Sexual Reproduction When reproduction takes place as a result of fusion of two gametes, one from each parent, it is called sexual reproduction The process of fusion of male and female gametes is called fertilization . The formation of gametes involves exchange of chromosomal (genetic) fragments between homologous chromosomes causing genetic recombination which leads to variation . Gametes : Special Reproductive cells are different from normal cells as they have half the number of chromosomes. e.g Human cells have 46 chromosomes but sperm and egg have 46/2=23 chromosomes. So when sperm and egg fuse, zygote will have 23+23= 46 chromosome. Male gamete : small in size and motile (has tail) Female gamete: big in size ( because of stored food reserve) and non motile. Sexual Reproduction in Plants It occurs mostly in flowering plants. In fact flowers are the reproductive organ of plants. FLOWERS ...
The ozone hole results from ozone-depleting chemicals (e.g. chlorofluorocarbons (CFCs)). When CFCs are hit by ultraviolet light, they release chlorine. Chlorine reacts with ozone, destroying it to produce chlorine monoxide and diatomic oxygen.
ReplyDeleteThese reactions are most effective when they occur on the surface of ice crystals, in the stratosphere. There are more ice crystals when it is most cold.
Antarctica is colder than the Arctic circle because the ratio of land to water is higher.
Therefore ozone depletion over the South Pole is greater than ozone depletion over the North Pole.
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