1. Sexual reproduction in animals involves three stages: pre-fertilization where gametes are produced, fertilization where the gametes fuse, and embryo formation where the zygote divides and develops. 2. Animals are either oviparous, where the embryo develops outside the body in eggs, or viviparous, where the embryo develops inside the mother's body. 3. Asexual reproduction methods in some animals include fission, budding, fragmentation, and spores, allowing reproduction without fertilization.