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INTRODUCTION
Chapter 1
Preface: J.R. Platt
1964. Strong Inference. Science 146:347-353
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Yes! The paper is sexist in a few places. In 1964,
mostly, science was done by men. Times have
changed. Looking beyond this annoying feature of
the paper,….
Presents a passionate plea for rigorous use of the
scientific method.
Platt was not an ecologist and he argues that some
fields of science are making more rapid progress
because they follow the scientific method more
effectively.
The use of Inductive reasoning.
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Inductive reasoning:
Start with a specific observation and move
towards a general conclusion
Given a specific observation:
 1. Devise alternative hypotheses;
 2. Devise a crucial experiment (or several of
them) , with alternative possible outcomes, each
of which will, as nearly as possible, exclude one
or more of the hypotheses;
 3. Carry out the experiments repeating as
needed to get clean, consistent results;
 1’. Recycle the procedure, making subhypotheses or sequential hypothesis to refine
the possibilities that remain…..
Strong Inference
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Platt likens this to the process of climbing a tree.
At each fork, we choose a path and climb to the
next fork.
A key component of this process is the use of
multiple working hypotheses. Don’t become too
attached to your “favorite” explanation.
Science makes progress by disproving alternative
hypotheses. We never, ever, prove anything in
science.
An Example:
The White Swan Hypothesis
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Specific Observation: “I sure have seen lots of
white swans.”
Hypothesis: “All swans are white.”
Repeated observations throughout North America,
Europe and Asia are consistent with this
hypothesis, however, this does not prove the
hypothesis. Failure to disprove is not proof.
All it takes is a single observation of a non-white
swan to disprove this hypothesis
The Black Swan (Cygnus atratus)
Western Australia
“But it’s only a theory”
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A theory is far more than a half-baked idea.
An hypothesis gradually gets transformed into a
theory as it withstands multiple attempts to
disprove it.
However, “a theory which cannot be mortally
endangered” (cannot be tested) “cannot be alive.”
Platt’s “The Question”
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What experiment could disprove your hypothesis?
Introduction
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Ecology: Study of relationships between
organisms and the environment.
 Simple definition does not convey the
extreme breadth of this discipline.
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What do ecologists do?
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Some examples……
Ecology of Forest Birds
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MacArthur – studied ecology of five species
of warblers in spruce forests in N.A.
 Theory predicted two spp. with identical
ecological requirements could not coexist
indefinitely.
 Warblers did coexist by feeding in
different zones of trees.
 Stimulated competition research.
Why do these differences exist?
Is it competition? How would you test this?
This
observation is
consistent with
the competition
hypothesis but
it is not “proof.”
Ecology of Bumblebees
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Heinrich estimated energy budget of
bumblebees foraging on different flowers and
under different temperatures.
 Energy Gain/Loss:
 Energy Intake – Energy Expenditure
 Amount of energy expended during flight was
independent of air temperature and bees
elevated temp. of thorax to stay warm in cool
climates.
Forest Nutrient Budgets
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Nalini Nadkarni: Nutrient stores in rainforest
canopies are associated with epiphytes
(plants living on branches / trunks of other
plants). Mass of epiphytes is 4X the mass of
leaves of host trees in forests on the
Olympic Peninsula of WA
 Epiphyte mats create small diverse
communities.
 Trees send roots up to epiphyte mats to
access nutrients.
Forest Nutrient Budgets - cont.
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Likens and Bormann estimated 90% of
nutrients in a New Hampshire forest were
locked up in soil organic matter.
Approximately 9.5 % was tied up in
vegetation, and rest was lost by
streamflow output.
Vegetation Change: Pollen Records
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Many env. changes take place over large
spatial scales and/or temporal scales.
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Davis monitored plant pollen deposited in
lake sediments in the Appalachian Mtns.
 Documented large temporal changes to
nearby plant communities.
Nature and Scope of Ecology
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Ecology: Study of relationships between
organisms and the environment.
 Wide variety of approaches.
 Large range of temporal and spatial
scales.
 Field
 Lab
 Observational
 Manipulative
Nature and Scope of Ecology
Kimmins 1997
Major Premise Of This Book:
Modern Ecology was built on a strong
foundational knowledge of natural history.
