Parasite can be microscopic prokaryotes, nonliving viruses, or multicellular organism
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i'd say that the moon rock is about 2.2 billion years old.

both male and female gametes are produced by meiosis of the germ cells. therefore, both male and female gametes are haploid. one male and one female gamete unite during the fertilization to form the diploid zygote. in seed bearing plants, pollen grain is the male gametophyte, which produces sperm cells.