Reproduction How Life Continues Class 9 Important Questions with Answers

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Important Questions of Reproduction How Life Continues Class 9

Class 9 Reproduction How Life Continues Important Questions

Very Short Answer Type Questions

Question 1.
Name the method by which spirogyra reproduces under favourable conditions. Is this method sexual or asexual?
Answer:
Spirogyra reproduces by a process known as fragmentation. This is an asexual method of reproduction.

Question 2.
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.

Question 3.
How does Plasomodium reproduce. Is this method sexual or asexual ?
Answer:
Plasmodium reproduces by a process known as multiple fission. It is a type asexual reproduction.

Question 4.
Name the part of Bryophyllum where the buds are produced for vegetative propagation.
Answer:
On the stems as well as the leaves of the Bryophyllum plant.

Question 5.
Give an example of a flower which contains both stamens and carpels.
Answer:
Hibiscus (China Rose).

Question 6.
Explain how do organisms create an exact copy of themselves.
Answer:
To build the copies of DNA or the genetic material, the cells use biochemical reactions.
Additional cellular apparatus along with the DNA copies are separated and so a cell divides to give rise to two almost identical cells.

Question 7.
Why cannot fertilisation take place in flowers if pollination does not occur ?
Answer:
If pollination does not occur, male gamete is not available, hence fertilisation will not take place.

Question 8.
Name one bacterial and one viral disease, which can be transmitted sexually.
Answer:
One bacterial disease which can be transmitted sexually is syphilis and one viral disease is AIDS.

Reproduction How Life Continues Important Questions Class 9

Short Answer Type Questions

Question 1.
With the help of diagram show the different stages of binary fission in Amoeba.
Answer:
In amoeba, asexual reproduction takes place by binary fission. In this process, the amoeba divides into two daughter cells and each one of them grows into an adult Fig. : Binary fission in amoeba. organism.

During this, the nuclear division takes place first, followed by the appearance of a constriction in the cell membrane, which gradually increases inwards and divides the cytoplasm into two parts. Finally, two daughter organisms are formed.

Question 2.
What is grafting ? What do the terms ‘stock’ and ‘scion’ mean in grafting ?
Answer:
Grafting is a method in which two parts of two closely related plants are joined in such a way that they grow as one plant.
‘Stock’ is the rooted plant in which grafting is performed. ‘Scion’ is the portion of other plant (bud, branch etc.) that is grafted on the stock. Example : Gonorrhoea, syphilis, AIDS and warts. AIDS damages the immune system of human body.

Question 3.
State the basic requirement for sexual reproduction. Write the importance of such reproduction in nature.
Answer:
The basic requirements for sexual reproduction to take place are involvement of two parents and fusion of haploid gamates.
Importance of sexual reproduction :
Fusion of garnets results in genetic variations in the off springs. This promotes diversity of characters off springs

Question 4.
Name the parts A, B and C shown in the following diagram and state one function of each.
Answer:
A : Stamen Function : It produces pollen grains containing male gametes.
B : Carpel Function: It makes ovules containing the gametes (Ovum or egg).
C : Ovules Function : A female gamete called ovum or egg is produced in each ovule.

Question 5.
What is meant by pollination? Name and differentiate between the two modes of pollination in flowering plants.
Answer:
Pollination : It is the process of transfer of pollen grains from the anther to the stigma of flower. If this transfer of pollen occurs in the same flower, it is referred to as self-pollination whereas if the pollen is transferred from one flower to another, it is known as cross-pollination.
Difference between self-pollination and cross-pollination

Self-pollination	Cross-pollination
1. It is the transfer of pollen grains from anther to stigma within the same flower.	1.It is the transfer of pollen grains from anther to stigma in another flower.
2.  It occurs either in the same flower or another flower of the same plant.	2. It occurs between two flowers which one on different plants but are of the same species.

Question 6.
List the two types of reproduction. Which one of the two is responsible for bringing in more variations in its progeny and how ?
Answer:
The types of reproduction are (i) Asexual reproduction, (ii) Sexual reproduction. Sexual reproduction is responsible for bringing in more variations in its progeny because it involves DNA copying mechanism which cannot be absolutely accurate and the resultant errors are a source of variation in the population of organisms.

Question 7.
Define reproduction. How does it help in providing stability to the population of species ?
Answer:
Reproduction: The production of new organisms from the existing organisms of the same species is known as reproduction.
The rate of birth and death in a given population determine its stability. The rate of birth should be approximately equal to the rate of death. So, by checking birth rate, which is increasing at an alarming rate, stability to population of species can be provided.

Question 8.
What is multiple fission? How does it occur in an organism? Explain briefly. Name one organism which exhibits this type of reproducton.
Answer:
Multiple fission: Division of single called organisms such as malarial parasite into many daughter cells simultaneously is termed multiple fission. During multiple fission, organism secretes a protective covering, the cyst around the cell. Inside the cyst, nucleus divides several times to form a number of daughter nuclei. Each daughter nucleus gets surrounded with a bit of cytoplasm. Thus, a large member of daughter individuals are formed. On the arrival of favourable conditions, the cyst ruptures and single-called daughter individuals one set free. Each grows into a complete organism. Multiple fission occurs in plasmodium (malarial parasite).

