| A | B |
|---|
| invertebrate | animal without a backbone |
| vertebrate | animal with a backbone |
| endotherm | maintains a constant body temperature |
| ectotherm | animal whose body temperature changes with the environment |
| external fertilization | egg is fertilized by the sperm outside of the body |
| internal fertilization | egg is fertilized by the sperm inside the body |
| exoskeleton | external skeleton found on arthropods |
| endoskeleton | internal skeleton |
| metamorphosis | process in which an animal changes form during development |
| amphibian | vertebrate that usually begins life in the water with gills and later develops lungs |
| reptile | vertebrate that develops from an amniotic egg and has thick dry skin |
| marsupial | mammal that gives birth to live young that develop inside the mother's pouch |
| monotreme | mammal that lays eggs |
| placental mammal | mammal that nourishes its unborn with a placenta |
| amniotic egg | contains amniotic fluid and usually surrounded by a hard shell |
| bilateral symmetry | two halves of the body are mirror images of each other |
| radial symmetry | body parts are arranged in a circle around a central point |
| gestation period | time and embryo develops inside the mother |
| brooding | when a bird sits on an egg until it hatches |
| parasite | organism that feeds on another organism without killing it |
