Sexual Reproduction:
* Gametes: Animals produce specialized sex cells called gametes (sperm and eggs).
* Fertilization: Sperm and egg fuse together to form a zygote, the first cell of a new individual.
* Development: The zygote undergoes cell division and differentiation, eventually developing into an adult organism.
Variations in Sexual Reproduction:
* Internal fertilization: Sperm meets the egg inside the female's body (e.g., mammals, birds, reptiles, insects).
* External fertilization: Sperm meets the egg outside the female's body (e.g., fish, amphibians, some invertebrates).
* Oviparity: Eggs are laid and development occurs outside the mother's body (e.g., birds, reptiles, amphibians, fish).
* Viviparity: Embryos develop inside the mother's body and receive nourishment through a placenta (e.g., mammals).
* Ovoviviparity: Eggs develop inside the mother's body but receive no nourishment from her (e.g., some reptiles, fish, insects).
Asexual Reproduction:
While sexual reproduction is the dominant form, some animals, particularly invertebrates, can reproduce asexually. This involves the creation of offspring from a single parent without the involvement of gametes:
* Budding: A new individual develops from an outgrowth or bud on the parent's body (e.g., hydra, corals).
* Fragmentation: The body of the parent breaks into pieces, each of which develops into a new individual (e.g., flatworms, sea stars).
* Parthenogenesis: A female produces offspring from an unfertilized egg (e.g., some insects, reptiles, fish).
Key Points:
* Sexual reproduction is the predominant form of reproduction in Kingdom Animalia.
* Asexual reproduction is less common but exists in some groups, primarily invertebrates.
* The specific mode of reproduction varies widely within the animal kingdom.
Let me know if you'd like to delve into any specific animal group or reproductive process!