Class 10 Science Chapter 8 How Do Organisms Reproduce? Solutions to each chapter is provided in the list so that you can easily browse throughout different chapters NCERT Class 10 Science Chapter 8 How Do Organisms Reproduce? and select need one.
Class 10 Science Chapter 8 How Do Organisms Reproduce?
Also, you can read the CBSE book online in these sections Solutions by Expert Teachers as per NCERT (CBSE) Book guidelines. These solutions are part of SEBA All Subject Solutions. Here we have given Assam BoardClass 10 Science Chapter 8 How Do Organisms Reproduce? Solutions for All Subjects, You can practice these here.
How Do Organisms Reproduce?
Chapter – 8
GENERAL SCIENCE
Textual Questions and Answers:
Page – 128
Q.1. What is the importance of DNA copying in reproduction?
Ans: The copying of DNA during reproduction is important because: The replication of DNA ensures that each daughter cell formed at the end of cell division, receives equal amount of DNA. If DNA won’t be copied then the daughter cells won’t receive all necessary genes.
Q.2. Why is variation beneficial to the species but not necessarily for the individual?
Ans: Variation is beneficial to the species but not necessarily for the individual because it lets a species adapt to the changing environment. Variations at individual level will not help in evolving, but would result in ageing, so variation from any source in an individual can be harmful. At species level, these variations make differences in generation which leads to evolution.
Page – 133
Q.1. How does binary fission differ from multiple fission?
Ans: In binary fission, the parent cell is divided into two daughter cells. In multiple fissions, the parent cell is divided into many daughter cells.
Q.2. How will an organism be benefited if it reproduces trough spores?
Ans: The reproduction by spores takes place in plants. Spores are covered by hard protective coat which enables them to survive under unfavourable condition like lack of food, lack of water and extreme temperatures. But when the conditions become favourable then the spores can grow to produce new plants. Thus, the reproduction by spores benefits the plants because by surviving under adverse conditions, the spores make these plants live forever.
Q.3. Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Ans: The tissues in complex organisms can not regenerate a new individual as they highly differentiated to perform specialised functions. For example, human skin cannot regenerate into a new individual as it is a highly differentiated tissue performing a designated function.
Q.4. Why is vegetative propagation practised for growing some types of plants?
Ans: Vegetative propagation is practised for growing some types of plants because:
(i) Characters of the plants can be preserved through successive generation.
(ii) Seedless plants can be grown through vegetative reproduction
(iii) Through cutting and grafting methods, flowers and fruits can be grown in a shorter time.
(iv) It is a cheaper, easier and more rapid method of plant propagation.
Q.5. Why is DNA copying an essential part of the process of reproduction?
Ans: Importance of DNA copying in a sexual reproduction is that the characteristics of the parent organisms are transmitted to its offsprings and at the same time some occasional variations are also produced in the offsprings.
Page – 140
Q.1. How is the process of pollination different from fertilisation?
Ans: Transfer of pollen grains from the anther to stigma is called pollination. On the other hand, the fusion of male and female gametes is called fertilisation. Pollination is a physical process in which movement of pollen grains are attained by certain physical factors. Fertilisation is a biochemical process. An ovary is the site of fertilisation and embryo is the product of fertilisation.
Q.2. What is the role of seminal vesicles and prostrate gland?
Ans: In human males, the seminal vesicle forms an accessory gland whose fluid secretion results in activation of the sperms.
Role of seminal vesicle:
- Produces the necessary fluids that eventually convert into semen.
- Supplies protection and required nutrition to the sperm.
The prostate gland is a part of the reproductive system in human males that envelopes the urethra. It passes an alkaline secretion to the semen when it flows through the urethra.
Role of the prostate gland:
- Stores the fluid that transports and nourishes the seminal fluid.
- Make sure that the sperm is firmly pressed into the prostatic urethra.
Q.3. What are the changes seen in girls at the time of puberty?
Ans: Puberty:
- Puberty refers to the physical transformation of a child’s body into an adult one capable of sexual reproduction.
- Girls often begin puberty at the age of eleven.
Changes that are seen in girls at the time of puberty:
- Girls’ breasts begin to develop during puberty.
- The ovaries grow in girls, and eggs begin to develop.
- Ovaries also begin to release mature eggs (Menstruation starts).
- As a result of increased sweat and sebaceous gland activity, girls develop acne and pimples.
