Ecology and Biosphere

* Study of the interactions of organisms with each other and their environment

* Biotic-living * Abiotic- non-living BioticAbiotic Biotic Abiotic

* Population-group of organisms of same species in a specific area * Community- all the populations in an area * Ecosystem- community + abiotic factors * Biome- Major ecosystem that occupies a broad geographic region influenced by climate and characterized by dominant vegetation * Biosphere- all portions of Earth inhabited by life / all of Earth’s ecosystems

* Determined by… * sunlight, * temperature, * water, * wind, * elevation

A. Interactions 1. Competition—usually for resources * Niche—organism’s role in its environment ~Can’t have 2 species with the same niche in the same area because of the Competitive Exclusion Principle—2 extremely similar species cannot co-exist in the same place because one will be slightly better at getting the resources and reproduce more. * Resource Partitioning—resources are divided so that species can co-exist and each have it’s own niche

2. Predation * Animal  animal = predator / prey * Animal  plant = herbivory 3. Symbiosis * Mutualism (+,+) * Parasitism (+,-) * Commensalism (+, 0)

B. Trophic Structures * Food web—Messy = Stable

2. Length of Food Chain in Food Web * Energetic Hypothesis—food chain can’t be long because there is an insufficient transfer of energy (10% Rule) * Dynamic Stability—shorter chains are more stable because disruptions are magnified as you go up (the lower you wipe something out, the more effect it has )

C. Community Stability 1. Dominant Species—highest in terms of biomass (usually a plant) 2. Keystone Species—not most abundant but most important due to ecological role. If it’s removed from ecosystem there’s a major effect 3. Succession—Predictable sequence of communities that follow each other after a disturbance

* Succession Terms * Disturbance—what originally “damages” ecosystem * Primary Succession—start with a virtually lifeless area * Secondary Succession—start with some biomass left * Pioneer Species—first species to come into an area * Climax Community—end stage / stable / due to climate

A. Density: # of organisms/area * Quantitative * 2 lions per mile 2 * Qualitative * The density of lions in my backyard is sparse. B. Distribution: How organisms are arranged/placed * Determined by resources and social behavior

C.Survivorship: See reading D.Life histories: See reading

D. Population Growth * Variables: dY = amount of changeN = population size dt = change in timeK = carrying capacity B = number of births r max = maximum per D = number of deaths capita growth rate of population b = per capita birth rate m = per capita death rate Population Growth: dN = B – D OR dN = bN - mN dt

Density Dependent Factors: Population limiting factors whose effect depends on population density Density Independent Factors: Population limiting factors that are not dependent on population density

A. Productivity—turning light into sugars 1. Gross Primary Productivity (GPP)—amount of light energy converted to chemical energy in photosynthesis over time 2. Net Primary Productivity— (amount of GPP) – (energy used by plant in cellular respiration [R]) NPP = GPP – R 3. Limits on Production—sun (intensity, depth, penetration); limits on photosynthesis (water); limiting nutrients (N & P)

Net Annual Primary Production vs. Mean Annual Precipitation

B. Ecological Pyramids (See Pictures) 1. Production / Energy—amount of energy stored at each level 2. Biomass—amount of biological mass at each level 3. Numbers—number of organisms at each level

Biomagnification—retained substances become more concentrated as you go up the trophic levels

C.Greenhouse Effect—Carbon Dioxide (and other gases) allow light through but trap the heat it generates in the atmosphere Global Warming—due to increased carbon dioxide levels, causing increased greenhouse effect