CBSE Class 10 Biology How Do Organisms Reproduce Worksheet Set N

Multiple Choice Questions

Question. To perform an experiment to identify the different parts of an embryo of a dicot seed, first of all you require a dicot seed. Select dicot seeds from the following group. 
Wheat, Gram, Maize, Pea, Barley, Ground-nut
(a) Wheat, Gram and Pea
(b) Gram, Pea and Ground-nut
(c) Maize, Pea and Barley
(d) Gram, Maize and Ground-nut
Answer: (b)

Question. On observing an embryo of a pea seed, a student listed its various parts as given below : Micropyle, Cotyledon, Plumule, Testa, Radicle, Tegmen. On examining the list the teacher remarked that out of these only three parts belong to embryo. Select these three parts : 
(a) Testa, Radicle, Cotyledon
(b) Tegmen, Radicle, Micropyle
(c) Cotyledon, Plumule, Radicle
(d) Cotyledon, Plumule, Testa
Answer: (c)

Question. The correct sequence of reproductive stages seen in flowering plants is :
(a) Gametes, zygote, embryo, seedling
(b) Zygote, gametes, embryo, seedling
(c) Seedling, embryo, zygote, gametes
(d) Gametes, embryo, zygote, seedling
Answer: (a)

Question. In Rhizopus tubular thread like structures bearing sporangia at their tips are called :
(a) Filaments
(b) Rhizoids
(c) Roots
(d) Hyphae
Answer: (d)

Question. The ability of a cell to divide into several cells during reproduction in Plasmodium is called :
(a) Budding
(b) Reduction division
(c) Multiple fission
(d) Binary fission
Answer: (c)

Question. Asexual reproduction takes place through budding in :
(a) Amoeba
(b) Yeast
(c) Plasmodium
(d) Leishmania
Answer: (b)

Question. The anther contains :
(a) Sepals
(b) Ovules
(c) Carpel
(d) Pollen grains
Answer: (d)

Question. In human females an event that reflects onset of reproductive phase is :
(a) Growth of body
(b) Change in voice
(c) Changes in hair pattern
(d) Menstruation
Answer: (d)

Question. During adolescence several changes occur in the human body. Mark one change associated with sexual maturity in boys.
(a) Loss of milk teeth
(b) Increase in height
(c) Weight gain
(d) Cracking of voice
Answer: (d)

Question. 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
Answer: (c)

Question. Which among the following diseases is not sexually transmitted ?
(a) HIV-AIDS
(b) Hepatitis
(c) Syphilis
(d) Gonorrhoea
Answer: (b)

Match the following

Question. Match the following
Column I
(a) Spirogyra
(b) Bryophyllum
(c) Rhizopus
(d) Hydra
(e) Planaria

Column II
(i) Regeneration
(ii) Spore formation
(iii) Fragmentation
(iv) Budding
(v) Leaves
Answer: (a) (iii), (b) (v), (c) (ii), (d) (iv), (e) (i).

Fill in the blanks

Question. Fill in the blanks
(a) The term used to refer to the transfer of pollen from the stamen of one flower to the carpel of another flower of the same species is ............................... .
(b) The cells involved in sexual reproduction are called ............................... .
(c) Fusion of gamets gives rise to a single cell called ............................... .
Answer: (a) Cross pollination, (b) Gametes, (c) Zygote

Very Short Answers Type Questions

Question. List in proper sequence four steps of obtaining germinating dicot seeds. 
Answer: (a) The root is formed when radicle of seed grows. (b) The root grows downward into the soil and absorbs water and minerals from the soil. (c) The shoot is formed from the upward growth of plumule. (d) The green leaves are developed when shoot comes above the ground.

Question. After examining a prepared slide under the high power of a compound microscope, a student concludes that the given slide shows the various stages of binary fission in a unicellular organism. Write two observations on the basis of which such a conclusion may be drawn. 
Answer: (a) The nucleus of mature cell seems elongated and a grove is formed in cell which divides the nucleus. (b) A single parent divides to form two daughter cells. Constriction appears due to the division of cytoplasm.

Question. Name the process by which an amoeba reproduces. Draw the various stages of its reproduction in a proper sequence. 
Answer: Amoeba reproduces by binary fission. Stages: Karyokinesis (nucleus division), Cytokinesis (cytoplasm division), followed by two Daughter amoeba.

