reproduction in humans

Angiosperms are a group of flowering plants that represent a major community in the plant kingdom. Angiosperms occur in all typical habits and constitute a very useful group of plants for animals and human beings. They include about 2,50,000 species distributed all over the world. They ar..

These are a group of diverse protozoans characterized by the presence fine hair like cilia as locomotor structures. They are aquatic and free living or parasitic forms. Ciliates show a high degree of morphological and physiological specialisation compared to other animal like protistans. They posse..

During copulation, the male inserts its erectile penis into the vagina of the female and releases about 3.5 ml of seminal fluid. The semen contains millions of sperms. This process is called inseminatio..

Industrial and municipal waste waters and mine run offs cause various metals and metallic compounds to be released into water. These pollutants also enter the water bodies as acid rain and their sulphate and nitrate ions make water acidic. Most inorganic compounds are toxic, particularly, those of..

As science became a part of human life, the classification of living organisms had to undergo a thorough modification. The advent of the microscope in the 17 t h century opened up a new world of organisms that were hitherto unexplored; the world of micro organisms. It was hard to believe ..

Cleavage (Segmentation) - Cleavage is an unique embryological process which transforms the single fertilised egg cell into a sphere of closely aggregated multitude of cells. Immediately after fertilisation the fertilised ovum (egg cell) undergoes a series of cell divisions. These divisions are call..

Two or more individuals with identical genetic make up formed from one parent by asexual reproduction are called clones. For example, daughter plants produced by strawberry runners and whole plants produced by tissue culture are clones. Similarly, the individuals formed by budding on the ..

. Organisms with hard parts - shells, carapaces and skeletons appeared. The first fish and the first vertebrates appeared; plants, previously restricted to the oceans, began the colonization of the land; the first insect evolved, and its descendants became the pioneers in the colonization of the la..

. In the long-term, radioactive fallout occurs over a wider area because of prevailing winds. The radioactive fallout particles enter the water supply and are inhaled and ingested by people at a distance from the blast. Scientists have studied survivors of the Hiroshima and Nagasaki bombings to und..