CBSE Class 10 Biology How Do Organisms Reproduce Worksheet Set I

Very Short Answer Type Questions :

Question. Write the role of testes in male reproductive system. 
Answer: Formation of sperms and to secrete hormone called testosterone.

Question. What is DNA?
Answer: DNA is the carrier of hereditary information from parents to the next generation. Hereditary material is present either DNA/RNA in all living cells.

Question. Name the type of reproduction mostly seen in unicellular organisms.
Answer: Asexual reproduction.

Question. What is a gene? 
Answer: Gene is a part of DNA that encodes the instructions that allow a cell to produce a specific protein or enzyme.

Question. When a cell reproduces, what happens to its DNA?
Answer: When a cell reprodues , its DNA makes – two copies , each divided call getting one .

Question. Name the parts of a bisexual flower that are not directly involved in reproduction.
Answer: Sepals/calyx
Petals/corolla
Thalamus

Question. Name the organs producing sperms and ova respectively in humans.
Answer: Testis: Sperms, Ovary: Ova.

Question. What is fertilisation? Where does it occur in a human female?
Answer: Fusion of male and female gamete is known as fertilization. It occurs in fallopian tube.

Question. Name two simple organisms having the ability of regeneration.
Answer: Planaria and Hydra.

Question. How does Plasmodium reproduce? Is this method sexual or asexual type of reproduction?
Answer: Plasmodium reproduces by a process known as multiple fission. Multiple fission is a type of asexual reproduction.

Short Answer Type Questions :

Question. (i) What is the fate of the ovules and the ovary in a flower after fertilization?
(ii) How is the process of pollination different from fertilization? 
Answer: (i) After fertilization, ovules become seeds and ovary forms the fruit.
(ii) Pollination is the transfer of pollen grains from anther to the stigma of a flower. 
Fertilization is the fusion of male and female gametes.

Question. In a flowering plant, summarize the events that take place after fertilization.
Answer: Fertilization results in formation of zygote.
Zygote divides several times to form an embryo.
The ovule develops a thick coat and changes into seed. The ovary grows rapidly and ripens to form the fruit.

Question. Give one example of each, the unisexual and bisexual flowers.
Answer: Unisexual flowers contain either stamens or carpels but never both.
Example: Papaya, watermelon.
Bisexual flowers contain both stamens and carpels.
Example: Hibiscus, Mustard.

Question. What is the main difference between sperms and eggs of humans? Write the importance of this difference. 
Answer: Sperms contain one of the two types of sex chromosomes i.e., X—chromosomes and Y— chromosomes.
Egg contains one type of sex chromosomes only i.e., X—chromosome.
This chromosomal difference helps in determination of sex. If sperm carrying Y-chromosome fuses with egg, the resultant zygote will develop in male. If sperm with X chromosome fuses with egg, the zygote will develop into a female child.

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, vegetative propagation occur through leaves where buds occur on their margins.
Rose leaves do not form buds.

Question. List four modes of asexual reproduction.
Answer: Four modes of asexual reproduction are:
(i) Binary fission
(ii) Budding
(iii) Multiple fission
(iv) Fragmentation.

Question. (i) What is meant by vegetative propagation?
(ii) How will a plant be benefitted if it reproduces by vegetative propagation? 
Answer: (i) Propagation by vegetative parts such as the roots, stems and leaves. 
(ii) Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds. Such method also makes possible the propagation of plants that have lost the capacity to produce seeds.

Question. Mention the functions of (a) placenta, (b) fallopian tube in the human female reproductive system. 
Answer: (a) Placenta: (i) Helps in the transportation of glucose and oxygen from the mother to the embryo.
(ii) Waste generated by the embryo is removed by transferring it to the mother’s blood. 
(b) Fallopian tube: (i) Egg is carried from the ovary to the uterus. 
(ii) Fertilization occurs here.

Question. List any two contraceptive methods practised only by women. Mention how these methods work? 
Answer: (i) Oral pills: Change hormonal balance so eggs are not released. 
(ii) Loop / Copper-T: Placed in the uterus. Prevent pregnancy by checking the entry of sperms through the vagina.

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? Justify your answer.
Answer: Any one of the following difference:
(i) In sexual reproduction, two opposite sexes are involved whereas in asexual reproduction, only one individual is involved.
(ii) In sexual reproduction, male and female gamete formation takes place whereas in asexual, no gamete formation occurs.
Sexually reproducing organisms have better chances of survival.
Because more variations are generated.

Question. In a germinating seed, which parts are known as future shoot and future root? Mention the function of cotyledon. 
Answer: Future shoot–Plumule
Future root–Radicle
Function of cotyledon–It stores food for the future plant or embryo.

Question. In the context of reproduction of species, state the main difference between fission and fragmentation. Also, give one example of each.
Answer: Fission: It is the method of asexual reproduction in unicellular forms of life.
In this process, the parent organism splits to form two or more daughter cells.
Example: Amoeba / Plasmodium / Paramecium.
Fragmentation: It is the process found in multicellular organisms. The filament breaks up into two or more pieces upon maturation. These pieces then grow into new individuals.
Example: Spirogyra.

