Oviparous and Viviparous Animals

Oviparous animals undergo external fertilisation, while viviparous animals undergo internal fertilisation.The zygote undergoes rapid division after fertilisation and moves down the oviduct. During this period, many protective layers form as a hard shell around the developing embryo.The chick hatches from the egg after three weeks.There are three distinct stages in the life cycle of a frog - egg, tadpole and adult.In the first stage, the egg fuses with a sperm to form a zygote. The zygote further divides to form an early tadpole, which matures into a late tadpole.During metamorphosis, the larva transforms into an adult frog.Our bodies undergo certain changes as we develop from childhood to adolescence stage.