Lecture 01
Ecology
Ecology as a Science
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What is ecology?
Characteristics of living things
Levels of organization of living things
Levels of organization of ecosystems
Basic relationships within ecosystems –
terminology
• Scientific logic – how we know (what we
think) we know
Living things are organized as organisms:
Atoms  compounds cells tissues 
organs and organ systems  organisms
All living things composed of cells
Not all organisms show all these levels of
organization!
Populations – single organisms – basic unit
in ecology - fill a niche (‘job’ or function)
communities - populations of many
types of organisms
ecosystems: All organisms
living in an area, and the physical
environment (habitat) with which these
organisms interact.
• "When we try to pick out anything by itself,
we find it hitched to everything in the
universe.“ John Muir
• Populations
• All the members of one species that live in
the same area make up a population.
• Community
• A community, together with its non-living
environment is referred to as an
"ecosystem".
• Pond
Tundra
• Largest Ecosystem is the Biosphere
Ecology vs. Environmentalism
Environmentalist:
• Save the world!
– An emotion, a cause
Ecologist:
• Understand the world!
– How does it work – uses scientific method
– Poses specific questions in the form of
hypothesis
– Involves controlled experiments and detailed
study
Observation: Hydrangeas of the same variety but
growing in different parts of the garden have
different colors.
Hypothesis: Something about the soil is different;
perhaps acidity (pH).
• Set up experiment to test hypothesis:
– Grow one group of Hydrangeas in acid pH
– Grow second group of hydrangeas in soil with
basic pH
– Keep everything else the same
– Observe:
Acid pH
Alkaline pH 
Scientific Theory
• Hypotheses are tentative explanations
– phenomenon in a particular situation
• Theories are widely accepted
explanations
– Support from many lines of evidence
– Basis of understanding
– May be revised or modified
– Theory of Evolution
Warbler Feeding Zones
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Organisms Require Resources
• Energy flows through ecosystems
– Trophic levels = ‘feeding’ levels
– Some energy is lost during transfer to each
higher trophic level
• Materials cycle
– Carbon, phosphorus, nitrogen, water cycle
through biotic and abiotic aspects of
ecosystems
– Global in scale
Biotic cycling
Biotic and Abiotic
Nutrients Cycle
• Include things like carbon, nitrogen,
phosphorus
– Some required in greater concentrations than
others
– Excesses may be toxic
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Top carnivores
Carnivores
Birds of prey
Herbivores
Photosynthesizers
Decomposers
Humans
Birds
Mammals
Mammals
Birds
Inorganic
nutrients
Arthropods
Fish
Meiofauna
Inorganic
nutrients
Bacteria and fungi
Algae
Inorganic
nutrients
Mollusks
Annelids
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Summary
Ecology is an investigative science that relies
on the scientific method
The scientific method requires observation,
creation of a hypothesis, and data collection to
refute or support the hypothesis.
Ecology and evolution are two separate
disciplines that overlap in their investigation of
the natural world.
An understanding of ecology may lead us to
sound environmental decisions