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Animal Reproduction and Development



Animal reproduction and development describes the entire life cycle of species in the kingdom Animalia. The ability to reproduce oneself is one of the major characteristics of life. Some organisms reproduce by splitting themselves in two, whereas others perform elaborate courtship displays to convince the opposite sex to exchange reproductive cells (gametes) with them. Sexual reproduction may involve external fertilization (when gametes fuse outside the bodies of the organisms) or internal fertilization. After fertilization, zygotes undergo rounds of cell division and subsequent growth and development. The continual changes throughout the life of an organism is referred to as aging.

At A Glance

  • Sexually reproducing organisms use gametes (sex cells) to reproduce.
  • In sexual reproduction, fertilization must occur for new organisms to form.
  • Some organisms have eggs that are fertilized externally.
  • Some organisms have eggs that are fertilized internally.
  • After fertilization, organisms go through the process of development, which, in many organisms, has multiple stages.
  • During gastrulation, early structures take on a form that gives rise to more complex structures in the organism, while during organogensis, organs form.
  • Organisms grow and change throughout their lives in a process called aging.