Extra Questions for Class 10 Science Chapter 8 How Do Organisms Reproduce
Q.1. Give one advantage of the asexual mode of reproduction.
Answer: Asexual mode of reproduction occurs very fast as it include processes like budding, fission, etc. While the sexual mode is very slow. Clones can be produced by asexual mode of reproduction but sexual mode cannot produce clones since there is a step called crossing over during cell division in sexual reproduction that leads to variations.
Q.2. Incorrect DNA copying can alter the reproduction process. List the effect of such a case.
Answer: When DNA replication occurs, due to some natural or artificial conditions wrong nucleotide base pairs could get attached and this may lead to “mutations.”
Now, these mutations could be non-harmful or harmful depending upon the sequence of DNA in which it occurred. One such example is “Down syndrome” in which there exists an extra copy of chromosome number 21 leading to several abnormalities.
Q.3. An existing population of birds was suddenly wiped out from an area. Give a suitable reason for the same.
Answer: There could be numerous causes for this,
a) There was some natural calamity like tornado or storm that caused it.
b) – There was no food left for those birds in that area.
c) – Due to human intervention environment in that area, survival became unsuitable for them.
d) The population of their predator might have grown huge which ate all birds.
But taking into consideration, it was a mass extinction which occurs mostly due to environmental factors.
Q.4. Name the blueprint responsible for making all basic body designs.
Answer: DNA (Deoxyribonucleic acid) is considered as the blueprint for making all basic design of an organism.
The DNA is present in the nucleus of a cell in the form of a condensed structure called chromosome.
Q.5. How does the reproduction process can be classified on the basis of germ cells involved?
Answer: On the basis of germ cells involved reproduction is of 2 Types,
a) Asexual reproduction: A single parent organism reproduces by the fragmentation of the cell of the parent organism to form daughter organism, thus includes processes like fission, budding, fragmentation, regeneration. E.g.:- Hydra, Yeast reproduce by the mode of asexual reproduction.
b) Sexual reproduction: – It involves the fusion of gametes from 2 sexually opposite parents one of them is called male, and other is female. E.g.: – mammals, plants reproduce by the mode of sexual reproduction.
Q.6. Name the kind of organisms that reproduce by spore formation.
Answer: Mostly lower organisms like algae, fungi, and bacteria lead to spore formation. E.g.- Albugo, Phytophthora.
Q.7. What is the significance of body design in determining the habitat of an organism?
Answer: Body design/ morphology of an organism defines the way how much he is fitted or suitable for a specific habitat. E.g.- a bacteria doesn’t need big houses or area to survive and also it’s nutritional requirements are very less but humans, on the other hand, need much larger space and have complex nutrition system. A fish can survive under water because of gills but a bird or human cannot.
Q.8. “Multicellular organisms can also reproduce asexually.” Give an example to support the above statement.
Answer: Yes, basically asexual mode of reproduction involves only 1 parent and processes like meiosis, gamete production, fertilization, parthenogenesis, and transfer of gametes between two individuals does not occur, In fungi and algae spores like zoospores, conidia, etc, are formed asexually.
Also in plants, vegetative reproduction in which a specific plant part, e.g. – eyes in potato, bulbils tubers, etc. can form a complete plant and is another example of asexual reproduction in multicellular organisms.
Q.9. Give one difference between sexual and asexual reproduction.
Answer: Asexual reproduction does not involve fusion of male and female gametes thus zygote formation doesn’t take place, and it is a quick method of reproduction while in sexual reproduction fusion of male and female gametes occur, and then zygote is formed, and these processes take a lot of time.
Q.10. A student noticed that an organism by mistake was cut into parts. After some time, both developed into new individuals.
(i) Name the mode of reproduction followed by the organism.
(ii) Give an example or organism which multiply by this process.
Answer: i) Mode of reproduction followed here is Regeneration.
In some organisms, each body cell possesses the ability to proliferate and form a complete body.
ii) e.g.- Planaria, Hydra
Q.11. A plant that has lost the capacity to produce seed. Name a process using which it can reproduce?
Answer: “Vegetative reproduction”
Plant body parts like roots, tubers, bulbils, stem, leaves, buds possess the ability to proliferate into parent plant if grown under correct conditions and the property is called “Totipotency”.
Q.12. Name the mode of reproduction occurring in Amoeba.
Answer: “Binary fission”
In this, the cytoplasm and nucleus of parent cell divide equally into two daughter cells,
and no mitosis occur.
Q.13. What are the advantages of vegetative propagation?
Answer: a) Maintain genetic stability. The plants produced are generically similar to the parent plant and have all its characteristics.
b) Plants raised by vegetative propagation can bear flowers and fruit earlier than those produced seeds.
c) It also makes possible the propagation of plants such as banana, orange, rose and jasmine, which have less capacity to produce seeds.
Q.14. Name two plants which are grown by the technique of tissue culture.
Answer: Tissue culture is a technique in which a plant tissue can be used to generate a complete plant under lab conditions.
E.g.:- Orchids, Nepenthes
Q.15. Give one difference between bisexual and unisexual flowers.