Question. When a cell reproduces, what happens to its DNA ? 
Answer: During the process of reproduction, transmission of DNA from parents to offspring takes place. Before reproduction, DNA is replicated, which means two copies of DNA are produced. When the cell divides, the two copies are distributed equally between the two daughter cells so that similar amount and type of DNA is transferred from the parent cell to the daughter cells. It maintains the consistency in the amount and type of DNA in the living organism of a particular species.

Question. Newly formed DNA copies may not be identical at times. Give one reason. 
Answer: During the process of replication of DNA, most of the base sequences in the new copies are identical to those in the parent DNA. However, some changes can occur either due to mutation or due to minor errors during replication process. Thus, the newly formed DNA copies may not be identical at times.

Question. Name the method by which spirogyra reproduces under favourable conditions. Is this method sexual or asexual ?
Answer: Under favourable conditions, spirogyra reproduces by fragmentation. This is an asexual method of reproduction.

Question. How does Planaria reproduce ? Is this method sexual or asexual ? 
Answer: Planaria reproduces by the process of regeneration. It is a type of asexual reproduction in which planaria is cut into any number of pieces each piece grows into a new organism.

Question. How does Plasmodium reproduce. Is this method sexual or asexual ?
Answer: Plasmodium reproduces by a process known as multiple fission. Multiple fission is a type of asexual reproduction in which a single parent cell divides into several daughter individuals. In this process, the parent nucleus divides several times into a number of daughter nuclei. Later the cytoplasm divides into as many pieces as the number of nuclei and each piece surrounds each nucleus. Each uninucleated piece develops an outer membrane and finally the parent cell divides into several uninucleate individuals.

Question. What is the end product of double fertilisation ?
Answer: In double fertilisation one of the male gametes fuse with egg cell to form a zygote whereas the other male gamete fuses with two polar nuclei to form primary endosperm that provides nourishment to the growing embryo.

Question. Name the agents which bring about cross pollination.
Answer: Insects, wind, water, animals etc., are the agents which bring about cross pollination.

Question. Where is the zygote located in the flower after fertilisation ?
Answer: Zygote is located inside the ovule which is present in the ovary part of the pistil.

Question. How does the chemical method help in preventing pregnancy ?
Answer: Chemical methods prevent the ovaries from releasing the egg hence no fertilisation can occur thus preventing pregnancy.

Question. Explain : (a) IUCD (b) STDs
Answer: (a) IUCD—Intra Uterine Contraceptive Devices. (b) STDs —Sexually Transmitted Diseases.

Question. Why is vegetative propagation practiced for growing types of plants ? 
Answer: Vegetative propagation practiced for growing types of plants because : (a) The plants which cannot produce seeds or produce non-viable seeds also can be easily propagated by this method. (b) It is a very easy, quick and cheapest method of propagation. (c) Seedless plants can be produced by vegetative propagation. (d) Flowers and fruits are produced in very short time. (e) Parental features are preserved.

Question. List any four modes of asexual reproduction. 
Answer: Fission, fragmentation, regeneration, budding, vegetative propagation, spore formation etc., are the modes of asexual reproduction.

Question. Describe briefly how regeneration is carried out in Planaria.  
Answer: When the body of Planaria by any means is cut into two or more number of pieces. Each piece contains specialised cells. These cells proliferate and make large number of cells. From this mass of cells different cells undergo changes to become various cell types and tissues finally developing into new organism.

Question. Name the organs producing sperms and ova respectively in humans.  
Answer: Testis produces sperms and ovary produces ova.

Question. You have to perform the experiment, ‘‘To identify the different parts of an embryo of a gram seed.’’ Describe the procedure that you would follow 
Answer: (a) Soak a few seeds of gram or Bengal gram and leave them overnight. (b) Drain the excess water. (c) Cover the seeds with a wet cloth and leave them for a day. (d) Cut open the seed carefully and observe the different parts.

Short Answers Type Questions

Question. What is carpel ? Write the function of its various parts.  
Answer: The flask-shaped organ in the centre of a flower is called carpel. It is also called as female reproductive organ of the plant. It is made up of three parts : (a) Stigma: It is the top part of carpel and is sticky. So, it receives the pollen from the anther of stamen. (b) Style: It connects stigma to ovary and acts as the passage for the growth of pollen tube. (c) Ovary: It contains female gametes of the plant and helps in reproduction it is the site of fertilisation.

