1) Population: individuals of same species in same general area. Has geographic boundaries and population size. Key traits: density (individuals per unit of area or volume) and dispersion (uniform, clumped, random).

1
1) Population individuals of same species in
same general area. Has geographic boundaries
and population size. Key traits density
(individuals per unit of area or volume) and
dispersion (uniform, clumped, random).
2) Demography studies changes in population
size. Births and immigration () deaths and
emigration (-).
3) Life histories affect reproductive output and
survival rate, thus population growth. Trade-offs
between survival and reproduction. Semelparity
(big-bang reproduction), iteroparity (repeated
reproduction).
4) Population growth exponential (J-shaped,
idealized, occurs in certain conditions) and
logistic (S-shaped. little more realistic,
carrying capacity). K-selection.
Density-dependent selection. r-selection.
Density independent selection.
5) Density-dependent changes in birth and death
rates usually slow down population growth rate.
Natural populations are characterized by
instability due to interaction of biotic and
abiotic factors. In some populations they result
in regular boom-and-bust cycles.
2
Does the number of seedlings affect population
growth ever?
The more, the better we are buddies and can
outcompete other plant species, so our population
will always grow.
There are always enough resources. No matter how
many we are, the population will always grow.
Its every seedling for itself. There is so much
water, soil and sun to go around. If we are
many, the population will eventually decline due
to competition.
The population might decline but never from
competition, we would never compete.
3
SOME questions from February 10th
1- Havent we seen whales breaching with giant
squids?
2- To what phyla do puffballs belong?
3- Is a forest or grassland considered a uniform
distribution
4- When calculating population sizes, do you
count migratory species?
5- Do we know the carrying capacity of the world
for humans?
4
Chapter 52 Population Ecology
Chapter 53 Community Ecology
5
Human Population 6,275,956,078 (Feb 20th, 2003)
6,418,752,524 (Feb 14th, 2005)
Fig. 52.20
Annual increase 1963 2.19 1984 1.7 2005
1.13 (200,782/day) 2049 0.47
pages 1168-1169
6
0.0
1.2
0.9
0.7
page 1169
7
BELLINGHAM
CensusScope
8
Fig. 52.23
sustreport.org
pages 1170-1171
World Wildlife Fund for Nature
9
Population ecology limiting factors
Organismal ecology coping
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
10
Community Ecology
Community. All the organisms of all the species
inhabiting an area. (assemblage of populations of
different species).
Community properties and structure are given by
species composition and species interactions.
Key measurements Relative abundance- Percentage
contribution of each species to the total number
of individuals in the community. Species
richness- Number of species in the community.
Species evenness- How individuals are apportioned
among the species. Even All species have same
number of individuals. Uneven Species have very
different numbers of individuals. Species
diversity- Relates species richness and species
evenness.
page 1174
11
What explains the particular species found in
each community?
Individualistic hypothesis. Species found in same
area due to similar abiotic needs. Assemblage by
chance. Interactive hypothesis. Species linked
due to mandatory biotic interactions. Assemblage
not by chance, community functions as an
integrate unit.
What does each hypothesis predict?
What hypothesis is supported by data?
For animals
Rivet model. Most species tightly associated with
other species.
Redundancy model. Most species not tightly
associated with one another.
Fig. 53.1
pages 1175-1176
12
Regardless of the correct model, be it one of
these two or another one, UNDERSTANDING COMMUNITY
STRUCTURE REQUIRES UNDERSTANDING INTERACTIONS
BETWEEN SPECIES
page 1176
Table 53.1
13
Competition. Both species incur a cost by
competing for a resource. Important in shaping
communities and adaptive evolution. Competitive
exclusion principle. Two species cannot coexist
if their ecological niches are identical.
Ecological niche. Biotic and abiotic resources
used by a species role of the species in the
environment.
pages 1176-1177
Fig. 53.2
14
If two species have identical niches, one might
be driven to extinction or evolve to use a
different set of resources.
Resource partitioning. Differentiation of niches
allowing similar species to coexist.
Fig. 53.3
page 1177
15
Predation. One species benefits and the other
one incurs a cost. Includes herbivory and
parasitism. Important factor in in adaptive
evolution predator adaptations, plant defenses
against herbivores, prey adaptations. Also
important in shaping communities.
pages 1178-1179
16
Mutualism. Both species benefit from the
interaction. Some are obligatory both species
cannot persist without the other others are
facultative the association is nonessential.
pages 1180-1181
funet.fi
Tree of Life
17
Corals, zooxanthellae
Pacific Northwest
Conifers Ectomycorrhizae Voles
18
Commensalism. Only one of the species benefits
from the interaction, whereas the other species
receives neither a benefit nor incur a cost.
Appear to be rare in nature.
page 1181
19
Species Interactions
Competition, Predation, Mutualism, Commensalism
Trophic Structure Dominant and Keystone
Species Community Organization
COMMUNITY STRUCTURE
20
TROPHIC STRUCTURE Feeding relationships between
organisms. Describe species interactions. Food
chain- Transfer of food energy all the way until
decomposers. Trophic levels- Links in the food
chain. Usually four or five. Food web-
Branching and interconnected food chains.
Fig. 53.10
page 1181
21
ANTARCTIC FOOD WEB
Fig. 53.11
page 1182
22
FOOD WEB TUESDAY LAKE, MI
Proc. Natl. Acad. Sci. 18 Feb 2003