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Reproduction can be either asexual or sexual. Plants can reproduce asexually, as can simple single celled organisms like bacteria and protozoa. Most animals and plants reproduce sexually which creates variation in populations. This variation can lead to natural selection and therefore evolution of a species.
Asexual reproduction in single celled organisms takes the form of budding or binary fission. In plants, it can be carried out artificially by taking cuttings or tissue culture and happens naturally by runners and rhizomes. Asexual reproduction gives rise to offspring that are genetically identical to each other and the parent.
Sexual reproduction requires that two sex cells merge to form a new cell. The technical name for any sex cell is 'gamete' and the new cell they form is called a zygote. These are useful words to remember as they appear often in questions about sexual reproduction. An animal zygote is implanted in the lining of the uterus where it develops to become a new individual. Fertilization can be carried out artificially in a process called in vitro fertilization.
In animals, the male gamete is sperm and the female gamete is the egg. When the sperm penetrates the egg, the egg is said to have been fertilized. The gametes of plants are the pollen and the ovule. A fertilized ovule becomes a seed.
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