspring as possible
• Each individual has a limited amount of energy to
  put towards life and reproduction
• This leads to a trade-off of long life or high
  reproductive rate
• Natural Selection has lead to two strategies for
  species r - strategists and K - strategists

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r - Strategists

• Spend most of their time in exponential growth
• High rate of reproduction
• Little parental care
• Minimum life
• Opportunist

K
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R Strategists

• 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

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K - Strategists

• Maintain population at carrying capacity (K)
• Maximize lifespan
• Competitor
• Follow a logistic growth curve

K
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K- Strategist

• Reproduce later in life
• Fewer, larger offspring
• High parental care and protection of offspring
• 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
• Prone to extinction

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Survivorship Curves

• Late Loss K-strategists that produce few young
  and care for them until they reach reproductive
  age thus reducing juvenile mortality
• Constant Loss typically intermediate
  reproductive strategies with fairly constant
  mortality throughout all age classes
• Early Loss r-strategists with many offspring,
  high infant mortality and high survivorship once
  a certain size and age

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Effects of Genetic Variations on Population Size
(9-3)

• Genetic diversity
• 1. Founder effect
• Few individuals move to a new location and are
  isolated from the original population
• Limited genetic diversity

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• 2. Demographic bottleneck
• Few individuals survive a catastrophe- fire,
  hurricane
• Lack of genetic diversity may limit these
  individuals to rebuild the population
• 3. Genetic drift
• Random changes in gene frequencies
• May help or hurt survival of a population
• Some individuals may breed more than others and
  their genes may eventually dominate the gene pool
  of the population
• 4. Inbreeding
• Members of a small population exchange genes

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Population Dynamics Outline

• Characteristics of a Population
• Population Dynamics and Carrying Capacity
• Reproductive Strategies
• Conservation Biology
• Human Impacts
• Working with Nature

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Conservation Biology

• Careful and sensible use of natural resources by
  humans
• Originated in 1970s to deal with problems in
  maintaining earth's biodiversity
• Dedicated to protecting ecosystems and to finding
  practical ways to prevent premature extinctions
  of species

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Conservation Biology

• Three Principles
• Biodiversity and ecological integrity are useful
  and necessary to all life on earth and should not
  be reduced by human actions
• Humans should not cause or hasten the premature
  extinction of populations and species or disrupt
  vital ecological processes
• Best way to preserve earths biodiversity and
  ecological integrity is to protect intact
  ecosystems that provide sufficient habitat

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Habitat Fragmentation

• Process by which human activity breaks natural
  ecosystems into smaller and smaller pieces of
  land
• Greatest impact on populations of species that
  require large areas of continuous habitat
• Also called habitat islands

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1949 1964 Habitat fragmentation in northern
Alberta 1982 1991
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Population Dynamics Outline

• Characteristics of a Population
• Population Dynamics and Carrying Capacity
• Reproductive Strategies
• Conservation Biology
• Human Impacts
• Working with Nature

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Human Impacts

• Humans have directly affected changes on about 83
  of Earths land surface.
• Humans have altered nature to meet our needs

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Human Impacts

• Fragmentation and degrading habitat
• Simplifying natural ecosystems
• Destruction of the Earths NPP
• Strengthening some populations of pest species
  and disease-causing bacteria by overuse of
  pesticides
• Elimination of some predators

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Human Impacts

• Deliberately or accidentally introducing new
  species
• Overharvesting potentially renewable resources
• Interfering with the normal chemical cycling and
  energy flows in ecosystem
• Increasingly dependent on nonrenewable energy
  from fossil fuels

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Population Dynamics Outline

• Characteristics of a Population
• Population Dynamics and Carrying Capacity
• Reproductive Strategies
• Conservation Biology
• Human Impacts
• Working with Nature

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Working with Nature

• Learn six features of living systems
• Interdependence
• Diversity
• Resilience
• Adaptability
• Unpredictability
• Limits

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Basic Ecological Lessons

1. Sunlight is primary source of energy
2. Nutrients are replenished and wastes are disposed
   of by recycling materials
3. Soil, water, air, plants and animals are renewed
   through natural processes
4. Energy is always required to produce or maintain
   an energy flow or to recycle chemicals

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Basic Ecological Lessons

1. Biodiversity takes many forms because it has
   evolved over billions of years under different
   conditions
2. Complex networks of and feedback loops exist
3. Population size and growth rate are controlled by
   interactions with other species and with abiotic
4. Organisms generally only use what they need

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Four Principles for Sustainable

1. We are part of, not apart from, the earths
   dynamic web of life.
2. Our lives, lifestyles, and economies are totally
   dependent on the sun and the earth.
3. We can never do merely one thing (first law of
   human ecology Garret Hardin).
4. Everything is connected to everything else we
   are all in it together.

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The Cats of Borneo

• What happened first?
• Arrange the sentence strips in chronological
  order

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Operation Cat Drop
One of the most bizarre events to accompany
this early use of DDT occurred when it became
necessary to parachute cats into remote jungle
villages in what was then Burma.  The following
account was taken from a source at Cornell
University In the early 1950s, the Dayak
people in Borneo suffered from malaria. The World
Health Organization had a solution they sprayed
large amounts of DDT to kill the mosquitoes which
carried the malaria. The mosquitoes died, the
malaria declined so far, so good. But there were
side-effects. Among the first was that the roofs
of people's houses began to fall down on their
heads. It seemed that the DDT was also killing a
parasitic wasp which had previously controlled
thatch-eating caterpillars. Worse, the
DDT-poisoned insects were eaten by geckoes, which
were eaten by cats. The cats started to die, the
rats flourished, and the people were threatened
by outbreaks of sylvatic plague and typhus. To
cope with these problems, which it had itself
created, the World Health Organization was
obliged to parachute14,000 live cats into Borneo.
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The Day they Parachuted Cats into Borneo

• WHO sent DDT to Borneo.
• Mosquitoes were wiped out.
• Caterpillar numbers went up.
• Caterpillars ate grass roofs.
• Roaches stored DDT in their bodies.
• Lizards ate roaches and got DDT.
• Lizards slowed down.
• Cats caught lizards containing DDT.
• Lizards disappeared.
• Cats died.
• Rats increased.
• Rats brought the plague.
• Cats were parachuted in.

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Homework Are They Competitors or Opportunists?
k-selected and r-selected species lab
Worksheet is online look at today's calendar,it
is also under Unit Five files. Either email it
to me or print it off. You will need a computer
with real player to view the video clips.