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3251.

Question : How will an organism be benefited if it reproduces through spores?

Answer»

Solution :The reproduction by spores takes place in plants. Spores are covered by a hard protective COAT which enables them to surviveunder unfavourable conditions, LIKE lack of food, lack of water and EXTREME temperature. Under favourable conditions the spores can grow to produce new plants. Thus, the reproduction by spores benefits the plant because by surviving under adverse conditions, the spores make these plants live LONGER.
Discussion
3252.

Question : How is a vein different from an artery gt?

Answer»

In CARRYING DEOXYGENATED blood
In having GREATER elasticity
In having VALVES
All of the above

Answer :d
Discussion
3253.

Question : How is a taxon (pl. taxa) defined ?

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Solution :Each CATEGORY in a taxonomical hierarchy REPRESENTS a RANK and is CALLED taxon.
Discussion
3254.

Question : How is a cancer cell different from a normal cell ?

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Solution :Cancer is an abnormal and uncontrolled division of CELLS that invade and destroy the surrounding tissue, forming a tumor or neoplasm. It is a heterogenous group of cells, that do not RESPOND to the NORMAL cell division. The cancer cells move to distant parts of bodies such as lungs, bones,liver, skin and BRAIN.
Discussion
3255.

Question : How human evolution take place over the years ?

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Solution :Human evolution. The study of human evolution indicates that all of human beings belong to a SINGLE species Homo sapiens that evolved in Africa.
1. DNA sequences have been used for studying human evolution.
2. Due to the diversified human forms and features, is the common way for identifying the races.
3. Few thousand YEARS ago some ancestors left Africa while others STAYED back.
4. The residents spread across Africa and the migrant spread across the planet from Africa to West Asia, Central Asia, Eurasia, South Asia, East Asia, Indonesia, Philippines, Australia and AMERICA.
5. They went forwards and backwards with groups separating from each other, or sometime coming TOGETHER.
6. Like all other species, they were also living their lives to the best of their ability.
Discussion
3256.

Question : How has the traditional use of wind and water energy been modified for our convenience ?

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SOLUTION :The TRADITIONAL use of wind energy has been modified by constructing wind FANS and wind energy farm to generate electricity.
The traditional use of WATER energy has been modified by constructing DAMS and convert the potential energy of falling water into electricity for our convenience.
Discussion
3257.

Question : How has the method of 'artificial selection' by humans helped in the evolution of different vegetables?

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Solution :A wild variety of a plant may show different variations. Humans have selected some such variants and grown them for GENERATIONS and during the course of time, they have become totally different species.
For example, variants in wild CABBAGE were selected on the basis of certain features to GENERATE different vegetables.
(i)Short distances between leaves, led to formation of green leaf buds-the common cabbage.
(ii) Arrested flower development has BRED broccoli.
(iii) The variant with sterile flowers has made the cauliflower.
(iv) Variant with swollen leaf parts-kohlrabi.
(v) Variant with larger leaves-kale.
Discussion
3258.

Question : How doest nervous system differ from the endocrine system is forming control and co-ordination in animals?

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SOLUTION :
Discussion
3259.

Question : How does we detect the smell of agarbatti ( incense stick )

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SOLUTION :OLFACTORY receptors of our nose detect the smell of AGARBATTI and ransmit this INFORMATION to the brain.
Discussion
3260.

Question : How does water affect the rate of photosynthesis in plants?

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Solution :Water controls the opening and closing of stomata. The deficiency of water causes stomata to open very LITTLE or it may even remain CLOSED. Therefore, `CO_(2)`(required as a RAW material for photosynthesis) cannot ENTER into the leaves and thus lack of water slows down the rate of photosynthesis.
Discussion
3261.

Question : How does use and disuse of an organ help in evolution of a new species?

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Solution :According to Lamarck, those organs which are used regularly become STRONG and more developed. On the other hand, those organs which are not used regularly become WEAK and DEGENERATE. Such CHARACTERS are inherited to the offsprings and so on. In the due course of time, such characters become permanent in later generations and become quite different from their ancestors, resulting in the formation of a new SPECIES.
Discussion
3262.