- Hair grows under the arms, above the thighs, and in the pubic region.
Q.4. How dose the embryo get nourishment inside the mother’s body?
Ans: The embryo gets nourishment inside the mother body through a special tissue called placenta. The embryo grows inside the mother’s womb and gets nourishment from mother’s blood through the tissue called placenta. The placenta is a temporary organ that develops in the uterus during pregnancy. It attaches the fetus to the uterine wall. It also provides nutrients to the fetus and also allows the fetus to transfer waste product’s to the mother’s blood.
Q.5. If a women is using a copper – T, will it help in protecting her from sexually transmitted diseases?
Ans: No, the use of copper – T for contraception will not protect a women from sexually transmitted diseases.
EXERCISES
Q.1. COM Asexual reproduction takes place through budding in:
(a) Amoeba.
(b) Yeast.
(d) Plasmodium.
(d) Leishmania.
Ans: (b) Yeast.
Q.2. Which of the following is not a part of the female reproductive system in human beings?
(a) Ovary.
(b) Uterus.
(c) Vas deferens.
(d) Fallopian tube.
Ans: (c) Vas deferens.
Q.3. The anther contains
(a) Sepals.
(b) Ovules.
(c) Carpel.
(d) Pollen grains.
Ans: (d) Pollen grains.
Q.4. What are the advantages of sexual reproduction over sexual reproduction?
Ans: Advantages of sexual reproduction over sexual reproduction:
- More variations are found in sexual reproduction.
- Survival of a species in a population is easy.
- Offspring has characteristics of both parents.
- It can lead to the formation of new species.
- The chances of evolution increase.
Q.5. Why are the functions performed by testes in human beings?
Ans: Testes perform 2 functions in human beings, basically males (testes are a part of male reproductive system; located outside the abdominal cavity in scrotum)-
(i) The produce male gametes/ sex cells known as sperms.
(ii) Also, they produce male sex hormone testosterone which is responsible for appearance of secondary sexual characters in boys, for example- beard, moustache, deep voice, etc.
Q.6. Why does menstruation occur?
Ans: As a woman, your period is your body’s way of releasing tissue that it no longer needs. Every month, your body prepares for pregnancy.
The lining of your uterus gets thicker as preparation for nurturing a fertilized egg. An egg is released and is ready to be fertilized and settle in the lining of your uterus.
If the egg is not fertilized, your body no longer needs the thicker lining of the uterus, so it starts to break down and is eventually expelled, along with some blood, from your vagina. This is your period, and once it’s over, the process starts all over again.
Q.7. Draw a labelled diagram of the longitudinal section of a flower.
Ans:
Q.8. What are the different methods of contraception?
Ans: The various method of contraception are: Barrier methods, chemical methods, use of Loop or copper – T and surgical method.
In the barrier methods of preventing pregnancy, the physical devices such as condoms and diaphragms are used.
In the chemical methods of preventing pregnancy, the femalls use oral pills.
The loop or copper – T are also very effective in preventing pregnancy. A loop or copper – T is placed inside the uterus by a doctor or a trained nurse.
Surgical methods of birth control are available for males as well as females. In males, a small portion of the sperm duct is removed by surgical operation and both the cut ends are ligated property. In females, a small portion of the oviducts is removed by surgical operation and the cut ends are ligated.
Q.9. How are the modes of reproduction different in unicellular and multicellular organisms?
Ans: The different modes of reproduction in unicellular organisms are fission, budding, etc. Here, the cell divides into two daughter cells and this process of cell division continues. Whereas, in multicellular organisms there is a different organ system for reproduction. The different modes of reproduction in multicellular organisms are vegetative propagation, spore formation, etc. In more complex organisms like humans and animals, the reproduction is through sexual reproduction.
Q.10. How does reproduction help in providing stability to populations of species?
Ans: Reproduction is the process of producing new individuals of the same species by existing organisms of a species, so, it helps in providing stability to population of species by giving birth to new individuals as the rate of birth must be at par with the rate of death to provide stability to population of a species.
Q.11. What could be the reasons for adopting contraceptive methods?
Ans: Contraceptive methods are mainly adopted because of the following reasons:
1. To prevent unwanted pregnancies.
2. To control population rise or birth rate.
3. To prevent the transfer of sexually transmitted diseases.
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