Ecology

1
Ecology

• Chapters 53 54 Review

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What is Ecology A Quick Review

• Word Derivation of Ecology
• Oikos Home or household
• Logos To Study
• To study home or household
• Ecology defined The scientific study of the
  interactions between organisms and their
  environments.
• The environment is made of two things
• Abiotic components (Non-living components)
• Temperature
• Light
• Water
• Nutrients
• Biotic components (Living components)

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Hierarchy in the Study of Ecology

• Organismal Ecology (Parts of Chapters 50 51)
• Concerned with how individual organisms deal with
  their physical environment (abiotic environment).
  
• Population Ecology (Chapter 52)
• Concerned with groups of individuals of the same
  species living in the same geographical area.
• Community Ecology (Chapter 53)
• Concerned with all organisms living in a
  particular area
• It deals with a variety of different populations
  of different species and their interactions with
  one another.
• It mainly deals with factors like
• Predation, Competition, Parasitism, Mutualism
• Ecosystem Ecology (Chapter 54)
• Concerned with the interrelationships between the
  organisms in a community and physical environment
  (all the abiotic factors).
• It mainly deals with
• The flow of energy through the system
• The cycling of chemicals

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Community Ecology Interspecific Interactions

• Since a community comprises all the species that
  occur at a particular location, one of the most
  important things about communities is how the
  species interact with one another.
• Four different types of interactions between
  different species (interspecific interactions)
  have been identified.
• Competition
• Two organisms mutually harm one another
• Predator-Prey or Parasite-Host
• One organism benefits, the other is harmed
• Mutualism
• Both organisms benefit
• Commensualism
• One organism benefits, the other is not affected

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Ecological Niche Concept

• Ecological Niche
• Sum total of an organisms use of the biotic and
  abiotic resources in an environment.
• It includes
• Space utilization
• Food consumption
• Temperature range
• Moisture requirements
• etc.
• Niche versus Habitat
• Habitat
• Like an address
• Where an organism lives
• Niche
• Like an occupation
• What an organism does
• Example Tropical Tree Lizards Niche
• Temperature range it tolerates
• Size of trees it lives on
• Time of day it is active

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Fundamental Niche versus Realized Niche

• Some species are not able to occupy their entire
  niche because of the presence or absence of other
  species.
• Interspecific competition occurs when two
  different species attempt to utilize the same
  resource and there is not enough of the resource
  for both species.
• Observation of this phenomenon in nature has led
  to the concepts of fundamental niche versus
  realized niche.
• Fundamental Niche The set of resources a
  population is theoretically capable of using
  under ideal conditions.
• Realized Niche The resources a population
  actually uses.
• The realized niche may be smaller than the
  fundamental niche because of interspecific
  interactions such as
• Competition
• Predation

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Joseph Connells Famous Experiment (pt 1)

• Two species of barnacles live in a stratified
  distribution in the intertidal region along the
  Scottish coast.
• Observation
• Balanus is most concentrated in the lower
  intertidal area.
• Chthamalus is most concentrated in the upper
  intertidal area.
• The free swimming larvae of each species can
  settle anywhere on the rocky shoreline and
  presumably be able to grow to be an adult.
• Question Why dont we see Balanus and Chthamalus
  growing together?

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Joseph Connells Famous Experiment (pt 2)

• Experiment 1
• Connell removed Chthamalus from the upper area
  and no Balanus replaced it.
• Conclusion Balanus could not survive in an area
  that experienced so much desiccation (due to low
  tides). Therefore, the fundamental niche and
  realized niche for Balanus was the same.
• Experiment 2
• Connell removed Balanus from the lower area and
  Chthamalus replaced it.
• Conclusion Balanus was a more successful
  competitor in the lower intertidal zone.
  Therefore, the fundamental niche and realized
  niche for Chthamalus were not the same. Its
  realized niche was smaller due to interspecific
  competition.
• Conclusion
• Competition occurs in nature and can explain the
  distinction of a fundamental niche from a
  realized niche.