Answer: Most plants have both male and female reproductive organs in the same flower and are known as bisexual flowers, E.g lily, rose, Hibiscus, mustard, etc. While others have either male or female reproductive parts in a flower known as unisexual flowers, E.g papaya, watermelon, etc.
Q.16. What is Zygote?
Answer: Zygote is the product when male and female gametes fuse under sexual reproduction. This zygote is diploid mostly and develops into a whole new organism.
Q.17. What constitutes a female reproductive part in a flower?
Answer: Carpel is the female reproductive part in plants.
This Gynoecium consists of three parts,
• Stigma: It is the terminal part of carpel which may be sticky. It helps in receiving the pollen grains.
• Style: It is the middle elongated part of carpel. It helps in the attachment of stigma to the ovary.
• Ovary: It is the swollen bottom part of carpel. It contains ovule having an egg cell.
The diagram is shown below:
Q.18. What are various agents of pollination?
Answer: Pollinators could be,
a) Biotic pollinators: – These include living organisms such as animals, insects, and humans.
b) Abiotic pollinators: – These include non-living vectors or natural carriers such as wind, water, gravity, fire etc.
Q.19. Why do spores remain viable during unfavorable conditions?
Answer: Sporulation occurs under an unfavorable environment like high temperature, ph., etc. Where a normal cell cannot survive. So bacteria and fungi can convert their cells into a spore. These spores have all the nutrition required for growth but have very less water content which makes it hard and unreactive to the harsh environment. Also, some spores have an extra protective covering of lipids, polysaccharides or some proteinaceous substance that makes it withstand the harsh environment.
Q.20. The fruit is developed from which floral part?
Answer: Ovary of the flower develops into fruit after fertilization.
Q.21. State one reason why cross-pollination is preferred over self-pollination.
Answer: Cross-pollination is the transfer of pollen from the flower of one plant to the stigma of the flower of another plant, as shown below:
Due to this, cross-pollination brings about recombination, variations, helps in the production of new varieties and disease resistant plants.
Q.22. Where can zygote be found in flower after fertilization?
Answer: After the fertilization process is done, i.e. male nucleus from pollen fused with a female nucleus in the egg cell inside ovary of a flower, this newly fertilized egg develops into zygote inside the ovary.
Q.23. What changes take place in boys during the reproductive phase?
Answer: In boys puberty starts near 14-15 years of age.
During this phase,
• Body is larger, more muscular, and stronger.
• Beard, moustache and chest hairs start appearing.
• Shoulders become broad.
• Voice becomes low pitched.
• Behavior becomes a little aggressive because of a spike in testosterone levels.
• Development of Adam’s apple is there.
Q.24. ‘The seed contains the future plant.’ Why is it said so?
Answer: After fertilization, ovules develops into seeds. These seeds could be monocot (with one cotyledon) or dicot (with two cotyledon) depending upon the plant variety.
These seeds contain the embryo, plumule, and radicle. Plumule develops in to shoot while Radicle develops into roots.
Q.25. Sperms are produced in testis, how do they reach the urethra for further passage into the female reproductive tract?
Answer: Testis are connected to the urethra with the help of a 40 cm long tube-like structure called “Vasa Deferentia”. It is slightly coiled at first near testis but then becomes straight as it enters the abdominal cavity where is passes over urinary bladder and join to the urethra.
Q.26. What is placenta? Discuss its role in the human body.
Answer: Placenta is a reddish brown disc that attaches to the wall of the uterus and the umbilical cord arises from it. Placenta form finger like projection called the villi toward embryo. This creats large surface for the exchange of glucose and oxygen between mother and the embryo.
Q.27. What is the function of testosterone in males?
Answer: Testosterone is the male sex hormone called “Androgen”. Testosterone’s secretions are at peak during male puberty and it is responsible for bringing about all the reproductive changes like beard, muscular body, penis enlargement, pubic hairs, etc.
Q.28. What is responsible for attainment of sexual maturity in both males and females?
Answer: Sexual maturity is attained due to the secretions of sex organs “testis” and “ovaries” in males and females respectively.
These secretions are Testosterone (male sex hormone) and Progesterone and Estrogen (female sex hormones) at puberty.
Q.29. Name the organ responsible for secreting seminal fluid.
Answer: Seminal fluid is the combination of secretions from accessory sex glands and mucus gland to the sperms i.e. sperms together with secretions from seminal vesicles, prostate gland, preputial gland and Cowper’s gland form a seminal fluid.
Q.30. What happens when fertilization does not occur in a female body?
Answer: In female, ovaries release ovum or egg once every 28 days from the age of puberty. The uterus prepares itself every month to receive a fertilized egg. Thus, its lining becomes thick and spongy. If the egg is not fertilized it lives for about one day. Afterwards this lining of uterus is no longer required and menstruation occurs. Menstrual is the time of uterine bleeding in which an unfertilized egg and the thick uterine lining. It occurs through the vagina as blood and mucus.
Q.31. What is the function of the Fallopian tube in the female reproductive system?
Answer: Fallopian tube or oviducts is about 10 to 12 cm long muscular tube. It has a funnel shaped opening near the ovary.
It carries ova or egg from ovary to the uterus and is the site of fertilization.
