NCERT Solutions For Class 10 Science Chapter 8 How do Organisms Reproduce

NCERT Books Solutions For Class 10 Science Chapter 8 How do Organisms Reproduce

Class 10 is the first stepping stone for a student in the competitive world. With the introduction of the CBSE Board Exam for class 10 a few years back, this has become an important gateway for a student as based on the results of class 10th a student selects his future stream of Science, Commerce, or Arts.

Takshila Learning provides you with detailed and well explained NCERT Solutions for Class 10 of each chapter of each subject for NCERT Class 10. These NCERT Solutions help you to easily understand every concept so that you can score high in your CBSE Class 10 Board Exams.

Below you can find the NCERT solution for Class 10th Science. You can get a Solution for the all-important question of “Chapter 8 Class 10th Science How do Organisms Reproduce?”

Ques 1: What is the importance of DNA copying in reproduction?

Answer: DNA is the genetic material present in the cells of all organisms. The genetic information from generation to generation is carried by DNA. It is therefore possible for the organism to produce organism of its own type due to DNA copying only. For the inheritance of traits of the parent, DNA copying is must. DNA copying also bring out variation, which forms the basis for the origin of new species

Ques 2: Why is the variation beneficial to the species but not necessarily for the individual?

Answer: Variations are beneficial to the species than individual because sometimes for a species, the environmental condition change so drastically that this is a viable becomes difficult. For example, if the temperature of water increases suddenly, then most of the bacteria living in that water would die. Only few variants that are resistant to heat would be able to survive. However, if these variants were not there, then the entire species of bacteria could have been destroyed. Thus, the variant help in survival of the species. However, all variants are not necessarily beneficial for the individual organism

Intext questions (set 2)

Page no.133

Ques 1: How does binary fission differ from multiple fission?

Answer: In binary fission a single cell divides into two equal halves. Amoeba and bacteria divide by binary fission.

In multiple fission, a single cell divides into many daughter cells simultaneously. Plasmodium divided by multiple fission.

Ques 2: How will an organism be benefited if it reproduces through spores?

Answer: Advantages of spore formation:

• Large numbers of spores are produced in one sporangium.
• Spores are distributed easily by air to far-off places to avoid competition at one place.
• Spores are covered by thick walls to prevent dehydration under unfavourable conditions.

Ques 3: Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?

Answer: Hire complex organism cannot give rise to new individuals through regeneration because complex organism have organ system level of organisation. All the organ systems of the body work together as interconnected unit. They can regenerate their lost body parts such as skin, muscles, blood etc. However, they cannot give rise to new individuals through regeneration.

Ques 4: Why is vegetative propagation practiced for growing some types of plants?

Answer: Vegetative propagation is practised for growing some type of plan because the following advantages:

• It is used to grow a plant in which viable seats are not formed are very few seats are produced such as orange, banana, pineapple.
• It helps to introduce plants in new areas where the seeds in germination fails to produce mature plan due to change in environmental factor in the soil.
• It is more rapid, easier and cheaper method.
• By this method a good quality of a race or variety can be preserved.

Ques 5: Why is DNA copying an essential part of the process of reproduction?

Answer: DNA copying is an essential part of reproduction as it passes genetic information from parents to offspring. It determines the body design of an individual. The reproducing sales produce a copy of the DNA through some chemical reaction and result into copies of DNA. The copying of DNA always takes place along with the creation of additional cellular structure. This process is then followed by division of a cell to form two cells.

Intext questions (set 3)

Page no.140

Ques 1: How is the process of pollination different from fertilization?

Answer: Pollination is the process of transfer of Pollens from Anther to stigma. It occurs with the help of certain pollinators such as air, water, birds, or some insects.

Fertilisation is the fusion of the male and female gametes. It occurs inside the ovule leads to the formation of zygote.

Ques 2: What is the role of the seminal vesicles and the prostate gland?

Answer: The secretion from seminal vesicles and prostate glands 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 other enzymes.

Ques 3: What are the changes seen in girls at the time of puberty?

Answer: The changes seen in girls at the time of puberty are:

• Increase in breast size and darkening of skin of the nipples present at the tip of the breasts
• Appearance of hair in the genital area.
• Appearance of hair in other areas of skin like underarms, face, hands, and legs
• Increase in the size of uterus and ovary.
• Beginning of menstrual cycle.
• More Secretion of oil from the skin, which result in the appearance of pimples.

