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Lecture 1: Introduction to the Course
Reading: Economy of Nature, pp. 1
-25.
Introduction to the study of ecology
Scope of the course
Levels of organization of life
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Atoms |
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Molecules |
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Compounds |
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Cells |
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Tissues |
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Organs |
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Organisms
(Individuals) |
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Populations |
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Species |
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Communities |
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Ecosystems |
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Biosphere |
"Ecology" = from the Greek "Oikos"
meaning "house", the immediate environment
Term coined by Ernst Haeckel (1869)
(best known for his biogenetic law, "ontogeny recapitulates phylogeny").
Present meaning:
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Study
of interactions between organisms and environment |
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The economy
of nature, the total relations of an organism to
both its organic and inorganic environment |
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Biotic
and abiotic interactions |
Levels of interest in modern Ecology
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Individual
(organism or cell)
interactions with environment
interactions between living things |
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Populations
(a group of individuals of one species)
presence or absence of a species at a given site
abundance (census)
change over time |
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Communities
(groups of populations)
structure
diversity
change over time |
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Ecosystems
(groups of communities)
flux in energy and matter |
Modern Ecology is interdisciplinary, a
synthetic science that draws from and builds upon the study of genetics,
physiology, biochemistry, evolution, and behavior.
Mathematical models are important in the
study of ecology because models can help us simplify complex phenomena,
and help identify critical variables in complex interactions (such as
population growth, competition, and predation).
Types of organisms
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Autotrophs |
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Heterotrophs |
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Animals |
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Plants |
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Protista |
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Fungi |
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Monera
(Bacteria and Cyanobacteria |
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Archaea
(non-bacterial prokaryotes) |
General principles
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conformity
to the laws of thermodynamics |
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physical
environment controls productivity |
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ecological
communities regulated by population processes |
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organisms
change over time, evolution
Populations are not static.
Populations change over time. |
Organism distributions
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distributions
neither random nor homogeneous |
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most distributions
are restricted = patchy |
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organism
often appear to fit their environment
form fits function, why? |
Natural selection and evolution
Process of evolution by natural selection
requires:
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phenotypic
variation |
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underlying
genetic variation (heritable variation) |
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differential
reproduction and/or differential survival to
age of reproduction (selection which causes) |
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differential
production of descendants (due to differences
between individuals in their interactions with the environment) |
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Interactions between an individual and
its environment result in natural selection, which determines individual
fitness.
Organisms in populations change over
time = they evolve.
Individuals may be well suited to their
present environment, and may be considered "adapted" to their
present environment, because it is similar to the environments experienced
by ancestors.
Organisms do not evolve for the present
or the future, change is a consequence of the past.
Fitness is the relative success of an
individual in a given population, and selection is between better and
worse. Perfection need not occur.
Yet, there is often a striking match
between form and function.
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Causes for selection
Darwin’s Hostile Forces of Nature
(factors that cause selection)
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weather |
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climate |
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predators |
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parasites
and diseases |
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resources
shortages (including mates) |
These hostile forces can also described
as
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Ecological
Limiting Factors |
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Limiting
Conditions |
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Limiting
Resources |
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