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There are about 5,200 kinds of mammal. All of them have hair and mammary glands, which make milk to feed their young.

Mammals are endotherms: they keep a fairly constant body temperature. Hair traps a layer of air close to the body to keep heat in, and special hairs called whiskers help them feel their way.

Most mammals have different kinds of teeth: incisors, canines, premolars and molars. Most also grow two sets of teeth in their lifetime, just as you have milk teeth first.

Experiment: Blubber test

1. Make a 'blubber bag': put a layer of shortening about 2–3 cm thick in a zip bag, push a second bag inside it and tape the tops together so the fat is trapped between the bags.
2. Make a 'no blubber' bag the same way, but with nothing between the two bags.
3. Put a thermometer inside the inner bag of each one. Record the starting temperatures.
4. Push both bags into the ice water at the same time, to the same depth.
5. Record the temperature inside each bag every minute for 10 minutes.
6. Fair test: what did you keep the same? Repeat if you have time, and draw a line graph of both bags.

Time (min)	Blubber bag (°C)	No blubber bag (°C)
0	Which bag will cool faster?
2	Which bag will cool faster?
4	Which bag will cool faster?
6	Which bag will cool faster?
8	Which bag will cool faster?
10	Which bag will cool faster?

Questions

1. Name the three groups of mammals and give one example of each.

2. Name the four kinds of mammal teeth.

3. In your blubber test, what did you change, what did you measure and what did you keep the same?

4. Use your results to explain how blubber helps a seal in cold water.

Sources for every fact on this sheet: echoesof.science/school/mammals/sources/

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