CBSE Class 10 Science How Do Organisms Reproduce Notes Set C

Question. Name the highly reactive metal that give violet colour to flame.

Question. Name the gas used in coloured advertising lights having 2 valence electron .

DEBATE AND DISCUSSION

A) Drawbacks of Mendeleev‘s and modern periodic table.

B) Achievements of Mendeleev‘s and modern periodic table.

C) Advantages of modern periodic table in understanding chemistry.

PROJECTS

1 Power point Presentation on the following topics:

1. Modern Periodic Table based on the similarity of properties of elements

2. Contribution by various Scientists towards the development of Periodic Table.

3. PERIODIC CLASSIFICATION

1.Making flash cards to study atomic numbers electronic configuration and other properties of elements.

2.Make an outline sketch of the Modern Periodic Table.

TOPIC 3: HOW DO ORGANISMS REPRODUCE?

GIST OF THE LESSON

1) Reproduction: process by which living organism produce new individual of their own kind.

2) Creation of DNA copy: when the cell divides into two, each new cell gets a copy of each DNA or chromosomes.

3) Importance of variation: variations are created by DNA copying mechanism during sexual reproduction.

4) Asexual modes of reproduction:

a) Fission—binary & multiple fission

b) Fragmentation

c) Regeneration

d) Budding

e) Vegetative propagation

f) Spore formation

5) Sexual reproductiona) In flowering plant

b) In human beings

6) Parts of flowers

7) Pollination: self and cross pollination

8) Fertilization: male and female germ cell fuses to form zygote.

9) Puberty: The age, when reproductive organs become functional,(in female 10-12 years, in male

13-14 years).

10) Male reproductive system in human beings.

11) Female reproductive system in human beings.

12) Reproductive healtha)

To have awareness about STDs, (sexually transmitted disease).

b) Some common STDs are gonorrhea, syphilis & HIV-AIDS.

13) Contractive methods: to avoid pregnancya)

barrier method b)chemical methods c) surgical methods

MIND MAP

FORMATIVE ASSESSMENT-III

Very short answer type question:

Note: each question carries 1 mark.

1) What is reproduction?

2) Have you seen seeds of rose or potato? Name some plants whose seeds you may have seen.

3) Can an amoeba and hydra reproduce like human beings?

4) What changes are observed in the uterus if fertilization occurs?

5) Define fertilization?

Short answer type questions

Note: each question carries two marks:

1) In the human body, what is the role of

(a) seminal vesicles      (b) prostate gland?

2) State the difference between menarche and menopause?

3) What is variation? Mention the importance of DNA copying in reproduction.

HIGHER ORDER THINKING SKILLS (HOTS) QUESTIONS
1) Give two reasons for the appearance or variation among the progeny formed by sexual reproduction.
2) Colonies of yeast fail to multiply in water but multiply in sugar solution. Give one reason.
3) Malaria parasite divides into many daughter individual simultaneously through multiple fission. State an advantage the parasite gets because of this type of reproduction.
4) What is the importance of DNA copying in reproduction?
5) How does reproduction help in providing stability to population of species?
6) Why is vegetative propagation practised for growing some types of plants?
7) Why would be the reason for adopting contraceptive methods ?
8) Name those parts of flower , which serve the same function as the following do in the animals
a) testies
b) Eggs,
c) Ovary ,
d) Sperms.

*Activity- to grow rhizopus & prepare its temporary slide.
Aim: to show asexual reproduction in an organism.
App: slice of bread, water, box, slide, cover slip.
Procedure: children grow rhizopus on slice of bread and make a temporary slide.

*Project: 1.a) To study manner of vegetative reproduction in some commercially useful plants.
b) To study the seeds during sprouting period.
2. How do organisms reproduce.
1.Seprating the various parts of any 5 flowers displaying and comparing them.
2.Growing some plants by vegetative propagation.

*Seminars: reproductive health and sexually transmitted disease: children form groups and discuss.

*Symposium: gender related problems: female infanticide.

*Group discussion: if there was no sexual reproduction…..

*Debate: is it necessary to learn about reproductive health from class VII?

TOPIC 4: HEREDITY AND EVOLUTION

POINTS TO REMEMBER:

1.HEREDITY: Transmission of features or characters from one generation to another or from parents to offspring through their genes

2.VARIATION: It occurs due to sexual reproduction, inaccuracies during DNA replicating (mutation) and due to environmental factors.

