A
Antarctic animals are exposed to some of the coldest environments on earth.Animals survive in these severe conditions by reducing the percentage of body heat that is lost to the environment.
Many Antarctic animals have either a windproof or waterproof coat.Emperor penguins are a very good example of this.These birds have four layers of scalelike feathers.These layers overlap each other，forming a good protection from the wind，even in snowstorm conditions.
Whales，seals and some penguins have thick fat layers.This is a little like covering yourself in a blanket，but on the inside.In some animals this is even further improved，with the animals selectively able to reduce the blood flow to the fat layers.The further the blood is from the skin surface，the less the heat is lost.Fat layers can also be used as energy reserves，for example，male elephant seals can live off their fat reserves during summer.
The term “extremities” is used to mean any body part that is furthest away from the main body.In humans，our hands and feet count as “extremities”．These are often the first places to feel cold in winter.The same applies to animals.Emperor penguins have very small bills(喙) and feet，which means less blood is required to these areas.
Emperor penguins are highly adapted to cold environments—and as the only warmblooded animal that produces young penguins during the Antarctic winter，they need to be.In addition to the adaptation described above，emperor penguins also have noses which recover much of the heat lost through breathing.
As with the physical means，emperor penguins have unique behavioral adaptation that enables them to survive the unkind winter.Emperor penguins form large huddles(挤在一起的一群人或东西)．Not only does this share body warmth，but it also shelters many of the penguins from the effects of the wind.Huddling can reduce heat loss by up to 50%.
★Which shows the development of ideas in the passage?
