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(syngamy) An essential part of sexual reproduction involving the fusion of haploid male and female gametes to form a diploid zygote, from which a new individual develops. External fertilization occurs in lower plants, where gametes are released and exist independently of the parent before fusion occurs. In this process the gametes are totally dependent on the availability of water. Internal fertilization occurs in higher plants, where fusion takes place within the tissues of the female parts, which serve to protect and nurture the developing zygote. Internal fertilization, in its more advanced forms, removes the dependence on water and has enabled such plants to exploit drier habitats.
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