Animal reproduction may be classified into two types: sexual and asexual. The zygote is formed by the union of haploid gametes during sexual reproduction. By meiosis, the animal that develops from a zygote can give rise to gametes.

The egg, the female gamete, is big and nonmotile, whereas sperm, the male gamete, is much smaller and motile. Asexual reproduction produces new people without the union of egg and sperm. Most asexual creatures reproduce only by mitotic cell division. Both asexual and sexual reproduction are frequent in animals.

Sexual reproduction necessitates the union of male and female gametes, resulting in the formation of a diploid zygote.

The generation of progeny without gamete fusion is referred to as asexual reproduction. Asexual reproduction mechanisms include budding, fission, and fragmentation with regeneration. Parthenogenesis, hermaphroditism, and sex reversal are all ways to change the method of reproduction. Reproductive cycles are controlled by hormones and environmental factors.

Fertilization can take place externally when both sperm and eggs are discharged outside the body, or internally when sperm implanted by the male fertilizes an egg in the female reproductive system. Fertilization, in any scenario, necessitates synchronized timing, which may be controlled by environmental signals, pheromones, or courting activity. Internal fertilization is frequently connected with fewer offspring and stronger parental protection of offspring.

Gamete production and delivery systems range from undifferentiated cells in the body cavity to sophisticated systems that include gonads that generate gametes as well as auxiliary tubes and glands that protect or transport gametes and embryos. Although

Sperm is generated in the testes, which are suspended outside the body in the scrotum in men. Ducts connect the testes to the penis and internal accessory glands.

The human female reproductive system is made up mostly of the labia and the glans of the clitoris on the outside and the vagina, uterus, oviducts, and ovaries on the inside. Eggs are generated in the ovaries and develop in the uterus after fertilization.

Gametogenesis, or gamete formation, is the process of male spermatogenesis and female oogenesis.

Human spermatogenesis is continuous and results in the production of four sperm each meiosis. Human oogenesis is discontinuous and cyclic, with one egg produced each meiosis.

In animals, GnRH from the brain controls the release of two hormones from the anterior pituitary, FSH and LH. FSH and LH regulate androgen (mostly testosterone) secretion and sperm production in males.

The ovarian and uterine cycles in females are orchestrated by cyclic production of FSH and LH via estrogens (mainly estradiol) and progesterone. Hormones are also secreted by the growing follicle and the corpus luteum, which aid in the coordination of the uterine and ovarian cycles via positive and negative feedback.

The endometrial lining is reabsorbed throughout estrous cycles, and sexual receptivity is restricted to a heat phase.

Many aspects of human sexual stimulation and orgasm shared by males and females are underpinned by reproductive systems with a shared genesis in development.

After fertilization and completion of meiosis in the oviduct, the zygote divides into a blastocyst before implantation in the endometrium. By 8 weeks, all main organs have begun to develop.

Acceptance of a pregnant woman's "foreign" offspring is most likely due to partial inhibition of the maternal immune response.

Contraception may prevent mature gametes from being released from the gonads, as well as fertilization.