Question : Howdoesthe pulmonaryarteryandpulmonary veindifferin theirfunction whencomparedto a normalarteryand vein ?

Answer»

SOLUTION :All arteries carry oxygenated BLOOD, except pulmonary arteries, which carry DEOXYGENATED blood from the right ventricle to the LUNGS.
All veins carry deoxygenated blood, except pulmonary veins, which carry Oxygenated blood from the lungs and to the left atrium of the Heart.
Discussion
3263.

Question : How does the process of budding differ from the process of spore formation.

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SOLUTION :
Discussion
3264.

Question : How does the process filtration occur in human nephron ? Draw a block diagram / flow chart.

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SOLUTION :
Discussion
3265.

Question : How does the mechanism of heredity work ?

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Solution :Both parents contribute equally to the inheritance of the progeny during sexual reproduction.
`rarr` Depending on the genes/factors inherited from parents, the traits in the progeny are decided.
Each offspring has two sets of genes of which one is paternal and other maternal one.
`rarr` The genes are transmitted through parent.s chromosomes.
`rarr` The diploid chromosome number is reduced to haploid by meiotic division at the time of gamete FORMATION.
When haploid GERM CELL (gamete) of male and female parents fuse to form zygote during fertilisation.
`rarr`Zygote is the first cell of new progeny.
`rarr` The normal number of chomosomes in the offspring in restored because it receives two COPIES of each chromosome, one each from the male and female parent through gametes involved in fertilisation.
`rarr` This ensures the stability of the DNA of the species.
Such MECHANISM of inheritance is used by all sexually reproducing organisms.
Discussion
3266.

Question : How does the light dependent reaction differ from the light independent reaction? What are the end product and rectants in each? Where does each reaction occur within the chloroplast?

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Solution :Light dependent photosynthesis is called Hill reaction or Light reaction. The Light independent reactions are called Biosynthetic PHASE.

In the light dependent reaction the CHLOROPHYLL absorb the light ENERGY and convert it into chemical energy ATP and `NADPH_2`. In the light independent reaction CO, is reduced into carbohydrates with the help of light generated ATP and `NADPH_2`. Light dependent reaction is carried out in the Grana of the chloroplast. The Light independent reaction is carried out in the stroma of the chloroplast.
Discussion
3267.

Question : How does the embryo get nourishment inside the mother's body ?

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SOLUTION :The embryo GETS nourishment from the mother.s blood with the help of special tissue CALLED placenta. Placenta contains villi on the embryo.s side of the tissue through which GLUCOSE and OXYGEN pass from the mother to embryo.
Discussion
3268.

Question : How does the creation of variations in a species promote survival?

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Solution :If the variation in an individual of a PARTICULAR species helps it to survive in an otherwise unfavourable environmental CONDITION, it WOULD be passed on to the future generations of the species, thereby promoting SURVIVAL of the species.
Discussion
3269.

Question : How does the creation of variations in a species promote survival ?

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Solution :DEPENDING on the nature of variations different individuals WOULD have different KINDS of advantage eg. Bacteria variants which can tolerate heat have better SURVIVAL chances in heat wave in comparison to non-variant bacteria having no capacity to tolerate heat wave.
Discussion
3270.

Question :How does stomatal pore open and close ?

Answer»

Solution :The OPENING and closing of the pore is a FUNCTION of the GUARD. The guard cells swell when water flows into them CAUSING the stomatal pore to open. Similarly the pore closes if the guard shrink.
Discussion
3271.

Question : How does respiration occur in the roots of the plant?

Answer»

Solution :Air is present in between the particles of the soil. The roots take the oxygen by the process of diffusion. Oxygen first diffuses into the root hairs and reaches all other cells of the root for RESPIRATION. `CO_(2)`produced in the cells MOVES out through the root hairs by the process of diffusion. For respiration, in OLDER roots, where root hair is not present, the EXCHANGE of GASES takes place through lenticels (tiny openings in the protective layer) by the process of diffusion.
Discussion
3272.

Question : How does respiration occur in the leaves?

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Solution :Leaves have TINY openings on their LOWER surface called STOMATA. The exchange of gases TAKES place through the stomata by the process of diffusion.
Discussion
3273.

