Revision Series | Science | General Science | 28

Answer- D

Answer- A

Answer- B

Hind brain consists of three parts-cerebellum, pons and medulla oblongata.

Cerebellum is concerned with coordination of muscular activity and body balance.

Pons carries impulses from one hemisphere of the cerebellum to the other and coordinates muscular movements on both sides of the body.

Medulla oblongata controls the activity of internal organs,heart beat, breathing etc

Answer- B

• The force that blood exerts against the wall of a vessel is called blood pressure.
• This pressure is much greater in arteries than in veins as arteries carry oxygenated blood from heart to other parts of body that emerge at high pressure and remains in the same.
• The pressure of blood inside the artery during ventricular systole (contraction) is called systolic pressure and pressure in artery during ventricular diastole (relaxation) is called diastolic pressure.
• The normal systolic pressure is about 120 mm of Hg and diastolic pressure is 80 mm of Hg. Blood pressure is measured with an instrument called sphygmomanometer.

Answer- c

Answer- A

If an opaque object on the path of light becomes very small, light has a tendency to bend around it and not walk in a straight line – this effect is known as the diffraction of light.

Answer- D

• Concave mirrors are commonly used in torches, searchlights and vehicles headlights to get powerful parallel beams of light as these mirrors possess the ability to focus parallel rays of light to a point, produce a large size image.
• They are often used as shaving mirrors to see a larger image of the face The dentists use concave mirrors to see large images of the teeth of patients. Large concave mirrors are used to concentrate sunlight to produce heat in solar furnaces

Answer- B

• Phosphorus, Iodine and Bromine are all non-metals. They do not generally react with water, but are highly reactive in air. Of the three, phosphorus is the most reactive non-metal. It catches fire on being exposed to air.
• To prevent the contact of phosphorus with atmospheric oxygen, it is stored in water. Bromine is the only non- metal which exists as a liquid in room temperature.
• Sodium is a metal which is highly reactive in nature. It reacts rapidly with air and water. A lot of energy is generated in these reactions. Therefore, it is stored in kerosene oil.

Answer- B

Chromosomes are thread-like structures located inside the nucleus of animal and plant cells.

Each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA).

Passed from parents to offspring, DNA contains the specific instructions that make each type of living creature unique.

The term chromosome comes from the Greek words for color (chroma) and body (soma).

Scientists gave this name to chromosomes because they are cell structures, or bodies, that are strongly stained by some colorful dyes used in research.

Humans have 23 pairs of chromosomes, for a total of 46 chromosomes.

In fact, each species of plants and animals has a set number of chromosomes. A fruit fly, for example, has four pairs of chromosomes, while a rice plant has 12 and a dog, 39.

Answer- D

• An organism comprising of one cell is called unicellular. Amoeba, paramecium, hen’s egg and White Blood Cells are all examples of unicellular organisms.
• Organisms made up of more than one cell are called multicellular.
• In unicellular organisms, the single cell itself performs all the activities that multicellular organisms do, like respiration, growth, excretion, reproduction, etc; which are performed by groups of tissues in multicellular organisms.