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