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Interactions in Interactions in EcosystemsEcosystems
Chapter 14
Every organism in the biosphere lives in a given
habitat. The address
The conditions that must exist for it to
live within it’s habitat is the niche.
Resource availability Resource availability determines the structure of determines the structure of
a communitya community
Resource Partitioning
Increases Biodiversity
Competitive Exclusion Principle
Two living separately okay,
living together one will cause the other to go extinct
Species interactions Species interactions defines the role and defines the role and
success of each organism success of each organism within the biospherewithin the biosphere
Predator Prey Interaction
What factors effect predator-prey relationships?
Symbiosis- three forms
1. Mutualism
- they both benefit!
Lichen- fungus and an algae, fungus provides the home, algae provides the food, pioneer organism
Symbiosis continued…..
2. Commensalism one benefits the other is neither helped nor harmed
3. Parasitism- one benefits, the other is harmed
There are two types of There are two types of population growth population growth
curvescurves
Exponential growth- J Exponential growth- J curvecurve
Overshoots carrying capacity, does not respond to limiting factors, can cause a sudden die off
Human Population Growth
Our population is currently 6.7 billion people
We reached 6 billion in August 1999
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
Limiting FactorsLimiting Factors factors that hold a population in checkfactors that hold a population in check
Density-Independent factorsWill kill everyone no matter what the density is
Earthquakes, floods, volcanic eruptions
Density-Dependent factors
Increase as the population of species increasesCompetition, predation, disease
P= (B + I) – (D- E)
P= population
B= births
I= immigration
D= death
E= emigration
Survivorship Curves- describe the life history of a
species
Type III no care of
young, they become part of the food
chain
Type I few young take care of young for a
long period of time
Type II Have equal chances of
living or dying
Primary SuccessionPrimary SuccessionThere is no
soil
Secondary SuccessionA disturbed environment
Begins with
weeds
Fire SuccessionA form of secondary
succession
Many plant communities depend upon fire to germinate seeds and maintain health