Post on 18-Jan-2016
Chp. 36What impact did BP disaster have
on the ocean ecosystem and population??
Reflect on this disaster….
The tale of two fish….population ecology
Read scenario p725Use population ecology to summarize this passage…
Read 36.1, 36.2, 36.4, 36.5, 36.6, 36.8, 36.11
36.1 Relate population with boundaries, population ecologist, population dynamics and population growth.
36.2 Example (other than one in the book) of population density
Example (other than ones in book) of clumped dispersion, uniform dispersion and random dispersion
36.4 Contrast exponential growth model and logistic growth model. Use per capita, limiting factors and carrying capacity, in discussion
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Introduction: A Tale of Two Fishes
• Population ecology is concerned with– Changes in population size– Factors that regulate populations over time
• It helps explain the biodiversity of an environment
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• Ecologists learn the structure and dynamics of natural populations
• With this information they are better equipped to– Develop sustainable food sources– Assess the impact of human activities– Balance human needs with the conservation of
biodiversity and resources
Introduction: A Tale of Two Fishes
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36.1 Population ecology is the study of how and why populations change
• Population– A group of individuals of a single species that occupy
the same general area
• Individuals in a population– Rely on the same resources– Are influenced by the same environmental factors– Are likely to interact and breed with one another
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• A population can be described by the number and distribution of individuals
• Population dynamics is the interactions between– Biotic and abiotic factors
• It is the cause of variation in population sizes– A population increases through birth and
immigration– Death and emigration out of an area decrease the
population
36.1 Population ecology is the study of how and why populations change
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36.2 Density and dispersion patterns are important population variables
• Population density is the number of individuals of a species per unit area or volume
• Examples of population density– The number of oak trees per square kilometer in a
forest– The number of earthworms per cubic meter in
forest soil
• Ecologists use a variety of sampling techniques to estimate population densities
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• Within a population’s geographic range, local densities may vary greatly
• The dispersion pattern of a population refers to the way individuals are spaced within their area
36.2 Density and dispersion patterns are important population variables
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• The dispersion pattern of a population refers to the way individuals are spaced within their area
• Dispersion patterns can be– Clumped– Uniform– Random
36.2 Density and dispersion patterns are important population variables
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• In a clumped pattern individuals are grouped in patches
• Unequal distribution of resources• Mating• Social behavior
• Plants and fungi clumped in areas where soil conditions favor germination
• Flies
36.2 Density and dispersion patterns are important population variables
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• In a uniform pattern individuals are equally spaced in the environment
• Territorial behavior• Interactions between individuals in same
population
36.2 Density and dispersion patterns are important population variables
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• In a random pattern of dispersion, the individuals in a population are spaced in an unpredictable way
• Wind-blown seeds• Habits and social interaction make random
pattern rare
36.2 Density and dispersion patterns are important population variables
Percentage of maximum life span
Per
cen
tag
e o
f su
rviv
ors
(lo
g s
cale
)
0 50 100
0.1
1
10
100
III
II
I
Copyright © 2009 Pearson Education, Inc.
36.4 Idealized models predict patterns of population growth
• Exponential growth model – The rate of population increases under ideal
conditions– Calculated using the equation G = rN
– G is the growth rate of the population– N is the population size– r is the per capita rate of increase
Time (months)
Po
pu
lati
on
siz
e (N
)
0 1 2 3 4 5 6 7 8 9 10 11 12
0
50
100
150
200
250
300
350
400
450
500
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• Logistic growth model– This growth model takes into account limiting
factors– Limiting factors are environmental factors that
restrict population growth– Formula
36.4 Idealized models predict patterns of population growth
(K N)G = rN
K
Year
Bre
edin
g m
ale
fur
seal
s(t
ho
usa
nd
s)
1915 1925 1935 19450
2
4
6
8
10
Copyright © 2009 Pearson Education, Inc.
• Idealized models describe two kinds of population growth
– Exponential growth – Logistic growth
36.4 Idealized models predict patterns of population growth
Time
Nu
mb
er o
f in
div
idu
als
(N)
0
K
G = rN
G = rN(K – N)
K
Test Weds. sections 36.1,2,4,5,6,7
Read 36.5, 36.6, 36.7 and takes notes on these sections. Make sure to include summaries of all figures….
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36.5 Multiple factors may limit population growth
• The logistic growth model– Population growth slows and ceases as population
density increases– Increasing population density results in a decrease
in birth rate, an increase in death rate, or both
Density of females
Clu
tch
siz
e
0 10 20 30 40 50 60 70 802.8
3.0
3.2
3.4
3.6
3.8
4.0
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• Abiotic factors may reduce population size before other limiting factors become important
36.5 Multiple factors may limit population growth
Apr May Jun Jul Aug Sep Oct Nov Dec
Nu
mb
er o
f ap
hid
s
Exponentialgrowth
Suddendecline
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• Most populations fluctuate in numbers
36.5 Multiple factors may limit population growth
Time (years)
Nu
mb
er o
f fe
mal
es
1975 1980 1985 1990 1995 20000
20
40
60
80
Males Females
Experimentaltransplant ofguppies
Predator: Killifish; preysmainly on small guppies
Guppies:Larger atsexual maturitythan those inpike-cichlid pools
Pools with killifish,but no guppies priorto transplant
Predator: Pike-cichlid preys mainly on large guppies
Guppies: Smaller at sexual maturity thanthose in killifish pools11 years
later
Mas
s o
f g
up
pie
sat
mat
uri
ty (
mg
)
40
80
120
160
200
67.5 76.1
161.5185.6
Ag
e o
f g
up
pie
sat
mat
uri
ty (
day
s)
Males Females
20
40
60
80100
48.558.2
85.792.3 Control:Guppies from poolswith pike-cichlidsas predators
Experimental:Guppies transplantedto pools with killifishas predators
36.536.61.613.3
36.718.6
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THE HUMAN POPULATION
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36.9 The human population continues to increase, but the growth rate is slowing
• Human population is expected to continue increasing for several decades
• 95% of the increase is in developing nations
1500
Year
Population increase
Total population size
To
tal p
op
ula
tio
n (
in b
illio
ns
)
1550 1600 1650 1700 1750 1800 1850 1900 1950 2000 20500
2
4
6
8
10
20
40
60
80
100
An
nu
al in
cre
ase
(in
mill
ion
s)
Year
Birth rate
Death rate
Rate of increase (r)
1900 19501925 1975 2000 2025 2050
0
10
20
30
40
50
Bir
th o
r d
eath
rat
ep
er 1
,000
po
pu
lati
on
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36.11 CONNECTION: An ecological footprint is a measure of resource consumption
• U.S. Census Bureau projection– 8 billion people within the next 20 years– 9.5 billion by mid-21st century
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• Ecological footprint helps understand resource availability and usage
• The United States has a– Big ecological footprint – Large ecological deficit
36.11 CONNECTION: An ecological footprint is a measure of resource consumption
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You should now be able to
1. Explain the factors that determine the characteristics of a population
2. Describe exponential growth and the factors that produce logistic growth of a population
3. Explain the limiting factors that influence population growth
4. Distinguish between r- and K-strategies5. Describe and give examples of the different types of
life histories
Copyright © 2009 Pearson Education, Inc.
6. Explain the factors the determine human population growth
7. Describe the concept of ecological footprint
You should now be able to
Chp. 37 Communities and Ecosystems
I will be able to relate structure and dynamics of ecosystems and
communities with how human activities can disrupt the balance
Read p741 Hungry Hippos!!
37.1 Community
Define population