Interactions in Ecosystems 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 determines the structure of a community

Resource Partitioning Increases Biodiversity

Competitive Exclusion Principle Two living separately okay, living together one will cause the other to go extinct

Species interactions defines the role and success of each organism within 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 population growth curves

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

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 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

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

Primary Succession There is no soil

Secondary Succession A disturbed environment Begins with weeds

Fire Succession A form of secondary succession Many plant communities depend upon fire to germinate seeds and maintain health