1. Name the three types of skeleton that
living organisms have. Give one example of
each.
2. a. Name the two organs protected by rib
cage.
b. Name the movable bone present in skull.
c. What is a tissue?
3. Describe a simple experiment to show
that light travels in a straight line.
4. List three properties of a shadow.
5. In what ways water is so important for
our body?
6. a. Why are magnetic keepers used to
store magnets?
b. Given a bar magnet, describe the method
you will use to magnetize an iron nail.
Answers
Answer:
1.Endoskeleton : Example- skeletons in human beings. Exoskeleton : Example- snails. Liquid skeletons : Example- Earthworms.
2.heart and lungs
3.Take three cardboards A,B and C each about 25cm square. Take a pin and make a small hole in each cardboard at the same height. Suspend the cardboard piece by separate threads vertically from a support such that each hole is at the same height, as shown. Pass a string through the holes and pull it. This makes the three holes in a straight line. Now take the string out. Place the lighted candle near one of the cardboard. Look at the candle flame from the other side of the cardboard C. The candle flame is clearly seen. Now slightly displaced one of the cardboard says B so that the holes no longer remain in a straight line. Again look at the candle flame from the other side of the cardboard C. you do not see the candle. The reason is that light travels in a straight line and the holes in the cardboard A,B and C are not in a straight line. Conclusion : light travels in a straight path called the rectilinear propagation of light.
4. They are always dark in colour.
They are formed opposite to the source of light.
They are formed when an opaque object comes between the source of light and the screen
5.Keep a normal temperature. Lubricate and cushion joints. Protect your spinal cord and other sensitive tissues. Get rid of wastes through urination, perspiration, and bowel movements
6.a.magnetic keeper is a piece of wood or soft iron which is used in storing magnets because bar magnets get demagnetised when the poles are left free for a long time. In order to preserve the magnetism of the magnets, a keeper is kept across a pair of bar magnets with unlike poles beside each other.
b. An iron nail can be magnetised by a bar magnet by a process of single touch method. In this method, one pole of a bar magnet is used to stroke the iron nail held firmly on a surface. Stroke the iron nail from one end to the other and after reaching the other end, lift the magnet and repeat the process by bringing it back to the first end again. After about 30 strokes, you will observe that the iron nail has become a magnet when suspended freely. If the iron nail has been stroked by north pole at the first end, that end becomes the north pole while the other end becomes the south pole