Question : How does respiration occur in the stem of the plant?

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SOLUTION :In the stem of herbaceous plants, stomatas are PRESENT. So, the exchange of gases takes place through stomata by the process of DIFFUSION. In the woody and HARD stems of big plants, the exchange of gases takes place through lenticels which are present on the bark of the stem.
Discussion
3274.

Question : How does reproduction link to variation ?

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Solution :Every organism produces offsprings either through asexual or through sexual reproduction.
`RARR` The offsprings produced through these reproductive processes are similar, but subtly different.
`rarr` In asexual reproduction, although all the offsprings resemble each other and to their single parent, yet minor variation ARISE in them.
`rarr` Very little differences AMONG the INDIVIDUAL plants can be seen in a field of sugar CANE.
`rarr` In most of sexually reproducing animals including human beings, quite distinct variations are visible among offsprings.
Discussion
3275.

Question : How does reproduction help in providing stability to the populations of species?

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Solution :The consistency of DNA copying during reproduction is important for maintenance of body design FEATURES that allow the organism to live in a particular area. This consistency of DNA copying provides stability to the populations of species. Reproduction is responsible for CONTINUATION of a species. Stability to populations of species is ATTAINED by equalising the birth and death RATIO of individuals. Birth is POSSIBLE only due to reproduction.
Discussion
3276.

Question : How does reproduction help in providing stability to populations of species?

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Solution :In sexual reproduction, more VARIATIONS are PRODUCED. Thus, it ENSURES SURVIVAL of species in a POPULATION.
Discussion
3277.

Question : How does reproduction help in providing stability to populations of species ?

Answer»

Solution :Reproduction gives rise to NEW offsprings of a species. No organism is immortal. High death-rate reduce the size of population. The rates of BIRTH and death in a GIVEN population will determine its size.
So, reproduction is the process by which organisms increase their population and HELP in PROVIDING stability to population of species.
Discussion
3278.

Question : How does rainwater harvesting structures recharge ground water?

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Solution :Rainwater HARVESTING is a technique of collecting and storing rainwater for future use. The main purpose of rainwater harvesting is to make the rainwater percolate under the GROUND, so as to recharge .groundwater level..
Methods of rainwater harvesting
(i) Roof TOP rainwater harvesting:
The rain water that falls on the roof of the houses, apartments and commercial buildings, etc, is collected and stored in the surface tank and is used for domestic purpose.
(ii) Recharge pit:
The collected rain water is directed into the percolation pits through pipes for filteration. After filteration the rainwater enters the recharge pits or ground wells.
Digging of tanks or lakes (Eris): Eris are constructed in such a way that, if the water in one eri overflows, it automatically GETS diverted to the eri of the next village, as these eris are interconnected.
Ooranis:
These are small ponds to collect rainwater. They are used for various domestic purposes.
Discussion
3279.

Question : How does photosynthesis take place on plants that have, red, brown and yellow leaves, and are not green? How do they prepare food?

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Solution :These leaves have a much LARGER concentration of chromoplasts, which synthesize and store pigments such as orange carotenes, yellow xanthophylls and other red pigments. But these leaves, still POSSESS CHLOROPHYLL ‘a’ and chlorophyll .b. and can synthesize food. But these leaves have more chromoplasts and so the leaves do not appear green. Yet they can PREPARE food.
Discussion
3280.

Question : (i)Howdoes overload and short-circuit occur in an electric circuit ? Explain . What is the function of fuse during this situation ?(ii)Mention two properties of magnetic field lines .

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Solution :OVERLOADING can oceur when the live wire and the neutral wire come into direct contact.
This occurs when the INSULATION OT wires is damaged or there is a fauli in the applianee.
u such a situation, the current in the cireuit abruptly increases.
The heating that TAKES place in thc luse melts it to break the electrie circuit and prevents the electric APPLIANCES trom possible damage.
(ii) No two ficld lines are found to cross each otiher.
he density of the magnetic field lines are more in their polcs.
The nagnetic ficld lines emerge from north pole and merge at south pole.
nside the nagnet, the direction of field lines is from its south pole to its north pole.
Thus ihe magnetie ficld lines are closed curves.
Discussion
3281.

