CBSE Class 10 Biology How Do Organisms Reproduce Worksheet Set L

ONE MARK QUESTIONS

Question: What is the importance of DNA copying in reproduction?
Answer: DNA copying is an important phenomenon of reproduction through which the organisms pass on their characteristics to their offspring. It maintains the characteristics in different generations of the species. It also produces variations which are useful for the survival of species for long time.

Question: Name the method by which Plasmodium reproduce under favourable conditions. Is this method sexual or asexual?
Answer:  Multiple Fission. Asexual

Question: Organisms have a varied body design. Name the property which gives the basic difference in body design.
Answer: Errors in DNA copying (variations).

Question: Where is DNA found in a cell?
Answer: Genes/Chromosomes.

Question: What are sexually transmitted diseases? Name an STD which damages the immune system of human Download more materials in free at :  body.
Answer: a. Diseases that spread through the sexual contact.
b. AIDS

Question: Name the life process of an organism that helps in the growth of its population.
Answer: Reproduction.

Question: List two functions performed by testis in human beings.
Answer: a. Testis produce sperms.
b. Produces male sex hormone, testosterone.

Question: Name the type of cells which undergo regeneration.
Answer: Regenerative cells can proliferate and make large number of cells.

Question: Give an advantage of vegetative propagation.
Answer: Vegetative propagation can be practised for growing such plants which usually do not produce seeds or produce non-viable seeds.

Question: What is the role of seminal vesicles and prostate gland?
Answer: Seminal vesicles are a pair of thin-walled muscular and elongated sacs which secrete a fluid for nourishment of sperms.
Prostate glands also produce a fluid which is released in the urethra along with secretion of seminal vesicle. It affects the vaginal pH so that sperms move smoothly inside the vagina.

Question: Organisms have a varied body design. Name the property which gives the basic difference in body design.
Answer: Errors in DNA copying (variations).

TWO MARKS QUESTIONS

Question: a. What is the location of the following:
(i) DNA in a cell (ii) Gene
b. Expand DNA.
Answer: 
a. (i) Nucleus. (ii) Located on the chromosomes.
b. Deoxyribo Nucleic Acid. 

Question: “Variations” are seen in the organisms. State the two main causes of variation.
Answer: Variations are caused by:a. Change in the genetic material, i.e., DNA at the time of DNA copying.
b. Environmental factors viz., light, temperature, nutrition, wind and water supply, etc.
c. Mutations.

Question: Explain how do organisms create an exact copy of themselves.
Answer: To build the copies of DNA or the genetic material, the cells use biochemical reactions. Additional cellular apparatus along with the DNA copies are separated and so a cell divides to give rise to two almost identical cells. 

Question: Define the following processes of asexual reproduction:
a. Spore formation
b. Regeneration
c. Multiple fission
Answer: a. Reproduction seen in organisms by formation of spores.
b. Organisms are cut into any number of pieces and each piece grows into a complete organism.
c. Unicellular organisms divide into many daughter cells simultaneously.

Question: What happens when the following situations are initiated:
a. A Planaria is cut into three different pieces.
b. Leaf of the Bryophyllum with notches falls on the soil.
c. Testosterone is released in the male reproductive system.
Answer: a. Each piece grows into a complete organism.
b. Develops into new plants.
c. Changes occurs in the appearance at the time of puberty.

Question: State the changes that take place in the uterus when a. implantation of embryo has occurred
b. female gamete/egg is not fertilized
Answer: a. Uterus wall becomes thicker due to development of blood vessels and glands in it and placenta develops from the side of foetus so that it can derive nutrition from mother and pass the waste to mother’s blood.
b. Uterus lining gets peeled and shed off along with mucus, blood, dead ovum during menstruation.

Question: Define variation in relation to a species. Why is variation beneficial to the species?
Answer: Variation means certain changes which occur in sexually reproducing organisms because of errors in DNA copying. Variations are beneficial for species because they given survival advantage even in the adverse environmental conditions.

Question: What is the main difference between sperms and eggs of human? Write the importance of this difference?
Answer: Sperms are motile and are produced in . large numbers by a male. Egg are non-motile and only one is produced at a time by the female.
Sperms are motile as they have to travel up to egg for fertilization. It becomes zygote, remains protected inside female’s body and gives rise to foetus and baby.

