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Egg and sperm cells are generated through a type of cell division called meiosis. Meiosis is a fundamental part of the life cycle of organisms that reproduce sexually. Meiosis reshuffles chromosomes, creating genetic variation. The genetic diversity resulting from the meiotic cell division allows natural selection to operate.

In this Lesson, we're going to learn about chromosomes, reproductive life cycles, and meiosis. We'll discuss how both sexual and asexual reproduction can be evolutionarily advantageous in different environmental situations.


  • Describe the basic mechanisms of parthenogenesis, binary fission, budding, and fragmentation and regeneration.
  • Understand the necessity of a reduction division during the sexual life cycle.
  • Describe what happens during each stage of meiosis I and meiosis II.
  • Compare and contrast the processes of meiosis in plant and animal cells.
  • Demonstrate how independent assortment, crossing over, and random fertilization generate genetic variation during meiosis.
  • Discuss the evolutionary advantages of both sexual and asexual reproduction.

Last modified: Friday, November 5, 2010, 8:46 AM