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Unformatted text preview: Measuring Extinction Rates Measuring Extinction Rates Species/area curves 90% loss in area results in 50% decline in species Minimum Viable Population estimates Minimum Dynamic Area Population Viability analysis Risk assesment analysis to determine persistance of a population Minimum Viable Population Minimum Viable Population Smallest number of individuals necessary to ensure population survival in a region for a specific time period Most indicate a few thousand individuals are necessary for survival beyond a few decades Minimum Dynamic Area Minimum Dynamic Area Minimum area of suitable habitat needed to maintain MVP Most small animals require 100—1000 square km 50 grizzly bears 49,000 square km Population Viability Analysis Population Viability Analysis Risk assessment model predicting viability of a population for a number of generations Based on: current resource needs and habitat conditions Genetic variability Reproduction rate Interaction with other species Types of Extinction Types of Extinction Local Extinction Species no longer found in an area, but still exists globally Ecological Extinction so few remaining members of a species exist, it no longer plays a role in ecosystem Biological Extinction Species no longer found Species Prone to Extinction Species Prone to Extinction Low reproductive rate Specialized niche Narrow distribution Fixed migratory patterns Rare Commercially Valuable Require large territories Factors Leading to Decline in Factors Leading to Decline in Species Environmental Stress Large Environmental Disturbance Extreme Environmental Conditions Resource Limitations Invasive nonnative species Geographic Isolation Ecosystem Structure Ecosystem Structure Ecosystems All of the organisms in a particular place and the environment with which they interact. Very complex systems difficult to predict how ecosystems will change with changes in environment, interactions with human activity. Communities The different populations of species found in ecosystem Ecosystem Energetics Ecosystem Energetics Flow of energy is the most basic interaction between organisms in an ecosystem Energy Flows From non living environment through living organisms and eventually lost as heat to environment. Autotrophs capture energy from the nonliving environment Chemosynthesis and Photosynthesis Autotrophs in turn provide food for heterotrophs The basic unit for energy flow is called a Trophic Level 1st Trophic level Producers (autotrophs) 2nd Trophic level Primary consumers Feed on Primary consumers (herbivores) 3rd Trophic level 2ndary consumers The collection of trophic levels makes a food chain or food web Most ecosystems can support 46 trophic levels Energy loss is significant at each transfer Plants capture about 1% of sunlight for photosynthesis Each trophic level assimilates 10% of the energy available from the previous level In most cases biomass of each level is at most 10% of previous level Decomposers recycle nutrients in organic material Nutrient cycles Parasites live in or on other individuals and cause harm Succession Succession Ecosystems change over time Succession Gradual change in species composition in a given area Pioneer species 1st to move in and colonize Climax community most stable Secondary succession follows a disturbance Species Interactions Species Interactions Competition When Resources are limited Mutualism Both organisms benefit Mycorhizae Flowers and Pollinators Plants and seed/fruit dispersers ...
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This note was uploaded on 12/16/2009 for the course BIOPL 2400 taught by Professor Silva,t. during the Fall '08 term at Cornell.
- Fall '08