Here's why:
* Sexual reproduction: This is the most common form of reproduction in animals. It involves the fusion of male and female gametes (sperm and egg) to create a genetically unique offspring. This diversity is crucial for adaptation and evolution.
* Asexual reproduction: Some animals can reproduce asexually, but this usually results in genetically identical offspring. Examples include:
* Parthenogenesis: A female produces offspring without mating (e.g., some lizards, insects).
* Budding: A new individual grows from an outgrowth or bud on the parent (e.g., hydra, corals).
* Fragmentation: A parent breaks into pieces, each capable of developing into a new individual (e.g., starfish, sea anemones).
In short, while asexual reproduction might seem like a form of self-reproduction, it still involves the creation of a new individual from the parent's own genetic material. No animal can truly reproduce a perfect copy of itself.