CBSE Class 10 Biology How Do Organisms Reproduce Worksheet Set A

Explanation: Ovum is the female sex cell, or female gamete; the male gamete is the sperm. A gamete, ovum or sperm, contains half the number of chromosomes found in the body cells of the parent, i.e., the gamete is haploid.

In human there are total 46 chromosomes, so human ovum has only 23 chromosomes.

Explanation: Hair and nails have a protein called keratin which allows them to grow. The process of growing of nails and hair is known as keratinization.

Explanation: In the honey bee, fertilized eggs (diploid zygotes) regularly develop into females, and unfertilized eggs (haploid gametes) develop into males by types of reproduction known as zygogenesis and generative or haploid Parthenogenesis, respectively.

Very Short Answers :

Answer :  The production of the new organisms from the existing organisms of the same species is called reproduction.

Question. The attachment of the embryo to the uterus is called .
Answer : implantation

Question. Which is the most basic event in reproduction?
Answer : Creation of a DNA copy.

Question. The ability of a cell to divide into several cells during reproduction in . is called .
Answer : Plasmodium, multiple fission

Question. The disease is caused by microorganism known as .
Answer : kala-azar, leishmania

Question. Do you know which part become a new plant in vegetation propagation?
Answer : Root, stem and leaves.

Question. A tiny animal having tentacles which reproduces by growing buds on the side of its body is .
Answer : hydra

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

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

Question. The gestation period in human beings is about days.
Answer : 280

Question. Name two organisms which are reproduced by binary fission.
Answer : Amoeba and leishmania are reproduced by binary fission.

Answer :  Fission is the process of reproduction in unicellular organisms such as amoeba, paramecium. 

Answer :  The new organisms produced by one parent through asexual reproduction are called clones.

Answer :  The process of getting back a full organism from its body parts is called regeneration.

 

Answer :  The antibiotic drug penicillin is made from penicillium fungus.

 

 

Short Answers :

i.

ii. The diagram show the process of germination of pollen on stigma. Which is necessary for passage of male gametes to ovary. In this the pollen grains develops pollen tube which enters the ovary and releases the 2 male gametes. One of which participate in syngamy and the other in triple fusion.

 

Question. Draw well labelled diagram of V.S of mature ovule of Angiosperms. 

Answer :  Mature ovule

Answer : A copper-T is placed safely inside the uterus. It prevents implantation in the uterus.

Question. How are the methods of reproduction different in unicellular and multicellular organisms?
Answer : An unicellular organism has a single cell so there is no specific organ system for reproduction. They divide by the process of cell division. The different modes of reproduction in unicellular organism are binary fission, multiple fission, budding etc. But in multicellular organism there are specific tissues and organ system to carry out this process. There is formation of male and female gametes. It is a very complex process and normally takes more time as compared in unicellular organisms.

Question. Write the functions of each of the following parts in a human female reproductive system.
(i) Ovary
(ii) Uterus
(iii) Fallopian tube
Write the structure and functions of placenta in a human female.
Answer : (i) Ovary: It produces female gametes and female sex hormones like estrogen, progesterone.
(ii) Uterus: It supports and nourishes the developing foetus. It expands according to the growth of the baby.
(iii) Fallopian tube: They are the site of fertilisation and carry eggs from ovary to uterus.
Placenta connects baby with mother’s body. It is a disc like structure embedded in uterine wall. It is a special tissue formed by the interlocking of two sets of villi, one set given by wall of uterus and other set from embryo. It is the site of exchange of materials between the blood of mother and baby. It provides nutrients, oxygen from mother to foetus and removes excretory substances, carbon dioxide from foetus.

Question. Answer the following:
(i) With the help of a diagram demonstrate the process of regeneration as seen in Planaria? 
(ii) Which type of cells are used by such multicellular organisms to regenerate?
Answer : (i) Regeneration is the process by which an organism has an ability to regenerate its lost parts of the body which might have been removed by injury or by some other methods. When Planaria is cut into many pieces, each piece grows into a complete organism. Regeneration is carried out by specialised cells which have the capacity to develop, proliferate and differentiate into various cell types and tissues.
(ii) A single pluripotent adult stem cell type (neoblasts) is used by such multicellular organisms to regenerate.

Question. What are the advantages of vegetative propagation?
Answer : Some advantages of vegetative propagation are:
(a) It is cheaper, easier and rapid method.
(b) The plants which cannot produce seeds also can be easily propagated by this method.
(b) The plants produced by this method bear fruits and flowers earlier.
(d) It produces new individuals with exactly identical qualities as the parent, which preserves the parental characteristics.