Furthering knowledge of natural history
improves our understanding of ecological
relationships.
Origins of Ecology
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The word ECOLOGY was coined by Ernst
Haeckel in 1869. It is derived from the
Greek oikos, meaning "household", "home,"
or "place to live" and logos, "the study of.“
More definitions for Ecology
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"...the investigation of the total relationships of the
animal both to its inorganic and its organic
environment..." (Haeckel 1869)
"...scientific natural history." (Elton 1927)
"...the scientific study of the distribution and
abundance of animals." (Andrewartha 1961)
"...the study of the structure and function of
nature" (Odum 1971)
"...the study of the adaptations of organisms to
their environment" (Emlen 1973)
"...the scientific study of the relationships between
organisms and their environments" (McNaughton
and Wolfe 1979)
More definitions for Ecology
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"...the scientific study of the interactions that
determine the distribution and abundance of
organisms." (Krebs 1985)
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"...the study of the principles which govern
temporal and spatial patterns for assemblages of
organisms" (Fenchel 1987)
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"...the study of the relationships between
organisms and the totality of the physical and
biological factors affecting them or influenced by
them" (Pianka 1988)
More definitions for Ecology
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A common thread in many of these definitions is
that:
The Environment influences Organisms
AND
Organisms influence the Environment
The fact that the atmosphere contains
21% oxygen is a striking example of
the power of organisms (green plants)
to influence the environment.
The history of Ecology
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Rooted in natural history and efforts to
understand the distribution and abundance of
animals and, to a lesser extent, plants too.
The Greeks and much later, Europeans, were
strong believers in the balance of nature or
"providential ecology" -- the notion that nature is
designed for the benefit of each species, or at the
very least, for the benefit of humans.
This "balance of nature" view prevailed for a very
long time. You can even see a bit of this in some
modern natural history writing but this is no longer
seen in mainstream scientific writing.
Challenges to the Balance of Nature View
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1. Dinosaurs! Fossils discovered during late 1700s and
early 1800s. Why is this a problem?
2. Thomas Malthus, an economist who wrote “An essay on
populations” in 1798. He made two key observations:
 The number of humans can potentially increase at a
geometric rate through time, but;
 The food supply is likely to increase at only a linear rate
at best
Malthus concluded that human populations would be kept
in check by food supply and there would be intense
competition for that food supply.
The result: Intense social strife and war. Malthus’ book was
a bombshell!
Though Malthus intended his ideas to be applied to human
societies, could this idea be relevant to other animals and
plant communities?
An alternative to the Balance of Nature:
Charles Darwin
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The voyage of the
Beagle (1831-1836):
the ultimate internship
Darwin published a
sort of travel memoir
about his voyage in
1839
He continued to refine
his ideas about
evolution over the next
20 years
An alternative to the Balance of Nature:
Charles Darwin
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Darwin read Malthus upon his return and
applied these ideas to observations made
during his voyage.
1858: Charles Darwin and Alfred Wallace
independently develop and each publish a
theory on the evolution of species through
natural selection
Darwin’s major work On the Origin of
Species by Means of Natural Selection was
published on Nov. 24, 1859.
Charles Darwin
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By applying Malthus' logic to the natural world,
Darwin noted that overproduction of young
would lead to intense competition, heavy
mortality, and therefore to a "natural" selection
process.
Darwin’s great insight was that, given sufficient
time, one species might split into several new
species, each with adaptations shaped by the
selective pressures of climate, food supply,
predation and competition.
Charles Darwin’s book,
On the Origin of the Species
Published in 1859
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A key argument in his book was the emphasis on
competition between individuals of the SAME SPECIES
as the chief mechanism of evolutionary change.
It had long been acknowledged that predators prey most
heavily on the old, weak or diseased individuals. This was
viewed as a “good” thing since it preserved the character of
the prey population.
These authors failed to see, as Darwin did, the potential
that competition within a population could have for
producing real change in the character of the population.
Natural selection is therefore a creative force, not one
that merely preserves the character of a species.
Darwin’s ideas have gained widespread
acceptance and they have fundamentally
changed the way we view the natural
world