"Internal reproduction" is a broad term that generally refers to the fertilization of an egg by sperm inside the body of the female. This is in contrast to external reproduction, where fertilization occurs outside the female's body, like in fish or amphibians.

Here's a breakdown:

Key Features of Internal Reproduction:

* Fertilization: Sperm and egg meet and fuse inside the female reproductive tract.

* Protection: The developing embryo is protected within the female's body, often within a specialized structure like a uterus.

* Nourishment: The female provides nourishment to the developing embryo through a placenta or other means.

* Higher Survival Rates: Internal reproduction generally results in higher survival rates for offspring compared to external reproduction.

Examples of Animals with Internal Reproduction:

* Mammals: Humans, dogs, cats, whales, etc.

* Birds: Chickens, ducks, eagles, etc.

* Reptiles: Lizards, snakes, crocodiles, etc.

* Some invertebrates: Earthworms, snails, etc.

It's important to note:

* Internal reproduction doesn't always involve live birth. Birds, for example, lay eggs, but fertilization still occurs internally.

* Internal reproduction can be more complex in some species. For example, some species have specialized mating behaviors or reproductive cycles.

Overall, internal reproduction is a successful evolutionary strategy that has allowed many species to thrive. It provides greater protection and nourishment for the developing offspring, leading to higher survival rates.