NCERT Solutions

Class 10 science

how do organisms reproduce

Q1) Asexual reproduction takes place through budding in

  • (a) amoeba
  • (b) yeast
  • (c) plasmodium
  • (d) leishmania

Answer:

(b)Yeast

Q2) 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

Answer:

(c)Vas deferens

Q3) The anther contains

  • (a) sepals/li>
  • (b) ovules
  • (c) carpel
  • (d) pollen grains

Answer:

(d)Pollen grains

Q4) What are the advantages of sexual reproduction over asexual reproduction ?

Answer:

Following are the advantages of sexual reproduction over asexual reproduction:
i. In sexual reproduction, cells with different genetic material fuse together. Thus, it leads to mixing of different characters and emergence of new characters.
ii. Accumulation of variations leads to formation of new species.
iii. Sexual reproduction has speeded up the process of evolution.

Q5) What are the functions performed by the testis in human beings?

Answer:

Functions of testes: ? Produce sperms, which contain haploid set of chromosomes of father. ? Produce a hormone called testosterone, which brings about secondary sexual characters in boys.

Q6) Why does menstruation occur ?

Answer:

Menstruation is a 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) prepares itself to receive the fertilized egg. Thus, the inner lining of the uterus gets thickened and is 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.

Q7) Draw a labelled diagram of the longitudinal section of a flower ?

Answer:

Descriptions of parts (optional)
Peduncle: This is the stalk of the flower.
Receptacle: It is that part of the flower to which the stalk is attached to. It is small and found at the centre of the base of the flower.
Sepals: These are the small, leaf-like parts growing at the base of the petals. They form the outermost whorl of the flower. Collectively, sepals are known as the calyx. The main function of the calyx and its sepals is to protect the flower before it blossoms(in the bud stage).
Petals: This layer lies just above the sepal layer. They are often bright in colour as their main function is to attract pollinators such as insects, butterflies etc to the flower. The petals are collectively known as the corolla.
Stamens: These are the male parts of a flower. Many stamens are collectively known as the androecium. They are structurally divided into two parts: Filament: the part that is long and slender and attached the anther to the flower.
Anthers: It is the head of the stamen and is responsible for producing the pollen which is transferred to the pistil or female parts of the same or another flower to bring about fertilization.
Pistil: This forms the female parts of a flower. A collection of pistils is called the gynoecium.

Q8) What are the different methods of contraception ?

Answer:

The different methods of contraption (controlling child birth) are:
(i) Hormonal methods: Various kinds of pills containing hormones which prevent the release of egg from the ovary, without interfering with other phases of menstrual cycle, are taken orally.
(ii) Barrier method: These are the physical barriers which prevent the sperms meeting the egg. Physical devices such as condoms, diaphragms and cervical caps are used.
(iii) Intrauterine Devices: Commonly called as I.U.Ds, they are the devices made of plastics and come in different shapes. The most commonly used is copper-'T'. These devices are placed inside the uterine cavity and prevents the implantation in the uterus.
(iv) Surgical methods: The surgical methods are safe and permanent. Vasectomy occurs in males and tubectomy occurs in females.
a. Vasectomy - In this procedure, a small piece of vas deferens is cut and removed and the two ends of the cut vas deferens are tied.
b. Tubectomy - In this procedure, fallopian tubes are cut and tied which prevents the passage of eggs.

Q9) How are the modes for reproduction different in unicellular and multicellular organisms?

Answer:

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

Q10) How does reproduction help in providing stability to populations of species ?

Answer:

Reproduction is the process through which an organism produces new organism of its own kind. It is necessary because in a population, organisms die due to old age or disease thus, it keeps the number of organisms in a population constant and provides stability to a population.

Q11) What could be the reasons for adopting contraceptive methods?

Answer:

Contraceptive methods are mainly 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.

Q1) Asexual reproduction takes place through budding in

  • (a) amoeba
  • (b) yeast
  • (c) plasmodium
  • (d) leishmania

Answer:

(b)Yeast