3.GENETICS: Branch of biology dealing with the study of heredity and variations

Assertion-Reason Type Questions

For question numbers 1 and 2 two statements are given-one labeled as Assertion (A) and the other labeled
Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both ‘A’ and ‘R’ are true and ‘R’ is correct explanation of the assertion.
(b) Both ‘A’ and ‘R’ are true but ‘R’ is not correct explanation of the assertion.
(c) ‘A’ is true but ‘R’ is false.
(d) ‘A’ is false but ‘R’ is true.

Question. Assertion: Cell division is a type of reproduction in unicellular organisms.
Reason: It leads to formation of two daughter cells where means is to produce more individuals.
Answer : A

Question. Assertion: Spores are formed in sporangia.
Reason: Spores grow into separate individuals in moist conditions.
Answer : A

Very Short Answer Type Questions

Question. Name the method by which hydra reproduces. Is this method sexual or asexual?
Answer : Hydra reproduces by budding. It is an asexual mode of reproduction.

Question. Name the part of Bryophyllum where the buds are produced for vegetative propagation.
Answer : Buds arise from the notches in the leaf margins of Bryophyllum.

Question. Give the respective scientific term used for studying.
(i) The mechanism by which variation are created and inherited and
(ii) The development of new type of organism from the existing ones.
Answer : (i) Heredity, (ii) Evolution.

Question. What happens when a Planaria gets cut into two pieces?
Answer : Each piece regenerates into new organism, planaria

Question. Name the type of cells which undergo regeneration.
Answer : Specialised cells called regenerative cells which can make large number of new cells

Question. Name two simple organisms which have ability of regeneration.
Answer : Planaria and Hydra

Question. What happens when a mature Spirogyra filament attains considerable length?
Answer : A mature spirogyra filament breaks into smaller fragments and each fragment grows into a new plant.
This process of reproduction is called fragmentation

Question. Select two plants from the following which are grown by vegetative propagation process: Banana, Wheat, Mustard, Jasmine, Gram.
Answer : Banana and jasmine are grown by vegetative propagation, because they do not produce seeds.

Question. What is the advantage of reproduction through spores?
                                                OR
How will organism be benefitted if it reproduces through spores?
Answer : Spore with a cell wall can survive even in adverse conditions. Large number of spores are produced in one sporangium. It is easily dispersed through wind as they are large in number and light in weight.

Question. Name the causative agent of the disease ‘kala-azar’ and its mode of asexual reproduction.
Answer : Leishmania causes ‘kala-azar’. It reproduces by binary fission in a definite orientation

Question. Regeneration is not possible in all types of animals. Why?
Answer : Regeneration is carried out by specialised cells which are present in few animals which can reproduce by regeneration.

Question. How does Plasmodium reproduce? Is this method sexual or asexual?
Answer : Plasmodium is a single celled organism which reproduces by the process of multiple fission. Multiple fission (i.e. breaking up of a single cell into many daughter cells) is an asexual mode of reproduction.

Question. “Cell division is a type of reproduction in unicellular organism”. Justify.
Answer : Cell division in a unicellular organism results in the formation of two or more daughter cells which means it produces more individual

Question. List two advantages of growing grapes or banana plants through vegetative propagation.
Answer : (i) Characteristics of parent plants are preserved.
(ii) Since these plants do not have viable seeds, therefore vegetative propagation is advantageous.

Question. Name the type of asexual reproduction in
(a) Planaria (b) Rhizopus
(c) Spirogyra (d) Hydra
Answer : (a) Regeneration (b) Spore formation
(c) Fragmentation (d) Budding

Question. What is a clone? Why do offsprings formed by asexual reproduction exhibit remarkable similarity?
Answer : Clones are organisms which are exact genetics copies of their parents. Their DNA is exactly identical to their parents, which is the cause of remarkable similarity

Question. List three conditions favourable for spores to germinate and grow.
Answer : (i) Availability of nutrition (food), (ii) moist place, (iii) warmth, (iv) dark place. (Any three)

Question. Leaves of bryophyllum fallen on the ground produces new plants, why?
Answer : Leaves of bryophyllum has adventitious buds or plantlets in the notches along the leaf margin. When buds fall on the soil, they develop into new plant under favourable conditions

Question. Name the method by which spirogyra reproduces under favourable conditions. Is this method sexual or asexual?
Answer : Under favourable conditions, spirogyra reproduces by a process known as fragmentation. This is an asexual method of reproduction.

