NCERT Class 10 Chapter 8 Organisms Reproduction CBSE Board Sample Problems Short Answer

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Question

(a) Explain the terms:

i) Implantation

ii) Placenta

(b) What ¡s the average duration of human pregnancy?

Solution

(a) (i) Implantation is the event during pregnancy in which a fertilized egg or zygote adheres to the walls of the uterus, inside the female body.

(ii) Placenta is a disc like vascular structure embedded in the uterine wall. The placenta supplies nutrients like glucose and oxygen to the developing embryo. It also removes waste substances generated by the embryo.

(b) The average duration of human pregnancy is nine months.

Question

i. Label the following diagram.

ii. Which process ¡s being shown in the diagram?

Label the following diagram

Label the Following Diagram

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Solution

i)

Germination of pollen on stigma

Germination of Pollen on Stigma

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ii. The diagram show the process of germination of pollen on stigma, which is necessary for passage of male gametes to ovary. In this the pollen grains develops pollen tube which enters the ovary and releases the 2 male gametes. One of which participate in syngamy and the other in triple fusion.

Question

Discuss spore formation in fungi.

Solution

  • Spore formation: The spores in fungi vary in shape. Spores are usually unicellular, thick walled, spherical. The thick walls provide protection till these come in contact with other surface and can begin to grow. Sometimes the spores may be multi cellular also.

  • Sometimes the spores are produced endogenously in special sac-like asexual reproductive bodies called sporangia. Spores in such cases are called sporangiospores. Spores on falling on ground or substratum grow new hypha, e.g. hizopus, Mucor and Penicillium.

Discuss spore formation in fungi

Discuss Spore Formation in Fungi

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Question

What are the various ways to avoid pregnancy? Elaborate any one method.

Solution

Methods to avoid pregnancy are called contraceptive methods. It includes

  • Surgical methods: Vasectomy refers to surgical method in which vas deferentia in human males are cut and sealed to prevent pregnancy by making seminal fluid devoid of sperms. Tubectomy refers to surgical process in which oviducts in human females are cut and sealed to prevent pregnancy by inhibiting released of egg.

  • Mechanical barrier-that prevent arrival of sperm to the egg. Example condom.

    • Chemical Drugs or contraceptive pills-Small dosage of female hormones that prevent released of egg.

  • Loop or copper-T - physical devices to prevent pregnancy.

Question

Define vegetative propagation. List its methods and advantages.

Solution

Vegetative reproduction (Vegetative propagation):

In vegetative propagation new plants are obtained from the parts of old plants (stem, leaves, or root) without the help of any reproductive organ.

Natural methods of vegetative propagation:

  • The green grass grows in the field after rain from the dry, old stem of grass plant present in the field by the method of vegetative propagation. Bryophyllum plants can be reproduced by vegetative propagation using leaves.

    • Plant: Vegetative propagation

    • Potato: Potato tuber (stem)

    • Begonia: Leaves.

    • Money: plant Stem

  • Vegetative propagation usually involves the growth and development of one or more buds present on the old part of the plant to form a new plant.

  • Artificial method of vegetative propagation: The process of growing many plants from one plant by manmade method is called vegetative propagation.

Cutting;

  • A small part of plant which is removed by making a cut with sharp knife is called cutting. A cut may be a piece of stem, root or leaves.

  • For example- Plants like rose, sugarcane, and cactus are grown by cutting. It is necessary that there are some buds on it.

Layering

  • In this method a branch of plant is pulled towards the ground and a part of it is covered with moist soil leaving the tip of branch exposed above the ground.

  • After some time new roots develop and then cut off from parent plant, growing into a new plant. For example-Jasmine, strawberry, hibiscus, guava etc.

Grafting

  • It is the method in which the cut stem of two different plants, one with root and other without root, are joined together in such a way that the two stem join and grow as a single plant. This new plant has the characteristics of both the plants.

  • The cut stem of the plant having roots is called stock and the cut stem of the other plant is called scion. For example - apple, peach, apricot, pear etc.

Advantages of vegetative propagation:

  • The new plant produced by artificial vegetative propagation will be exactly like parent plant.

  • The fruit trees grown from cutting or grafting start to bear fruits much earlier.

  • Many plants can be grown from just one parent plant.

  • We can also get seedless plant by artificial propagation

Question

What ¡s placenta? Mention its role during pregnancy.

