Zygote

the cell produced by the fusion of male and female germ cells (GAMETES) during the initial stage of FERTILIZATION. The zygote is a DIPLOID cell, formed by the fusion of the haploid male gamete and the haploid female gamete.

Taken from Dictionary of Science

««««««««««««««««««««

A zygote (from Greek ζυγωτός zygōtos "joined" or "yoked", from ζυγοῦν zygoun "to join" or "to yoke"), or zygocyte, is the initial cell formed when a new organism is produced by means of sexual reproduction. A zygote is synthesized from the union of two gametes, and constitutes the first stage in a unique organism's development. Zygotes are usually produced by a fertilization event between two haploid cells — an ovum from a female and a sperm cell from a male — which combine to form the single diploid cell. Such zygotes contain DNA derived from both the mother and the father, and this provides all the genetic information necessary to form a new individual. The term zygote is also used more loosely to refer to the group of cells formed by the first few cell divisions, although this is properly referred to as a morula.

In mammalian reproduction, after fertilization has taken place the zygote travels down the fallopian tube, while dividing to form more cells without the zygote actually increasing in size. This cell division is mitotic, and is known as cleavage. All mammals go through the zygote stage of life. Zygotes eventually develop into an embryo, and then a fetus. A human zygote exists for about four days, and becomes a blastocyst on the fifth day.

Taken from Wikipedia

Dark Reaction

a stage in PHOTOSYNTHESIS which is not directly dependent on light. It takes place within the CHLOROPLASTS of the cells of green plants.

Taken from Dictionary of Science

_________________

Photosynthesis, or the light-independent reactions, are chemical reactions that convert carbon dioxide and other compounds into glucose. The reactions occur in the stroma, the fluid-filled area of a chloroplast outside of the thylakoid membranes. These reactions take the products of the light-dependent reactions and perform further chemical processes on them. There are three phases to the light-independent reactions, collectively called the Calvin Cycle: carbon fixation, reduction reactions, and ribulose 1,5-diphosphate (RuDP) regeneration.

The light-independent reactions are sometimes referred to as the dark reactions, though that term may be misleading as they do not actually require darkness to proceed. The term "light-independent" is used to emphasize that the reactions continue even in the absence of light as long as the proper substrate compounds are available. However, because the availability of substrates in plants depends on photosynthesis, the reactions cannot be said to be entirely "light-independent." The term "dark reactions" may be more accurate in CAM (Crassulacean acid metabolism) plants, which only take up CO₂, which is necessary for the reactions to proceed, at night.

Taken from Wikipedia