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Monday, January 30, 2012

Science Class 6 Answers of Chapter 8 – Body Movements




Question 1: Fill in the blanks:

(a) Joints of bones help in the _________ of body.

(b) A combination of bones and cartilages forms the _________ of the body.

(c) Bones at the elbow are joined by a _________ joint.

(d) The contraction of the _________ pulls the bones during movement.

Answer 1: (a) Joints of bones help in the movement of body.

(b) A combination of bones and cartilages forms the skeleton of the body.

(c) Bones at the elbow are joined by a hinge joint.

(d) The contraction of the muscle pulls the bones during movement.

Question 2: Indicate true (T) or false (F) for the following sentences.

(a) Movement and locomotion of all animals is exactly the same. ( )

(b) Cartilages are harder than bones. ( )

(c) Finger bones do not have joints. ( )

(d) The fore arm has two bones. ( )

(e) Cockroaches have an outer skeleton. ( )

Answer 2: (a) Movement and locomotion of all animals is exactly the same. (False)

(b) Cartilages are harder than bones. (False)

(c) Finger bones do not have joints. (False)

(d) The fore arm has two bones. (True)

(e) Cockroaches have an outer skeleton. (True)

Question 3: Match the items in Column I with one or more items in Column II.
Column I
Column II
Upper jaw
have fins on the body
Fishes
has an outer skeleton
Ribs
can fly in the air
Snail
is an immovable joint
Cockroach
protect the heart
-
shows very slow movement
-
have a streamlined body
Answer 3:  
Column I
Column II
Upper jaw
is an immovable joint
Fishes
have a streamlined body; have fins on the body
Ribs
protect the heart
Snail
shows very slow movement
Cockroach
has an outer skeleton; can fly in the air

Question 4: Answer the following:

(a) What is a ball and socket joint?

(b) Which of the skull bones are movable?

(c) Why can our elbow not move backwards?

Answer 4: (a) Ball and socket joint is a movable joint. It consists of a bone that has a round head, which fits into a cup like depression of another bone. This helps the bone to rotate freely. Examples of such joints are hip and shoulder joints.

(b) Mandible bone which forms the lower jaw is the only skull bone that is movable.

(c) The elbow has a hinge joint. This type of a joint allows the movement in one plane only. Therefore, our elbow cannot move backwards.

Thursday, January 26, 2012

Answers of The Living Organisms and Their Surroundings Class 6 Science Chapter 9


Question 1: What is a habitat?

Answer 1: A habitat is a natural environment where an organism lives. It is basically the address of an organism. Different plants and animals live in different habitats. For example, the habitat of a frog species is fresh water, while the habitat of a camel is a desert.

Question 2: How is a cactus adapted to survive in a desert?

Answer 2: A cactus is able to survive in the desert as it is adapted to the hot and humid conditions of the desert. To survive in a desert, the cactus has the following adaptations:

(i) It has long roots that go deep inside the soil for absorbing water.

(ii) Its leaves are present in the form of spines to prevent water loss through transpiration.

(iii) Its stem is covered with a thick waxy layer to retain water.

Question 3: Fill in the blanks:

(a) The presence of specific features, which enable a plant or an animal to live in a particular habitat, is called _________.

(b) The habitats of plants and animals that live on land are called _________ habitat.

(c) The habitats of plants and animals that live in water are called _________ habitat.

(d) Soil, water, and air are _________ factors of a habitat.

(e) Changes in our surrounding that makes us respond to them are called _________.

Answer 3: (a) The presence of specific features, which enable a plant or an animal to live in a particular habitat, is called __adaptation__.

(b) The habitats of plants and animals that live on land are called __terrestrial_ habitat.

(c) The habitats of plants and animals that live in water are called __aquatic__ habitat.

(d) Soil, water, and air are __abiotic__ factors of a habitat.

(e) Changes in our surrounding that makes us respond to them are called __stimuli__.

Question 4: Which of the things in the following list are non-living?

Plough, Mushroom, Sewing Machine, Radio, Boat, Water Hyacinth, Earthworm.

Answer 4: In the given list, the non-living things are plough, sewing machine, radio, and boat. On the other hand, mushroom, water hyacinth, and earthworms are living things.

Question 5: Give an example of a non-living thing that shows any two characteristics of living things.

