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...
MammalLast Updated on 2014-10-15 22:58:09
Mammalia is a group of warm-blooded, air breathing vertebrates. With the common name mammal, each species is endowed with the characteristic of fur and three-boned middle ear; but the most remarkable element of group identity is an advanced brain element known as the neocortex, that functions as a center of complex cognition; no species except mammals have this well defined brain structure. Having pronounced inherent sexual dimorphism, the females have mammary glands capable of producing milk. There are approximately 5400 described mammalian species comprising around 1200 genera.
Mammals span a size range from the three centimeter Bumblebee Bat to the 33 meter long Blue Whale. Feeding habits vary widely among species, including carnivores and insectivores who prey on animals, to frugivores and granivores who eat fruit or seeds. Earliest mammals arose approximately 200 to 130... 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 »
GymnospermLast Updated on 2014-09-06 20:29:55A gymnosperm is one of a number of non-flowering seed bearing vegetation species, including conifers, cycads, Ginkgo and Gnetales. These species arose first in the Carboniferous Period. The word gymnosperm derives from the Greek root gymnospermos for naked seed, meaning the exposed presentation of their ovules prior to fertilization. This naked seed condition differs from the seeds of angiosperms (flowering plants), which are enclosed during pollination. Seeds of the gymnosperm develop on the surface of scale or leaf-like appendages of cones.
Gymnosperms first appeared in the late Carboniferous Period, although precursor characteristics of seed plants were evident in fossil progymnosperms from the late Devonian Period aproximately 380 million years before present. Within the mid-Mesozoic period, pollination of some extinct groups of gymnosperms were by extinct species of... More »
CactusLast Updated on 2014-08-20 18:54:05Cactus 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, and 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 »
Amphibian ecology and evolutionLast Updated on 2014-07-23 18:38:53
Amphibians are found in ponds, streams, wetlands of all types, under rotten logs, in leaf litter, in trees, underground, even in pools of rain water inside large leaves. However, they are not able to osmoregulate in salt water and, therefore, are not found in the ocean. Although some amphibians defy the rules and thrive in cold or dry conditions, the group reaches its highest diversity and numbers in warm, humid climates.
In the wet tropics, amphibians remain active all year around, but in the temperate zone, winter temperatures cool their bodies, forcing them to become inactive.
In the autumn, environmental cues direct amphibians to find moist, sheltered places like muddy pond bottoms or deep leaf litter to hibernate.
The wood frog (Rana sylvatica) has the most northerly range of any amphibian, crossing the Arctic circle, into the Mackenzie River valley in the Northwest... More »
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