Question. Answer the following:
(i) Name the structures where spores are formed? Give the terms used for non-flagellated, non-motile spores and flagellated, motile spores?
(ii) Give one example of plant where modified tuberous roots can be propagated vegetatively when planted in soil?
Answer : (i) Spores are formed in sporangia. Non-flagellated, nonmotile spores are called aplanospores and flagellated, motile spores are called zoospores.
(ii) Sweet potato is an example of plant where modified tuberous roots can be propagated vegetatively when planted in soil.

Question. When a cell reproduces what happens to its DNA?
Answer : During the process of reproduction DNA is transmitted from parents to offspring. But DNA is replicated before reproduction i.e., two copies of DNA are produced. During the time of cell division the two copies of DNA are equally distributed between the two daughter cells. Each daughter cell receives same type and amount of DNA from parent cell. Thus, the consistency in type and amount of DNA is maintained in the particular species of a living organism.

Question. Newly formed DNA copies may not be identical at times. Give one reason.
Answer : During the time of DNA replication most of the base sequence in daughter cells is identical to the parent DNA but sometimes due to mutations or some errors during replication some changes in the newly formed DNA copies may occur. So, it is said that newly formed DNA copies may not be identical at times.

Question. Why is variation beneficial to the species but not necessary for the individual? 
Answer : Due to recombination and crossing over in meiosis process during formation of gametes as well as during sexual reproduction the mixing up of male with female gametes produce some variations in the offsprings. These variations are necessary for survival of a particular species to the changing environment. If there would be no variations then there will be less chance of a particular species to get adapted to the changed environment and with course of time that particular species may extinct. Variations also lead to evolution of the species. Thus it is said that variation is beneficial to the species but not necessary for the individual.

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 : There are two types of reproduction- sexual and asexual. Sexual reproduction is responsible for bringing in more variations in its progeny as it involves fusion of male and
female gametes from two different organisms which leads to more diversity of characters in offsprings. Gametes are formed by meiosis process which brings new combinations of genes
due to crossing over and homologous recombination. Due to all these factors sexual reproduction is responsible for bringing in more variations in its progeny.

Question. Write one difference between sexual and asexual mode of reproduction. Which species is likely to have better chances of survival the one reproducing asexually or the one reproducing sexually? 
Answer : In sexual reproduction male and female gametes from two different individuals unite leading to variations in offsprings due to mixing up of genetic material whereas in case of asexual reproduction only single parent is involved and there is no formation of gametes. The ones that are produced sexually have better chances of survival as due to mixing up of genetic material between two different individuals there is increase in genetic variations in the offsprings which provides maximum chances for the survival of species in the changing
environment as well as under unfavourable conditions. This variation in species is also essential for evolution.

Question. Fallen leaves of Bryophyllum on the ground produce new plants whereas the leaves of rose do not. Explain this difference between the two plants?
Answer : In Bryophyllum new plants develop from the adventitious buds on their leaves through vegetative propagation but buds do not develop from the leaves of rose plants hence new plants cannot grow from the fallen leaves of rose plant.

Question. The embryo gets its nutrition from the mother’s blood with the help of special tissue.
(i) What is this special tissue called?
(ii) Give any other function of this tissue apart from one mentioned above.
(iii) Explain the structure of this special tissue.
Answer : (i) This special tissue is called placenta.
(ii) Besides providing nutrition to the embryo, placenta helps in removing waste products from embryo, it also helps in providing oxygen to the embryo and eliminating carbon
dioxide from embryo.
(iii) Placenta is a disc like structure which is attached to the wall of the uterus. It is formed by two sets of minute finger like process called villi. One set from uterine wall and other set
from the embryo. The blood flows through fine capillaries of the placenta.

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

Question. Answer the following questions:
(i) What happens to the ovule and ovary after fertilisation?
(ii) Which group of plants show double fertilisation?
Answer : (i) After fertilisation ovule develops into seeds and ovary into fruit.
(ii) Mostly angiosperms show double fertilisation.

Question. Answer the following questions:
(i) List two sexually transmitted diseases in each of the following cases:
(a) Bacterial infections
(b) Viral infections
(ii) How may the spread of such diseases be prevented?
Answer : (i) (a) Gonorrhoea and syphilis are bacterial infections.
(b) AIDS, warts are viral infections.
(ii) They can be prevented by avoiding sexual contact with the infected persons, using barriers like condoms, maintaining personal hygiene.

