Q.Why are offspring of oviparous animals at a greater risk as compared to offspring of viviparous animals?

Oviparous animals (e.g., most reptiles, birds, many fish, and insects) reproduce by laying eggs. After the eggs are laid, they are typically deposited in an external environment (a nest, soil, water, etc.) and develop and hatch outside the mother's body.

Viviparous animals (most mammals, including humans) give birth to young ones directly, because the developing embryo is retained and nourished inside the mother's body, typically connected via a placenta, until it is sufficiently developed to be born.

Why oviparous offspring are at greater risk:

• Lack of physical protection: Eggs laid outside the body are directly exposed to the external environment and are vulnerable to being eaten by predators, damaged, or disturbed, since the parent cannot shield them as continuously or completely as an internally developing embryo is shielded.
• Exposure to environmental fluctuations: Eggs developing outside the body are subject to variation in temperature, humidity, and other physical conditions of the surroundings, which can adversely affect the developing embryo, whereas the maternal body provides a much more stable, regulated internal environment for a developing viviparous embryo.
• Limited/indirect nourishment: An egg must contain all the nutrients (yolk) the embryo will need until hatching, since the mother cannot supply extra nourishment once the egg is laid; whereas in viviparous animals, the mother continuously supplies nutrients and oxygen to the growing embryo through the placenta, supporting healthier development.
• Vulnerability during incubation: Eggs may need to be incubated (guarded/warmed) for a period, during which they can be lost to predation, accidents, or abandonment, before the young even hatch. …

Contrast the location and conditions of development — external/unprotected/fixed-nutrient (oviparous) versus internal/protected/continuously-nourished (viviparous) — to explain why oviparous …

• Only stating 'oviparous animals lay eggs, viviparous give birth to young' without explaining WHY this difference translates into a survival-risk difference.
• Forgetting to mention the maternal protection/stable-environment/continuous-nourishment (placenta) advantage that viviparity provides. …