population ecology 2014
DESCRIPTION
Population ecology 2014TRANSCRIPT
AP Biology
Population Ecology
population
ecosystem
community
biosphere
organism
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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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Life takes place in populations Population
group of individuals of same species in same area at same time
rely on same resources
interact interbreed
rely on same resources
interact interbreed
Population Ecology: What factors affect a population?Population Ecology: What factors affect a population?
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Abiotic factors sunlight & temperature precipitation / water soil / nutrients
Biotic factors other living organisms
prey (food) competitors predators, parasites,
disease
Intrinsic factors adaptations
Factors that affect Population Size
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Characterizing a Population Describing a population
population range pattern of Dispersion Density of population
#individuals per unit area
1937
19431951
19581961
196019651964
1966 1970
1970
1956
Immigrationfrom Africa
~1900
Equator
range
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Population Range Geographical limitations
abiotic & biotic factors temperature, rainfall, food, predators, etc.
habitat
adaptations topolar biome
adaptations topolar biome
adaptations torainforest biomeadaptations to
rainforest biome
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Population Dispersion Spacing patterns within a population
uniform
random
clumped
Provides insight into the environmental associations & social interactions of individuals in population
Provides insight into the environmental associations & social interactions of individuals in population
Why uniform?
Why clump?
Why random?
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Population Size Changes to
population size can occur by:
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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 #females at reproductive age in cohort?
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Life tableLife table
Demography Study of a populations vital statistics and
how they change over time Life tables, Age Structure Diagrams and Survivorship
Graphs
Why do teenage boys pay high car insurance rates?Why do teenage boys pay high car insurance rates?
females males
What adaptations have led to this difference
in male vs. femalemortality?
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Age structure Relative number of individuals of each age
What do these data imply about population growth in these countries?
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Survivorship curves Graphic representation of life table
Belding ground squirrel
The relatively straight lines of the plots indicate relatively constant rates of death; however, males have a lower survival rate overall than females.
The relatively straight lines of the plots indicate relatively constant rates of death; however, males have a lower survival rate overall than females.
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Survivorship curves Generalized strategies
What do these graphs tell about survival & strategy of a species?
What do these graphs tell about survival & strategy of a species?
0 25
1000
100
Human(type I)
Hydra(type II)
Oyster(type III)
10
150
Percent of maximum life span
10075
Su
rviv
al p
er
tho
us
and
I. High death rate in post-reproductive years
I. High death rate in post-reproductive years
II. Constant mortality rate throughout life span
II. Constant mortality rate throughout life span
III. Very high early mortality but the few survivors then live long (stay reproductive)
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
To increase reproduction may decrease survival: (think about…)
age at first reproduction investment per offspring number of reproductive cycles per lifetime parents not equally invested offspring mutations
Life History determined by costs
and benefits of all adaptations.
Natural selection favors a life history
that maximizes lifetime
reproductive success
Natural selection favors a life history
that maximizes lifetime
reproductive success
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Reproductive strategies K-selected
late reproduction few offspring invest a lot in raising offspring
primates coconut
r-selected early reproduction many offspring little parental care
insects many plants
K-selected
r-selected
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Trade offsNumber & size of offspring
vs.
Survival of offspring or parent
Number & size of offspring
vs.
Survival of offspring or parentr-selected
K-selected
“Of course, long before you mature, most of you will be eaten.”
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Survivorship Curves with Reproductive Strategy
0 25
1000
100
Human(type I)
Hydra(type II)
Oyster(type III)
10
1
50
Percent of maximum life span
10075
Su
rviv
al p
er
tho
us
and
K-selection
r-selection
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Population Growth Rate Models Exponential growth
Rapid growth No constraints
Logistic growth Environmental constraints Limited growth
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Population Growth Math Change in population = Births – Deaths Per capita birth rate = b Per capita death rate = d # of individuals = N Rate of population growth (r) = b – d Survivorship = % surviving
Ex: If there are 50 deer in a population, 13 die and 27 are born the next month. What is the population size the following month?
(Answer: 27-13 = 14, so new population is 64)
Ex: What is the birth rate for the deer? #Births/N = b Answer: 27/50 = .54 Death rate (d) = 13/50 = .26
Ex: What is the rate of growth for the deer? r = .54 -.26 = .28
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Exponential Growth (ideal conditions)
No environmental barriers Growth is at maximum rate
dN/dt = rmaxN
N = # individuals
Rmax = growth rate
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African elephantprotected from hunting
Whooping cranecoming back from near extinction
Exponential Growth Characteristic of populations without
limiting factors introduced to a new environment or rebounding
from a catastrophe
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K =carryingcapacity
K =carryingcapacity
Logistic rate of growth Can populations continue to grow
exponentially? Of course not!Of course not!
effect of natural controlseffect of natural controls
no natural controlsno natural controls
What happens as N approaches K?
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Logistic Growth Equation
dN/dt = rmaxN(K-N)/K
K = carrying capacity of populationEx: If a population has a carrying capacity of 900 and the rmax is 1, what is the population growth when the population is 435? 1 x 435 (900-435)/900 = 224
What if the population is at 850?
What if it is at 1010?
Explain the results of each problem.
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500
400
300
200
100
0200 10 30 5040 60
Time (days)
Nu
mb
er o
f cl
ado
cera
ns
(per
20
0 m
l)
Maximum population size that environment can support with no degradation of habitat varies with
changes in resources
Time (years)1915 1925 1935 1945
10
8
6
4
2
0
Nu
mb
er o
f b
ree
din
g m
ale
fu
r se
als
(th
ou
san
ds)
Carrying capacity
What’s going on with the plankton?
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Changes in Carrying Capacity Population cycles
predator – prey interactions
KK
KK
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Regulation of population size Limiting factors
density dependent competition: food, mates,
nesting sites predators, parasites,
pathogens density independent
abiotic factors sunlight (energy) temperature rainfall
swarming locusts
marking territory= competition
competition for nesting sites
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Introduced species Non-native species (INVASIVE)
transplanted populations grow exponentially in new area
out-compete native species reduce diversity examples
African honeybee gypsy moth
kudzu
gypsy mothgypsy moth
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Zebra musselssel
ecological & economic damage
~2 months
reduces diversity loss of food & nesting sites
for animals economic damage
reduces diversity loss of food & nesting sites
for animals economic damage
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Purple loosestrife
19681968 19781978
reduces diversity loss of food & nesting sites
for animals
reduces diversity loss of food & nesting sites
for animals
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AnyQuestions?