Question : How does our body maintain blood sugar level ?

Answer»

Solution :TIMING and amount of hormone released are regulated by feed back mechanisms. If sufar LEVEL in blood rises, cells of pancreas DETECT and secrete more INSULIN which leads to the FALL of sugar level.
Discussion
3282.

Question : How does natural selection differ from genetic drift?

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Solution :Natural selection selects those VARIATIONS in a POPULATION which give a survival advantage and HELPS the better population to fit their environment better.
On the other hand, genetic drift can alter gene frequencies in small populations and PROVIDE diversity WITHOUT any survival benefits.
Discussion
3283.

Question : How does natural vegetative propagation occur?

Answer»

Solution :Natural vegetative propagation occurs from modified stems, roots, leaves and bulbs. Modified short stems, onion BEAR bulbs which when grown in soil DEVELOP into a new plant. Runners - stems of doob grass have nodes and internodes. From nodes, roots are developed that formed a new plant. Rhizome of ginger is a horizontal underground stem. If kept in soil with ADEQUATE moisture it develops into a new plant. TUBER of potato bears eyes (buds), which if sown (entire or in pieces) in soil develops into a new plant.
Modified root tubers of sweet potato also grow into a new plant.
Buds produced in the NOTCHES along the leaf margin of Bryophyllum fall on the soil and develop into new plants.
Discussion
3284.

Question : How does mining cause pollution ?

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SOLUTION :MINING causes pollution because of the large AMOUNT of discarded SLAG when a ton of metal extracted.
Discussion
3285.

Question : How does Mendel's experiment show that traits may be dominant or recessive?

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SOLUTION :The character which GETS expressed in the presence of its contrasting form is TERMED dominant trait. The trait which remains unexpressed in the presence of its contrasting form is termed as recessive trait.
Discussion
3286.

Question : How does locomotion take place in leech?

Answer»

Solution :Locomotion in leech takes place by
(a) Looping or Crawling MOVEMENT: This type of movement is BROUGHT about, by the contraction and relaxation of muscles. The two suckers, serve for attachment, during movement on a substratum.
(B) Swimming movement: Leeches swim very ACTIVELY and perform undulating movements in water.
Discussion
3287.

Question : How does leech suck blood from the host?

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Solution :The Anterior SUCKER HELPS in FEEDING, while both the suckers, HELP in attachment and locomotion.
Discussion
3288.

Question : How does leech respire?

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SOLUTION :LEECH RESPIRE through SKIN.
Discussion
3289.

Question : How does insulin deficiency occur ?

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SOLUTION :Insulin deficiency occurs by the DESTRUCTION of B-cells of the pancreas and BLOOD glucose levels are increased (HYPERGLYCEMIA).
Discussion
3290.

Question : How does frog respire with the help of skin

Answer»

Solution :(1)Respiration through SKIN is called cutaneous respiration.
(2)This type of respiration is seen in some invertebrates and vertebrates
(3)In frog, skin is an additional or secondary or accessory respiratory organ. (Similarly Earthworm also respires through skin only. It lives in moist places only )

(4)Frog keeps their skin moist . Skin has a large number of mucus glands which secrete mucus ONTO the surface of the skin.
(5)The mucus layer retains water and reduces evaporation of water from body .
(6)Frog skin is supplied with a large number of blood vessels which help in absorbing oxygen from the water.
Discussion
3291.

Question : How does fossilization occurs in plants?

Answer»

Solution :The process of formation of fossil in the rocks is called Fossilization. The common methods of fossilization includes :
1. Petrifaction : Minerals like silica slowly penetrate in and replace the original organic tissue and forms a rock like fossil. This method of fossilization can preserve hard and soft parts mostly bones and wood fossils are petrified.
2. Mold and cast : A replica of a PLANT or animal is preserved in sedimentary rocks. When the organism gets buried in sediment it is DISSOLVED by underground water leaving a hollow depression called a mold. It shows the original shape, but does not reveal the internal structure.
Minerals or sediment fill the hollow depression and forms a cast.
3. Preservation : Original remains can be preserved in ice or amber (tree sap). They protect the organisms from decay. The entire plant or animal is preserved.
4. Compression :
When an organism dies, the hard parts of their bodies settle at the bottom of the sea bed and are covered bysediment. The process of sedimentation goes on continuously and fossils are formed.
5. Infiltration or REPLACEMENT :
The precipitation of minerals takes place which later on infiltrate the cell wall. The process is brought about by several mineral elements such as silica, calcium carbonate and magnesium carbonate. Hard parts are dissolved and replaced by these minerals.
Discussion
3292.

