Lecture 1 unit 4 Ecology The scientific study of the interactions between organisms and the environment o Ecology is studied at multiple levels of organization Individual Population a group of individuals of the same species living in an area Community a group of populations of different species in an area Ecosystem the community of organisms in an area and the physical factors with which those organisms interact Biosphere the global system the sum of all the planet s ecosystems and landscapes Global Ecology examines how the regional exchange of energy and materials influences the functioning and distribution of organisms across the biosphere o Ecology is the study of factors influencing the distribution and abundance of organisms Climate the long term prevailing weather conditions in a given area o Macroclimate patterns on the global regional and landscape level o Microclimate very fine localized patterns Global climate patterns are determined largely by the input of solar energy and earth s movement o Latitudinal variation in sunlight intensity o Solar radiation near the equator initiates a global pattern of air circulation and precipitation Surface heating drives air circulation Climate factors can be modified by seasonal variation in climate large bodies of water and in space mountain ranges o Ocean currents influence climate along the coasts of continents by heating or cooling overlying air masses that pass across the land Due to the high specific heat of water oceans and large lakes tend to moderate the climate of nearby land o When warm moist air reaches a mountain the air rises and cools releasing moisture on the windward side of the peak temperature and rainfall Mountains also affect the amount of sunlight reaching an area and thus the local The structure and distribution of terrestrial biomes are controlled by climate and disturbance o Biome major life zones characterized by vegetation type in terrestrial biomes or by the physical environment in aquatic biomes Terrestrial Biomes determined by temperature and moisture o Tropical Forest found in equatorial and subequatorial regions high precipitation high temperature little seasonal variation o Desert occur in bands near 30 north and south latitude or in the interior of continents low and highly variable precipitation highly variable temperature o Temperate Broadleaf Forest found mainly in midlatitudes in the northern hemisphere Zonation in aquatic biomes o Photic zone the upper layer where there is sufficient light for photosynthesis o Aphotic zone lower layer where little light penetrates o Pelagic zone made up of both the photic and aphotic zones o Benthic zone the bottom of all aquatic biomes deep or shallow Aquatic Biomes determined by proximity to shore light bottom vs open water and available nutrients o Lakes o Wetlands a habitat that is inundated by water at least some of the time and that supports plants adapted to water saturated soil o Streams and rivers o Estuaries a transition area between land and sea o Intertidal zones o Oceanic pelagic zone a vast realm of open blue water constantly mixed by wind driven o Coral Reefs formed largely from the calcium carbonate skeletons of corals in the photic oceanic currents zone o Marine Benthic Zone the seafloor below the surface waters of the coastal or neritic zone and the offshore pelagic zone Interactions between organisms and the environment limit the distribution of species o One factor that contributes greatly to the global distribution of organisms is dispersal the movement of individuals or gametes away from their area of origins or from centers of high population density o Biotic factors or other species may limit where a population lives even if it can disperse o Abiotic factors such as temperature water oxygen salinity sunlight or soil may also limit and adapt elsewhere a species distribution Lecture 28 Populations and Life History Chapter 53 1 53 2 Density the number of individuals per unit area or volume Dispersion the pattern of spacing among individuals within the boundaries of the population Mark recapture method one of the ways of estimating a population size o m number of individuals originally marked o n number of individuals in 2nd sample o x number of individuals in both samples o N estimated population size o x n m N ex m 180 n 44 x 7 N x n m N xN nm N nm x N 44 180 7 1131 4 Population density changes through births immigration the influx of new individuals from other areas mortality and emigration the movement if individuals out of a population and into other locations Patterns of dispersion o Clumped individuals are aggregated in patches Example starfish or fungi Can occur because of a particular resource or because of social interactions o Uniform evenly spaced Example king penguins o Random the position of each individual is independent of other individuals unpredictable Often due to territoriality spacing Example Dandelions Demography the study of the vital statistics of populations and how they change over time o Life tables age specific summaries of the survival pattern of a population o Cohort a group of individuals of the same age o Survivorship curve a plot of the proportion or numbers in a cohort still alive at each age Used to construct a life table 3 types of curves Type I a curve that is flat at the start reflecting low death rates during early and middle life then drops steeply as death rates increase among older age groups o Example many large mammals including humans Type II relatively straight diagonal line that indicates relatively constant rates of death looks like o Example squirrels Type III drops sharply at the start reflecting high death rates for the young but flattens out as death rates decline for those few individuals that survive the early period of die off o Example animals that produce a lot of offspring such as fish oysters etc Reproductive table or fertility schedule an age specific summary of the reproductive rates in a population A way of studying the demographics of sexually reproducing species Per capita rate of increase o N population size o N t Change in N with change in time bN dN where b and d are the rates of individuals dying or being born over the time interval in question t o b d r rate of increase o So N t rN change over time period t o Described as instantaneous change dN dt rinstN o Under ideal conditions you get exponential growth assumes that resources are unlimited and that there are no
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