CBSE Class 10 Science How Do Organisms Reproduce Worksheet

Question. How does the embryo gets nourishment from the mother?
Answer : Through placenta.

Question. What happens if egg is not fertilized?
Answer : If fertilization does not occur then menstruation occurs, i.e., blood and mucus comes out through thevagina. 

Question. Name two ways of vegetative propagation practiced by gardeners.
Answer : Cutting and grafting.

Question. List two functions of ovary of human female reproductive system ?
Answer : Ovaries produces the ova or eggs and they produce hormones like oestrogen and progesterone. Oestrogen helps in development of secondary sexual characters in females at the time of puberty whereas progesterone prepares the uterus for receiving the fertilised egg.

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

Question. State the method of growing rose plant and jasmine plant ?
Answer : Vegetative propagation like cutting is used to grow rose plant and layering method is used to grow jasmine plant.

Question. Name the largest cell present in the human body.
Answer : Ovum is the largest cell present in the, human body.

Question. Name the method by which Hydra reproduces ? Is this method sexual or asexual ?
Answer : Hydra can reproduce by budding and regeneration. Both are asexual method.

Question. Where is DNA found in cell?
Answer : DNA is found inside the nucleus in a cell.

Question. What is the significance of testes being located in scrotal sacs outside abdomen?
Answer : The formation of sperms requires a temperature of 2°C–3°C lower than body temperature. So testes are located in a sac like structures called scrotum outside the abdomen.

Question. How does Planaria reproduce? Is this method sexual or asexual?
Answer : Planaria reproduces by regeneration process. This method is an asexual mode of reproduction. In this process, if Planaria is cut into many pieces each piece grows into a new Planaria.

Question. Explain the roles of gamete and zygote in sexual reproduction?
Answer : Gametes play an important role in sexual reproduction because fusion of male and female gametes lead to formation of a zygote. Zygote formed as a result of fertilisation develops into embryo and finally into a new individual.

Question. Name a tiny fresh water animal which reproduces by the same method as that of yeast ? What is this method known as ?
Answer : Hydra is a tiny fresh water animal which reproduces by the same method as that of yeast and this method is known as budding.

Question. An organism which is a worm has very simple eyes, that are really eye spots which detect light. Name the organism.
Answer : Planaria.

Question. What is a clone? Why do offsprings formed by asexual reproduction exhibit remarkable similarity?
Answer : Clone is an exact replica of an organism produced as a result of asexual reproduction. Since all the offsprings formed by asexual reproduction have exact copies of DNA of their parent so they exhibit remarkable similarity.

Question. List two functions performed by testes in human beings.
Answer : In human testes, sperms are produced by the process of spermatogenesis and interstitial cells present in testes produce the male hormone testosterone.

Question. Name the causative agent of the disease kala-azar and its mode of asexual reproduction.
Answer : Leishmania causes kala-azar and its mode of asexual reproduction is binary fission.

Question. Name a unisexual and a bisexual flower.
Answer : Watermelon is an unisexual flower whereas Hibiscus is a bisexual flower.

Question. Name the causative organism of the disease “Kalaazar” and its mode of asexual reproduction.
Answer : Leishmania, Binary fission.

Question. Draw a labelled diagram of
a. Spore formation in Rhizop us
b. Multiple fission in Plasmodium.
Answer : 

Question. Write two differences between binary fission and multiple fission in a tabular form as observed in the cells of the organisms.
Answer : 

Question. Differentiate between plumule and radicle.
Answer : 

Question. Name the type of asexual reproduction in:
a. Planaria
b. Rhizopus
c. Spirogyra
d. Hydra
Answer : a. Regeneration
b. Spore formation
c. Fragmentation
d. Budding

Question. Label any four parts.

Answer : 1. Stigma
2. Anther
3. Style
4. Filament
5. Petal
6. Ovary
7. Sepal

Question. What are the functions of the following in male reproductive system?
a. Seminal vesicles
b. Prostate gland
Answer : a. In human males, seminal vesicles store sperms temporarily before ejaculation.
b. Both seminal vesicles and prostate gland add their secretions so that the sperms remain in a fluid which makes their transport easier and also this fluid provides nutrition.

