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Alkaloids are classified according to the amino acid that provides both the nitrogen atom and the fundamental portion of the alkaloid skeleton, and these are discussed in turn.
Process by which an early metazoan embryo becomes a gastrula, acquiring first two and then three layers of cells.
A biome is a major biotic unit bearing a characteristic and easily recognized array of plant life. Botanists long ago recognized that the terrestrial environment of the earth could be divided into large units having a distinctive vegetation, such as fores
Among all living organisms, flowers, which are the reproductive structures of angiosperms, are the most varied physically and show the greatest diversity in methods of reproduction of all biological systems.
Mutations are heritable changes in the genetic material that give rise to alternative forms of any gene. These alternate forms are called alleles. There are two broad types of mutations, those that affect the gene and those that affect whole chromosomes (
This organism is widespread in the environment, but rare in the flora of healthy individuals. Its carriage increases with hospitalization.
Bilateral nervous systems, the simplest of which occur in flatworms, represent a distinct increase in complexity over the nerve net of radiate animals.
In botany, a herbarium is a collection of preserved plant specimens. These specimens may be whole plants or plant parts: these will usually be in a dried form, mounted on a sheet, but depending upon the material may also be kept in alcohol or other preser
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance.
Ameboid movement is a form of movement especially characteristic of amebas and other unicellular forms; it is also found in many wandering cells of metazoans, such as white blood cells, embryonic mesenchyme, and numerous other mobile cells that move throu
In vertebrates, the actual tissue from which gonads arise appears in early development as a pair of genital ridges, growing into the coelom from the dorsal coelomic lining on each side of the hind-gut near the anterior end of the kidney (mesonephros).
Three different prokaryotic DNA polymerases are known, of which DNA polymerases I and II are meant for DNA repair and DNA polymerase IN is meant for actual DNA replication
A bacteriophage is a virus that infects bacteria. Like all viruses, phages are obligate intracellular parasites, devoid of protein synthesizing machinery and energy conversion systems.
Packed inside an insect no bigger than a jellybean is a venom strong enough to cause intense pain in humans - and occasionally death, in people who are allergic to it.
A tissue is a group of similar cells (together with associated cell products) specialized for the performance of a common function.
Discoveries in molecular biology have allowed scientists to duplicate natural genetic transfer phenomena in the laboratory and to develop methods to introduce almost any type of genetic information into an organism.
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