Question. How does binary fission differ from multiple fission?
Answer : In binary fission cell divides into two cells whereas in multiple fission a cell divide into many daughter
cells

Question. How does Planaria reproduce? Is this method sexual or asexual?
Answer : Planaria reproduces by a process known as regeneration. It is a type of asexual reproduction in which if Planaria can be cut into any number of pieces, each piece grows into a new individual orga

Short Answer Type Questions

Question. Name the type of asexual reproduction in which two individuals are formed from a single parent and the parental identity is lost. Write the first step from where such a type of reproduction begins. Draw first two stages of this reproduction.
Answer : Binary fission, e.g. Fission in Amoeba
Elongation of cell and its nucleus is the first step.

Question. Why is vegetative propagation practised for growing some types of plants?
Answer : (i) Vegetative propagation is used to grow plants in which seeds are not formed or very few seeds are formed, e.g. banana, pineapple, orange.
(ii) It helps to grow plants in conditions where seed germination fails due to change in environment.
(iii) It is a faster, easier and cheaper process.
(iv) The plants produced are genetically similar and good quality or variety can be preserved easily

Question. Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Answer : Those organisms which reproduce by regeneration have similar and non-differentiated cells throughout the body, therefore body parts of organism grows into new organism.
In multicellular complex organisms, the cells get differentiated and perform different functions. In such organisms, body parts like skin, muscles, i.e. tissues can be regenerated, but the whole organism cannot be reproduced by regeneration

Question. What is multiple fission? How does it occur in an organism? Explain briefly. Name an organism which exhibits this type of reproduction.
Answer : The process in which parent cell divides into several small and equal sized daughter cells, which grows into a new organism is called multiple fission.
The nucleus of a cell divides into large number of nuclei and cytoplasm separates, forming a membrane around it. All this occurs within a protective covering. Plasmodium exhibits multiple fission.

Question. What happens when
(i) Planaria gets cut into two pieces
(ii) A mature spirogyra filament attains considerable length
(iii) On maturation sporangia burst
Answer : (i) Each piece will regenerate into complete organism. Cells at the location of the site of cut or wound, forms a small ball of cells that will differentiate into new tissues and regenerate the missing parts of the cut piece of the planaria.
(ii) When spirogyra attains considerable length, it breaks into smaller fragments and each fragment grows into a new plant.
(iii) On maturation, sporangial wall breaks and spores are dispersed to grow into new individual. These spores are very light and easily dispersed by wind.

Question. Identify the following methods and give one example of each:
(a) Process in which reproduction takes place by breaking up of parent into several fragments.
(b) Process of dividing of organisms into many cells simultaneously.
(c) Process of reproduction by formation of bud on the parent body.
(d) Process of reproduction by formation of spores.
(e) Process used by multi-cellular organisms to reproduce by cutting into many pieces and each piece forms a new individual.
Answer : (a) Fragmentation, Spirogyra (b) Multiple fission, Plasmodium
(c) Budding, Yeast/Hydra (d) Spore formation, Rhizopus
(e) Regeneration, Planaria

Question. In the context of reproduction of species state the main difference between fission and fragmentation. Also give one example of each.
Answer : Fission
It takes place in unicellular organisms
The cell splits into two or more cells, giving rise to daughter cells, e.g. amoeba, paramecium
Fragmentation
It takes place in multicellular organisms
The body of the organism simply breaks into smaller pieces, which upon maturation grow into new individual, e.g. spirogyra.

Question. (a) Identify the organism A, B and mode of asexual reproduction exhibited by them.
(b) How will an organism be benefitted if it reproduces through spores?
(c) Mention the two asexual methods by which hydra can reproduce. Explain briefly any one such method.
Answer : (a) ‘A’ is Bryophyllum–Vegetative propagation; ‘B’ is Plasmodium–Multiple fission
(b) Spores are covered with thick walls which protect them until they come into contact with a moist surface.
(c) Budding and regeneratio 

Question. What is vegetative propagation? Give examples of plants which can be propagated by their:
(a) Stem (b) Roots (c) Leaves
Answer : Budding: In this process hydra (or any other organism like yeast) use regenerative cells for reproduction. A bud develops as an outgrowth due to repeated cell division which develop into new individuals.
(a) Stem—Potato, Onion, Ginger (b) Roots—Banana, Asparagus
(c) Leaves—Bryophyllum