Question : How does fertilization take place in human beings? Fertilization takes place once in a month. Comment.

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Solution :a] Sperm enters through the VAGINAL passage during sexual intercourse and moves upwards.
b] Ovum (egg cell) released from the ovary reaches the oviduct.
c] Sperm encounters ovum in the oviduct and they FUSE to FORM zygote. This process is termed as FERTILIZATION.
Fertilization takes place only once in a month in human FEMALE because only one egg (ovum) in released from ovary every month.
Discussion
3293.

Question : How does fertilisation take place in human beings ? Fertilisation occurs once in a month. Comment.

Answer»

Solution :Fertilisation takes place in the oviduct. The fusion of sperm and ovum results in fertilisation. The sperms enter through the vaginal PASSAGE during sexual INTERCOURSE. They travel upwards and reach the oviduct where they may encounter the egg. The fertilised egg (zygote) starts dividing and form a BALL of cells or embryo. The embryo is implanted in the lining of the UTERUS where they continue to grow and DEVELOP organs to become foetus.
Fertilisation occurs once in a month because only one egg is released during each menstrual cycle, which is about 28 days. When a girl is born, the ovaries contain thousands of immature eggs. These eggs mature one at a time during puberty, each month. Hence, only one egg is released from the ovary during each cycle. Thus fertilisation can happen only once during each month.
Discussion
3294.

Question : How does exchange of gase take place in roots of plants ?

Answer»

Solution :Root cells take up OXYGEN from soil by the process of diffusion. Root hair remain in contact with `O_(2)`present in between the soil particles. `O_(2)` diffuses into the root hair and PASSES into other cells of root . Simulataneously, `CO_(2)` moves out into the soil . Older protionsof root do not have root hairIn suchareastiny openings called lenticelsare presentthrough which exchange takes place :
NOTE : In older stem ALSO lenticels are present for GASEOUSEXCHANGE whilein youngherbaceous stems, stomata are present for this purpose.
Discussion
3295.

Question : How does embryo get nourishment inside the mother's body ?

Answer»

Solution :EMBRYO gets nourishment through placenta. Placenta is a disc embedded in the wall of uterus. It contains villi on the embryo side of tissue. On the MOTHER side are blood spaces which SURROUND villi. Placenta serves to bring the foetal and maternal blood close enough to permit exchange of MATERIALS between the two.
Discussion
3296.

Question : Howdoesdevelopingembryogetsitsnouroshmentinsidethe mother 'sbody?

Answer»

Solution :The PLACENTA allows the EXCHANGE of food materials, diffusion of OXYGEN, excretion of nitrogenous wastes and elimination of carbon-di-oxide. A cord, CONTAINING BLOOD vessels tha connects the placenta with the foetus is called the umbilical cord.
Discussion
3297.

Question : How does chemical coordination takes place in animals ?

Answer»

SOLUTION :CHEMICAL COORDINATION takes place in animals by the hormones released by endocrine glands directly into the blood WITHOUT the involvement of special ducts from where they REACH the target tissue.
Discussion
3298.

Question : How does carbon monoxide, a poisonous gas, emitted by automobiles, prevent transport of oxygen into the body tissues ?

Answer»

By changing oxygen into carbon dioxide
By OBSTRUCTING U1e reaction of oxygen with hemoglobin
Thermal POWER project
By FORMING a stable component with haemoglobin

Answer :D
Discussion
3299.

Question : How does chemical coordination occur in plants?

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Solution :CHEMICAL coordinates OCCURS in plant by the help of plant HORMONES.
Discussion
3300.

Question : Howdoesbinaryfissiondifferfrommultiplefission ?

Answer»

SOLUTION :
Discussion