Biology%20213%20Chapter%2053

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Biology 213 Chapter 53

• Introduction to Ecology
• Population Ecology Part 1

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You will be able to

• List various fields of study in Ecology
• Explain what factors change populations
• Calculate population rate changes
• Compare and contrast density-dependent to
  density-independent factors

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• Ecology
• Oikos home Ology study of
• Integrates all biological fields
• Organismal ecology physiology, behavior,
  interactions with environment
• Population ecology factors affecting groups of
  individuals in an area.
• Community ecology interactions between species
  in an area

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• Ecosystem ecology biotic and abiotic
  interactions E flow chem. Cycles
• Landscape ecology exchange of E materials
  across multiple ecosystems
• 6. Global ecology biosphere regional exchange
  of E materials affecting entire functioning
  distribution of organisms wotldwide.

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Ecology evolution changes in environment
impacting populations alleles over
time. Ecology environmental issues Complexity
of Nature Why are some species present in an
area? Dispersal difficulties (accessibility?) Beha
viour limits distribution (habitat
preference)? Biotic factors competition/parasitis
m/predation/etc Abiotic factors Chem H2O, O2,
pH, salinity, nutrients Phys Macro micro
climate Temp, light, fire, soil composition,
moisture
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• Estimate one million years to get from 2.5
  million to human population of 5 million people
  in 6000 B.C. (2x)
• population did not reach 500 million until almost
  8,000 years later -about 1650 A.D (100x)
• doubled roughly once every thousand years or so
• reached a billion 1850, doubling in 200 years
• reached two billion around 1930 doubling in 80
  years
• 1970s it reached 4 billion 40 year doubling
  time
• Todays population 7 billion

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What factors have allowed human population to
increase so rapidly?
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Ecologists study population trends rather than
individual organisms. Properties of populations
include

• Population size
• Population density
• Patterns of dispersion
• Demographics
• Population growth
• Limits on population growth

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• Population density
• individuals of a species per unit
  at a given time
• Population dispersion (spacing)
• How are individuals distributed in a habitat?
• Why would this be important to know if you were
  studying a population?
• What does a dispersion pattern tell you?

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• Individual members distributed in a of
  different ways
• Clumped -
• Uniform -
• Random -

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Why would a clumped population pattern form?
individuals _____________ to each other, or
__________________________________.
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What factors encourage a
uniform population pattern?
individual organisms actively _____ each other
or all _________________________________
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What abiotic or biotic features would encourage a
random population pattern?
Rare in nature - occurs in absence of strong
attractions or repulsions among individuals.
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Dispersion patterns and density may change over
time

• Habitat changes food, nutrients, water, sunlight
  (plants)
• Age / size / developmental stages change

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• Four factors that produce changes in population
  size

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Natality birth rate
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Mortality rates
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Mortality rate of cheetahs

• Increased Infant
• Mortality
• Is the cheetah dangerously inbred?
• Majority of deaths in wild due to predation.
• Future for cheetah population?

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• How a population changes
• D in of individuals
• in a certain period of time
• N
• r

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• How a population changes
• D in individuals / time
• N individuals
• r
• Per 1,000 individuals
• Growth rate

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• Example N 300,000 humans
• 3,000 births 1,500 deaths in one year
• r (birth rate) (death rate)

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• Example N 300,000 humans
• r (birth rate) (death rate)
• r
• r

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• Example N 300,000 humans
• r 0.005 x 100 0.5 increase
• rN 0.5 x 300,000
• rN

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• If r is positive, increase in pop.
• If r is negative, pop. is decreasing
• If r 0, population is stable

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• Are there other factors besides birth and death
• and
• size of a population
• that can change a population?

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Immigration

• What causes immigration biologically?
• Favorable factors

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• Factors encouraging immigration
• New environment made available
• Natural disasters large and small
• Competitive or predatory species goes extinct /
  moves away
• Climate change or new resources
• Hitch-hiking (alien species)
• Less competition in new area

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Succession after a disaster
Immigrants have an opportunity to invade Reduced
competition
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Factors that encourage successful immigration

• Distribution methods
• dispersal is at or near ground level vs.
• aerial dispersal
• dispersers actively engage in searching,
  
• or not
• dispersers able to orient toward preferred
• habitat from some distance,
• or not

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Wind dispersing Golden Orb spiders
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Emigration
Unfavorable Factors Excessive competition
mates or food Lack of resources Disease Avo
idance of in-breeding
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• Population change includes immigration and
  emigration
• r (birth rate) (death rate) plus
• (immigration emigration)
• e.g. Example N 300,000 humans
• 3000 births 1500 deaths in one year
• 3,000 immigrated into the area
• 9,000 emigrated out of the area

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• r (b d) (i e)
• b d (10/1000) (5/1000) 0.005
• i e 1/1000 3/1000
• 0.001 0.003 -0.002
• r (b d) (i e)
• (0.005) (-0.002) 0.003 x 100 0.3
• Growth rate rN (0.3)(300,000)
• 900 more people in the population

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• Intrinsic rate of increase (rmax)
• Maximum rate at which species or
• population can increase under ideal
• conditions
• Exponential population growth

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Exponential population growth
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According to Malthus

• Population, when unchecked, increases in a
  geometrical ratio.
•  
• Subsistence increases arithmetically.