Question. Explain the term ‘Regeneration’ as used in relation to reproduction of organisms. Describe briefly how regeneration is carried out in multicellular organisms like Hydra.
Answer : Regeneration is the ability to produce an organism from their body parts. Many fully differentiated organisms show ability to reproduce by regeneration. In hydra, if the body is cut into two or three pieces, the lower part will develop head while the upper part will develop rest of the body. If its cells are separated, hydra will reform its structure by regeneration

Long Short Answer Type Questions

Question. Explain budding in hydra with the help of labelled diagrams only.
Answer : A bud is an outgrowth from the body part of parent due to repeated cell division at a specific site. These buds develop into new individuals, which detach from the parent body on maturation.
In hydra, the cells divide very fast at a specific site as an outgrowth called bud. These bud develops into a small individual, while remaining attached to the parent. When it matures, it detaches from the parent body to exist as an independent organism.

Question. (a) List in tabular form two differences between binary fission and multiple fission.
(b) What happens when a mature spirogyra filament attains considerable length.
Answer : Binary fission
Nucleus divides into two parts
It occurs in normal conditions
It give rise to two new individuals
Cytoplasm divides after each division e.g. in Amoeba
Multiple fission
Nucleus divides into more than two parts
It occurs in abnormal conditions
It give rise to many new individuals.
Cytoplasm does not divide after every nuclear division e.g. in plasmodium
(b) A mature spirogyra filament breaks into smaller fragments and each fragment grows into a new plant. This process of reproduction is called fragmentation.

Question. What happens when:
(a) Accidently, Planaria gets cut into many pieces?
(b) Bryophyllum leaf falls on the wet soil?
(c) On maturation sporangia of Rhizopus bursts?
Answer : (a) When Planaria gets cut into many pieces, it will undergo a process known as regeneration due to which each piece will grow into a new planaria organism.
(b) When bryophyllum leaf falls on the wet soil, the buds that are produced in the notches along the leaf will develop into new plants by the process known as vegetative propagation.
(c) When the sporangia of Rhizopus bursts upon maturation, the spores present inside it spread in the open environment. Then, with the help of different agents, they are carried to different places and when they land on a favourable surface, they start growing and produce new organis 

Question. Define the term pollination. Differentiate between self pollination and cross pollination. What is the significance of pollination?
Answer : Pollination: The process in which pollen is transferred from stamen to the stigma is called pollination
Self pollination
If the transfer of pollen occurs in the same flower, it is called self pollination.
Cross pollination
If the transfer of pollen occurs from one flower to another, it is called cross pollination.
Significance: After the pollen lands on suitable stigma, it needs to reach the female germ cells in the ovary where fertilisation takes place, zygot is formed. Zygot divides several times to form embryo with in ovule which develops a tough coat around it called seed coat and seed is formed. The ovary grows rapidly and ripens to form fruit

Question. What is binary fission in organisms? With the help of suitable diagrams, describe the mode of reproduction in amoeba.
Answer : Binary fission is a fission in which two daughter cells are formed of nearly equal size after replicating the genetic material of a single cell. Single-celled organisms like amoeba undergoes binary fission

Question. (i) Describe the various steps involved in the process of binary fission with the help of a diagram.
(ii) Why do multicellular organisms use complex way of reproduction?
Answer : (i)

(ii) Multicellular organisms cannot reproduce by cell because they are not simple random collection of cells.
They have specialised cells, organised as tissues which are organised into organs.
Cell-by-cell division would be impractical (not practical).
Multicellular organisms require to use more complex ways of reproduction.

Question. What is vegetative propagation? State two advantages and two disadvantages of this method.
Answer : Vegetative propagation is a mode of asexual reproduction in which new plants are obtained from vegetative parts of the plants. It does not involve the production of seeds or spores for the propagation of new plants.
Two advantages of vegetative propagation are:
(i) Plants which do not produce seeds are propagated by this method, for example sugarcane, potato, etc.
(ii) Vegetative propagation is a cheaper, easier, rapid method of propagation in plants than growing plants from their seeds. For example, lilies grow very slowly and take 4 to 7 years to develop flowers when grown through their seeds, but flowers are produced only after a year or two when grown vegetatively.
Two disadvantages of vegetative propagation are:
(i) As there is no genetic variation, there is no chance of development of new and better varieties.
(ii) The vegetatively propagated plants are more prone to diseases that are specific to the species. This can result in the destruction of an entire crop.

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