Download Development and growth

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 230-231
• 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