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Chapter 3
The Principles of
Ecology
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I- The Beginning of Ecology
Natural history lead to ecology
• Science that studies the interaction
between organisms and their
environment
• Combines knowledge between many
sciences: Biology, chemistry, physic and
earth science
I- B. The living Environment:
Biotic factors
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• All living things are found in a layer
called the Biosphere
• Biosphere is made up of different
environments : Aquatic / Terrestrial
• Environment consist of
–Nonliving factors ( Abiotic factors)
–Living factors ( Biotic factors)
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I- C. Abiotic Factors
• Abiotic factors can have obvious
effects on living things and often it
determines which species can
survive.
• Example: Grasslands only support
small plants and many grassing
animals
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II- Levels of Organization
• All organisms depend on others for food,
shelter, reproduction or protection.
• Ecologist study interaction among
organisms at several different levels.
• Levels of organization provide a tool to
use in planning their research.
–Example: Studying bees Vs. foxes
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Levels of organization. Page 59
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Individual
Populations
Communities
Ecosystem
Biospheres
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II- A. Interaction within Populations
KINDS OF COMPETITIONS:
• among individuals in a population
• between populations in a community
• between communities in an Ecosystem
HOW TO AVOID COMPETION
• Alternating generation
• Metamorphosis
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ALTERNATING GENERATION
METAMORPHOSIS
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II- B. Individuals interact in
Communities
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• No population or organisms lives
independently of other species.
• Community is a collections of
interacting populations
• Change in one population causes change
in another
–Example: more people less vegetation
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II- C. Interaction between Abiotic
and Biotic factors
• Ecosystems are interaction among the
populations in a community and their
physical surroundings.
• Kinds of ecosystems:
–Terrestrial
–Aquatic ( 75% of earth’s surface)
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II- D. Where and how organisms live
• Every organism plays a role in their
community
• All help maintain a balance
(Homeostasis)
• Role played is the organism’s NICHE
• Habitat is place where organism lives
–many species usually share habitats
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III- How organisms Interact
Feeding relationships: How organisms
obtain energy
• Autotrophs = capture and store light
energy
• Heterotrophs = depend on autotrophs for
a food source
• Carnivores = organism that depends on
other heterotrophs as a food source
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III- How organisms Interact part 2
• Scavengers = depend on dead organisms
as food source
• Omnivores = eat a variety of food both
plants and animals
• Decomposers = break down and absorb
nutrients from dead organisms
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III- B. Close relationship for survival
• Symbiosis : close and permanet
association between organisms of
different species.
• Commensalism: one species is benefited
and the other is neither helped or harmed
• Mutualism: both species benefit
• parasitism: one benefits at the expense of
the other
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III- B. Close relationship for survival
• more Symbiotic relationships
–parasitism: one benefits at the expense
of the other
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IV- A. Matter & Enery in Ecosystem
• Food Chain
–each link provides less energy then the
previous. (energy loss by heat and
motion)
–3links in a food chain good / 5 are bad
–each level or link is called a Trophic level
–many food chains cross and interconnect
this is called a (Food Web)
Food Web
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Pyramid numbers
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Energy Pyramid
IV- C. Cycling maintains
Homeostasis
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Water cycle
Carbon dioxide cycle
Nitrogen cycle
Phosphorus cycle
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Water cycle
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Carbon Dioxide cycle
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Nitrogen cycle