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(Population Ecology (Turtle Tracks (each year along the Florida coast…

- - - - Investigating how factors such as predators and light affect the size of a loggerhead turtle population is and example of population ecology
  - - - Density and Dispersion
        
        In some cases population size and density can be determined by counting all individuals within the boundaries of the population
        
        dispersion is the pattern of spacing among individuals within the boundaries of the population
        
        Density: A dynamic perspective
        
        in some cases population size and density can be determined by counting all individuals within the boundaries of the population
        
        additions occur through birth and immigration the influx of new individuals from other areas
        
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  - - - imagine a population consisting of a few individuals living in an ideal unlimited environment
        
        changes in population size=births+immigrants entering population-deaths-emigrants leaving population
        
        Exponentional growth
        
        earlier we described a population whose members all have access to abudant food and are free to reproduce at their physiological capacity
  - - - we can modify our mathematical model so that the per capita population growth rate decreases as N increases.
        
        The logistic model and real populations
        
        the growth of laboratory populations of some small animals such as beetles and crustaceans and of some microorganisms such as bacteria paramecium and yeasts fits an S-shape curve fairly well under conditions of limited resources
  - - - Diversity of Life Histories
        
        reproductive begins, how often the organism reproduces and how many offspring are produced per reproductive episode
        
        "Trade-offs" and life histories
        
        no organism could produce thousands of offspring yet provision each of them as well as does a white rhinoceros caring for its single calf
  - - - to understand why a population stop growing when it reaches a certain size ecologists study how the rates of birth death immigration and emigration change as population density rises
        
        mechanisms of density-dependent population regulation
        
        the principle of feedback regulation applies to population dynamics
        
        population dynamics
        
        all populations show some fluctuation in size
        
        stability and fluctuation
        
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  - - - the human population has grown explosively over the last four centuries
        
        regional patterns of population change
        
        we have describe changes in the global population but population dynamics vary widely from region to region
        
        Age structure
        
        another important factor that can affect population growth is a country's age structure the relative number of individuals of each age in the population
        
        infant mortality and life expectancy
        
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- - - - population ecology- analyzes factors that affect population size and how and why it changes through time
        
        community ecology- examines how interactions between species such as predation and competition affect community structure and organization
        
        ecosystem ecology- emphasizes energy flow and chemical cycling between organisms and the environment
        
        Landscape ecology- focuses on the factors controlling exchanges of energy materials and organisms across multiple ecosystems
        
        global ecology- examines how the regional exchange of energy and materials influences the functioning and distribution of organisms across the biosphere
  - - - determined largely by the input of solar energy and Earth's movement in space
        
        Regional and Local effects on climate
        
        climate varies seasonally and can be modified by other factors such as large bodies of water and mountain ranges.
        
        Seasonality
        
        In the middle to high latitudes earth's tilted axis of rotation and its annual passage around the sun cause strong seasonal cycles in a day length solar radiation and temperatures
        
        Bodies of water
        
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  - - - because climate has a strong influence on the distribution of plant species it is a major factor in determining the locations of terrestrial biomes
        
        General Features of Terrestrial Biomes
        
        Most terrestrial biomes are named for major physical or cliimatic features and for their predominant vegetation
        
        Disturbance and Terrestrial Biomes
        
        Biomes are dynamic and disturbance rather than stability tends to be the rule
        
        in many biomes even the dominant plants depend on periodic disturbance
  - - - Many aquatic biomes are physically and chemically stratified vertically and horizontally as illustrated for both a lake and a marine environment
        
        Thermal energy from sunlight warms the surface warms to whatever depth the sunlight penetrates but the deeper waters remain quite cold
        
        in both freshwater and marine environments communities are distributed according to water depth degree of light penetration distance from shore and whether they are found in open water or near the bottom
  - - - one factor that contributes greatly to the global distribution of organisms is dispersal the movement of individuals or gametes away from their area of origin or from centers of high population density
        
        Natural Range Expansions and adaptive radiation
        
        the importance of dispersal is most evident when organisms reach an area where they did not exist previously called a range expansion
        
        Species Transplants
        
        to determine if dispersal is a key factor limiting the distribution of a species ecologists may observe the results of intentional or accidental transplants of the species to areas where it was previously absent
        
        Biotic Factors
        
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- - - - Competition
        
        competition is a -/- interaction that occurs when individuals of different species compete for a resource that limits the survival and reproduction of each species
        
        competitive exclusion
        
        even a slight reproductive advantage will eventually lead to local elimination of the inferior competitor an outcome called competitive exclusion
        
        ecological niches and natural selection
        
        competition for limited resources can cause evolutionary change in populations
        
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  - - - Trophic Structure
        
        In addition to species diversity the structure and dynamics of a community also depend on the feeding relationships between organisms
        
        Food Webs
        
        a food chain is not an isolated unit separate from other feeding relationship in a community
        
        limits on food chain length
        
        each food chain within a food web is usually only a few links long
        
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  - - - characterizing disturbance
        
        the types of disturbances and their frequency and severity vary among communities
        
        ecological succession
        
        changes in the composition and structure of terrestrial communities are most apparent after a severe disturbance such as volcanic eruption or a glacier strips away all the existing vegetation
        
        Human Disturbance
        
        ecological succession is a response to disturbence of the environment and the strongest disturbances today are human activities
  - - - in the 1850s both Charles Darwin and Alfred Wallace pointed out that plant and animal life was generally more abundant and diverse in the tropics than in other parts of the globe
        
        Area Effects
        
        in 1807 naturalist and explorer alexander von humboldt described one of the first patterns of species richness to be recognized the species are curve
        
        Island Equilibrium Model
        
        because of their isolation and limited size islands provide excellent opportunities for studying the biogeographic factors that affect the species diversity of communities
  - - - the ecological importance of disease can be highlighted by how pathogens have affected coral reef communities
        
        community ecology and zoonotic diseases
        
        3/4 of emerging human diseases and many of the most devastating established diseases are caused by zoonotic pathogens those that are transferred to humans from other animals either through direct contact with an infected animal