A community with more species variation have
(a) less variation in productivity
(b) more resistant to natural disturbances
(c) more resistant to invasion by alien species
(d) all.
Answers
Answer:
A community is a group of interacting species that inhabit a particular location at a particular time. Community ecologists study the number of species in a particular location and ask why the number of species changes over time. They also study communities in different locations, and ask why the number of species differs with location.
Community ecologists often study a narrow group of species. For example, a community ecologist who studies stream fishes may study the fishes that occur in small streams. Another community ecologist may study parasites of sharks. These narrower communities are defined as assemblages, species that share an attribute of habitat or taxonomic similarity, or taxon.
Multiple communities might be spread across an area. An interesting question becomes, why do the communities not have the same numbers of species or the same abundances of species? Comparisons can be made among communities using attributes such as species richness, species diversity, and evenness. Species richness is simply the number of species in a community. Species diversity is more complex, and includes a measure of the number of species in a community, and a measure of the abundance of each species. Species diversity is usually described by an index, such as Shannon’s Index H'. Species evenness is a description of the distribution of abundance across the species in a community. Species evenness is highest when all species in a sample have the same abundance. Evenness approaches zero as relative abundances vary. Species evenness can also be described using indices, such as the J' of Pielou (1975). Figure 1 is a simple diagram to describe species richness and species evenness. All diversity indices are criticized because they combine the number of species and the relative species abundances for one area into a single index, confounding these variables (Ludwig & Reynolds 1988).