Class Ten Science Chapter 8 NCERT Solutions
Chapter 8: How Do Organisms Reproduce?
Q.1. What is the importance of DNA copying in reproduction?
Ans. DNA contains information for the inheritance of characteristics from parents to the next generation. DNA present in the nucleus of cells is the information source for making protein. If information is different, a different type of protein will be made that will lead to altered body design.
Q.2. Why is variation beneficial to the species but not necessarily for the individual?
Ans. Variations are useful for the survival of species in changed environmental situations. If a population of reproducing organism were suited to a particular niche and if the niche is drastically altered the population could be wiped out. However, some variations are present some species will survive. Thus, variation is useful to species but not the individual.
Q.3. How does binary fission differ from multiple fission?
Ans. Binary fission: In this splitting of the unicellular organism occurs into two daughter cells. Example: Amoeba.
Multiple fission: In this splitting of the unicellular organism occurs into many daughter cells. Example: Malarial parasite Plasmodium.
Q.4. How will an organism be benefitted if it reproduces through spores?
Ans. The spores are covered by thick walls that protect them until they come in contact with the suitable moist surface and begin to grow.
Q.5. Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Ans. The reason is that complex organism are not further merely a random collection of cells. Specialized cells are organised in them as tissues which are organised into organs. These organs have to be placed at definite positions in the body. So, regeneration is not possible in multicellular organisms.
Q.6. Why is vegetative propagation practised for growing some types of plants?
Ans. (i) Plants raised by vegetative propagation can bear flower and fruits earlier than that produced from seeds.
(ii) Such methods also make possible the propagation of plants such as banana, orange, rose and jasmine that has lost the capacity to produce seeds.
(iii) All plants produced by this method are genetically similar enough to the parent plant to have all characteristics.
Q.7. Why is DNA copying an essential part of the process of reproduction?
Ans. DNA contains information for the inheritance of features from parents to the next generation. DNA present in the nucleus of cells is the information source for making protein. If information is different, a different type of protein will be made that will lead to altered body design.
Q.8. How is the process of pollination different from fertilisation?
Ans. Differences between pollination and fertilisation.
Pollination: Pollination refers to the process of transfer of pollen grains from anther to stigma of the flower.
Fertilisation: Fertilisation refers to the fusion of male and female gamete to form a zygote.
Q.9. What is the role of the seminal vesicles and the prostate gland?
Ans. The secretions from seminal vesicles and the prostate gland lubricate the sperms and provide a fluid medium for easy transport of sperms. Their secretion also provides nutrients in the form of fructose, calcium, and some enzymes.
Q.10. What are the changes seen in girls at the time of puberty?
Ans. During puberty,
breast size begins to increase
girls begin to menstruate at around this time.
growth of pubic hair occurs.
the oil glands and sweat glands become more active in the skin and result in the appearance of pimples.