reproduction in humans

Introduction - 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..

Parthenogenesis and Tissue Culture - Parthenogenesis is a form of reproduction in which the ovum develops into a new individual without fertilisation. Natural parthenogenesis has been observed in many lower animals (it is characteristic of the rotifers), especially insects, e.g., the aphi..

The process of attachment of the blastocyst (blastula) on the endometrium of the uterus is called implantation. It generally occurs on the seventh day after fertilisation, thus establishing pregnancy. After implantation, the endometrium undergoes profound changes and is called the decidua. The deci..

Inorganic Chemicals and Metals - 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 a..

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 called cleavage divisions, whi..

Aneuploidy is a condition, which represents a change in chromosome number. Such a change is most commonly caused in the reproductive cells during the process of gametogenesis. The most common cause for aneuploidy is a phenomenon called non-disjunction. It represents a failure in the sepa..

Cloning of Organisms - 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 fo..

. 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..

) Feathers Hair Respiratory organs Gills Lungs Lungs Lungs Lungs Locomotor organs Fins Limbs Limbs Limbs Limbs Heart Two chambers Three chambers Three chambers Four chambers Four chambers Aortic arch On both sides On both the sides On both the sides Only on right side Only on left side Mode of ..