Solution

Placenta is a special tissue connection between embryo and uterine wall. Role of placenta:

  • It possesses Villi that Increase the surface area for absorption of nutrients.

  • It facilitates the passage of nutrition and oxygen to embryo from mother through blood.

  • Waste substances produced by embryo are removed through placenta into mother’s blood.

Question

Draw a labelled diagram of a human male reproductive system.

Solution

Human male reproductive system

Human Male Reproductive System

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Question

Draw a labelled diagram of a human female reproductive system and explain the function of each organ.

Solution

  • Functions of ovary: Production of female gamete and female hormone oestrogen.

  • Functions of fallopian tube: It is the site of fertilization. Transfer of female gamete from ovary takes place through it.

  • Functions of uterus: Implantation of zygote and nourishment of developing embryo.

Human Female Reproductive System

Human Female Reproductive System

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Human Female Reproductive System

Question

Explain Binary Fission in Amoeba and Multiple fission in Plasmodium.

Solution

In the process of fission, a unicellular organism splits to form two or more new organisms. It is of two types.

a. Binary fission:

  • In Binary Fission, the parent organism splits to form two new organisms. For example- Amoeba, Paramecium Leishmania, Bacteria etc., are reproduce by binary fission.

  • When the amoeba cell has reached its maximum size of growth, then first the nucleus of amoeba lengthens and divides into two parts. After that cytoplasm of parent amoeba divides to form two smaller daughter amoebae.

  • In amoeba fission take place in any plane but in Leishmania splitting of parent cell during fission takes place in definite place longitudinal with respect to flagellum at its end.

Binary fission in amoeba

Binary Fission in Amoeba

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b. Multiple Fission:

In multiple fission the parent organism splits to form many new organisms at same time. For example: Plasmodium.

Multiple flassion in Plasmodium

Multiple Flassion in Plasmodium

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  • During unfavorable conditions, a cyst or protective wall is formed around the cell of plasmodium. Inside the cyst the nucleus of cell splits several times to form many daughter nuclei and then cytoplasm collects around each daughter nuclei.

  • Thin membranes are formed. So many new daughter cells are formed within a cyst. When favorable conditions arrive the cyst breaks open and daughter cells are released, each forming a new organism.

Question

How will an organism benefit if it reproduces through spores?

Solution

  • The reproduction by spores takes place in plants. Spores are covered by hard protective coat which enables them to survive in unfavourable conditions such as lack of food, water and extreme temperatures.

  • When the conditions are favourable the spores can grow to produce new plants.

  • Thus, the reproduction by spore’s benefits the plant because by surviving under adverse conditions, the spores make these plants live forever.

The reproduction by spores takes place in plants

The Reproduction by Spores Takes Place in Plants

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Question

What is reproduction? Lists its two types.

Solution

Reproduction:

  • The production of new organism from the existing organism of the same species is called reproduction.

  • Reproduction is essential for the survival of species on this earth. The process of reproduction ensures continuity of life on earth. Reproduction gives rise to more organism with the same basic characteristics as their parents.

  • Types of Reproduction -There are two main methods of reproduction in living.

  • Asexual reproduction.

  • Sexual reproduction.

Asexual Reproduction-

The production of new organism from a single parent without the involvement of sex cells (or gametes) is called asexual reproduction.

Sexual Reproduction

The process of production of new organism from two parents by making use of sex cells is called Sexual reproduction.

Methods of Asexual Reproduction: It takes place by 6 methods.

  • Fission

  • Budding

  • Spore formation

  • Regeneration

  • Fragmentation

  • Vegetative Propagation

Question

How is reproduction in Leishmania different from that in plasmodium though both are unicellular?

Solution

Leishmania shows binary fission. Plasmodium shows multiple fission.

Question

Which part of the flower changes into seed after fertilization?

Solution

Ovule

Question

Cell division is a type of reproduction in unicellular organisms. Justify with an example.

Solution

In amoeba, cell division results in 2 daughter cells (binary fission) each of which forms new individuals. Hence cell division is a type of reproduction in unicellular organisms.

Question

Name a surgical contraceptive method in case of females.

Solution

Tubectomy

Question

The fertilized egg always has one_____ chromosome.

Solution

X

Question

Animals produce gametes which fuse to form a

Solution

Zygote