Answer 5: Car is an example of a non-living thing that shows two characteristics of living things. A car can move from one place to another. Also, it requires energy just like living things.

Question 6: Among the non-living things listed below, which things were once a part of living things?

Butter, Leather, Soil, Wool, Electric Bulb, Cooking Oil, Salt, Apple, Rubber

Answer 6: The non-living things which were once a part of living things are butter, leather, wool, cooking oil, apple, and rubber. The sources of these non- living things are given below:

(a) Butter is made by churning milk, which is obtained from dairy animals.

(b) Leather is obtained from animal skin.

(c) Wool is a fabric made from the hair of sheep.

(d) Cooking oil is obtained from the seeds of the some plants.

(e) Apple is a fruit obtained from apple tree.

(f) Rubber is obtained from the latex of rubber tree.

Soil, electric bulb, and salt are non-living things which were never a part of any living thing.

Question 7: List the common characteristics of living things.

Answer 7: Some common characteristics of living things are that they

(a) require food

(b) respire and excrete waste material

(c) respond to stimuli in their environment

(d) reproduce to maintain their number

(e) move from one place to another

(f) grow and die

Question 8: Explain why speed is important for survival in the grasslands for animals that live there (Hint: There are few trees or places for animals to hide in grasslands habitat).

Answer 8: In grasslands, mainly grasses are found. Trees are very few in number. Predators such as lion, tiger, etc. that feed upon other animals are commonly found in these regions. It is very easy for these predators to locate their prey in the grass. Therefore, to protect themselves from these predators, animals adapt themselves by increasing their speed. The increased speed of the animal helps the weaker animals to escape their predator, thereby protecting themselves and increasing the chances of their survival.

Wednesday, January 18, 2012

Answers to Science Class 6th Ch. 13 – Fun With Magnets


Question 1: Fill in the blanks:
(i) Artificial magnets are made in different shapes such as ___________, ____________, and ___________.
(ii) The materials which are attracted towards magnets are called ___________.

(iii) Paper is not a ___________material.

(iv) In olden days, sailors used to find direction by suspending a piece of ____________

(v) A magnet always has ___________ poles.

Answer 1: (i) Artificial magnets are made in different shapes such as bar magnets, horse-shoe magnets, and cylindrical magnets.
(ii) Materials which are attracted towards magnets are called magnetic materials.
(iii) Paper is not a magnetic material.
(Paper is not attracted by magnet. Hence, it is not a magnetic material)
(iv) In olden days, sailors used to find direction by suspending a piece of bar magnet .
(A freely suspended magnet always comes to rest in the North-South direction. Hence, sailors used to find direction by suspending a piece of bar magnet)
(v) A magnet always has two poles.
A magnet has two poles called the south pole (S) and the north pole (N).
Question 2: State whether the following statements are ‘True’ or ‘False’.
(i) A cylindrical magnet has only one pole.

(ii) Artificial magnets were discovered in Greece.

(iii) Similar poles of a magnet repel each other.

(iv) Maximum iron filings stick in the middle of a bar magnet when it is bought near them.

(v) Bar magnets always point towards the North−South direction.

(vi) A compass can be used to find the East−West direction at any place.

(vii) Rubber is a magnetic material.
Answer 2: (i) False
Magnets always have two poles; the north pole and the south pole. A cylindrical magnet also has two poles.
(ii) False
Artificial magnets were not discovered in Greece. Only natural magnets were discovered in Greece.
(iii) True
Like poles of magnets repel each other, while unlike poles of magnets attract each other. The south pole of a magnet attracts the north pole of another magnet and repels the south pole of that magnet.
(iv) False
The amount of iron filings that stick to a bar magnet depends on the strength of the magnet. The magnetism of a bar magnet is maximum at its two poles and minimum in the middle. Hence, maximum iron filings will stick at the two ends of the magnet and minimum in the middle.
(v) True
A freely suspended magnet always points towards the North−South direction.
(vi) True
A magnetic compass always points towards the North−South direction.
If the North−South direction is known, then the East−West direction can also be determined. This direction is perpendicular to the North-South direction, i.e., perpendicular to the compass needle in the same plane.
(vii) False 
Rubber is not attracted by a magnet. Hence, it is a non-magnetic material

Question 3: It was observed that a pencil sharpener gets attracted by both the poles of a magnet, although its body is made of plastic. Name a material that might have been used to make some part of it.

