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Transcript
ECOLOGY ECOLOGY examines… 1. 2. 3. 4. Distribution of organisms Frequency of organisms Interactions between organisms (biotic influences) Interactions between organisms and environment (abiotic influences) Levels of Ecological Study: Organismal Ecology Population Ecology Community Ecology Ecosystem Ecology Important Terms Species a group of organisms which can interbreed and produce fertile offspring Population a group of organisms of the same species who live in the same area at the same time Community a group of populations living and interacting with each other in an area Ecosystem a community, along with the ways in which all of the organisms interact with each other and the ways they interact with their abiotic environment The Biosphere Entire portion of Earth inhabited by life Atmosphere up to an altitude of several km Land down to and including water-bearing rocks 3km below ground Lakes, streams, caves and oceans down to a depth of several km The biosphere consists of all the world’s ecosystems, which are interdependent and interrelated Ecosystems function together in the biosphere Ecosystems are rarely isolated because organisms can move back and forth between them Examples of organisms moving between ecosystems Swallows spend winter in Africa and summer in Europe Examples of organisms moving between ecosystems Blackpoll warbler breeds in northern U.S. and in Canada, but migrates to South America for winter Examples of organisms moving between ecosystems Amphibians and several insects have larval stages in water, but as adults are on land or in the air Result of organisms moving between ecosystems Since the organisms feed and die, energy and nutrients move between ecosystems. Divisions of Biosphere BIOMES Tropical Rain Forests Deserts Savannas Taigas Grasslands Tundras Deciduous Forests Aquatic (fresh H2O/marine) http://earthobserv atory.nasa.gov/La boratory/Biome/ Population Ecology Pertains to the number and age groups of particular species found in a specific area, using the same resources. Offers explanations as to why the above changes over time. Population Size, Density, and Dispersion Size (N): total number of individuals in the population Density: number of individuals per unit of habitat area at a given time Dispersion: Pattern of spacing among individuals w/in geographic boundaries of population Dispersion Types: Random Uniform Clumped (aka Aggregated) Population Density as described by Age Structure What is Age Structure? no. of individuals @ each age What does AS tell about PD? Large portion of the population is young… RAPID POPULATION GROWTH Large number of old, small number of young … DECLINING POPULATION GROWTH Equal numbers of old and young … ZERO POPULATION GROWTH Population Density as described by Survivorship Curves Survivorship Curves: measure the mortality rates of individuals w/in a population Type I Survivorship Curve: Species where most individuals survive to middle age. After middle age, mortality increases Type II Survivorship Curve Random survival length for individuals in population. Death is likely at any age. Type III Survivorship Curve Most individuals die young. Few survive to reproduce. Measuring Change in Populations Critical Factors: Natality * Mortality * Immigrants Emigrants Population Growth Equation: N T = B-D N T = bN - dN Growth Rate Equation: r = b-d N r = reproductive (growth) rate Biotic Potential maximum rate at which a population could increase under ideal conditions. (rmax) Aka : Intrinsic Rate of Growth What affects Biotic Potential? Age at reproductive maturity No. of offspring @ each reproductive event Frequency of reproduction Reproductive lifetime Survival of offspring to repro. age Biotic Potential cont’d. Limiting Factors: those conditions that prevent a population from attaining its biotic potential May be density dependent or density independent Limiting Factors Density Dependent Limiting effect becomes more intense as population density increases Predation Disease Competition (intraspecific & interspecific) Density Independent Occur independent of population density Natural Disasters Extreme Climates Carrying Capacity (K) Maximum no. of individuals of a population that can be maintained for an indefinite period of time by a particular environment - Population Growth Patterns A. Exponential Growth: occurs whenever r > 0 Exponential Growth Curve B. Logistic Growth: occurs when limiting factors restrict size of population to the carrying capacity Growth slows as K is reached. Logistic Growth Curve How does Logistic Growth influence reproductive rate (r) ? Equation. When N is low, K-N K is large and :. r is only slightly changed from rmax When N is large and when resources are limited, K–N K Is small and :. Significantly lower than rmax So what does this all mean? Some species populations are naturally “r - selected” Ex: insects, weeds Some species populations are naturally “K – selected” Ex: humans