People have sex for pleasure, reproduction, or both. Pregnancy happens when an egg and sperm successfully meet through intercourse or in vitro fertilization. What do they look like, and how many do we all have?
Fertilizationunion of a spermatozoal nucleusof paternal origin, with an egg nucleus, of maternal origin, to form the primary nucleus of an embryo. In all organisms the essence of fertilization is, in fact, the fusion of the hereditary material of two different sex cellsor gameteseach of which carries half the number of chromosomes typical of the species. The most primitive form of fertilization, found in microorganisms and protozoans, consists of an exchange of genetic material between two cells.
Sperm is the male gameteproduced in the testis of a male, while Ovum is the female gameteproduced in the ovary of a female. Ovum, also known as egg cell and is said to be the largest cell in the female body. On the contrary Sperm cells is the smallest cell in the male body.
Gametes are reproductive cells sex cells that unite during sexual reproduction to form a new cell called a zygote. Male gametes are sperm and female gametes are ova eggs. In seed-bearing plants, pollen is the male sperm producing gametophyte. In animals, gametes are produced in male and female gonads.
But although millions of babies have now been born by IVFthe technique can offer no help to couples eager to have a child that is genetically theirs but who lack the eggs or sperm to make it: men whose testes produce no sperm, say, or women who have undergone surgery for ovarian cancer. Some opt for donor eggs or sperm, but an alternative may be on the way. Scientists are making steady progress towards creating human eggs and sperm — the so-called gametes that combine in fertilisation — artificially in a petri dish.
Still others lack the energy to finish the long journey through the female reproductive tract, or they get snared in sticky fluid meant to impede all but the strongest swimmers. For the subset of a subset of spermatozoa that reach their trophy, the final winner would be determined by one last sprint to the end. The exact identity of the sperm was random, and the egg waited passively until the Michael Phelps of gametes finally arrived.
In species with two separate sexes, the sex that produces the smaller and more motile sex cell or gamete is called the male. Male mammals produce gametes called sperm while female mammals produce gametes called eggs. Gametes are produced by the process of gametogenesis, and it differs markedly between males and females.
In species that produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual that produces the larger type of gamete—called an ovum — and a male produces the smaller tadpole -like type—called a sperm. In short a gamete is an egg cell female gamete or a sperm male gamete. This is an example of anisogamy or heterogamythe condition in which females and males produce gametes of different sizes this is the case in humans; the human ovum has approximatelytimes the volume of a single human sperm cell  .
NCBI Bookshelf. A complex dialogue exists between egg and sperm. The egg activates the sperm metabolism that is essential for fertilization, and the sperm reciprocates by activating the egg metabolism needed for the onset of development.