Community Ecology 2 & Ecosystems Ecology PDF

Community Ecology 2 and Ecosystems Ecology: Tropic Structure of a Community: note there are many levels to the food chain. See figure 37.8 in v.8 of text. Food Webs: of course it is more complex than that, there are actually many organisms at each layer, and an organis...

Community Ecology 2 and Ecosystems Ecology: Tropic Structure of a Community: note there are many levels to the food chain. See figure 37.8 in v.8 of text. Food Webs: of course it is more complex than that, there are actually many organisms at each layer, and an organism can be considered to be in more than one layer. An organism may be on more than one trophic level in a food web. For example, the mouse in the illustration above is a primary consumer as it eats leaves and seeds of plants, but also a secondary consumer as it eats grasshoppers (which are primary consumers as it eats leaves and seeds of plants) 50-55% indigestible and passed as Energy budgets of trophic levels: “frass”. 35 – 40% used up in processing energy. 1% of the energy from the sun is converted by plants into energy for the next trophic level (primary 5 – 20 % left for consumers). 1,000,000 k cal sunlight  10,000 kcal biomass of plant material. 100 kilocalories plant matter caterpillar (kcal) 10 % of energy is transferred from each of the trophic levels to the next higher one (or 90% or energy is lost: 1 Here is a model of the energy budget in a food chain: Tertiary 10 kcal consumers 100 kcal Secondary consumers Primary 1,000 kcal consumers 10,000 kcal Producers 1,000,000 kcal of sunlight NOTE: From producer to primary consumers 90% of the energy is lost and 10% is maintained in the animal and available for the next higher level of consumer. Implications: 1 Limit to the number of trophic levels No more energy in an ecosystem. 2. It is more efficient to eat plants than animals: 2 Nutrient cycling: Biogeochemical cycles are generalized cycles that chemicals take that involve the biotic and the abiotic components of an ecosystem. The diagram to the right shows a generalized biogeochemical cycle. The boxes represent reservoirs (or pools) where nutrients are stored. The arrows represent fluxes, or movement of nutrients between reservoirs. We will discuss 2 nutrient cycles: carbon (C) and nitrogen (N). The carbon cycle Carbon (C) is the major chemical ingredient of life. All life on Earth depends on carbon. The major carbon reservoirs are the atmosphere, rocks and soils, and the ocean. Fig. 37.19 in your book shows the carbon cycle. Through the process of photosynthesis, plants remove CO2 from the atmosphere and incorporate it into molecules that can then be consumed by primary consumers (such as rabbits). Carbon is passed along the food chain to secondary consumers (and so on). CO2 is returned to the atmosphere through respiration, and when detritus (dead material) is broken down by decomposers. Humans are having a major influence on the carbon cycle. By burning fossil fuels and trees, humans move CO2 from terrestrial pools back into the atmosphere very rapidly. 3