Population & Community Ecology (College Board AP® Biology): Flashcards
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- FrontPopulation Ecology
Define population.
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Cards in this collection (28)
Define population.
Population is a group of organisms of the same species, occupying a particular space at a particular time.
Define population dynamics.
Population dynamics are the changes in a population's size, structure and composition over time.
According to the equation dN/dt = B − D, on which two rates does the growth of a population depend?
The birth rate (B) and the death rate (D).
What two broad categories of factor determine whether a population grows or declines?
Biotic factors (living, e.g. predation, competition) and abiotic factors (non-living, e.g. temperature, water availability).
Define exponential growth.
Exponential growth is the growth of a population when reproduction is unconstrained, described by dN/dt = rmaxN and producing a J-shaped curve.
In the exponential growth equation dN/dt = rmaxN, rmax is the maximum per capita of a population.
In the exponential growth equation dN/dt = rmaxN, rmax is the maximum per capita growth rate of a population.
True or False?
Exponential growth produces a J-shaped curve.
True.
When reproduction is unconstrained the population increases faster and faster, giving the characteristic J-shaped curve.
Define density-dependent factor.
Density-dependent factor is a factor that has a stronger effect as population density increases, e.g. competition for resources, predation and disease.
Define density-independent factor.
Density-independent factor is a factor that affects a population regardless of its density, e.g. natural disasters and extreme weather.
What shape is the population growth curve described by the logistic growth model?
A sigmoid, or S-shaped, curve.
Name the four phases of the logistic growth curve, in order.
Lag phase
Exponential (logarithmic) phase
Transition phase
Plateau (stationary) phase
Define carrying capacity.
Carrying capacity is the maximum population size an ecosystem can support sustainably, based on available resources and environmental conditions.
The plateau phase of logistic growth occurs at the , where the environment cannot sustain further increase.
The plateau phase of logistic growth occurs at the carrying capacity, where the environment cannot sustain further increase.
True or False?
If a population exceeds its carrying capacity, it will simply continue to grow.
False.
If a population exceeds carrying capacity, resource depletion causes the population to decline until balance is restored.
Define community.
Community is a group of interacting populations of different species that live in the same area and change over time based on the interactions between those populations.
Define species diversity.
Species diversity is a measure of community structure that takes into account both the number of different species in an area (species richness) and the evenness of abundance across those species (species evenness).
Define Simpson's index of diversity.
Simpson's index of diversity is a value (D) used to quantify the biodiversity of an area based on the abundance of the different species present.
What two components of a community does species diversity take into account?
Species richness — the number of different species in an area
Species evenness — the evenness of abundance across those species
In Simpson's index formula, is the total number of organisms of a single species, while N is the total number of organisms of all species.
In Simpson's index formula, n is the total number of organisms of a single species, while N is the total number of organisms of all species.
What are the steps used to calculate Simpson's index of diversity?
Step 1: calculate n / N for each species
Step 2: square each of these values
Step 3: add them together and subtract the total from 1
What does a Simpson's index value close to 1 indicate about an area?
A high level of biodiversity. Values of D range from 0 to 1, and values near 1 indicate high biodiversity.
True or False?
A Simpson's index of diversity (D) value near 0 indicates high biodiversity.
False.
A value near 0 indicates low biodiversity; it is values near 1 that indicate high biodiversity.
Define niche partitioning.
Niche partitioning is when natural selection drives species to occupy slightly different niches, or use resources slightly differently, in order to reduce competition.
Define trophic cascade.
Trophic cascade describes the effects of adding or removing a top predator from a food web, which impacts all species and the distribution of energy through the community.
What are the three types of symbiosis that can drive population dynamics?
Parasitism — one organism is harmed while the other benefits
Commensalism — one organism benefits while the other is neither helped nor harmed
Mutualism — both organisms benefit
In a symbiotic relationship called , both organisms benefit, e.g. oxpeckers feeding on ticks from the backs of rhinos.
In a symbiotic relationship called mutualism, both organisms benefit, e.g. oxpeckers feeding on ticks from the backs of rhinos.
True or False?
The structure of a community is dependent on energy availability.
True.
Survival of species relies on sufficient energy being available in the previous trophic level, which then determines the energy and matter available to the next.
Why can a change to community structure affect many different species?
Because the species within a community are interdependent, so a change has a knock-on effect on all species that rely on those interactions.
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