Bright blue marble spinning in space

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organism
population
community
ecosystem
biosphere
Population Ecology
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Life takes place in populations

• Population
• group of individuals of same species in same area
  at same time

• rely on same resources
• interact
• interbreed

Population Ecology What factors affect a
population?
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Why Population Ecology?

• Scientific goal
• understanding the factors that influence the size
  of populations
• general principles
• specific cases
• Practical goal
• management of populations
• increase population size
• endangered species
• decrease population size
• pests
• maintain population size
• fisheries management
• maintain maximize sustained yield

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Factors that affect Population Size

• Abiotic factors
• ____________________
• ____________________
• ____________________
• Biotic factors
• ____________________
• ____________________
• ____________________
• ____________________ ____________________
• Intrinsic factors
• adaptations

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Characterizing a Population

• Describing a population
• population ___________
• pattern of spacing
• ____________
• size of population

range
density
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Population Range

• Geographical limitations
• abiotic biotic factors
• temperature, rainfall, food, predators, etc.
• habitat

adaptations topolar biome
adaptations torainforest biome
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Changes in range

• Range expansions contractions
• changing environment

result of competition
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At risk populations

• Endangered species
• limitations to range / habitat
• places species at risk

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Population Spacing

• Dispersal patterns within a population

Provides insight into the environmental
associations social interactions of
individuals in population
clumped
random
uniform
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Clumped Pattern (most common)
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Uniform
May result from direct interactions between
individuals in the population ? territoriality
Clumped patterns
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Population Size

• Changes to population size
• adding removing individuals from a population
• birth
• death
• immigration
• emigration

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Population growth rates

• Factors affecting population growth rate
• sex ratio
• how many females vs. males?
• generation time
• at what age do females reproduce?
• age structure
• how females at reproductive age in cohort?

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Demography
Why do teenage boys pay high car insurance rates?

• Factors that affect growth decline of
  populations
• vital statistics how they change over time

Life table
females
males
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Survivorship curves

• Graphic representation of life table

The relatively straight lines of the plots
indicate relatively constant rates of death
however, males have a lower survival rate overall
than females.
Belding ground squirrel
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Age structure

• Relative number of individuals of each age

What do the data imply about population growth in
these countries?
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Survivorship curves
What do these graphs tell about survival
strategy of a species?

• Generalized strategies

I. High death rate in post-reproductive years
II. Constant mortality rate throughout life span
III. Very high early mortality but the few
survivors then live long (stay reproductive)
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Trade-offs survival vs. reproduction

• The cost of reproduction
• increase reproduction may decrease survival
• investment per offspring
• reproductive events per lifetime
• age at first reproduction

Natural selection favors a life history that
maximizes lifetime reproductive success
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Parental survival

• Kestrel Falcons
• The cost of larger broods to both male female
  parents

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Reproductive strategies

• _____________________________
• _________________________
• _________________________
• _________________________
• primates
• coconut
• _____________________________
• _________________________
• _________________________
• _________________________
• insects
• many plants

K-selected
r-selected
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Trade offs

• Number size of offspring
• vs.
• Survival of offspring or parent

r-selected
K-selected
Of course, long before you mature, most of you
will be eaten.
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Life strategies survivorship curves
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Population growth

• change in population births deaths

• Exponential model (ideal conditions)
• dN riN
• dt

growth increasing at constant rate
N of individuals r rate of growth ri
intrinsic rate t time d rate of change
every pair has 4 offspring
every pair has 3 offspring
intrinsic rate maximum rate of growth
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Exponential growth rate

• Characteristic of populations without
  _______________________
• introduced to a new environment or rebounding
  from a catastrophe

African elephant protected from hunting
Whooping crane coming back from near extinction
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Regulation of population size
marking territory competition

• Limiting factors
• ____________________
• _____________________
• _____________________
• _____________________
• _____________________
• ____________________
• _____________________
• _____________________
• _____________________
• _____________________

swarming locusts
competition for nesting sites
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Introduced species

• Non-native species
• transplanted populations grow exponentially in
  new area
• out-compete native species
• loss of natural controls
• lack of predators, parasites, competitors
• reduce diversity
• examples
• African honeybee
• gypsy moth
• zebra mussel
• purple loosestrife

kudzu
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Zebra mussel
2 months
ecological economic damage
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Purple loosestrife

• reduces diversity
• loss of food nesting sites for animals

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Logistic rate of growth

• Can populations continue to grow exponentially?

Of course not!
no natural controls
K Carryingcapacity
effect of natural controls
What happens as N approaches K?
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Carrying capacity

• Maximum population size that environment can
  support with no degradation of habitat
• varies with changes in resources

Whats going on with the plankton?
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Changes in Carrying Capacity

• Population cycles
• predator prey interactions

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Human population growth
Population of China 1.3 billion India 1.1
billion
adding 82 million/year

• What factors have contributed to this exponential
  growth pattern?

2005?6 billion
Is the human population reachingcarrying
capacity?
Bubonic plague "Black Death"
1650?500 million
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Distribution of population growth
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uneven distribution 90 of births in developing
countries
10
high fertility
9
uneven distribution of resources increasing gap
between rich poor
medium fertility
8
7
low fertility
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World total
World population in billions
What is K for humans? 10-15 billion?
5
4
Developing countries
3
2
1
Developed countries
0
1950
1900
2000
2050
Time
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Distribution of population growth
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uneven distribution 90 of births in developing
countries
10
high fertility
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uneven distribution of resources increasing gap
between rich poor
medium fertility
There are choices as to which future path the
world takes
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7
low fertility
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World total
World population in billions
What is K for humans? 10-15 billion?
the effect of income education
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4
Developing countries
3
2
1
Developed countries
0
1950
1900
2000
2050
Time
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Ecological Footprint
over-population or over-consumption?
uneven distribution wealthiest 20 of world 86
consumption of resources 53 of CO2 emissions
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Ecological Footprint
deficit
surplus
Based on land water area used to produce all
resources each country consumes to absorb all
wastes it generates
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Any Questions??