Knowledge hub

Ques: Why is parallel arrangement used in domestic wiring? Ans: Parallel arrangement is used in domestic wiring because (i) Each and every appliance gets the same amount of voltage as that of the mains supply. (ii) If one component is switched off, others appliances can work properly. (iii) Fault in any branch of the connection can be easily identified. 

Ques: How does use of a fuse wire protect electrical appliances? Ans: The fuse wire is always connected in series combination with the live wire or electrical devices. If the flow of current exceeds the specified preset value due to some reason, then, the heat produced melts it and disconnects the circuit or the device from the mains. In this way, the fuse wire protects the electrical appliances from damage.

Ques 1: What is the importance of DNA copying in reproduction?   Ans 1: DNA (Deoxyribonucleic acid) is the genetic material found in the chromosomes, present in the nucleus of the cell. The DNA (Deoxyribonucleic acid) is the information site for making proteins and each specific type of protein leads to the specific type of body design.  Thus, it is the DNA molecule that specifies the body design of an individual. Therefore, it can be concluded that it is the DNA that gets transferred from parents to their offsprings and makes them look similar.   Ques 2: Why is variation beneficial to the species but not necessarily for the individual?   Ans 2: Variations are beneficial to the species than individual because s sometimes for a species,  the environmental conditions change so drastically that their survival becomes difficult.   For example, if the temperature of water increases suddenly, then most of the bacteria living in that water may die. Only few species that are resistant to

Ques 1. Development of a country can generally be determined by (i)  its per capita income (ii) its average literacy level (iii)  Health status of its people (iv)  all of the above Answer : (iv) all of the above   ( UNDP publishes the human development report(HDR) comparing the countries on the basis of educational level of the people, their health status and per capita income.  Ques 2. Which of the following neighbouring countries has better performance in terms of the human development than India?  (i) Bangladesh (ii) Sri Lanka (iii) Nepal (iv) Pakistan Answer : (ii) Sri Lanka ,  HDI(human development index) of Sri Lanka is 73 which is much higher than the Bangladesh, Nepal and  Pakistan which have 139,145 and 147 respectively.  Ques 3. Assume there are four families in a country. The average per capita income of these families is Rs 5000. If the income of three families are Rs 4000, Rs 7000 and Rs 3000 respectively, what is the income of the fourth family?  (i)  Rs 750

Ques 1: Asexual reproduction takes place through budding in   (a) amoeba. (b) plasmodium. (c) yeast. (d) leishmania. Ans 1: (c) Asexual reproduction takes place  in yeast through budding.   Ques 2: Which of the following is not a part of the female reproductive system in human beings?   (a) Ovary (b) Uterus (c) Vas deferens (d) Fallopian tube Ans 2: (c) Vas deferens is not a part of the female reproductive system, it is present in the male reproductive system in human beings.   Ques 3: The anther contains   (a) sepals. (b) carpel. (c) ovules. (d) pollen grains. Ans 3: (d) The anther contains pollen grains. Ques 4: What are the advantages of sexual reproduction over asexual reproduction?   Ans 4: Advantages of sexual reproduction:  » In sexual reproduction, more variations are produced. Thus, it ensures the survival of species in a population.   » The new formed individual is having the characteristics of both the parents. » Variations are more viable in

                                  Page: 119 Ques 1: What is the difference between a reflex action and walking?  Ans 1: » A reflex action is an automatic, rapid response to a stimulus. It does not involve any thinking. For example, we close our eyes immediately when the bright light is focused on our eyes.  » Walking, on the other hand, is a voluntary action. It is u under our conscious control.  Ques 2: What happens at the synapse between two neurons?  Ans 2: A very small gap that occurs b/w the last portion of the axon of one neuron and the dendrite of other neuron is known as a synapse. It acts as an one way valve to transmit impulses in one direction only. This one-directional transfer of impulses occurs as the chemicals are produced on only one side of the neuron i.e., the axon’s side. From axon, the impulses t travels across the synapse to the dendrite of the other neuron. Ques 3: Which part of the brain maintains posture and equilibrium of the body?  Ans 3: Cereb

Ques 1: Which of the following is a plant hormone?  (a) Insulin (b) Thyroxin  (c) Oestrogen (d) Cytokinin.  Ans 1: (d) Cytokinin is a hormone present in plants.  Ques 2: The gap between two neurons is called a  (a) axon. (b) synapse. (c) dendrites. (d) impulse. Ans 2: (b) The gap between two neurons is known as synapse.  Ques 3: The brain is responsible for  (a) thinking. (b) regulating the heart beat. (c) balancing the body. (d) all of the above. Ans 3: (d) The brain is responsible for neuro muscular co-ordination, thinking, regulating the heart beat and balancing the body. Ques 4: What is the function of receptors in our body? Think of situations where receptors  do not work properly. What problems are likely to arise?  Ans 4: Receptors are sensory structures (organs/tissues or cells) present all over the  body. The receptors are either grouped in case of eyes or ears, or scattered in case   of skin. Functions of receptors:  » They sense the ex

                                  Page: 95 Ques 1: Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans? Ans 1: In multi-cellular organisms, all the cells cell may not be in direct contact with the surrounding environment. Thus, simple diffusion can’t meet the requirements of all the cells. Ques 2: What criteria do we use to decide whether something is alive? Ans 2: Any visible movement such as walking, breathing, or growing, showing locomotion is generally used to decide whether something is alive or not. However, a living organism can also have movements, which are not visible to us through the naked eyes. Therefore, the presence of molecular movement inside the organisms is used to to decide whether something is alive or not. Ques 3: What are outside raw materials used for by an organism? Ans 3: An organism uses outside raw materials mostly in the form of food (Since life on earth depends on  CO 2  based molecules, most of

Ques 1: The kidneys in human beings are part of the system for  (a) nutrition. (b) respiration. (c) excretion. (d) transportation. Ans 1: (c) In human beings, the kidneys are part of the system for excretion.  Ques 2: The xylem in plants are responsible for  (a) transport of water. (b) transport of food. (c) transport of amino acids. (d) transport of oxygen. Ans 2: (a) In a plant, the xylem is responsible for transportation of water.  Ques 3: The autotrophic mode of nutrition requires  (a) carbon dioxide and water. (b) chlorophyll. (c) sunlight. (d) all of the above. Ans 3: (d) The autotrophic mode of nutrition requires carbon dioxide( CO 2)  , water( H 2 O) , chlorophyll and sunlight. Ques 4: The breakdown of pyruvate to give carbon dioxide, water and energy takes place in  (a) cytoplasm. (b) mitochondria. (c) chloroplast. (d) nucleus. Ans 4: (b) The breakdown of pyruvate to give  carbon dioxide( CO 2)  , water( H 2 O)  and energy takes place in