Saturday, May 10, 2014

10th CBSE Biology Solved Questions

Chapter - 6  Life Processes , Chapter - 7  Control And Co-ordination , Chapter - 8  How Do Organisms Reproduce ,Chapter - 9  Heredity And Evolution 

Chapter - 6  Life Processes

Q. 1 While eating you are advised not to talk. Why are you advised so? 1 Mark 

Ans. We are advised so because while eating some food particles might enter the wind pipe which can lead to choking. 

Q. 2 We say that movement is a characteristic of living organisms but we always don’t see visible movements in plants. Comment. 1 Mark 

Ans. We always don’t see visible movements in plants. It does not mean that they are not alive. Molecular movements take place in their body. 

Q. 3 If a person is working on a treadmill in a gymnasium, will it effect his rate of breathing? How? 2 Marks 

Ans. Yes, it will affect his rate of breathing. The rate of breathing will become fast to supply more oxygen to meet the increased demand of energy. 

Q. 4 If you compare your rate of breathing by feeling your chest movement with the number of times a fish opens and closes its mouth. Which will be higher and why? 2 Marks 

Ans. The number of times a fish opens and closes its mouth will be higher as the amount of dissolved oxygen in water is fairly low compared to the amount of oxygen in the air. Therefore, rate of breathing in aquatic organisms is much faster than in terrestrial organisms. 

Q. 5 Mucus is not used for churning the food or digesting it. Then why is it secreted in the stomach? 2 Marks 

Ans. Mucus is secreted in the stomach to protect its inner lining from being damaged by HCl. Excessive secretion of HCl can damage the lining and lead to peptic ulcer. 

Q. 6 In the process of Photosynthesis food A is prepared which gets converted into food B. What are A and B? Why is A converted to B? 2 Marks 

Ans. Food A is glucose and food B is Starch. 
A is converted to B as B is insoluble form of carbohydrate. It is more compact and hence, suitable for storage. 

Q. 7 When we are asleep we are not performing any activity still our life processes are going on. Why? 2 Marks 

Ans. “The maintenance functions of living organisms must go on even when they are not doing anything particular.” That is why the life processes are going on even while we are asleep or not performing any activity. 

Q. 8 Leaves of a healthy potted plant were coated with petroleum jelly. How will it affect the plant? State two reasons. 3 Marks 

Ans. The plant will not remain healthy for long due to the following reasons:- 

1. There will be no transpiration. 

2. There will be no exchange of gases which will affect the rate of photosynthesis. 

Chapter - 7  Control And Co-ordination 

Q. 1 A person suffered a head injury, due to which he faces breathing problem. No problem was detected with his respiratory system. What could be the cause of this problem? 1 Mark 

Ans. As the problem is caused due to head injury, it could be related to “Pons” a part of Hind brain responsible for regulation of respiration. 

Q. 2 A man becomes unconscious due to head injury. A pin is pricked on his foot, he withdraws his foot. Why? Explain. 3 Marks 

Ans. It is reflex action. Stimulus is perceived by receptor (skin). Sensory nerve sends the sensation from receptor to the spinal cord. Then spinal cord sends the message through motor nerves to the effectors. Effectors i.e. muscles help in withdrawing his foot. 

Q. 3 In a family of normal sized members, there are two exceptions, one member is dwarf and one is tall like “Khali”. What could be the cause of it? 2 Marks 

Ans. In case of dwarfs, there is a deficiency of growth hormone from Pituitary gland and in case of giants excess of growth hormone is produced during childhood. 

Q.4 Why do you blink your eyes as bright light is focused on you? 1 Mark 

Ans. We blink in order to protect the eye from bright light which otherwise would damage the retina. 

Q. 5 There is a potted plant in your drawing room, after few days you note that plant has bent to one side. What could be the reason? How has this movement been co- coordinated? 1 Mark 

Ans. The plant has bent to one side due to phototropic movement of the stem. This movement is due to unequal growth of the stem on both sides. This growth is initiated by the hormone auxin. 

