| A | B |
|---|
| nest | the female bird usually lays eggs in a __________- |
| feathers and scales | birds have _____________ |
| incubate | birds __________ their eggs |
| amniotic egg | birds reproduce by laying an _______ with a shell |
| reptile | bird eggs have the same kind of membranes as ______ eggs |
| contour | ___________ feathers give birds their coloring and shape |
| down | _______ feathers provide insulation |
| preening | process in which the bird rubs oil over its feathers |
| hollow | most of the bones of a bird are __________ |
| swim | penguins use their wings to _______ under water |
| quickly | the digestive system of of birds breaks down food _______ |
| mammals | endothermic vertebrates that have hair, and produce milk to feed their young |
| skin | covers and protects the bodies of all mammals |
| incisors | teeth that bite and cut |
| herbivores | animals that eat only plants |
| carnivores | animals that eat only animals |
| omnivores | eat plants and animals |
| four | all mammals have a __ chambered heart |
| lungs | mammals have_____ for breathing |
| long | herbivores have a _______ digestive system |
| monotremes | mammals that lay eggs with tough, leathery shells |
| marsupials | pouched mammals that give birth to tiny immature offspring |
| placental mammals | develop inside the female in the uterus |
| gestation period | time in which the embryo develops inside the uterus |
| umblilcal cord | attaches the embryo to the placenta |
