Biodiversity is the variation in living organisms, viewed within a given habitat, ecosystem or in the world as a whole. The concept is usually applied to the species diversity, although the notion of genetic biodiversity is applied to the variation in genes within an individual species. While most people think of rainforests as loci of great biodiversity, biomes such as oceans and grasslands are the likely repositories for even greater variation. Retention of diverse biota is important, since intact ecosystems are thought to be essential for provision of ecosystem services to humans, including maintenance of a diverse foodbank, pollination, clean water, flood control, pest control, waste decomposition, biomass energy resources and climate stability. Biodiversity is presently critical since we live in the era of the Mass Holocene Extinction, a period of species loss caused by man, and unrivaled in rate of species loss. Although the number of total species numbers in the tens of millions, most have not yet even been described. The extinction of a species is almost always related to destruction of habitat or man-made pollution.
The Permian period lasted from 290 to 248 million years ago and was the last period of the Paleozoic Era. The distinction between the Paleozoic and the Mesozoic is made at the...
BiodiversityLast Updated on 2014-09-15 23:53:05
The word "biodiversity" is a contracted version of "biological diversity". The Convention on Biological Diversity defines biodiversity as:"the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species, and of ecosystems."
Thus, biodiversity includes genetic variation within species, the variety of species in an area, and the variety of habitat types within a landscape. Perhaps inevitably, such an all-encompassing definition, together with the strong emotive power of the concept, has led to somewhat cavalier use of the term biodiversity, in extreme cases to refer to life or biology itself. But biodiversity properly refers to the variety of living... More »
SpeciesLast Updated on 2014-09-15 11:53:19A species is a group of organisms capable of interbreeding and producing fertile offspring of both genders, and separated from other such groups with which interbreeding does not characteristically occur: however, for asexual organisms, a distinct species may be considered a collection of organisms which have very similar DNA or physical characteristics. Certain species are further subdivided into subspecies.
The early Greeks and Romans had a well established set of taxonomic names for species of animals and plants, based upon the macroscopically observable characteristics of organisms, with Aristotle being the chief architect of this codification; even earlier, the Egyptians and Cretans developed basic symbols and names for species important in farming and culture. It was not until the year 1686 when English naturalist John Ray introduced the concept that species were... More »
AmphibianLast Updated on 2014-09-09 10:57:59
The term amphibian comes from the Greek amphibios meaning "both lives". This is an apt description because most adult amphibians are better adapted to life on land than in water, while their larval phases are entirely aquatic.
For much of their lives, which may last a couple of months or several years depending on the species, larval amphibians bear little resemblance to their adult forms. Then something miraculous happens. In a matter of weeks or even days, the once fish-like larvae metamorphose into terrestrial, air-breathing quadrupeds!
There are three extant orders in the Class Amphibia: Anura (frogs and toads), Caudata (salamanders), and Apoda (caecilians). The order Anura has the most extant species, with 4000 members worldwide. Of Caudata, 390 salamander species exist worldwide. The third amphibian group, the caecilians, is smaller still with a total of only 162... More »
AngiospermLast Updated on 2014-09-09 10:39:17
The Angiosperms, or flowering plants, described taxonomically as the division Magnoliophyta, are the largest grouping within the plant kingdom (Kingdom ''Plantae'' or "Viridiplantae") in terms of the numbers of described species. Approximately 260,000 species of flowering plant have been named so far -- constituting nearly 90% of all known species of plants. Even so, taxonomists describe many new species annually, and estimates of total angiosperm diversity reach as high as 400,000 species. There are about 450 families of flowering plants, and they display extremely diverse life-histories and ecological adaptations. In addition to dominating plant biodiversity, angiosperms are the dominant photosynthesis/photosynthetic organisms (primary producers) in most terrestrial ecosystems (an important exception to this rule are the boreal forests,... More »
PlantLast Updated on 2014-09-08 22:26:25
A plant is any one of the vast number of organisms within the biological kingdom Plantae; in general, these species are considered of limited motility and generally manufacture their own food. They include a host of familiar organisms including trees, forbs, shrubs, grasses, vines, ferns, and mosses. Conventionally the term plant implies a taxon with characteristics of multicellularity, cell structure with walls containing cellulose, and organisms capable of photosynthesis. Modern classification schemes are driven by somewhat rigid categorizations inherent in DNA and common ancestry.
Throughout most of the history of science from Aristotle to Linnaeus and into the 20th century, species were divided into two kingdoms: animals and plants. Driven by DNA characterizations and other modern analysis, fungi and bacteria have now been removed to separate kingdoms; in particular,... More »
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