Question: How can pregnancy be prevented surgically?
Answer: Pregnancy can be prevented surgically by adopting:
a. Vasectomy: When vas deferens in males are blocked surgically, sperm transfer will be prevented.
b. Tubectomy: When fallopian tubes are blocked, eggs will not be able to reach the uterus.

THREE MARKS QUESTIONS

Question: Compare the following:
a. Unisexual and bisexual flower.
b. Self-pollination and cross pollination.
c. Style and filament.
Answer: a. Unisexual flowers have either stamens or carpels, e.g., Papaya and Watermelon. Bisexual Flowers have both stamens and carpels, e.g., Mustard and Hibiscus.
b. Self-Pollination is transfer of pollen grains from the stamen to the stigma of same flower. Cross Pollination is transfer of pollen grains to another flower by agents like wind, water or animals.
c. Style is the middle elongated part of the carpel. It acts as a passage for pollen to reach ovary for the fertilization. Filaments is the elongated part of stamen.

Question: Mention the total number of chromosome along with sex chromosome. Explain how in a sexually reproducing organism chromosome number of parents and their offsprings is the same.
Answer: Total number chromosomes is 23 pairs. The last pair is called sex chromosome. If they are similar, they are termed as XX chromosome. They are present in the females. If they are dissimilar, they are called XY. They are present in the males. DNA doubling is always followed by cell division. But multicellular organisms have special linkages of cells in specialised organs which have only half the number of chromosomes and half the amount of DNA. Thus, when these germcells from two individuals combine during sexual reproduction to form a new individual, it results in re-establishment of number of chromosome and DNA content.

Question: List four steps in sexual reproduction. Write two of its advantages.
Answer: a. Four steps in sexual reproduction :
b. Formation of gametes in the sex organs.
c. Transfer of male gamete to female gamete which involves release of both types of gametes in the medium outside.
d. Fusion of gametes, either inside or outside the female parents body.
e. Development of zygote to embryo and then complete individual.
Advantages:
a. Variations are produced among the progeny.
b. Such populations are able to adapt well to
changing environment and thus evolves faster.

Question: Reproduction is one of the most important characteristics of the living beings. Give three reasons in support of your answer.
                                                                    or
Define reproduction. How does it help in providing stability to the population of species?
Answer: a. Reproduction is the process of producing individuals of its own kind. Through reproduction, the continuity is maintained.
b. Members of population are eliminated due to old age, disease, accidents and other reason. They have to be replaced by new members in order to maintain a stable population.
c. Reproduction brings variation so that population may adapt better and evolution in species takes place. Ultimately new species originate from preexisting ones.
d. Reproduction is not essential for an individual as its survival is not dependent upon it but is essential for a species for its survival.

Question: What happens when:
a. Accidentally Planaria is cut into three different pieces.
b. Bryophyllum leaf fall on the wet soil.
c. On maturation sporangia of Rhizopus burst.
Answer: a. Three new Planaria will form due to regeneration.
b. New plantlets will form from these buds helping the plant to propagate vegetatively.
c. Spores are released which upon finding suitable substratum germinates to form new individual.

Question: State the basic requirement for sexual reproduction. Write the importance of such reproduction in nature.
Answer: Sexual reproduction takes place in multicellular organisms with complex body design. There are specialized (sex) organs in which through a special type of cell division, number of chromosome is reduced to half and male and female germ cells/gametes form.
These gamete fuse to form zygote on fertilization,thus the characteristic number of chromosome and the normal DNA content for a cell is regained.
Sexual reproduction gives rise to more variations which are essential for evolution as well as survival of species under unfavorable conditions. Species reproducing sexually have better chances of survival.

Question: List three techniques to prevent pregnancy. Which of them is not meant for males? How does the use of such techniques have an impact on health and prosperity of a family?
                                                                    or
List any four methods of contraception used by humans. How does their use have a direct effect on the health and prosperity of a family?
Answer: Three techniques to prevent pregnancy:
a. Mechanical barrier — male or female.
b. Taking oral pills/i-pill/saheli – changing the hormonal balance of the body so that eggs are not released.
c. Use of the loop or the Copper-T.
d. Surgical method – tubectomy / vasectomy Use of hormonal preparations is not meant for males.
Effect on Health and Prosperity:
a. Health of women is maintained
b. Parents can give more attention to children
c. More resources can be made available.

