Transcript Community Ecology

Population of
Ecology
Ecology
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Study of the interactions of organisms in
their biotic and abiotic environments
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Organism  population community
Ecosystem  biophsere
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Demographics of populations
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Demography – statistical study of a population
(density, distribution, growth rate)
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Population density - # of individuals per unit
area (can be misleading)
Population distribution – pattern of dispersal
across an area (controlled by resources and
limiting factors) clumped, random, uniform
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Population growth
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Rate of natural growth (r) based on birth
and death rate.
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Biotic potential – highest possible growth
rate with unlimited resources.
Survivorship curves
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Probability that newborn will survive to
certain ages.
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Curve I – characteristic of a population in
which most individuals survive well past
midpoint of lifespan. Ex. Large mammals,
humans
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Curve II – survivorship decreases at a
constant rate throughout the life span. Ex.
Songbird, small mammals (death is
usually unrelated to age)
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Curve III – most individuals die young. Ex.
Insects, fish, humans in less developing
countries.
Age distribution
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Age structure diagrams
Increasing population
 Prereproductive
ages is largest, birth rate is higher
than death rate.
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Stable population (bell shape)
 Reproductive
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ages equal prereproductive ages
Decreasing population (urn shape)
 reproductive
ages is larger than prereproductive
ages, postreproductive age is largest
Population Growth Models
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2 patterns of population growth:
breeding – single reproductive event
 Continuous breeding – many reproductive
events
 Research: not always have to be one or the
other.
 Discrete
Exponential Growth
Number of individuals added each
generation increases as the total # of
females increases.
 Lag phase – growth is slow to start
 Exponential growth phase – accelerated
growth
 J shaped curve
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Logistic growth
S-shaped curve
 Lag phase, exponential growth phase
 Deceleration phase – growth slows
 Stable equilibrium phase – little to no
growth, BR = DR
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Carrying capacity
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Maximum # of individuals of a species an
environment can support.
Exponential growth can not continue due to
carrying capacity
 Resources become scarce
 Competition and predation
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Exponential growth occurs when population size
is much lower than carrying capacity.
Population stabilizes when carrying capacity is
reached.
Regulation of population size
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Density independent factors – those that
are not dependent on numbers
 Weather,
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natural disasters
Density dependent factors – occur
because of population of species
 Competition,
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predation, parasitism
Intrinsic factors? – anatomy, behavior
have an affect on population?
Life History Patterns - Opportunistic
r – strategists
 Small individuals, short life span, fast to
mature, many offspring, little/no care for
offspring, early reproductive age
 Bacteria, fungi, insects, rodents, annuals
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Life History Pattern - Equilibrium
K-strategists
 Large individuals, long life span, slow to
mature, few and large offspring, care for
offspring, most live to reproductive age
 Large mammals, birds of prey, long-lived
plants
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Human population growth
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MDC’s – North America, Europe, Japan,
Australia, growth is slow
LDC’s – Latin America, Africa, Asia, population
rising rapidly
Ways to reduce projected population increase:
 Strengthen
family planning
 Education, raising status of women, reduce child
mortality
 Delay onset of childbearing, wider spacing of births
Population Growth and
Environmental Impact
LCD = population growth in numbers
 MCD = consume larger proportion of
Earth’s resources
 Average family in North America
consumes the amount of resources and
produces wastes of 30 people from India.
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