Question. Distinguish between pollination and fertilisation. Mention the site and the product of fertilisation in a flower.  
Answer: (a) The transfer of pollen grains from anther of a stamen to the stigma of a carpel is called pollination whereas fertilisation is the process when the male gamete present in pollen grain joins the female gamete present in ovule. (b) Pollination is an external mechanism whereas fertilisation is an internal mechanism which takes place inside the flower. Site of fertilisation in flower is ovary. Product of fertilisation in flower is zygote.

Question. Write one main difference between asexual and sexual mode of reproduction. Which species is likely to have comparatively better chances of survival—the one reproducing asexually or the one reproducing sexually ? Give reasons to justify your answer. 
Answer: Asexual mode of reproduction is uniparental and does not involve fusion of gametes. Sexual mode of reproduction is biparental and involves fusion of male and female gametes. Species reproducing sexually have better chances of survival because sexual reproduction leads to variation. Accumulation of variations over long time leads to evolution and helps the species to adapt to drastic environmental changes like global warming, meteorite hits etc.

Question. Reproduction is one of the most important characteristics of living beings. Give three reasons in support of the statement.  
Answer: Reproduction is highly essential for all the living beings because of the following reasons : (a) Reproduction helps in increasing the number of members of a population. (b) By replacing the dead members with the new ones, it minimises the risk of extinction of a species. (c) It brings about variations in species, thus, leading to their evolution.

Question. What is vegetative propagation ? State two advantages and two disadvantages of this method.   
Answer: Vegetative propagation is a mode of asexual reproduction in which new plants are obtained from vegetative parts of the plants such as shoots or stem. Advantages: (a) Plants which do not produce seeds are propagated by this method. (b) It is a cheaper, easier and rapid method. Disadvantages: (a) No genetic variation, so no chance of development of better varieties. (b) Plants are more prone to diseases that are specific to the species.

Question. List three techniques that have been developed to prevent pregnancy. Which one of these techniques is not meant for males ? How does the use of these techniques have a direct impact on the health and prosperity of a family ?  
Answer: Three techniques are : (a) Mechanical Methods : Include condoms, diaphragm, IUCDs, etc. (b) Chemical Methods : Include oral contraceptive pills, spermicide. (c) Surgical Method : Includes vasectomy and tubectomy. Chemical methods are not meant for males. Impact: (a) Controlling family size improves economic status. (b) Spacing children improves mother's health and vitality.

Question. Describe reproduction by spores in Rhizopus.  
Answer: Rhizopus is a fungus that reproduces by spore formation. The fungal hyphae give rise to a globular structure known as sporangium. The sporangium gives rise to several spores by repetitive division of its nucleus. Each nucleus gets surrounded by a part of cytoplasm and develops into a spore. Once mature, the sporangium bursts to release spores into the environment. These spores land on various sites and if conditions are favourable, they germinate into new hyphae.

Question. List the two types of reproduction. Which one of the two is responsible for bringing in more variations in its progeny and how ?  
Answer: The two types are Sexual and Asexual. Sexual reproduction brings more variation because it involves fusion of gametes from two different individuals. Also, during gamete formation, meiosis occurs which brings new combinations of genes, leading to more variations in progeny.

Question. What happens when : (a) Accidently, Planaria gets cut into many pieces ? (b) Bryophyllum leaf falls on the wet soil ? (c) On maturation sporangia of Rhizopus bursts ?  
Answer: (a) Each piece will grow into a new Planaria organism via regeneration. (b) Buds produced in the notches along the leaf will develop into new plants. (c) Spores are released into the environment, carry to different places, and grow into new organisms on favourable surfaces.

Question. State the basic requirement for sexual reproduction. Write the importance of such reproduction in nature. 
Answer: Basic requirement is the involvement of two parents and fusion of their haploid gametes. Importance: (a) Results in genetic variations in offspring. (b) Promotes diversity of characters. (c) Leads to evolution and better adaptation to changing environments.

Question. State the changes that take place in the uterus when : (a) Implantation of embryo has occurred. (b) Female gamete/egg is not fertilised. 
Answer: (a) The inner lining of the uterus thickens and is richly supplied with blood vessels to provide nourishment to the growing embryo. (b) The egg lives for about one day. The thickened uterus lining breaks down and comes out through the vagina as blood and mucous (menstruation).

