Reproduction is the vital process by which an animal species perpetuates itself. When we consider the subject carefully, we realize the complexity of the mechanisms that can come into play, as they are so varied. In animals, scientists distinguish two ways of reproducing: sexual reproduction and asexual reproduction.
Sexual reproduction of animals
Sexual reproduction is that carried out by human beings. It brings together two individuals of different sexes, a male and a female. They mate to produce offspring that are genetically different from the parents. Sexual reproduction generally involves a reproductive cycle which is characterized by a phase of rapprochement between male and female, followed by a phase of fertilization, then gestation (in certain animals) which culminates in birth. Fertilization is that process by which a sperm (male reproductive cell) fuses with an egg (female reproductive cell) to form a zygote, which then develops into a new individual.
Asexual reproduction of animals
Asexual reproduction involves only one parent. The resulting offspring are then genetically identical to their parent because they are produced by cloning or cell division. There are different methods: binary division, in which an organism divides into two identical individuals (this is common in bacteria and certain unicellular organisms), budding, a process where the new individual is formed from an outgrowth or of a “bud” from the parent (hydras, also called freshwater polyps use it) and fragmentation, during which an organism divides into several pieces, each capable of developing into a new individual (the starfish are an example).
Organisms that use asexual production are simpler organisms than those that use sexual reproduction.
Animal reproduction strategies
Reproductive strategies vary greatly among different animal species. The chosen strategy is often adapted to the species’ environment. Biologists often use the concept of “R” and “K” strategies to classify species based on their level of parental investment.
“R” (or breeding) species tend to produce large numbers of offspring, which does not allow for much educational investment per individual. The survival of the species depends on the quantity rather than the quality of offspring.
“K” species (or “niche carriers”) produce fewer children but invest more in each of them, providing parental care and resources to maximize their survival and reproductive success.
“K” species are more common in stable, predictable environments, while “R” species can thrive in more unstable environments.
The life cycles of animals
Animals go through different stages of development. The life cycle begins with the birth or hatching of an egg. Then the animals go through a youthful period or a larval phase. They are generally vulnerable. Animals grow to reach sexual maturity, which marks the point at which animals are capable of reproducing. The age of sexual maturity varies considerably between species.
Assisted animal reproduction
In some situations, humans and zoologists use assisted reproduction techniques to help animals breed in captivity, save endangered species, or study reproductive biology.