a) Hibernation is the winter sleep. In winter some animals go into very deep sleep and during sleep metabolic rate slows down to save energy. It also lowers their body temperature than normal. It occurs for the long duration. For example, bear, tortoise, ground squirrel and many reptiles. Whereas aestivation is the summer sleep. During summer some animals go into the deep sleep to protect themselves from high temperature. It is a quite smaller duration. For example, frog, desert lizards etc.b) Ectotherms are those organisms that not able to maintain a constant temperature so, their body temperature fluctuates with environment temperature. They are also called as cold blooded animals or poikilotherms. For example, fish, amphibians. Whereas endotherms are those that maintains their constant body temperature also called warm-blooded animals or homeothermic. For example, birds and mammals.