Question. List any four steps involved in sexual reproduction and write its two advantages ?  
Answer: Steps: (a) Formation of gametes through meiosis. (b) Transfer of male gametes into the female body. (c) Fertilisation. (d) Post fertilisation changes. Advantages: (a) Source of genetic variation. (b) Gives rise to individuals more adapted to the environment.

Question. How will an organism be benefited if it reproduces through spores ? 
Answer: Benefits: (a) Spores are covered with thick walls for protection against adverse conditions. (b) They are light and easily dispersed. (c) The mode is simple and faster. (d) Large numbers are produced at once.

Question. What is the importance of DNA copying in reproduction ? 
Answer: DNA copying is necessary as parents transmit their characters to offspring through DNA. It ensures offspring resemble parents while also producing variations that help adaptation to the changing environment.

Question. Name the following parts : (a) The organ where foetus develop during gestation period. (b) A funnel like structure near the posterior end of ovary. (c) Technical term given to the stalk of the flower. (d) Three parts of carpel.
Answer: (a) Uterus (b) Fallopian tube (c) Pedicel (d) Stigma, style, ovary

Question. What could be the reasons for adopting contraceptive method ? 
Answer: (a) Preventing unwanted pregnancies to control population growth. (b) Protection from STDs like AIDS, Syphilis. (c) Maintaining health of mother and child. (d) Ensuring sufficient gap between offsprings.

Question. How does binary fission differ from multiple fission ?  
Answer: Binary Fission: Single parent divides into two daughter cells; Nucleus divides once; Occurs under favourable conditions (e.g., Amoeba). Multiple Fission: Results in many daughter cells; Nucleus divides repeatedly; Occurs under unfavourable conditions (e.g., Plasmodium).

Question. Distinguish between a gamete and zygote ?
Answer: Gamete: Contains haploid number of chromosomes (n); Formed by meiosis. Zygote: Contains diploid number of chromosomes (2n); Formed by fusion of male and female gametes.

Question. What are acquired traits ? Why are these traits generally not inherited over generations ? Explain.  
Answer: Characters acquired during a person’s life time. They are not inherited because changes do not occur in reproductive tissues/DNA of germ cells, so they are not passed to the next generation.

Question. (a) Why is the increasing human population a cause of concern for all of us ? (b) Name two diseases that can be sexually transmitted. 
Answer: (a) Limited natural resources make it difficult to sustain a large population. (b) HIV-AIDS, syphilis, gonorrhoea.

Question. (a) Write the functions of the following parts of human male reproductive system : (i) Testes (ii) Vas deferens (iii) Urethra (iv) Prostate (b) List any two common pubertal changes that appear in human males.   
Answer: (a) (i) Testes – Sperm formation and testosterone secretion. (ii) Vas deferens – Delivery of sperms. (iii) Urethra – Ejaculation. (iv) Prostate – Nourishes sperms. (b) Thick hair growth on face, voice cracking.

Long Answers Type Questions

Question. (a) ‘‘Use of a condom is beneficial for both the sexes involved in a sexual act.’’ Justify this statement giving two reasons. (b) How do oral contraceptive help in avoiding pregnancies ? (c) What is sex selective abortion ? How does it affect a healthy society ? 
Answer: (a) Condoms prevent transmission of infections (STDs) and lead to effective birth control/prevent unwanted pregnancy. (b) Oral contraceptives change the hormonal balance so eggs are not released. (c) Surgical removal of female foetuses. It creates an imbalance in female-male sex ratio, which is detrimental to society.

Question. Define pollination. Explain the different types of pollination. List two agents of pollination? How does suitable pollination lead to fertilization?
Answer: Pollination is the transfer of pollen from the anther of the stamen to the stigma of the pistil with the help of air, water and insects. Types of pollination: (a) Self pollination: Transfer of pollen grain from the anther to the stigma of the same flower. (b) Cross pollination: Transfer of pollen grain from the anther of one flower to the stigma of other flower of the same species. Two agents of pollination are air, water, insects winds etc. When correct species of pollen grain lands on the stigma it results in some chemical response from the ovary that causes the growth of pollen tube from pollen grain. The pollen grain slides down the pollen tube and enters the ovary where it meets the egg. This process is called as fertilization and leads to the formation of zygote.

Question. What is contraception? List three advantages of adopting contraceptive measures.
Answer: Contraception is the method by which a female inhibits fertilization and hence prevents pregnancy. The three advantages of contraception are: (i) It makes the people more aware about the concept of family planning keeping population under control. (ii) It educates the people about Sexually Transmitted Diseases and ways to avoid it. (iii) It helps the female to space children. (iv) It reduces the risk of unwanted pregnancies. [Handwritten Note]: 1) They are adopted to prevent unwanted pregnancies. 2) They help to maintain the reproductive health of women & in order to control birth & death rate.

