Download 021005PopulationEcologyWeb

1) Interactions between organisms and environment determine
distribution and abundance: dispersal, habitat selection, biotic
factors, abiotic factors (climate very important: temperature and
water).
2) Temporal and spatial scales of studies are important.
3) Global climate mostly determined by solar energy and earth’s
movement in space. Permanent tilt on Earth’s axis causes
seasonal variation in light, temperature and wind patterns.
Hence, seasonal variation in distribution and abundance of
organisms.
4) Aquatic biomes occupy the largest part of the biosphere;
oceans have a major effect on global and local climate;
freshwater biomes are closely linked to terrestrial biomes.
5) The distribution of terrestrial biomes is based mainly on
regional variations in climate.
Largest component. Vertical stratification: light, temperature, salinity, density.
Oceans (3% salt): rainfall, climate, wind. Give O2 and take CO2.
Freshwater (< 1% salt): linked to soil and biota of terrestrial biomes.
Fig. 50.17
Aquatic
Biomes
pages 1106-1109
Ocean
zonation
Fig. 50.22
Distance to shore & water depth, light penetration, substrate.
pages 1109-1112
Terrestrial Biomes
Determined by climate: latitudinal and regional patterns.
Vertical stratification based on vegetation. Characteristic life forms.
Gradation in boundaries: ecotone. Dynamic, not stable.
Fig. 50.24
pages 1112-1113
SOME questions from February 8th
1- Are we going to be tested on material that you have not covered
in lecture?
2- When will the review sheet be posted? Will we have a
study/review session?
3- Will there be questions about the third article on the test?
4- Do any chemicals evaporate with water or does water always
separate from anything it is mixed with?
5- What is the Ekman transport vector? Why is it important?
6- What are the lowest points in the ocean? What could possibly
live there?
Chapter 52- Population Ecology
Organismal
ecology
Population
ecology
coping
limiting factors
Community ecology
interspecific interactions and diversity
Ecosystem ecology
energy flow and chemical cycling
Landscape ecology
effects on interactions at lower levels
Biosphere ecology
global effects
Population: Group of individuals of
the same species occupying the
same general area.
67,171- 2000 Census
71,080- 2004 Estimate
Density.
Dispersion.
pages 1151-1152
Fig. 52.2
Uniform
page 1153
Clumped
Dispersion
Patterns
Random
Changes in Population Size
Additions (+)
Natality (births).
Immigration.
pages 1153 (1154)
Subtractions (-)
Mortality (deaths).
Emigration.
Demography: Studies vital statistics that affect population size.
Life Histories
Reproductive success. Number
of surviving offspring produced
by an individual and that reach
reproductive age.
Island of Rhum, Scotland
Natural selection. Differences in
reproductive success due to
heritable differences in
individuals.
Life histories. Patterns of
resource allocation to
maintenance (survival), growth,
Fig. 52.5
and reproduction.
Individuals expected to behave so as to promote their own RS.
pages 1156-1158
Life Histories
Semelparity (“once” and “beget”)
Three basic life history “decisions”
(remember not conscious choice except us):
-When to begin reproducing?
-How often to breed?
-How many offspring to produce during
each reproductive episode?
pageTID
1156
Iteroparity.
(“repeat” and “beget”)
Population Growth
Finite rate of increase
λ = number of individuals at time t + 1
divided by
number of individuals at time t
population is growing ( >1 )
population is declining ( <1 )
zero population growth ( 1 )
population is growing ( r+ )
population is declining ( r- )
zero population growth ( r = 0 )
Instantaneous rate of change
r = ln λ
pages 1158-1159
λ
r
% change
Nt
Nt+1
115
100
0.87
-0.14
-13
100
115
1.15
0.14
15
100
100
1
0
0
Population Growth
Exponential model
Ideal conditions: population growth constrained only by life history.
rmax = maximum growth rate for the species
Intrinsic rate of growth rate
dN
dt
= rmaxN
exponential population growth
or
geometric population growth
pages 1159-1160
Population Growth
Logistic model
There is a limit to number of individuals that can occupy a habitat.
Carrying capacity (K). Maximum population size an environment
can support at a time with no habitat degradation. Not a fixed value.
Population growth rapid when population size well below K, slow
when close to K and zero when at K.
K = 100; N = 1; (K-N)/K = 0.99
K-N
K = 100; N = 90; (K-N)/K = 0.1
K
K = 100; N = 100; (K-N)/K = 0
dN
pages 1160-1161
dt
= rmaxN
K-N
K
Population Growth
20000
15000
10000
5000
r = 0.02
r = 0.02
0
Exponential curve. Population grows indefinitely.
S-shaped curve. Population growth levels off as population size
approaches carrying capacity.
pages 1161-1162
Halichoerus grypus
Sable Island, CAN
ICES J. Mar. Sci. 2003
Phoca vitulina
J. Wildl. Manage. 2003
pages 1162-1163
Population-Limiting Factors
Many factors cause changes in birth and death rates in relation to
population density: increased predation, competition for food or
space, stress, parasitism, etc; slowing population growth rate.
Why do they represent an
example of negative feedback?
Eubalaena glacialis
Food-limited
CRESLI
Mandarte Isl., BC
Fig. 52.14
pages 1164-1165
Dynamics of Populations
They result from the interaction between biotic and abiotic factors.
Long-term studies indicate that such factors make natural
populations unstable.
Assigned
paper to
read for
Quiz IV.
Isla Royale, Michigan
pages 1165-1167
Fig. 52.17
Fig. 52.19
-Geographic variations due to largescale climate effects (apparent lack
of lynx migration between regions).
PNAS 2004
-Fluctuations of food species.
-Predation by various species.
pages 1167-1168
-Hare fluctuations.
Some populations have regular boom-and-bust cycles.