Vertebrates reproduce sexually, with internal or external fertilization depending on habitat. They exhibit three reproductive strategies: oviparity, where eggs hatch outside the mother; ovoviviparity, where eggs hatch inside the mother; and viviparity, where embryos develop internally and receive nourishment from the mother. Sexual reproduction involves the fusion of male sperm and female eggs to form genetically diverse offspring. Vertebrates display various sexual reproduction patterns including dioecy, parthenogenesis, and hermaphroditism. While increasing genetic diversity, sexual reproduction requires finding mates and has energy costs that asexual reproduction avoids.