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Competition The Competitive Exclusion Principle
(pt 1)

• Lotka and Volterras Theory
• These two biologists predicted that no two
  species with similar requirements for resources
  (food, shelter, etc.) could coexist in the same
  niche without competition driving one to local
  extinction.
• Gauses Experiment
• A Russian scientist, G.F. Gause, tested the
  Lotka-Volterra theory.
• Used two different species of Paramecium
• Grew them each alone under identical conditions.
• Populations grew to their carrying capacity and
  leveled off- showed a logistic growth pattern
  (see graph).
• Put them together and discovered that one species
  died out (it couldnt compete)

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Competition The Competitive Exclusion Principle
(pt 2)

• Conclusion
• Two species competing for limited resources
  cannot coexist in the same place at the same
  time.
• This concept was named the competitive exclusion
  principle ( or Gauses Principle)

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Resource Partitioning

• Consequences of Gauses competitive exclusion
  principle
• If competition for a limited resource is intense,
  then
• Either one species will drive the other to
  extinction
• Or natural selection will reduce the competition
  between them.
• Robert MacArthur of Princeton University did a
  famous study, in the late 1960s, of 5 species of
  warbler (small insect eating songbirds).
• It appeared that they all were competing for the
  same resources on spruce trees.
• On closer inspection he realized the 5 species
  were each feeding on different parts of the tree
  and therefore eating different insects (see
  illustration).
• In essence, each species had evolved to utilize a
  different portion of the spruce tree resource.
  They had subdivided the niche, partitioning the
  available resource to avoid direct competition
  with one another.
• This process became known as resource
  partitioning.

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Character Displacement

• A comparison of allopatric versus sympatric
  populations of species shows evolutionary
  evidence of competition in nature.
• Example Galapagos Finches
• When two species occur on the same island
  (sympatric populations) they tend to exhibit
  greater differences in morphology (shape of beak)
  and resource use than when found on different
  islands (allopatric populations).
• According to your text, This tendency for
  characteristics to be more divergent in sympatric
  populations of two species than in allopatric
  populations of the same two species is called
  character displacement.
• Character displacement allows the two species to
  avoid competition.

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Insterspecific Interactions and Community
Structure

• A huge question that has occupied ecologists is
  the influence of interspecific interactions
  (competition, predation, mutualism, etc.) on the
  structure of a community.
• One of the most dramatic examples of the
  interdepency of species and community structure
  is in the concept of keystone species.
• The classic experiment was done by Robert Paine
  of the University of Washington in the intertidal
  region.

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Keystone Species (1)

• Robert Paines famous experiment involved two
  species of intertidal invertebrate, the sea
  star, Pisaster ochraceous, and mussel, Mytilus
  californicus.
• Normally these two different species live in a
  harmonious balance in their intertidal community.
  
• The sea star is an important predator. When Paine
  removed this predator from experimental areas,
  what had been diverse communities of algae and
  invertebrates (like what we saw when we snorkeled
  at Catalina Island), became overgrown with solid
  stands of the California Mussel!!
• So, even though the California Mussel is a good
  competitor, its populations had been held in
  check by sea star predation. With the predator
  gone, the species diversity and structural
  complexity of the habitat changed radically.

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Keystone Species (2)

• Keystone Species
• A term coined by Paine to indicate a species that
  has an exceptionally great impact on the
  surrounding species relative to its abundance.
• Another Example
• Sea Otters are a keystone species.
• They feed heavily on large herbivorous
  invertebrates such as sea urchins.
• When sea otters keep sea urchin populations low,
  the huge algae (called kelp) can grow more
  readily and form forests that are home to a
  diversity of fish and invertebrates.
• If sea otter populations are reduced then the
  near shore community is overrun with sea urchins
  and species diversity is reduced.