الأسبوع 17 · المحور 3، الباب 1 «أنماط التغير» (ب): تكيف الكائنات الحية والشحم والتمويه · 3 دروس
2
Blubber and camel humps
Discover P3 Term 2: Axis 3, Chapter 1
GoalExplain how blubber and fat keep animals warm, and compare a plain bag with a bag with a fat layer in cool water.
New words
blubber · a thick layer of fat under the skin of some sea animalsinsulator · something that slows down the movement of heathump · the lump on a camel’s back that stores fatstore · to keep something to use later
Explanation
Heat always moves from a warm place to a cold place. A warm body in cold water loses heat. Fat is an insulator: it slows down the heat. Seals, whales and walruses live in cold seas, and under their skin they have a thick layer of fat called blubber. It keeps the heat in their bodies. Penguins have fat and thick feathers too. A camel’s hump is not full of water. It is a store of fat. When there is little food, the camel’s body can use that fat for energy, so the camel can walk far in the desert. Having its fat in one hump also lets the rest of the camel’s body lose heat on hot days. These are adaptations that help animals live in very cold or very hot places.
Worked examples
Child
Plain bag
Bag with fat
Youssef
4
2
Mariam
5
2
Omar
4
1
Salma
5
2
The blubber test. A grown-up fills a bowl with cool water (not freezing) and prepares two bags: a plain bag and a bag with a layer of solid cooking fat. Each child puts a hand in each bag, into the water for a few seconds, and scores how cold it feels from 1 (not cold) to 5 (very cold).
Adding the scores. Plain bag: 4 + 5 + 4 + 5 = 18. Bag with fat: 2 + 2 + 1 + 2 = 7. The difference is 18 − 7 = 11. The fat layer kept the cold out.
eats well→fat is stored in the hump→little food in the desert→the body uses the fat
A camel store. A camel’s hump stores fat, not water. On a long walk with little food, the camel’s body uses the fat.
Class activity
The blubber test, with a grown-up. A grown-up prepares a bowl of cool water, never freezing, one plain zip bag, and one bag with a thick layer of solid cooking fat. First, predict which hand will feel colder. Put one hand in each bag, lower both into the water for only a few seconds, and take them out. Give each a score from 1 to 5. Do the test with four friends, record the scores in a table and add each column. Dry your hands. The fat is never tasted.
Practice
1
What is blubber?
A thick layer of fat under the skin that keeps sea animals warm.
2
A camel’s hump stores water. True or false?
False. It stores fat.
3
Scores for the plain bag are 3, 4 and 5. Scores for the bag with fat are 1, 2 and 1. What is each total, and what is the difference?
Bag
Scores
plain
3, 4, 5
with fat
1, 2, 1
3 + 4 + 5 = 12 and 1 + 2 + 1 = 4. 12 − 4 = 8.
4
Which hand do you expect to feel colder in the cool water, the one in the plain bag or in the bag with fat? Why?
The one in the plain bag, because fat slows down the movement of heat out of the hand.