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Carrying capacity

• Carrying capacity (K) largest population
  maintained without degrading environment they
  live in
• Changes as environment changes
• Logistic population curve
• (S-shaped curve)

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Carrying capacity and logistic population growth
Limiting Factors
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• Density-dependent factors
• Regulate population growth by affecting large
  proportion of population as population rises

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• Density-dependent factors
• What do you think would impact a population as it
  got bigger?
• Predation
• Disease
• Competition
• Toxic wastes

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Density-dependent factors and negative feedback
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• Density-independent factors
• Limit population growth but are not influenced by
  changes in population density usually ABIOTIC
• Examples include natural disasters
• Hurricanes
• Blizzards
• Forest fires
• Mudslides
• Volcanoes, tsunamis, and earthquakes

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Limiting Factors

• Biotic and abiotic,
• Density dependent or independent
• factors that limit a populations growth
• What would be a limiting factor?

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• What can you think of that would be a
• limiting factor?
• Which are biotic and which are abiotic?
• increase death rate
• decrease birth rate
• limits immigration
• encourages emigration
• Any factors that slows population growth.

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How are up down cycles explained? Can be very
complex relationships and factors.
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Biology 213 Chapter 53

• Introduction to Ecology
• Population Ecology Part 2

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You will be able to

• Explain what factors change populations
• Calculate population rate changes
• Compare and contrast density-dependent to
  density-independent factors
• Analyze human population patterns and make
  predictions about future trends

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• Semelparous reproduction
• Expend their energy in a
• Iteroparous reproduction
• Exhibit ________________________
• throughout their lifetimes

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Semelparity Expend energy to reproduce in one
big effort Most insects, invertebrates,
many annual plants, and some fish Whats the
advantage?
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Iteroparous reproduction

• Expend energy to reproduce in cycles
• Most vertebrates, perennial plants.
• Whats the advantage?

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• Species exhibiting an r strategy
• Emphasizes a high growth rate
• Organisms typically have
• small body size
• high reproductive rates
• short life spans
• inhabit variable environments
• Often

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• Species exhibiting a K strategy
• Maintains a population near carrying
  capacity (K) of environment
• Species often have
• large body size
• low reproductive rates
• long life spans
• inhabit stable environments
• Often

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• Survivorship curves
• Type I
• Mortality is greatest in old age
• Type II
• Mortality is spread evenly across all ages
• Type III
• Mortality is greatest among the young

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Survivorship curves
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Survivorshipcurve for a herring gull population
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• Source habitats
• Preferred habitats
• Local reproductive success is gt local mortality
• Local individuals disperse from source habitats
  to other regions

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• Sink habitats
• Lower-quality habitats
• Individuals may suffer death or poor reproductive
  success
• What would make an organism move then?

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Source sink populations in a hypothetical
metapopulation
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• Human population growth
• World population reaches 6,668,926,425 by May 20,
  2008
• Per capita growth rate declined from peak in
  1965 of about 2 per year
  (doubling time 35 years)
• to 1.3 per year (doubling time of 54 years)
• birthrate necessary for zero population growth is
  2.1 births per woman

7,000,000,000
The year 2011
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Human population growth
exponential J-shaped curve so far
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logistic population growth
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Chapter 53 Clicker Question 4 Often growth
cycles of one population affects the cycle of
another. As moose populations increase, wolf
populations also increase. If we consider the
logistic equation for the wolf population dN
rN (K-N) dt K which of the above
factors accounts for the strongest impact on the
moose population? A. K B. dN C. rN D. dt
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• Population characteristics
• Highly developed countries
• low birth rate
• low infant mortality
• low fertility rate
• long life expectancies
• high GNI PPP
• GNI PPP per capita is the gross national income
  in purchasing power parity divided by mid-year
  population.

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Population characteristics

• Developing countries
• high birth rate
• high infant mortality
• high fertility rate
• short life expectancies
• low GNI PPP

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What trends do we see world-wide?
China and Indias populations increasing
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Birth rate decline lags behind as death rate
decreases e.g. in Mexico, 19002000
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• Age structure influences population dynamics
• Possible for country to have replacement-level
  fertility and still experience population growth
• Young age structure causes a positive population
  growth momentum as large pre-reproductive age
  group matures

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Age structure diagrams comparing
Kenya to USA
to Germany
15-to-40 range reproductive rates are high
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Carrying-capacity" definition of overpopulation

• not population density, but s of people in an
  area relative to resources capacity to sustain
  human activities
• a condition of overpopulation might be corrected
  with
  no change in the number of people!

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Ecological Footprint

• Developing countries tend to have people
  overpopulation that degrades the environment
• Developed countries have consumption
  overpopulation that degrades the environment

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USA Mexico One weeks food supply. One weeks
food costs the American family 341.98




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One weeks food Egypt Ecuador




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Above Bhutan Below Chad
One weeks food costs the Chad family 1.23
 
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• China has 22 of worlds population
• India has 17 of worlds population
• Both nations are modernizing rapidly
• USA uses has 4.4 of the world population and
  uses 25 of worlds energy resources
• What happens to global resources when developing
  countries want to enjoy a developed nation
  lifestyle like ours?