DEVELOPMENT AND GROWTH Chapter 6 lesson 4

Where Do Embryos Develop? After fertilization, the offspring may continue to develop in different ways. 1. Egg-laying Animals- most animals without a backbone (invertebrates) lay eggs. Many fishes, reptiles, and birds lay eggs, too. The contents of the eggs provide all the nutrients that the developing embryo needs. The eggs of land vertebrates are called amniotic egs. They are covered with a leathery shell. See page 221

Egg-Retaining Animals- an embryo develops inside an egg that is kept within the parent’s body. The embryo receives nutrition from the egg, not the mother. The egg hatches either before or after being released from the parent’s body. Placental Mammals- The embryo develops inside the mother’s body. The mother provides the embryo with everything it needs to develop. Materials are exchanged between the embryo ad the mother through the placenta. See page 222

How Do Animals Care for Their Young? No Parental Care: Most aquatic invertebrates, fishes, and amphibians release many eggs into water and then completely ignore them. The offspring are able to care for themselves from the time of birth. Parental Care: Birds- lay their eggs in nests that one or both parents build. Then one or both parents sit on the eggs, keeping them warm until they hatch. Most parent birds feed and protect their young until they are able to care for themselves. Mammals- young mammals are usually helpless for a long time after they are born. All young mammals are fed with milk from their mother’s body. One or both parents may continue to care for offspring until the young animals are independent.

Complete pp Plant and Animal Flash Cards- on one side of a card, write the name of the organism. On the other side, write a description of the organism’s life cycle, write key words, or draw a diagram to show the organism’s life cycle