Definition of Ecology
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1866 Ernst Haeckel: the comprehensive
science of the relationship of the organism to
the environment
1927 Charles Elton: Scientific natural history
1963 E. P. Odum: The study of the structure
and function of nature
1972 C. J. Krebs: The scientific study of the
interactions that determine the distribution
and abundance of organisms
Ecological spectrum
Biosphere, Landscape, Ecosystem, Community,
Population, Organism, Organ system, Organ,
Tissue, Cell, Subcellular organelles, Molecules
Branches of Ecology
Chemical, Molecular, Physiological, Behavioral,
Population, Community, Ecosystem, Landscape,
Evolutionary, Theoretical, Conservation and
management, Biodiversity
Journals: Behavioral Ecology, Biological
Conservation, Chemical Ecology,
Conservation Biology, Conservation Ecology,
Ecological Application, Ecological Modeling,
Ecological Monograph, Ecologist, Ecology,
Environmental Management, Evolutionary
Ecology, Functional Ecology, Journal of
Animal Ecology, Journal of Applied Ecology,
Journal of Wildlife Management, Landscape
Ecology, Molecular Ecology, Oecologia,
Oikos, Trends in Evolution and Ecology, etc.
Methods of studying ecology
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To understand, describe, explain,
predict and control
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Scale
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Lab experiment, field experiment,
natural trajectory experiment, natural
snapshot experiment, mathematical
model
Ecology of forest birds
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5 warbler sp. of similar ecological
requirement
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Feeding zones
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In the presence or absence of other
species
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Competition and partitioning
Energy budget of bumblebee
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How to keep warm in cold environment?
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Energy gain for feeding – energy loss
from flying, feeding and keeping warm
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Lab and field studies
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Number and kinds of flower visited, sugar
content of flower
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Energy loss at different temperature
Brown trout v.s. Native Galaxias
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Fish → Mayfly nymph → algae
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Activity pattern (lab and field exp.)
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Habitat preference (natural exp.)
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Community effect (field exp.)
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Trophic cascade – effects flowing down
from one trophic level to the next and
the next
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Energy flow
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Primary production: trout >> Galax
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Secondary production: trout >> Galax
Succession of old fields
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Natural trajectory vs. natural snapshot
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Correlation vs. mechanism
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within field comparison indicated
introduced sp.↑and prairie sp.↓ as N↑
Field experiment
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sp. composition and N supply
Nutrients in the rain forest canopy
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Epiphytes mats ~ ½ to 4x of the
nutrient content of the foliage of the
canopy trees
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Photosynthesis, migratory birds, bats
Fox-rabies (math model)
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Assumptions: no recovery or immune,
no migration, random contact
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Biology: life span 2 yrs., 1 cub/yr,
latent phase 28 days, die 5 days after
becoming infectious
N=S+L+I
dS/dt = (b-d)S -αSI
dL/dt = αSI - dL - βL
dI/dt = βL - dI - γI
α - contact rate
β - reaction rate
γ - rabies-induced mortality
Merits of model
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Summarizing current knowledge
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Approximation and simplification
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Hypotheses testing
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Exploring scenarios and situations
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Caution in evaluation and prediction
Factors affecting the abundance
and distribution of species
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Historical factors
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evolution and speciation
continental drift
geological and climatic changes
Abiotic factors
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chemical and physical environment
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Biotic factors
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competition, predation, mutualism, etc.
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Dispersal
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Behavioral factors
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Human factors
Darwinian evolution
by natural selection
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individual variation
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variation is heritable
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differential reproductive rate
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the interaction between the
characteristics of individual and the
environment
Fitness
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a measure of biological success
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# of gene or genome put into the
next generation
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the proportionate contribution that
an individual makes to future
generation
The fittest individual
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those that leave the greatest # of
descendants
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those that transport more gene to the
next generation
Example
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Model: an annual, only one gene,
asexual reproduction, reproduce only
once in life time.
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5 genotypes: A, B, C, D, and E
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G, S, F = proportion of energy devoted
to growth, survival (against predator),
and fecundity
# of seed Genotypes Spring/Summer Fall
10
10
10
10
10
Total
A
B
C
D
E
2 large
9 small
2 small
4 medium
5 med-small
2 seeds
1 seeds
4 seeds
5 seeds
4 seeds
Survival
4
9
8
20
20
61
G:F:S in A=6:1:1, B=1:1:6, C=1:6:1, D=1:1:1, E=1:1:2
Genotype frequency before
after one generation
A
10/50=0.2
4/61=0.06
B
0.2
9/61=0.15
C
0.2
8/61=0.13
D
0.2
20/61=0.33
E
0.2
20/61=0.33
Fitness = # of gene/genome put into the next generation
Fitness of D&E = 20/10 = 2
Fitness of C
= 8/10 = 0.8
Fitness of B
= 9/10 = 0.9
Fitness of A
= 4/10 = 0.4
Questions
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Is the population biologically successful?
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Are those genotypes equally successful?
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What if increase herbivory?
Within species variation
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Perennial Achillea lanulosa, transplant
and reciprocal transplant
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Natural selection by pollution
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Industrial melanism
Natural selection by predation