Science Class 6 part-II NCERT

7. Plants
1. Plants can be classified into three categories: herbs, shrubs and trees.
1. Plants with green and tender stems are called herbs. They are usually short and may not have many branches
2. Some plants have the stem branching out near the base. The stem is hard but not very thick. Such plants are called shrubs
3. Plants with weak stems that cannot stand upright and spread on the ground are called creepers, while those that take support on neighbouring structures and climb up are called climbers
2. Pattern of veins on the leaf is called venation. It can be reticulate or parallel
3. Plants having leaves with reticulate venation have tap roots while plants having leaves with parallel venation have fibrous roots.
4. The part of a leaf by which it is attached to the stem is called petiole. The broad, green part of the leaf is called lamina
5. Water comes out of leaves in the form of vapor by a process called transpiration. Plants release a lot of water into the air through this process
6. We eat some of food stored plant in roots— li carrot, radish, sweet potato, turnip and tapioca
8. Body movement
1. Bones and cartilage form the skeleton of the human body. It gives the frame and shape to the body and helps in movement. It protects the inner organs.
2. The joint where our neck joins the head is a pivotal joint. Parts of the skeleton that are not as hard as the bones and which can be bent are called cartilage.
3. When contracted, the muscle becomes shorter, stiffer and thicker. It can only pull the bone. Bones are moved by alternate contractions and relaxations of two sets of muscles.
4. Strong muscles and light bones work together to help the birds fly. They fly by flapping their wings
5. Fish swim by forming loops alternately on two sides of the body
6. Snakes slither on the ground by looping sideways. A large number of bones and associated muscles push the body forward
7. The body and legs of cockroaches have hard coverings forming an outer skeleton. The muscles of the breast connected with three pairs of legs and two pairs of wings help the cockroach to walk and fly.
8. Earthworms move by alternate extension and contraction of the body using muscles. Tiny bristles on the underside of the body help in gripping the ground.
9. Snails move with the help of a muscular foot.
10. Mandible bone which forms the lower jaw is the only skull bone that is movable.
9. Living organisms and habitats
1. Desert - animals like rats and snakes, which do not have long legs that a camel has. To stay away from the intense heat during the day, they stay in burrows deep in the sand
1. leaves in desert plants are either absent, very small, or they are in the form of spines. This helps in reducing loss of water from the leaves through transpiration.
2. stem is also covered with a thick waxy layer, which helps to retain water in the tissues of cacti.
2. Mountains
1. trees are normally cone shaped and have sloping branches. The leaves of some of these trees are needle-like. This helps the rainwater and snow to slide off easily.
3. Grasslands
1. Lions have eyes in front of the face allow it to have a correct idea about the location of its prey
2. Deer have long ears to hear movements of predators. The eyes on the side of its head allow it to look in all directions for danger.
4. Aquatic
1. In plants, roots are much reduced in size and their main function is to hold the plant in place
2. stems of these plants are long, hollow and light. The stems grow up to the surface of water while the leaves and flowers, float on the surface of water.
5. Respiration is a process that takes place in seeds even when some of the other life processes may not be very active (such as in a sack of wheat).
10. Measurement
1. A cubit as the length from the elbow to the finger tips was used in ancient Egypt. In ancient India, small length measurements used were an angul (finger) or a mutthi (fist).
Motion in a straight line is called rectilinear motion. In circular motion an object moves such that its distance from a fixed point remains the same. Motion that repeats itself after some period of time is called periodic motion
11. Light travels in straight lines and so cannot move around an object that is in its path. The result is a dark area or shadow wherever an object blocks light. Mirror reflection gives us clear images
12. Electricity
1. All electric cells have two terminals; a positive terminal and a negative terminal. In an electric circuit, the direction of current is taken to be from the positive to the negative terminal of the electric cell
2. Thin wire that gives off light is called the filament of the bulb.
13. Magnets
1. Freely suspended bar magnet always comes to rest in a particular direction, which is the North-South direction
2. Iron, nickel, cobalt are magnetic in nature.
3. Opposite poles of two magnets attract each other whereas similar poles repel one another.
4. Cassette tapes, video tapes and floppy disks are just a few examples of storage devices that use magnetic tape to store data. Because they use this type of tape, a magnet can erase or damage data stored on them.
14. Air - Air in motion is called wind. Air occupies space. Air is present in water and soil. Air is a mixture of nitrogen, oxygen, carbon dioxide, water vapor and a few other gases and dust particles
1. Why do earthworms come out mostly during rains?
15. Solid waste -
1. Blue bin is for materials that can be used again — such as plastics, metals and g ass. Green bins are for collecting kitchen and other plant or animal wastes
2. Method of preparing compost with the help of redworms is called vermicomposting. Redworms do not have teeth. They have a structure called ‘gizzard’, which helps them in grinding t food