Ques 4: How does the embryo get nourishment inside the mother’s body?

Answer: After fertilisation the lining of uterus thickens and is richly supplied with blood to nourish the growing embryo. The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. It is embedded in the uterine wall. Placenta contains Villi on the embryos side of the tissue and blood spaces on mother’s side surrounding the villi. This provides a large surface from mother to the embryo and waste products from the embryo to the mother.

Ques 5: If a woman is using a Copper-T, will it help in protecting her from sexually transmitted diseases?

Answer: No, because copper-T will not prevent contact body fluids. Thus, it will not protect her from sexually transmitted diseases.

Exercise:

Page no.141

Ques 1: Asexual reproduction takes place through budding in 

a)Amoeba
b) Yeast
c) Plasmodium
d) Leishmania

Answer: (b) Yeast.

Ques 2: Which of the following is not a part of the female reproductive system in human beings?

1. a) Ovary
   b) Uterus
   c) Vas deferens
   d) Fallopian tube

Answer: (c) Vas deferens .

Ques 3: The anther contains:

1. a) Sepals
   b) Ovules
   c) Pistil
   d) Pollen grains

Answer: (d) Pollen grains.

Ques 4: What are the advantages of sexual reproduction over asexual reproduction?

Answer: Advantages of sexual reproduction:

• In sexual reproduction, more variants are produced. Thus, it ensures survival of species in the population.
• The newformed individual has characteristics of both the parents.
• Variations are more viable in sexual mode than in asexual one. This is because in asexual reproduction, DNA has to function inside the inherited cellular apparatus.

Ques 5: What are the functions performed by the testis in human beings?

Answer: Functions of testes:

• Produces sperms, which contain haploid set of chromosomes of father.
• Produce a hormone called testosterone, which brings about secondary sexual characters in boys.

Ques 6: Why does menstruation occurs?

Answer: Mensuration is the process in which blood and mucous flows out every month through the vagina. This process occurs every month because one egg is released from the ovary every month and at the same time, the uterus(womb) prepare itself to receive the fertilised egg. Thus, the inner lining of the uterus gets a thick in any supplied with blood to nourish the embryo. If the egg does not get fertilised, then the lining of the uterus breaks down slowly and gets released in the form of blood and mucous from the vagina.

Ques 7: Draw a labelled diagram of the longitudinal section of a flower. 

Answer:

Ques 8: What are the different methods of contraception?

Answer: The contraceptive methods can be broadly divided into the following types:

• Natural method: It involves avoiding the chances of meeting of sperm and ovum. In this method, the sexual act is avoided from the 10th to 17th of the menstrual cycle because during this period, ovulation is expected and therefore the chances of fertilisation are very high.

• Barrier method: In this method, the fertilisation of over means permits prevented with the help of barriers. Barriers are available for both males and females. Condom score barriers made of thin rubber that are used to cover penis in males and vagina and females.

• Oral contraceptives: In this method, tablets or drugs are taken orally. These contain small doses of hormone that prevent the release of eggs and thus fertilisation can’t occur.

• Implants and surgical methods: Contraceptive devices such as the loop or copper-T are pleased in the uterus to prevent pregnancy some surgical methods can also be used to block the gamete transferred. It includes the blocking of vas deferens that prevent the transfer response known as vasectomy. Similarly, fallopian tubes of the female can be blocked so that the egg will not reach the uterus known as tubectomy.

Ques 9: How are the modes for reproduction different in unicellular and multicellular organisms?

Answer: In a unicellular organisms, reproduction occurs by the division of the entire cell. The mode of reproduction in unicellular organisms can be fission, budding, etc. Whereas in multi-cellular organisms, specialised reproductive organs are present. Therefore, they can reproduce by complex reproductive methods such as vegetative propagation, spore formation, etc. In more complex multi-cellular organisms such as human beings and plants, the mood of reproduction is sexual reproduction.

Ques 10: How does reproduction help in providing stability to populations of species?

Answer: 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.

Ques 11: What could be the reason for adopting contraceptive methods?

Answer: Contraceptive methods army adopted because of the following reasons:

• To prevent unwanted pregnancies.
• To control, population rise or birth rate.
• To prevent the transfer of sexually transmitted diseases.