BIO 101 1nd Edition Lecture 21 Outline of Last Lecture II What is ecology III Density Dependent factors IV Poverty in India V Variation Outline of Current Lecture VI Biosphere VII Carbon cycle VIII Nitrogen cycle Current Lecture The Trophic structure of an ecosystem describes the feeding relationships Energy enters an ecosystem as sunlight Trophic level 4 tertiary consumers Trophic Level 3 Secondary consumers Trophic Level 2 Primary consumers Trophic Level 1 primary producers autotrophs self feeders Decomposers break down nonliving matter At each energy conversion heat is released Elements cycle through the biosphere Energy flows through ecosystems Chemical elements such as carbon and nitrogen cycle through the biosphere Elements move from abiotic reservoirs such as air soil and water to biotic components of ecosystems in a biogeochemical cycle These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Biogeochemical cycles occur both locally and globally Abiotic reservoirs o Include the atmosphere rocks and ocean Biotic Reservoirs o Living things The carbon cycle is an example of a biogeochemical cycle The carbon cycle is affected by human activities primarily the burning of fossil fuels which releases trapped carbon into the atmosphere as CO2 The nitrogen cycle is an example of a biogeochemical cycle Nitrogen is only available to living things after soil bacteria convert N2 to compounds that plants can take up Human effects on the nitrogen cycle are show in red Is energy recycled NO Energy flow is one way o Energy input from sun autotrophs heterotrophs Energy is transformed from one form to another o Light energy heat energy o Light energy chemical energy heat energy HEAT ENERGY CANNOT BECOME ANY FORM OF ENERGY THAT ORGANISMS CAN USE TO LIVE Too much nitrogen or phosphorus Abundance of nutrients o Leads to Increased pant growth o Leads to Unbalanced food web o Leads to Dead plants being decomposed which removes oxygen from the water called HYPOXIA o leads to Death of many organisms Acid rain occurs because the following biogeochemical cycle is disrupted Nitrogen and Sulfur Which state has the most acidic precipitation Pennsylvania Most of the coal burning power plants are in the Midwest and southeast So why is there more acidic rain on the eastern united states Prevailing winds from the west Energy transformation is wasteful Net primary productivity Different ecosystems can be compared by the amount of energy their primary producers can store in their tissues Limiting factors abiotic factors that limit the primary productivity of an ecosystem o Amount of water o Amount of sunlight o Availability of nutrients o Appropriate temperatures Abiotic limiting factors Terrestrial biomes are limited by o Temperature o water Aquatic Biomes are limited by o Energy o Nutrients Ecologists categorize the earth surface into a series of biomes Very important Because limited energy is available to organisms the survival of an organism depends on the ability to get enough energy Therefore organisms must compete with other organisms of their same species and with other species in order to survive Biologists describe smaller environments as habitats What does a habitat contain o Biotic factors o Abiotic factors How is a habitat related to a community What is a niche A set of conditions within which an organism can maintain a viable population abiotic and biotic factors too More than just a place for living a niche is a complete way of living Niche Features o The space an organism requires o The types and amount of food an organism utilized o The timing of an organisms reproduction o An organisms temperature and moisture requirements and other necessary living conditions You cant always get what you want Fundamental niche o The full range of environmental conditions under which a species can live Realized niche o Where and how a species is actually living Competition for resources between different species two outcomes Competitive exclusion two species cannot occupy the same niche Or o Resource partitioning Keystone species who is top dog A species who absence would create significant change in a community Often top predators Not all communities have keystone species