Q. 6 A leaf shaped gland is present above the intestine. The secretion of this gland regulates the metabolism of sugar in blood. Name the secretion and gland. 1 Mark 

Ans The name of the gland is pancreas. The secretion is Insulin from special cells in it. 

Chapter - 8  How Do Organisms Reproduce 

Q. 1 A couple wants to space the birth of their second child. Suggest one preventive method which could be observed 1 Mark 

(a) By the husband (b) By the wife for the same. 

Ans. (a) Use of condoms by the husband 

(b) Use of oral pills or loop or Copper-T by the wife. 

Q. 2 A girl attains her puberty at the age of 11 years and a boy at 13 years but, still they are asked to refrain from sex, why? 2 Marks 

Ans. They are asked to refrain from sex because:- 

1. They are not physically, emotionally mature enough to be able to bear the responsibility of the child. 

2. They may suffer from reproductive tract infections. 

Q.3 A pregnant woman visits a doctor to determine the sex of her child. The doctor refused to perform the test. Why is she being denied? 2 Marks 

Ans. The doctor refused to perform the test in order to prevent female foeticide which leads to an alarming decline in child sex ratio. 

Q. 4 Blue prints of body design are stored in the DNA. Why? 3 Marks 

Ans. The chromosomes present in the nucleus of a cell contain information for inheritance of features from parents to next generation in the form of DNA molecule. The DNA is the information source for making proteins. Thus, blueprints of the body design are stored in the DNA. 

Q. 5 Producing individuals by parents consume a lot of energy. So, why should an individual organism waste energy in the process, it does not need to stay alive? 3 Marks 

Ans. Reproduction, unlike other life processes is not essential to maintain the life of an individual organism. But it is essential for providing stability to the population of species. Maintaining the species is essential for maintaining balance in nature. 

Q. 6 Protozoan reproduce by binary fission as well as by multiple fission. In your opinion which process is better and why? 

Ans. Multiple fission is better than binary fission because:- 

(a). More number of individuals is produced. 

(b). It helps to tide over unfavourable conditions. 

Chapter - 9  Heredity And Evolution 

Q. 1 Clones of sheep are carbon copy of each other except physical health. What kind of variation is it? 1 Mark 

Ans Phenotypic variation 

Q. 2 What will be the sex of a baby if sperm carrying X chromosome fertilizes egg in human beings. Why? 2 Marks 

Ans. It will be a baby girl because fusion of gametes having X chromosomes leads to homozygous condition producing zygote with XX composition. 

Q. 3 Feather imprints were preserved along the dinosaur’s bones but dinosaurs could not fly. What was the significance of feathers in reptiles and later on for other species? 2 Marks 

Ans. It is believed that feathers in dinosaurs might have provided insulation in cold weather but later on became useful for flights in birds. 

Q. 4 Wild cabbage was converted into number of variants like cauliflower, broccoli and cabbage by man. What is this process known as? Does it play an important role in organic evolution? 3 Marks 

Ans. This process is known as artificial selection. It plays an important role in organic evolution because it is parallel to natural selection. It helps to produce new species having useful traits in less time. 

Q. 5 How are variant genotypes produced? 3 Marks 

Ans. Variant genotypes can be produced by:- 

1. Mutation in genes and chromosomes.   2. Recombination of genes.  3. Hybridization of genes. 

Q. 6 Can geographical isolation lead to speciation? How?

Ans. Yes, geographical isolation can lead to speciation. Due to geographical isolation, the members of two sub groups may not be able to interbreed as a result of genetic drift. Natural selection also operates differently in these subgroups. This leads to speciation. 

Q. 7 What will be the blood groups of offspring’s produced by the parents having following genotype?                    Male  -  IAIB

          Female -IOIA
IAIA (ii)

Ans.  Blood groups will be:

(i) A          (ii) A          (iii) B           (iv) AB

Q. 8 A woman with blonde curly hair married a man with black soft hair. All of their children in first generation had black soft hair but in next generation children had different combinations in the ratio of 9:3:3:1. State the law that governs this expression.

Ans. Law of independent assortment which states that the factors of different pairs of contrasting characters do not influence each other. They are independent of one another in their assortment.

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