Question: Explain the term “Regeneration” as used in relation to reproduction of organisms. Describe briefly how regeneration is carried out in multicellular organisms like Hydra.
Answer: The ability to give rise to new individuals from the body parts of the parent individual is called regeneration, e.g., Hydra and Planaria, if their bodies get broken into many pieces, each piece is capable of re-growing into a complete individual.

Question: In the process of reproduction as used by Spirogyra,the organism splits itself into small pieces.
a. What is this process of reproduction called?
b. Is this type of reproduction sexual or asexual?
c. Is this process same as regeneration?
Answer: a. Fragmentation.
b. Asexual as only one parent is involved,
c. In fragmentation, the body of a simple multicellular organism breaks down into many ‘fragments’. All cells undergo division and the organism develops from each fragment. In regeneration, body of a multicellular organism get broken into many pieces, each piece is capable of re-growing into a complete individual.

Question: “Regeneration is not same as reproduction”.
a. Justify the statement.
b. What is meant by regeneration?
c. How is this process different from fragmentation?
Answer: a. Regeneration is not the same as reproduction, since most organisms would not normally depend on being cut up to be able to reproduce.
b. The ability to give rise to new individuals from the body parts of the parent individual is called regeneration.
c. In fragmentation, the body of a simple multicellular organism breaks down onto many ‘fragments’. All cells undergo division and the organism develops from each fragment. Regeneration occurs only through some specialised cells.
Question: Explain the process of regeneration in Planaria. How is this process different from reproduction?
Answer : Regeneration is the ability to give rise to new individuals from the body parts of the parent individual e.g., Hydra and Planaria, if their bodies get broken into many pieces, each piece is capable of re-growing into a complete individual.
In some organism regeneration occurs but only to regain lost body parts like in tail of lizard, arm of a star fish. In the case of Planaria, it is a way of reproduction that is producing organisms of its own kind.

Question: Give the functions of the following in the process of reproduction:
a. Pollen tube.
b. ovary,
c. Stigma.
Answer: a. Pollen tube carries male gamete from stigma to ovule.
b. Ovary has ovule and forms fruit to protect and dispersal of seeds.
c. Stigma receives pollen during pollination.

Question: Study the diagram given below: 
a. Identify the process.
b. Which organism uses the above method of reproduction?
c. How is the above method different from the process of fragmentation?
                                                          or
In context of reproduction of species, state the main difference between fission and fragmentation. Also give one example of each.
Answer: a. Binary fission.
b. Amoeba.
c. Binary fission occurs in unicellular organisms only. In fragmentation the body of a simple multicellular organism breaks down into many ‘fragments’. All cells undergo division and the organism develops from each fragment.

Question: What is vegetative propagation? List two advantages and two disadvantages of vegetative propagation.
Answer: Method of producing new plants from vegetative parts like roots, stem and leaves is called vegetative propagation.
Advantages are:
a. The plants bear flowers and fruits earlier than those propagated sexually.
b. Plants have lost capacity to form seeds hence they are propagated vegetatively.
Disadvantages are:
a. Such plants are genetically similar to parent plants and are vulnerable to infections and diseases.
b. They do not have variations therefore do not adapt well to changing environment, the plant species does not evolve.

Question: Explain the structure of the female reproductive system of humans.
Answer: Female Reproductive System consists of ovaries, fallopian tubes, uterus and vagina.
a. Ovaries are located inside the abdominal cavity, near the kidney. It performs two functions:
- Produce female germ – cells/eggs. Every month one egg is produced
- Secrete hormones like Estrogens which stimulate the development of secondary sexual characteristics at puberty.
b. Fallopian Tubes carry the egg from ovary to the womb; egg gets fertilized in the oviducts only if it meets a sperm.
c. Uterus is a elastic bag like structure. The fertilized egg, the zygote gets implanted in the fining of uterus and develops into an embiyo.
d. Vagina (Birth Canal) receives the sperms as well as child is borne through it.

FIVE MARKS QUESTIONS

Question: How does vegetative propagation occur in nature? Explain with four different examples.
Answer: There are many plants in which parts like the root, stem and leaves develop into new plants under appropriate conditions. This is called as vegetative propagation. Examples of vegetative propagation:
a. Adventitious buds: In Bryophyllum, adventitious buds grow in the notches along the leaf margin,which when fall on the soil, develop into new plants.
b. Cutting: A piece of stem, root, leaf or even a bulb scale is placed partly under moist soil which grows into a new plant, e.g., rose.
c. Layering: A part of the stem is pulled out and buried in the soil. The layered stem grows into a new plant, e.g., Pudina.

d. Grafting: In grafting, two parts from two different plants are joined together so that they can unite and grow into a new plant, e.g., sugarcane.