Question. (i) Take a potato and observe its surface. Can notches be seen ?
(ii) Cut the potato into small pieces such that some pieces contain a notch or bud and some do not.
(iii) Spread some cotton on a tray and wet it. Place the potato pieces on this cotton. Note where the pieces with the buds are placed.
(iv) Observe changes taking place in these potato pieces over the next few days. Make sure that the cotton is kept moistened.
Which are the potato pieces that give rise to fresh green shoots and roots ?
Answer : Potatoes having buds show the growth of fresh green shoots and roots and those who do not have buds does not show any growth of new plants.

Question. (i) Select a money-plant.
(ii) Cut some pieces such that they contain at least one leaf.
(iii) Cut out some other portions between two leaves.
(iv) Dip one end of all the pieces in water and observe over the next few days.
Which ones grow and give rise to fresh leaves ?
Answer : The portion of money plant having at least one leaf develops fresh leaves and branch as they have axillary bud present in exile of leaf. Other parts did not show any growth.

Question. (i) Soak a few seeds of Bengal gram (chana) and keep them overnight.
(ii) Drain the excess water and cover the seeds with a wet cloth and leave them for a day. Make sure that the seeds do not become dry.
(iii) Cut open the seeds carefully and observe the different parts.
Compare your observations with the below Fig. and see if you can identify all the parts.
Answer : The seed contains two cotyledons which store food, when seed germinates plumule and radicle are seen which grows into shoot and root respectively. Yes we can see all the parts as shown in figure above.

Question. List four points of significance of reproductive health in a society.
Name any two areas related to reproductive health which have improved over the past 50 years in our country.
Answer : Significance of reproductive health in a society are:
(a) It helps in controlling population growth.
(b) It helps in preventing the transmission of sexually transmitted diseases like syphilis, AIDS etc.
(b) It helps in family planning.
(d) It helps in knowing the suitable age for marriage and giving birth to child so that the mortality rates of mother and new born child can be reduced.
The two areas related to reproductive health which have improved over the past 50 years in our country are less mortality rate in new born and mother.

Question. What are the changes seen in girls at the time of puberty? 
Answer : Changes seen in girls during puberty are:
(a) Appearance of thick hair in genital parts and under arm pits.
(b) Enlargement of breasts.
(b) Darkening of skin surrounding the nipples.
(d) Start of menstrual cycle.
(e) Oily skin and pimples.

Question. How is the process of pollination different from fertilisation ?
Answer : Pollination is the process of transfer of pollen grains from anther to the stigma of pistil. It is carried out by various pollinating agents like water, wind, insects, animals etc.,
whereas fertilisation is the process of fusion of male gamete with a female gamete to produce a zygote. It occurs in the embryo sac present inside ovule.

Question. What are the advantages of sexual reproduction over asexual reproduction ?
Answer : The advantages of sexual reproduction over asexual reproduction are :
(a) Variations are produced due to sexual reproduction which helps in better survival of offsprings to the changing environment.
(b) More diversity is seen in case of sexual reproduction as compared to asexual reproduction.
(b) Due to recombination and crossing over in meiosis process during formation of gametes and as there is mixing of male and female gametes, genetic variations are seen which is the
main cause of evolution.

Question. Give reasons:

i. Placenta is extremely essential for foetal development.

ii. Blocking of vas deferens prevents pregnancy.

iii. Wind acts as a pollinating agent.

iv. Use of condoms prevents pregnancy.

v. Blocking of Fallopian tubes prevents pregnancy. 

Question. Define pollination. Explain the different types of pollination. List two agents of pollination. How does suitable pollination lead to fertilisation?*
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, 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 fertilisation and leads to the formation of zygote.

Question. Study the diagram and answer the following:
(i) What does the figure represent and label the parts A and B.
(ii) Name a hormone produced by X and what is its function?
(iii) Mention the substances carried by ducts C and D. 

Answer : (i) The figure represents human male reproductive system.
Part A is seminal vesicle and B is prostate gland.
(ii) The organ represented by X is testes and Hormone produced by it is testosterone which helps in developing secondary sexual characters in males at the time of puberty.
(iii) Duct C is vas deferens which carries sperms and Duct D is urethra which carries both sperms and urine.

Question. Draw a diagram of Rhizopus labelling the reproductive and nonreproductive parts. Explain the process of reproduction in Rhizopus.
Answer : Spores are reproductive parts and Hyphae are nonreproductive parts of Rhizopus. Rhizopus reproduces through asexual method by spore formation. During spore formation a
structure called sporangium develops from the fungal hypha.
The nucleus divides several times within the sporangium and each nucleus with small amount of cytoplasm develops into a spore. The spores are liberated and develop into new hypha on the substratum when conditions become favourable. 

