Interactions in Ecosystems

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Interactions in Ecosystems

• Chapter 14

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Every organism in the biosphere lives in a given
habitat. The address

• The conditions that must exist for it to live
  within its habitat is the niche.

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Resource availability determines the structure of
a community
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Resource Partitioning
Increases Biodiversity
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Competitive Exclusion Principle
Two living separately okay, living together one
will cause the other to go extinct
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Species interactions defines the role and success
of each organism within the biosphere
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Predator Prey Interaction
What factors effect predator-prey relationships?
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Symbiosis- three forms

• 1. Mutualism- they both benefit!

Lichen- fungus and an algae, fungus provides the
home, algae provides the food, pioneer organism
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Symbiosis continued..
2. Commensalism one benefits the other is neither
helped nor harmed
3. Parasitism- one benefits, the other is
harmed
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There are two types of population growth curves
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Exponential growth- J curve
Human Population Growth

• Overshoots carrying capacity, does not respond to
  limiting factors, can cause a sudden die off

Our population is currently 6.7 billion people We
reached 6 billion in August 1999
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Logistic Growth- S curve

• Curve found in nature where species population is
  held in check by limiting factors.
• Limit of population is called the carrying
  capacity, fluctuates with climatic changes

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Limiting Factors factors that hold a population
in check

• Density-Independent factors
• Will kill everyone no matter what the density is
• Earthquakes, floods, volcanic eruptions
• Density-Dependent factors
• Increase as the population of species increases
• Competition, predation, disease

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P (B I) (D- E)

• P population
• B births
• I immigration
• D death
• E emigration

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Survivorship Curves- describe the life history
of a species
Type I few young take care of young
for a long period of time
Type III no care of young, they become part of
the food chain
Type II Have equal chances
of living or dying
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Primary Succession
There is no soil
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Secondary SuccessionA disturbed environment
Begins with weeds
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Fire SuccessionA form of secondary succession

• Many plant communities depend upon fire to
  germinate seeds and maintain health