Why cannot fertilization take
Question: Why cannot fertilization take place in flowers if pollination does not occur ? Solution: Pollination is essential for bringing the male gametes. In the absence of pollination, there will be no male gamete to perform fertilization....
Read More →In Tobacco, male gametes have 24 chromosomes.
Question: In Tobacco, male gametes have 24 chromosomes. (a) What is the number of chromosomes in the female gamete ? (b) What is the number of chromosomes in the zygote ? Solution: (a) 24 (b) 48....
Read More →Correlate the number of chromosomes with
Question: Correlate the number of chromosomes with the size of the organism and answer the following questions : (a) Do larger organisms have more number of chromosomes/cell ? (b) Can organism with fewer chromosomes reproduce more easily than organism with more number of chromosomes ? (c) More the number of chromosomes/cell, greater is the DNA content. Justify. Solution: (a) No. There is no correlation between chromosome number and size of the individual. (b) No. Chromosome number does not affec...
Read More →Would a Planaria cut vertically
Question: Would a Planaria cut vertically into two halves regenerate into two individuals ? Solution: Yes. Each piece of Planaria is able to grow the missing parts and form the complete organism....
Read More →Give two reasons for the appearance
Question: Give two reasons for the appearance of variations among the progeny formed by sexual reproduction. Solution: Variations appear in the progeny of sexually reproducing organisms due to Random separation and coming together of chromosomes during gamete formation and gamete fusion Crossing over and mutations. Coming together of chromosomes of the parents....
Read More →Why does Bread Mould grow profusely
Question: Why does Bread Mould grow profusely on a moist slice of bread rather than on a dry slice of bread ? Solution: Growth of Bread Mould requires both water and nutrients. Dry slice of bread contains nutrients but no water. Therefore, Bread Mould does not grow over it. Moist slice possesses both water and nutrients. Hence, Bread Mould grows over it....
Read More →Colonies of yeast fail to multiply in water
Question: Colonies of yeast fail to multiply in water but multiply in sugar solution. Give one reason for this. Solution: Yeast is heterotrophic. It obtains its nourishment from outside. Plain water cannot provide nourishment to yeast while sugar solution can do so. Therefore, Yeast multiplies in sugar solution and not in plain water....
Read More →Explain how, offspring and parents
Question: Explain how, offspring and parents of organisms reproducing sexually have the same number of chromosomes/DNAs.(CCE 2014, CBSE Delhi 2017) Solution: The parents are diploid (2n) as each of them has two sets of chromosomes (DNAs). They form haploid (In) male and female gametes through the process of meiosis. The haploid gametes have one set of chromosomes (DNAs). During fertilization, one male gamete fuses with one female gamete. It restores the diploid (2n) chromosome/DNA number in the ...
Read More →What is a clone ?
Question: What is a clone ? Why do offspring formed by asexual reproduction exhibit remarkable similarity ? Solution: Clone is an exact genetic replica of another individual. All the offspring formed from a parent through asexual reproduction are clones of one another as well as their parent. The remarkable similarity of asexually produced daughter individuals is due to genetic similarity as they possess exact copies of DNA of their parent....
Read More →Can you consider cell division as a type
Question: Can you consider cell division as a type of reproduction in unicellular organisms ? Give one reason. Solution: Yes. Cell division in a unicellular organism which produces two dughter cells, actually forms two daughter individuals....
Read More →In a bisexual flower, inspite of the young
Question: In a bisexual flower, inspite of the young stamens being removed artificially, the flower produces fruit. Provide a suitable explanation for the above situation. Solution: The open flowers are generally cross pollinated. Removal of stamens of a bisexual flower will not affect pollination of its intact pistil and formation of fruit....
Read More →Why the flow of signals in a synapse is from
Question: Why the flow of signals in a synapse is from axonal end of one neuron to dendrite end of another neuron but not the reverse ? Solution: As the electrical impulse reaches the axon terminal in the region of axon-dendrite synapse, it stimulates the exocytosis of vesicles containing neurotransmitter (e.g. acetylcholine). Neurotransmitter attaches to the chemoreceptor sites of the membrane covering the dendrite end of synapse. It creates a new impulse that travels through cell body and axon...
Read More →How does chemical co-ordination
Question: How does chemical co-ordination take place in animals ? Solution: In animals, chemical coordination is achieved through the agency of hormones which function as chemical messengers or informational molecules. Hormones are secreted by ductless glands in response to specific conditions or nervous stimulation. Timing and amount of a hormone released are regulated by feed-back mechanism. After a meal, sugar level of blood rises. It is detected by pancreas. Pancreas responds by producing ho...
Read More →“Nervous and hormonal systems together
Question: Nervous and hormonal systems together perform the function of control and coordination in human being. Justify the statement. Solution: Both nervous system and hormonal (or endocrine) system are involved in control, regulation and coordination of body parts. Nervous system is connected to receptors of all senses. Information obtained from sensory organs is passed rapidly to CNS for interpretation. On the basis of interpretation, a message is sent to effector organ or organs (muscles, g...
Read More →What are reflex actions ?
