AP Biology Review – Ecology part 1

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Ecology
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The study of the distribution and abundance of organisms and their interactions with the world and others
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Population
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Group of individuals all of the same SPECIES LIVING in the SAME AREA.
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Community
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Group of populations living in the same area.
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Ecosystem
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This describes the interrelationships between the organisms in a community and the environment.
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Biosphere
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This is composed of all the regions on the earth that contains living things. IE soil, oceans, lower 10 km of the atmosphere.
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Habitat
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Place where organisms live. Can be described through temperature, soil quality, water salinity.
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Niche
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Describes all the biotic (living) and abiotic (nonliving) resources in the environment used by an organism.
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Population Ecology
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Study of the growth, abundance, and distribution of populations.
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Size (of a population)
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Total number of individuals in the population (Represented by N)
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Density (of a population)
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The total number of individuals per area of volume occupied. (IE 100 mice/km^2)
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Dispersion
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Describes how individuals in a population are distributed. (IE clumped [people in cities], uniform [trees in orchards], or random [trees in forest])
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Age Structure
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Describes the abundance of individuals of each age; Often shown in age structure diagrams.
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Survivorship Curves
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Describes how mortality of individuals in a species varies during their lifetimes.
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Type I Survivorship Curve
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Curve that describes species where most individuals survive to middle age. After that, mortality is high. (humans)
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Type II Survivorship Curve
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Curve that describes organisms in which the length of survivorship is random, death likelihood is the same at any age. (rodents and hydras)
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Type III Survivorship Curve
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Curve that describes species in which most individuals die young, with only a few organisms surviving long enough to reproduce and beyond. (oysters, plankton)
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Biotic Potential
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Maximum growth rate of a population under ideal conditions, with unlimited resources and without growth restrictions
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Factors that may affect biotic potential
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Age to reproduce, Clutch size (# of offspring produced at reproduction), Frequency of reproduction, Reproductive lifetime, and Survivorship of offspring long enough to reproduce.
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Carrying Capacity
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Maximum number of individuals of a population that can be sustained by a particular habitat.
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Limiting Factors
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Elements that prevent a population from attaining its biotic potential.
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Density-Dependent Factors
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[a limiting factor] Agents whose limiting effect becomes more intense as the population density increases (IE parasites/disease, resources, toxic effect of waste products, and predation)
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Density-Independent Factor
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[a limiting factor] Occurs independently of the density of the population (IE natural disasters, climate change)
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Equation for the growth of a population
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r=(births – deaths)/N where r=reproductive/growth rate and N=initial population size
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Exponential Growth
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Pattern of population growth that occurs whenever the reproductive rate is greater than zero. (Forms a J-shaped curve when graphed)
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Logistic Growth
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Pattern of population growth that occurs when limiting factors restrict the size of the population to the carrying capacity of the habitat.(Forms an S-shaped curve [a sigmoid] when graphed.
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Population Cycles
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Fluctuations in population size in response to varying effects of limiting factors
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r-selected species
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Species that exhibit rapid growth (J-shaped curve), where opportunistic species (grass/insects) quickly invade habitats, reproduce, and die. Offspring are small, mature fast, and require little care
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k-selected species
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Species where population size remains constant (IE humans) and produce a small number of relatively large offspring that require much care until maturation.
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Human Population Growth
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Growth that began 1000 years ago, grew exponentially.
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Exponential Growth Factors [of humans] include
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Increase in food supply, reduction in disease, reduction in waste, expansion of habitat

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