oviparously

Oviparously is an adverb describing a reproductive mode in which offspring develop from eggs laid outside the parent's body. In oviparous reproduction, embryos grow within eggs that are deposited and then incubated externally, with development largely dictated by the egg’s yolk and surrounding environment. This contrasts with viviparous reproduction, where live offspring are born after internal gestation and direct nourishment by the parent, and with ovoviviparous reproduction, where eggs hatch inside the parent's body rather than after laying.

In oviparous species, fertilization is typically internal before egg deposition, though there are exceptions in some groups with external fertilization. After laying, eggs may be incubated by heat from the environment, incubation structures, or parental warmth, and parental care ranges from avoidance to extensive guarding.

Examples of oviparous animals include the majority of birds and reptiles, as well as most amphibians and fishes. Among mammals, monotremes such as the platypus and echidnas are notable for still laying eggs, making them oviparous. The precise incubation strategies and developmental timelines vary widely across groups, from sturdy external eggs with long incubation to softer eggs in nests that are closely tended by parents.

Etymology and usage: the term derives from Latin ovum (egg) and parere (to bear), with oviparous meaning egg-bearing. The adverb oviparously is primarily found in scientific writing; in everyday language, “egg-laying” is more common. The term is a precise descriptor within discussions of reproductive biology.