April 22, 2009 ? Lecture Keystone Species Keystone Species By eating competitive species, they increase diversity EX: Otter Removal results in major changes in community dynamics May reduce species diversity Disturbances Definition: events that damage communities, removes organisms from them, alters the availability of resources ? followed by ecological succession Ecological Succession: a transition in species composition of a community following a disturbance 1. Primary Succession ? may or may not follow a disturbance ? it is the colonization of bare rock followed by lichens 2. Secondary Succession ? does follow a disturbance ? has soil present Disturbance is a natural part of an ecosystem Invasive Species Definition: an introduced species that becomes invasive (it spreads and colonizes and damages any suitable habitat it finds) ? alters interspecies interactions of native species EX: Rabbit ? (1950?s ? biological control ? they released a lethal rabbit virus) - Coevolution followed (it selected for resistant rabbits and less lethal forms of the virus) Coevolution makes biological control challenging *Click Question 5* Q: What type of relationship do the bunnies and the virus have? Competitive Symbiotic Mutualistic Predatory A: B Ecosystem Ecology Chemical Cycling: chemicals stay within an ecosystem Primary Production Biomass: the amount of living organic matter in an ecosystem Primary Production: the rate at which producers convert sunlight energy into chemical energy stored in biomass Some ecosystems produce more than others (per unit area) Energy Supply and Food Chains Food: biomass 1. break it down and convert it into energy in order to fuel chemical reactions 2. enhance or amend our biomass High level predators require a lot of territory to find food ? their territory has to support enough middle consumers so they can get adequate nutrients from their direct food sources Most food chains are limited to about 3-5 levels Meat is a luxury Nutrient Cycles Description: Recycle between 2 major reservoirs (biomass & abiotic reservoirs) Nutrients in the abiotic reservoir (soil, air, & water) are taken up by producers, converted into biomass, eaten by consumers, eaten by other consumers, ETC Biomass and abiotic reservoirs vary from nutrient to nutrient 2 Major Abiotic Reservoirs 1. Carbon dioxide in the atmosphere 2. Wood and Fossil Fuels Air and the food chain play a major role in the carbon cycle Nitrogen Cycle Decomposers play a huge role in nitrogen cycling Phosphorous Cycle The food chain plays a minimal role Chemical Cycle Disruption Chemical cycling depends upon? the integrity of the food web Drastic Alterations: total removal of vegetation = increases the runoff of soil nutrients >>> lose nutrients from the ecosystem Acid Rain: leaches calcium from the soil = inhibition of new plant growth >>> calcium is absolutely necessary for plants to grow Eutrophication Where does the nutrient runoff end up? Aquatic ecosystems Cultural eutrophication: nutrient runoff causes excess growth of algae and bacteria >>> use oxygen to produce energy at night Oxygen levels decrease at night = results in the death of other aquatic organisms and overall this reduces species diversity and harm water quality Phosphorous is the chemical that is particularly associated with eutrophication April 24, 2009 - Lecture Conservation Biology Definition: one of the only branches of biology that is goal driven ? it seeks to counter the biodiversity crisis Biodiversity Includes: 1. Genetic Diversity: makes micro-evolution and adaptation possible 2. Species Diversity: making sure communities stay diverse 3. Ecosystem Diversity: making sure that you have diverse habitats that are interconnected in energy and nutrients Benefits of biodiversity: 1. Valuable for its own sake 2. Provides food, clothing, shelter, medicines, & it provides basic ecosystem services (photosynthesis, decomposition, flood prevention)
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