Answer 3: The blade of a pencil sharpener is made of iron. Iron is a magnetic material. Since magnets can attract objects made of magnetic materials, a pencil sharpener gets attracted towards both poles of a magnet.

Question 4: Column I shows different positions in which one pole of a magnet is placed near the other. Column II indicates the resulting action between them for each situation. Fill in the blanks.

Column I
Column II
N − N
_________
N − __
Attraction
S − N
_________
__ − S
Repulsion
Answer 4: Like magnetic poles repel each other, while unlike magnetic poles attract each other.

Column I
Column II
N − N
Repulsion
N − S
Attraction
S − N
Attraction
S − S
Repulsion
Question 5: Write any two properties of a magnet.
Answer 5: Two properties of a magnet are:
(i) Magnets attract objects made of magnetic materials like iron.
(ii) Like magnetic poles repel each other, while unlike magnetic poles attract each other.
Question 6: Where are the poles of a bar magnet located?
Answer 6: The poles of a bar magnet are located at both ends.
The north pole (N) and the south pole (S) of a bar magnet are located at its two ends (as shown in the given figure).
Question 7: A bar magnet has no markings to indicate its poles. How can you find out the location of the north pole?
Answer 7: A freely suspended bar magnet always comes to rest in the North−South direction. The north facing end of the magnet is its north pole, and the south facing end is its south pole (as shown in the given figure).

Hence, the unknown poles of a bar magnet can be marked by suspending it freely by a string.



Or,
You already know that the compass needle is a small bar magnet. You also should remember that the end of the compass needle which points north is the north pole of the magnet and the end which points south is the south pole.  Ordinarily, when a compass is not close to another magnet, it is attracted to the earth’s magnetic field.  (More about that later!)  However, once you bring another magnet close to the compass needle, the strength of your magnet is much greater than the earth’s magnetic field, and the compass needle is attracted to it.  You have also seen that opposite poles attract when two magnets are brought close to one another. Since opposite poles attract, if the north pole of the compass swings toward the end of your magnet, the end it is attracted to would be the south pole.  Likewise, if the south pole of the compass is attracted to the end of the magnet, that end of your magnet is the north pole of that magnet.



Question 8: You are given an iron strip. How will you make it into a magnet?
Answer 8: ‘Touch and stroke’ method can be used to make an iron strip into a magnet. For this, a bar magnet is required. The bar magnet is moved along the length of the iron strip starting from one end to the other end (as shown in the given figure).
Then, the bar magnet is lifted from the other end and brought to the starting point again with the same pole of the bar magnet. On repeating the process for at least 40 to 50 times, the iron strip will become a bar magnet with two poles.
If North pole of magnet was rubbed with the front of the iron bar then front of iron bar will become north and back will become south.
Question 9: How is a compass used to find directions?
Answer 9: A compass always points towards the North−South direction. The red arrow of the compass needle indicates its north pole. The arrow always points in the North direction (as shown in the given figure).

If we know the North direction, then we can find all the other three directions at that place. If North is towards the front, then South would be towards the back, East towards the right of North, and West towards the left of North.




Question 10: A magnet was brought from different directions towards a toy boat that has been floating on water in a tub. The effect observed in each case is stated in Column I. Possible reasons for the observed effects are mentioned in Column II. Match the statements given in Column I with those in Column II.


S. No
Column I
Column II
1.
Boat gets attracted towards the magnet
Boat is fitted with a magnet with the north pole towards its head
2.
Boat is not affected by the magnet
Boat is fitted with a magnet with the south pole towards its head
3.
Boat moves towards the magnet when the north pole of the magnet is brought near its head
Boat has a small magnet fixed along its length
4.
Boat moves away from the magnet when the north pole is brought near its head
Boat is made of magnetic material
5.
Boat floats without changing its direction
Boat is made of a non-magnetic material
Answer 10:  

S. No
Column I
Column II
1.
Boat gets attracted towards the magnet
Boat is made of a magnetic material
2.
Boat is not affected by the magnet
Boat is made of a non-magnetic material
3.
Boat moves towards the magnet when the north pole of the magnet is brought near its head
Boat is fitted with a magnet with the south pole towards its head
4.
Boat moves away from the magnet when the north pole is brought near its head
Boat is fitted with a magnet with the north pole towards its head
5.
Boat floats without changing its direction
Boat has a small magnet fixed along its length
Concepts behind answers:
1. Magnetic materials get attracted towards a magnet.
2. Non-magnetic materials do not get attracted towards a magnet.
3. Unlike poles of magnets attract each other.
4. Like poles of magnets repel each other.
5. Magnets always point towards the North-South direction.