Question: Explain what happens when:
a. Testosterone is released in males.
b. Pollen grain falls on the stigma of the flower.
c. Egg fuses with sperm cell.
d. Planaria is cut into many pieces.
e. Buds are formed on the notches of the Bryophyllum leaf.
Answer: a. (i) Formation of sperms, change in appearance.
(ii) Thick hair growth on the face and voice begin to crack.
b. A tube grows out of the pollen grain and travel through the style to reach the ovary.
c. Zygote is formed (fertilization).
d. Each piece grows into a complete organism.
e. Buds may fall on the soil and develop into new plants.

Question: What happens when
a. Testosterone is released in the male reproductive system.
b. Pollen grain falls on the stigma of flower.
c. Egg fuses with the sperm cell.
d. A Planaria is cut into three different pieces.
e. Buds are formed on the notches of leaf of the Bryophyllum.
Answer: a. The male shows masculine features and attains fertility/ sperm starts forming in testis.
b. Pollen tube forms and male gametes are carried by it to the ovule.
c. Fertilization occurs and a zygote forms.
d. Three new Planaria will form due to regeneration.
e. New plantlets will form from these buds helping the plant to propagate vegetatively.

Question: (A) What is fragmentation in organisms?
Name a multicellular organism which reproduces by this method.
(B) How does regeneration take place? Why is this process not possible in all animals? 
Answer: (A) Fragmentation: This is a type of asexual reproduction in which a body breaks into several fragments, which later develop into complete organism. e.g. 
etc. Spirogra is a multicellular organism which reproduces by fragmentation.
(B) Regeneration: Regeneration is a type of asexual reproduction in which the organism is capable of regrowing certain body parts or whole body e.g. sponge.
Regeneration is possible only for animals with simple cell structure. In complex cell structure, tissue structure is also different.
Therefore regeneration is not possible in complex organisms.

Question: Differentiate between:
a. Pollen tube and Style
b. Fission of Amoeba and Plasmodium
c. Fragmentation and regeneration
d. Bud of Hydra and bud of Bryophyllum
e. Vegetative propagation and spore formation.
Answer: a. Pollen tube forms and male gametes are carried by it to the ovule.
Style is part of female part- carpel through which pollen tube passes.
b. Amoeba shows binary fission where one cell splits into two equal halves.
Plasmodium (malarial parasite) shows multiple fission where one cell divides into many daughter cells simultaneously.
c. Fragmentation occurs in multi-cellular organisms with simple body organisation like Spirogyra (a filamentous alga). It involves breaking up of a filament into many fragments and each fragment growing into new individual.
Regeneration is the ability to give rise to new individuals from the body parts of the parent individual, e.g., Hydra and Planaria, if their bodies get broken into many pieces, each piece is capable of regrowing into a complete individual.
d. In Hydra, a bud is formed at a specific site by repeated cell division and develops into a tiny hydra.
In Bryophyllum, vegetative buds arise from the notches of its leaves and develops into a new plantlet.
e. Vegetative Propagation is the development of new plants from parts like root, leaf and stem under suitable conditions, e.g., Bryophyllum vegetative buds arise from the notches of its leaves. In potato, ginger, garlic etc. it occurs through stems.
Spore formation: A spore is a special cell protected by thick coating. It is capable of germinating into a new plant when comes in contact with suitable and environment conditions and moist surface, e.g., in Rhizopus (bread mould), they are formed inside reproductive, bob¬like sacs called sporangia.

Question: a. Name the human male reproductive organ that produces sperms and also secretes a hormone. Write the functions of the secreted hormone.
b. Name the parts of the human female reproductive system where
(i) Fertilization takes place,
(ii) Implantation of the fertilized egg occurs.
Explain how the embryo gets nourishment inside the mother’s body.
Answer: a Testis – secrete male hormone – testosterone.
Functions : (i) Formation of sperms, (ii)Development of secondary sexual characters.
b. (i) fallopian tube/oviduct. (ii) uterus.
Placenta is a special disc like tissue embedded in the mother’s uterine wall and connected to the foetus/embryo. Placenta provides a large surface area for glucose and oxygen/ nutrients to pass from the mother’s blood to the embryo/ foetus.