Question: What are reflex actions ? Give two examples. Explain a reflex arc. Solution: Definition:Reflex actions seem to have evolved quite early in the physiology of animals when complex neuron network for processing had not been evolved. Even after evolution of processing centres, reflex actions have continued to persist because of their more efficiency for quick responses.Two Examples: On being pricked or coming in contact with hot surface, hand is withdrawn even before pain is perceived (by ...
Read More →Name the various plant hormones.
Question: Name the various plant hormones. Also give their physiological effects on plant growth and development. (CCE 2016) Solution: Five types auxin, gibberelin, cytokinin, ethylene and abscisic acid. Auxin:Cell enlargement, root formation, apical dominance, inhibition of abscission, fruit growth. Gibberellin:Growth in stem and leaves, higher fruit yield, overcoming dormancy. Cytokinin:Essential for cell division, differentiation, prevention of senescence and overcoming apical dominance. Ethy...
Read More →Mention one function for each of these hormones.
Question: Mention one function for each of these hormones. (a) Thyroxine (b) Insulin (c) Adrenaline (d) Growth hormone (e) Testosterone. (CCE 2010, 2013, 2015) Solution: (a)Thyroxine: Regulates metabolism of carbohydrates, fats and proteins, release of energy and body activity. (b)Insulin:Regulates blood glucose by its absorption in liver, muscles (for formation of glycogen) and individual cells (for metabolic activity). (c)Adrenaline:For meeting an emergency by increasing heart rate and supply ...
Read More →What constitutes the central and
Question: What constitutes the central and peripheral nervous systems ? How are the components of central nervous system protected?(CCE 2012) Solution: Central Nervous System (CNS):It is hollowed part of nervous system that lies along the mid-dorsal part of the body. It has two parts, brain (located in the head) and spinal cord (located in the trunk). Peripheral Nervous System (PNS):It is soild lateral part of nervous system that develops from CNS and connects different parts of the body with CN...
Read More →What are the major parts of the brain ?
Question: What are the major parts of the brain ? Mention the function of different parts. Solution: Major Parts of BrainFore-Brain: Olfactory lobes (2), Cerebral hemispheres (2) or cerebrum, Diencephalon.Mid-Brain: Cerebral peduncles, Corpora quadrigemina.Hind Brain: Pons, Cerebellum, Medulla oblongata.Functions Olfactory Lobes: Receive sensation of smell from olfactory epithelium and relay the same to temporal lobes of cerebral hemispheres. Cerebral Hemispheres: Frontal Lobes: Centres of intel...
Read More →Draw the structure of a neuron and
Question: Draw the structure of a neuron and explain its function. (CCE 2011) Solution: Functions: Dendrites: Picking up sensations and transmitting the same to cell body. Cell Body: Sustaining structure and function of dendrites and axon, Functioning as passageway for transmission of sensation or impulse to axon. Axon: Carrying impulse to another neuron, muscle, gland and organ. A single impulse can be transmitted to several structures with the help of axon terminals....
Read More →Answer the following : (a) Name the endocrine gland
Question: Answer the following : (a) Name the endocrine gland associated with brain. (b) Which gland secrets digestive enzymes as well as hormones ? (c) Name the endocrine gland associated with kidney. (d) Which endocrine gland is present in males but not in females ? Solution: (a) Endocrine Gland Associated with Brain. Pituitary. (b) Gland with Digestive Enzymes and Hormones. Pancreas. (c) Endocrine Gland Associated with Kidneys. Adrenal glands. (d) Endocrine Gland in Males only. Testis....
Read More →Answer the following :
Question: Answer the following : (a) Which hormone is responsible for the changes noticed in female at puberty ? (b) Dwarfism results due to deficiency of which hormone ? (c) Blood sugar level rises due to deficiency of which hormone ? (d) Iodine is necessary for synthesis of which hormone ? Solution: (a) Puberty Changes in Females. Oestrogen. (b) Dwarfism. Growth hormone. (c) Blood Sugar. Insulin. (d) Iodine Hormone. Thyroxine...
Read More →What happens at the synapse between the neurons ?
Question: What happens at the synapse between the neurons ? Or State the events in sequence that take place when an electrical impulse travels from a dendritic tip of a nerve cell to another nerve cell. (CCE 2011, 2012, 2013) Solution: At synapse, axon terminal is expanded to form presynaptic knob. The dendrite terminal that lies close to it is slightly broadened and depreseed to form post-synaptic depression. A fluid filled narrow space, called synaptic cleft, occurs between the two. When an im...
Read More →What will happen if intake of iodine
Question: What will happen if intake of iodine in our diet is low ? Solution: Low intake of iodine will affect production of thyroxine. Reduced thyroxine reduces metabolism of protein, carbohydrate and fat. Physical activity and consumption of energy are impaired. With continued reduced intake of iodine, thyroid gland enlarges (in order to produce more thyroxine). It results in swelling of neck called goitre....
Read More →What is a tropic movement ?
Question: What is a tropic movement ? Explain with an example. (CCE 2011) Solution: Tropic Movement:It is directional paratonie growth movement of curvature in which direction of movement is determined by the direction of the stimulus. They mostly occur in cylindrical organs. Growth response occurs due to differences in the distribution of auxin. Example. On unidirectional exposure to light, shoots bend towards the source of light (positive phototropism) while roots may bend away from the source...
Read More →