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, where a cell divides into undifferentiated mass of cells called callus which
is transferred to different nutrient medium to grow into plantlets.
All the above methods are artificial method of vegetative propagation.
In natural methods of vegetative propagation underground roots [Root tubers of Dahlia] or underground stems [bulbs of onions, rhizomes of ginger] or adventitious buds on leaves
[Bryophyllum] grow into new plants.

Question. (i) Collect water from a lake or pond that appears dark green and contains filamentous structures.
(ii) Put one or two filaments on a slide.
(iii) Put a drop of glycerine on these filaments and cover it with a coverslip.
(iv) Observe the slide under a microscope.
Can you identify different tissues in the Spirogyra filaments ?
Answer : Spirogyra is a multicellular, filamentous, green algae where cells are alike and there is no differentiation of tissues.

Question. The picture given below depicts the process of reproduction in a single cell organism. Answer the following questions based on it: 

(i) Name the process depicted above and define it?
(ii) What is meant by asexual reproduction?
Answer : (i) The diagram given above represents multiple fission. The process by which there is division of a parent cell into several daughter cells is called multiple fission. During this process the nucleus of parent cell divides into many daughter nuclei along with the division of cytoplasm.
(ii) The reproduction which involves only one parent and occurs without the formation and fusion of gametes and there is no mixing of genetic material is called asexual reproduction.

Question. Answer the following questions:
(i) Name the different types of asexual reproduction seen in living organisms. Give examples for each.
(ii) 

Identify the process occurring in the above figure. Briefly describe the process.
Answer : (i) The different types of asexual reproduction seen in living organisms are:
(a) Fission: It is the process in which a unicellular organism splits into two or more daughter cells. They are mainly of two types- Binary fission which is seen in Amoeba, Leshmania,
Paramecium and Multiple fission seen in Plasmodium.
(b) Fragmentation: It is seen in Spirogyra.
(c) Regeneration: It is seen in Hydra, Planaria.
(d) Budding: It is seen in Yeast, Hydra.
(e) Spore formation: Here reproduction occurs through formation of spores. Spores under favourable conditions give rise to new individuals. It is seen in Rhizopus, Mucor etc.
(f) Vegetative propagation: It is mainly seen in plants.
(ii) The figure depicts fragmentation process in Spirogyra. In the process of fragmentation organism after maturation breaks into smaller fragments and each fragment grows into a new
individual. This process is called fragmentation.

Question. With the help of suitable diagrams explain the various steps of budding in Hydra.
Answer : Budding is a form of asexual reproduction and is the process of production of new individual from an outgrowth called bud formed on the parent body. Regenerative cells present in Hydra are used for budding. Due to repeated mitotic divisions an outgrowth called bud develops from the parent body which enlarges in size and finally develops into a small hydra. After attaining suitable maturity the offspring gets detached from the parent body and becomes an independent individual. 

Question. Describe the role of the following in a male reproductive system and label them in a figure:
(i) Testis
(ii) Vas deferens
(iii) Epididymis
(iv) Scrotum
(v) Seminal vesicle
Answer : (i) Testes are the primary sex organs in a human male which produce sperms by the process of spermatogenesis. They also produce male sex hormone testosterone which helps in the development of secondary male characteristics at the time of puberty.
(ii) Vas deferens also called sperm ducts carries the sperms from testes to urethra.
(iii) Epididymis stores the sperms for some days where they get mature and become motile in nature.
(iv) Scrotum or scrotal sacs are pouch like structures located outside the abdomen in which testes are placed. It provides an optimum temperature for sperm formation.
(v) The secretion of seminal vesicles helps in transportation of sperms and provides nourishment to the sperms. 

Question. Answer the following questions:
(i) Identify the given diagram. Name the parts 1 to 5. 

(ii) What is contraception? List three advantages of adopting contraceptive measures.
Answer : (i) The parts of the female reproductive system are as follows:
(1) Fallopian tube or Oviduct
(2) Ovary
(3) Uterus
(4) Cervix
(5) Vagina
(ii) Contraception is the method by which a female inhibits fertilisation and hence prevents pregnancy.
The three advantages of contraception are:
(a) It makes the people more aware about the concept of family planning.
(b) It educates the people about sexually transmitted diseases and ways to avoid it.
(b) It helps the female to space children.
(d) It reduces the risk of unwanted pregnancies.