Question. How is the process of binary fission different in Amoeba and Leishmania? 
Answer: Amoeba reproduces through simple binary fission.
Leishmania reproduces asexually through binary fission that occurs along a definite orientation related to the whip like structure at one end of the cell.

Question. Write two functions of each (i) Testis, (ii) Ovaries.
Answer: (i) Testis: It produces sperms and secretes male sex hormones called testosterone. 
(ii) Ovary: It produces ovum and secretes female sex hormones called estrogen and progesterone.

Question. What is regeneration? Give one example of an organism that shows this process and one organism that does not. Why does regeneration not occur in the latter?
Answer: (i) Regeneration: Ability of organisms to give rise to new individual organisms from their body parts. 
(ii) Planaria/Hydra
iii) Amoeba / Rhizopus / Banana / Sugarcane / any other does not show regeneration. 
(iv) Regeneration is carried out by specialized cells which are not present in non-regenerating organisms.

Long Answer Type Questions :

Question. Different organisms reproduce by different methods suitable to their body designs.
(i) Justify the above statement using examples of three different organisms which reproduce by different methods of asexual reproduction.
(ii) Differentiate between sexual and asexual modes of reproduction.
Answer: (i) Amoeba: Binary fission
Plasmodium: Multiple fission
Hydra: Budding
Planaria: Regeneration (Any three + Explain)
(ii) Sexual two parents; Asexual single parent.

Question. (i) Describe the role of prostate gland, seminal vesicle and testes in the human male reproductive system.
(ii) How is the surgical removal of unwanted pregnancies misused?
(iii) Explain the role of oral contraceptive pills in preventing conception.
Answer: (i) Prostate and the seminal vesicles produce fluid that nourishes the sperm. This fluid provides most of the volume of semen, the fluid in which the sperm is expelled during ejaculation.
Testes secrete testosterone which brings about changes in the appearances in the boys at the time of puberty.
(ii) Female foeticides/illegal sex selected abortion of female foeticide.
(iii) Interfere in release of egg and eggs are not released.

Question. (a) Draw a diagram to show spore formation in Rhizopus.
(b) With the help of an example differentiate between the process of Budding and Fragmentation.
(c) Why is vegetative propagation practiced for growing some type of plants?
Answer: (a) Spore formation in Rhizopus:
(b) Differences between Budding and Fermentation:
(c) Vegetative propagation is practiced for growing some type of plants because: 
(i) Only one parent is required for reproduction; this eliminates the need of special mechanisms (pollination) and fusion of gametes i.e., fertilization.
(ii) Many plants are able to tide over unfavourable conditions because of the presence of vegetative reproductive parts like tubers, corns and bulbs.
(iii) Plants that do not produce seeds can be propagated by this method, e.g., sugarcane and potato.
(iv) Vegetative propagation is a cheaper, easier and rapid method of reproduction in plants than growing plants from seeds. For examplelilies grow very slowly and take up to seven years to develop flowers when their seeds are grown, but when grown vegetatively, flowers are produced only after a year or two.
(v) The trait (character) of the parent plant is preserved and the offsprings are genetically identical.

Question. Define pollination. Explain the different types of pollination. List two agents of pollination. How does suitable pollination lead to fertilization?
Answer: Pollination: Transfer of pollen from anther / stamen to stigma of the flower Types of Pollination:
(a) Self pollination: Transfer of pollen from anther/ stamen to stigma occurs in the same flower.
(b) Cross pollination: Pollen is transferred from anther stamen of one flower to stigma of another flower.
Agents of pollination: Wind, Water, Insects and Animals 
A tube grows out of the pollen grain and travels through the style, to reach the female germ cell in the ovary to cause fertilization.

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? (State any one consequence)
Answer: (a) (i) Prevents meeting of sperm and ova
(ii) Protects against sexually transmitted diseases (b) Oral pills contain hormones which prevent the ovaries from releasing ovum into the oviduct.
(c) Selective abortion means abortion (termination) of pregnancy, especially female foeticide.
Effect: Society will have imbalance in the male female ratio.

Question. Give one example each of unisexual and bisexual flowers. Differentiate between the two types of pollination that occur in flowers. What happens when a pollen lands on a suitable stigma? Write about the events that occur till the seed formation in the ovary. 
Answer: Unisexual Flower: Papaya/Water-melon
Bisexual Flower: Hibiscus/Rose/
Self pollination: The pollen grains are transferred from the anther to the stigma of the same flower or to the flower of the same plant. 
Cross pollination: The pollen grains are transferred from the anther to the stigma of a flower of a different plant.
- After pollen lands on a suitable stigma, a pollen tube grows out of pollen grain and travels through the style to reach the ovary. 
- The male germ cell fuses with the female germ cell to form a zygote. 
- Zygote divides several times to form an embryo within the ovule. 
- The ovule develops tough coat and gradually gets converted into a seed.