Tuesday, January 17, 2012

Some Important Questions from The Living Organisms and Their Surroundings



Q. 1. How are the bodies of organisms specially designed or adapted to help them live in their own habitat ?

Ans. 1: The bodies of animals are adapted or specially designed to help them live in their own habitat. For example, squirrels have sharp curved claws to give them grip when they climb the trees they live in. They have strong back legs for jumping among the branches, and big, bushy tails to keep them steady when they jump. In the same way, moles live under the ground, and they have feet like spades for digging their tunnels.
In case of plants, Cacti live in the hot, dry desert and these plants have fleshy stems for storing any rainwater that falls.

Q. 2. Describe the various types of plants and animals on the basis of their habitat.

Ans. 2: Types of plants on the basis of their habitat :
(i) Hydrophytes. Also called aquatic plants, they are the plants living in water like lotus, water lily, water hyacinth, etc.
(ii) Mesophytes are the plants that grow on land with sufficient water, e.g., most herbs and trees.
(iii) Xerophytes are on land in dry climate having scarcity of water, as in a desert, e.g., cacti and babool.
Types of animals on the basis of their habitat :
(i) Aquatic. These are the animals that live in water, e.g., fish.
(ii) Terrestrial. These are the animals that living on land, e.g., horse and elephant.
(iii) Amphibious. These are the animals that live both on land and in water, e.g., frog, toad, etc.
(iv) Arboreal. The animals that live living on trees, e.g., squirrels, monkeys, etc.

Q. 3. Explain in detail the characteristics of the living beings.

Ans 3: Following are the characteristics of the living beings :

(1) Cellular Organisation. All living beings are made up of cells. Some living things consist of only a single cell, e.g., amoeba. Such living things are called unicellular organisms. The organisms that are made up of more than one cells are called multicellular organisms, e.g., rose plant, man, housefly, etc.

(2) Nutrition. Food is required by all living things as it provides us energy to perform different activities. It also helps in body growth as well as its maintenance and repair.
Green plants can prepare their own food. They obtain water and minerals through their roots. For preparing their food, plants also require carbon dioxide. This is absorbed from the atmosphere by the leaves through present on their surface. The green plants utilize (i) carbon dioxide from air, (ii) water and minerals from soil, and (iii) sunlight to prepare their food. This process of preparation or manufacture of food is called photosynthesis.
Animals, on the other hand, feed on plants or other animals for their food.

(3) Respiration. All living things respire. They take in or breathe in oxygen from the air and give out carbon dioxide. The oxygen is used to produce energy from the food consumed by the organisms which is utilised to perform various life activities.

(4) Growth. Growth is a permanent and irreversible process. All living things grow from a single cell. However, the pattern of growth, however, is different in plants and animals.

(5) Excretion. Excretion means the removal of waste materials from the body. Accumulation of waste materials is harmful for the body. It excreted mainly in the form of sweat, carbon dioxide by the living animals.
In plants, carbon dioxide and water vapour are excreted from small pores in their leaves. In some plants, wastes are given out in the form of gums or a thick fluid called latex.

(6) Reproduction. All living organisms have the ability to produce young ones of their own kind, e.g., a cat produces kittens who grow into adult cats. In case of plants, take the example of a mango tree, which bears fruits which possess seeds. The seed develops into a young seedling and in due course of time, into a tree. This means that living beings can make more of their own kind.

(7) Movement. Living things show movement. The movement in plants is not the same as in animals, like those of like walking, running swimming or flying. In plants, the stem moves towards light, the roots grow downwards in the soil in search of water and in sunflower plant and the flowers change their position to face the sun.
However, some animals like sponges, corals and sea-anemones do not move from place to place.

(8) Response to Stimuli. Living things respond to stimuli or changes in their surroundings, e.g., if our hand touches a hot object, we respond by quickly withdrawing it. In sensitive plant, the leaves curl up on being touched by hand.