AP Bio: Ch.53: Population Ecology – Flashcards
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population ecology
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study of the biotic and abiotic factors that affect population size, density, distribution, and age structure
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population
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a group of individuals of a single species that occupy the same area at the same time
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what are 2 important characteristics that a population includes
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density (amount of individuals) and dispersion (how it's spread out)
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density
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number of individuals per unit area or volume
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the density increases by; decreases by
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births or immigration (organisms coming into a population); deaths or emmigration (organisms leave a population)
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what is an example of density
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Trees 5,000/km^2
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dispersion
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pattern of spacing among individuals of the population
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what are the 3 types of dispersion
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clumped, uniform, and random
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clumped dispersion
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most common form of dispersion; individuals are found in patches, usually around a required resource; may increase the chances of survival
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what are examples of clumped dispersion
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trees along a stream and flocks of birds around a pond
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uniform dispersion
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often the result of antagonist interactions between individuals
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what are examples of uniform dispersion
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territories and spacing between desert plants
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random dispersion
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often the result of the absence of strong attractions or repulsions between individuals; these are not a common pattern
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what is an example of random dispersion
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dandelion or any kind of flower
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demography
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the study of the vital statistics that affect population size
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what are examples of demography
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birth and death rates
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survivorship curve
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a graphic way to show birth and death rates in a population
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what are the 3 curve types of survivorship
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Type 1, Type 2, and Type 3
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Type 1
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low and early midlife deaths; high death rate in older age groups
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what are examples of a Type 1 survivorship curve
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humans and other large mammals (elephants)
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Type 2
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constant death rate over the life span
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what are examples of a Type 2 survivorship curve
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annual plants and many prey species (rodents/rabbits)
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Type 3
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high early death rates and low late deaths
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what are examples of a Type 3 survivorship curve
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trees, oysters, and frogs
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life history strategies
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traits that affect an organism's schedule of reproduction and survival make up it's life history
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life histories have 3 variables:
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when reproduction begins (age of sexual maturation), how often the organism reproduces, and the number of offspring in each reproductive event
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what are the 2 types of life history strategies
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1. "r" or opportunistic species and 2. "K" or equilibrial species
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"r" species increase their fitness by
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producing as many offspring as possible
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"r" species can increase their fitness by doing this:
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early maturation, many reproductive events, and many offspring
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the result of "r" species would be to
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maximize reproduction so that at least a few offspring survive to the next generation; however, most offspring die (TYPE 1 SURVIVORSHIP CURVE)
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"k" species increase their fitness by
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having the most offspring survive
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"K" species can increase their fitness by doing this:
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high parental care, late maturation, few reproductive events, and few offspring
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the result of "K" species would be to
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maximize survivorship of each offspring; they have few offspring, but the most survive (TYPE 1 SURVIVORSHIP CURVE)
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population growth is where---list equation
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(change in population)= N (change over time) = t === b (birth rate) - d (death rate)
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rate of increase
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r is equal to the difference between birth rate and death rate
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exponential growth is a characteristic of the
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"r" species; it produces a J-shaped growth curve; only holds for ideal conditions and unlimited resources
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logistic growth
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describes how a population grows more slowly as it nears it's carrying capacity where resources become limited when the population is too large; it is a characteristic of the "k" species
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K=
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carrying capacity
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carrying capacity of a population
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the maximum population size that a certain environment can support at a particular time
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K is not a
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constant value
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populations often oscillate around "K" as the
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environment changes
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populations often overshoot "K", then drop back to or below
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"K"
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what are the 2 types of regulation of population size
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density-dependent and density-independent factors
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density-dependent factors
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affect is related to the number of individuals in a population (N); as N increases, morality increases
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what are examples of density-dependent factors
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competition for resources, territoriality, disease, and predation
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density-independent factors
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affect is not realted to N; mortality is not related to population size; things that could affect population whether big or small
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what are examples of density-independent factors
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weather and climate; natural disasters like naturally occurring fires
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human population trends: our population is
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no longer increasing exponentially, but it is still increasing rapidly
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since about 1970. the rate of growth has
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fallen by nearly 50% because of geographic transition--fewer people are having less kids
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demographic transition occurs when
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a population goes from high birth rates to high death rates to low birth rates to low death rates
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the global carrying capacity for humans is
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not known
