Researchers, physicians, and others have investigated the dark crevices of the gene, trying to untangle clues that might indicate that gene function could be altered by more...
CactusLast Updated on 2015-04-08 23:49:44Cactus is a family of plants that are specially adapted to survive arid conditions, most often having leaves reduced to spines, and succulent characteristics. The scientific family name Cactaceae is applied to this group comprising 121 different genera. This plant family is concentrated in the Americas and has a surprisingly broad latitude range in both the Northern and Southern Hemispheres.
A considerable number of cacti species are threatened, chiefly due to habitat loss to agriculture, trampling by illegal human immigration into the southwestern USA, large-scale desert solar power projects, as well as overcollecting.
The cactus family is generally considered native to the Americas. A notable exception is Mistletoe cactus, Rhipsalis baccifera, which is thought to have spread, fairly recently, from the American tropics to the subtropics and the deserts of the... More »
PredationLast Updated on 2015-02-28 19:11:16
Predation is an interaction between species in which one species uses another species as food. Predation is a process of major importance in influencing the distribution, abundance, and diversity of species in ecological communities. Generally, successful predation leads to an increase in the population size of the predator and a decrease in population size of the prey. These effects on the prey population may then ripple out through the ecological community, indirectly changing the abundances of other species. One example of such indirect effects of predation involves the trophic cascade. As the name implies, a trophic cascade occurs when the effects of predation "cascade" down the food chain to affect plants or other species that are not direcrtly eaten by the predator. Typically, a trophic cascade involves a predator feeding on herbivores and reducing their abundance,... More »
Species diversityLast Updated on 2014-12-07 19:11:57
Species diversity is a measure of the diversity within an ecological community that incorporates both species richness (the number of species in a community) and the evenness of species' abundances. Species diversity is one component of the concept of biodiversity.
Species diversity is influenced by species richness. All else being equal, communities with more species are considered to be more diverse. For example, a community containing 10 species would be more diverse than a community with 5 species.
Species diversity is also influenced by the relative abundance of individuals in the species found in a community. Evenness measures the variation in the abundance of... More »
Species richnessLast Updated on 2014-11-09 19:13:40Species richness is simply the number of species present in a sample, community, or taxonomic group. Species richness is one component of the concept of species diversity, which also incorporates evenness, that is, the relative abundance of species. Species diversity is one component of the broader concept of biodiversity. About 1.75 million living species and 300,000 fossil species have been described by scientists. Estimates of the total species richness of the Earth range from three to 10 million, with some estimates as high as 50 million.
Patterns of species richness can be observed at a variety of levels. The causes of these patterns remain active areas of research in ecology, biogeography, and evolutionary biology.
Some taxonomic groups of organisms have more species than other groups. For example, there are almost three times more species of beetles (Order Coleoptera) than... More »
Species range limitsLast Updated on 2014-11-09 18:49:44Species range limits (SRLs) are defined as the spatial boundaries beyond which no living individuals of a given species occur. Populations occurring near or at SRLs are often referred to as “marginal,” “peripheral,” “edge,” or “border” populations. SRLs may represent areas beyond which individuals cannot physiologically tolerate ecological conditions or areas where they have not yet dispersed. SRLs may be stable (i.e., at equilibrium) or may represent areas where range expansion through migration or population growth is in the process of occurring. SRLs are significant to ecology, evolution, and conservation for several reasons. They provide opportunities to understand the conditions under which populations expand or contract, and the conditions under which populations may evolve new forms. Additionally, SRLs... More »
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