Flashcards in chapter 18 Deck (54)
an assemblage of species living together in an area
Community zonation also occurs in
Communities are often categorized by their
dominant organisms or by physical conditions that affect the distribution of species.
Aquatic systems are often categorized by
physical characteristics (e.g., stream or lake communities) or by dominant organisms (e.g., coral reef communities).
Ecologists rarely study every species in a community; rather, they
focus on a subset of species that live in an area
a boundary created by sharp changes in environmental conditions over a relatively short distance, accompanied by a major change in the composition of species.
Some species move between
most species live in
one of the communities and spread into the ecotone.
Ecotones support a large number of species
including those from adjoining habitats, and species specifically adapted to the ecotone
communities in which species depend on each other to exist.
communities in which species do not depend on each other to exist.
If species are interdependent, removing a species should cause
other species to decline
if species are independent, removing a species should cause
neutral or positive changes in other species’ fitness
the # of species in a community.
the proportion of individuals in a community represented by each species.
In a typical community, only a few species have
low or high abundance
most species have intermediate
if a species has intermediate abundance they follow a
log normal distribution
a curve that plots the relative abundance of each species in a community in rank order from the most abundant species to the least abundant species.
a comparison of the relative abundance of each species in a community.
The species richness of a community can be affected by
the amount of available resources.
To understand the influence of resources, ecologists have examined the relationship between
productivity and species richness.
observed patterns across aquatic and terrestrial environments
what is the most commonly observed relationship between diversity and productivity
hump shaped curve
Experiments have manipulated productivity by
adding nutrients (e.g., nitrogen) to an ecosystem.
Added fertility commonly causes a decline in the species richness of
producers (e.g., plants and algae).
The reason species richness declines with increased habitat fertility
For plant communities, increased fertility may cause
dominant plants to cast more shade on competitively inferior plants.
Communities with a higher diversity of habitats should offer
more potential niches (e.g., places to feed and breed) and a higher diversity of species.