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. Draw labelled diagrams to illustrate budding in Hydra.
Answer : a. In sexual reproduction, fusion of male and female gametes takes place, these germ-cells/gametes contain half the number of chromosomes and by the fusion of these gametes the zygote is formed with full set of chromosomes.
b. When male and female gametes fuse at the time of fertilization, it restores the original number of chromosomes (of the parent), ensuring the stability of species.

Question. Leaves of Bryophyllum fallen on the ground produce new plants. Why?
Answer : Leaves of Bryophyllum bears adventi¬tious buds/ plantlets in the notches along the leaf margin. When the buds fall on the soil they develop into new plant under favourable condi-tions.

Question. Differentiate between self-pollination and crosspollination.
Answer :

Question. What is meant by DNA copying? Mention its importance in reproduction.
Answer : Cells use chemical reactions to build copies of their DNA. This creates two copies of the DNA in a reproducing cell. DNA copying is accompanied by the creation of an additional cellular apparatus to facilitate the DNA copies to separate with its own cellular apparatus. DNA copying gives rise to some inbuilt tendency for variation during reproduction which is the basis for evolution.

Question. Distinguish between the functions of ovary and testis.
Answer : 

Question. Give reasons:
a. Wind acts as a pollinating agent.
b. Variation is essential and beneficial to a species.
c. Use of condoms prevents pregnancy.
Answer : a. Transfer of pollen grains from anther to stigma.
b. Helps in evolution and survival.
c. Prevents fertilization - Barrier method.

Question. DNA content has the tendency to double itself during sexual reproduction due to combining of the genetic materials from the two parents. How the problem of DNA doubling can be solved to maintain the consistency of the genetic material throughout the species?
or
“The chromosome number of the sexually reproducing parents and their offsprings is the same”. Justify the statement.
Answer : DNA doubling is always followed by cell division. Due to this special cell division, gametes form with half the content of DNA and single set of chromosomes. These gamete fuse to form zygote on fertilization. Thus the characteristic number of chromosome and the normal DNA content for a cell is regained.
Thus the consistency of the genetic material throughout the species is maintained and for the same reason the chromosome number of the sexually reproducing parents and their offsprings is the same.

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.

Question. What are secondary sexual characters in humans? Name one such character of male and female.
Answer : The characters which distinguish a male from female are called secondary sexual characters. Secondary sexual characters of male are moustache, beard, thick growth of hair on body, strong muscles and harsh voice.
Secondary sexual characters of female are less hair on body, broad hips, development of breasts and soft voice.

Question. Give two examples each of the following:
a. Plants having unisexual flowers
b. Agents of pollination
c. Physical changes on puberty that are common to both boys and girls.
Answer : a. Papaya, watermelon
b. Insects, air, water, etc.
c. (i) Appearance of pubic hair.
(ii) Skin becomes oily and may develop pimples.

Question. Why are the testes located outside the abdominal cavity? Mention the endocrine and exocrine function of testes.
Answer : Sperm formation requires a lower temperature than the normal body temperature. This temperature is 1-3°C lower than the temperature of the body. Testes are thus located outside so that scrotum provides an optimal temperature for the formation of the sperms.
Endocrine function: Production of male hormone (testosterone).
Exocrine function: Production of male gametes (sperms).

Question. Name and explain the method by which Rhizopus reproduces.
Answer : Rhizopus reproduces by spore formation. Method: It is a method of asexual reproduction.

Spores are produced in a structure called sporangium.

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 sexually or the one reproducing asexually? Justify your answer.
or
How is sexual reproduction better than asexual reproduction?
Answer : a. Asexual reproduction does not involve genetic fusion while sexual reproduction involves fusion of male and female gametes to form a zygote.
b. Species reproducing sexually have better chances of survival.
Reason :
Sexual reproduction gives rise to more variations which are essential for evolution as well as survival of species under unfavorable conditions.

Question. What are chromosomes? Explain how in sexually reproducing organisms, the number of chromosomes in the progeny is maintained?
Answer : Chromosomes are thread like structures made-up of DNA found in the nucleus. The original number of chromosomes becomes half during gamete formation. Hence, when the gametes combine, the original number of chromosome gets restored in the progeny.