Question. Write the function of following parts in human female reproductive system: (i) Ovary, (ii) Oviduct, (iii) Uterus.
Answer: Topper’s Answers Q. 6. (a)(i) Ovary has following functions: - It releases matured egg (female germ cell) once every month to uterus, so responsible for produce & release (oogenesis & ovulation) of ovum. - It secretes oestrogen & progesterone. Oestrogen controls secondary sexual characteristics in females at time of puberty & also promotes release / maturation of egg. (ii) Oviduct / Fallopian tube carries the released egg to the uterus. It is also the site of fertilization. (iii) Uterus is a bag like structure where embryo is developed & implanted. It helps the embryo to grow into foetus & also develops a thick lining of blood vessels every month in order to receive a fertilized egg. Its rhythmic contraction helps the baby to come out from mother's body (womb).

Question. Describe in brief the structure and function of placenta.
Answer: (b) Placenta is a disc shaped tissue embedded in uterine wall once implantation of embryo takes place. It has villi on the embryo's side & blood spaces on mother's side. It helps in nourishment of child inside mother's womb. It also helps in exchange of nutrients, oxygen & waste products (released by embryo) between mother's & embryo's blood & thus, is responsible for maturation of embryo.

Question. Write the functions of each of the following parts in a human female reproductive system: (i) Ovary, (ii) Uterus, (iii) Fallopian tube.
Answer: (a) (i) Functions of the Ovary: 1. It produces female gametes (ova). 2. It secretes female sex hormones. (ii) Functions of Uterus: 1. It supports and nourishes the developing foetus. 2. It expands according to the growth of the baby. (iii) Functions of Fallopian tubes: 1. They carry eggs from the ovary to the uterus. 2. They act as the site for fertilisation.

Question. Write the structure and functions of placenta in a human female.
Answer: Placenta is the connecting link between the mother’s body and the baby. It is a disc embedded in the uterine wall. This special tissue contains villi on the embryo’s side of the tissue. The mother’s end of placenta has blood spaces, which surrounds the villi. Placenta functions as a site of exchange of materials between the blood of mother to the baby. The developing embryo generates certain waste substances that are also removed through placenta. Thus, the placenta serves as the nutritive, respiratory and excretory organ of the foetus.

Question. Name the organ that produces sperms as well as secretes a hormone in human males. Name the hormone it secretes and write its functions.
Answer: The organ that produces sperms as well as secretes male hormones is testis. The hormone secreted by it is testosterone. Its important functions are as follows: (i) It stimulates sperm production. (ii) It stimulates the development of secondary sexual characters in males like growth of facial hairs, low pitch voice, etc. (iii) It involves the development, maturation and functioning of male accessory sex organs like vas deferens and seminal vesicles.

Question. Name the parts of the human female reproductive system where fertilisation occurs.
Answer: In human females reproductive system, the process of fertilisation takes place in one of the fallopian tubes.

Question. Explain how the developing embryo gets nourishment inside the mother’s body.
Answer: The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. Placenta is a vascular membranous organ that connects the developing foetus to the uterine wall of the mother. It contains villi on the embryo’s side of the tissue. This provides a large surface area for glucose and oxygen to pass from mother to the embryo. The placenta draws nourishment and oxygen, which it supplies to the foetus, from the maternal circulation. In turn, the placenta receives carbon dioxide and wastes of fetal metabolism and discharges them into the maternal circulation for disposal.

Question. What is vegetative propagation? Describe various methods of vegetative propagation.
Answer: The growth of new plants from vegetative parts of the plant like roots, stem, leaves other than the seeds is called vegetative propagation. Various methods of vegetative propagation are: (a) Cutting: Small piece of plant part like roots, stem or leaves is cut and is used for propagation. Examples: Rose, china-rose, sugarcane etc. (b) Layering: It is the process where roots are induced when a stem comes in contact with the ground. Examples: Grapevine, jasmine, litchi, mango etc. (c) Grafting: It is a process of joining a part of a living plant like stem or bud to another plant and they grow as one plant. Examples: Lime, lemon etc. (d) Propagation by plant tissue culture: In this method plant cells are cultured in an artificial culture media