Question 9.
List six specific characteristics of sexual reproduction.
Answer:
Characteristics :

• Two parents are involved.
• Two dissimilar gametes are formed, gamete formation involves meiosis.
• Variations are produced.
• Occurs in all the higher and some of the lower organisms.
• Fertilization of gemates leading to zygote formation.
• Slow.

Question 10.
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: It is the ability to give rise to new organism, when the individual is cut or broken-up into many pies.
Hydra use regenerative cells for reproduction in the process of budding. In hydra, a bud develops as an outgrowth due to repeated cell division at one specific site. These buds develop into tiny individuals and when fully manture, detach from the parent body and become new independent individuals.

Question 11.
How do organisms, whether reproduced asexually or sexually maintain a constant chromosome number through several generations? Explain with the help of suitable example.
Answer:
Chromosomes are thread like structures made up of DNA found in the nucleus.
The original number of chromosomes becomes half during gamete formation. Hence, when the gametes combine, the original number of chromosomes gets restored Cx the progeny.

Question 12.
Mention the total number of chromosomes alongwith the sex chromosomes that are present in a human female and a human male. Explain how in sexually producing organisms the number of chromosomes in the progeny remains the some as that the parent.
Answer:
Total number of chromosomes is 46. In humans, two sex hormones present are X and Y while in human female, both sex chromosomes are X. During sexual reproduction, a female gamete or egg cell fuses with a male gamete or sperm cell which are haploid to form Zygote. Zygote is deploid which contains 23 chromosomes from mother and 23 from father. In this way, an equal genetic contribution of male and female parents is ensured in the progeny.

Question 13.
Define vegetative propagation. Give two examples of plants reproduced by this method.
Answer:
Vegetative propagation is a type of asexual reproduction in plants in which new plants develop from the vegetative parts (root, stem, or leaf) of the parent plant, producing genetically identical individuals.
Examples:

1. Potato — new plants grow from eyes/nodes of the tuber,
2. Bryophyllum — tiny plantlets grow on the margins of leaves.

Question 14.
What is meiosis? Why is it important in sexual reproduction?
Answer:
Meiosis is a special type of cell division in which the chromosome number of a parent cell (diploid/2n) is reduced to half (haploid/n) in the daughter cells called gametes.
Importance:

1. It ensures the chromosome number remains constant across generations — when two haploid gametes fuse during fertilisation, the zygote has the same chromosome number (2n) as the parents,
2. During meiosis, random mixing of chromosomes creates genetic variation among offspring, which is essential for evolution and adaptation.

Question 15.
Explain the process of fertilisation and seed formation in flowering plants.
Answer:
After a pollen grain lands on a compatible stigma, it germinates and produces a pollen tube that grows down through the style into the ovary. The male gamete travels through the pollen tube and reaches the ovule, where it fuses with the egg cell (female gamete). This fusion of gametes is called fertilisation. The fertilised egg is called a zygote, which develops into an embryo. The ovule hardens and develops into a seed, while the ovary wall enlarges and develops into a fruit.

Question 16.
Describe the menstrual cycle in human females. What happens when the egg is not fertilised?
Answer:
The menstrual cycle repeats every 21—35 days (typically ~28 days):

• Day 1-5: Menstruation — shedding of the thickened uterine lining with blood.
• Day 6-14: The uterine lining gradually rebuilds; an egg matures in the ovary.
• Day 14: Ovulation — a mature egg is released from the ovary.
• Day 15-28: Uterine lining becomes thicker and rich in blood vessels (preparing for implantation).

If the egg is not fertilised: It remains viable for about a day, then degenerates. The uterine lining that had prepared for a zygote is no longer needed and sheds — this is menstruation. The cycle then repeats.

Question 17.
Why does asexual reproduction produce offspring that are genetically identical to the parent?
Answer:
In asexual reproduction, only one parent is involved and the new organisms are produced through mitosis — a type of cell division that
produces daughter cells with the exact same number and type of chromosomes as the parent cell. Since no mixing of genetic material from two parents occurs, all offspring are genetically identical to the parent and to each other. These identical organisms are called clones.

Question 18.
What are the differences between external and internal fertilisation? Give examples of animals that show each type.
Answer:
External Fertilisation: Fertilisation occurs outside the female’s body, usually in water. The female releases eggs and the male releases sperm over them. Many eggs are laid but many are destroyed or eaten, so survival rate is low. Example: Fish (lOOs-lOOOs eggs), Frogs (5,000-50,000 eggs).
Internal Fertilisation: Fertilisation occurs inside the female’s body. The embryo is better protected; fewer eggs are produced but survival rate is higher. Example: Reptiles (lizards, 2—20 eggs), Birds (1-15 eggs), Mammals (humans, usually 1 offspring at a time).

Question 19.
In a bisexual flower inspite of the young stamens being removed artificially, the flower produces fruit. Provide a suitable explanation for the above situation.
Answer:
The pistil is intact. Cross-pollination has occurred leading to fertilisation and formation of fruit.

Question 20.
Can you consider cell division as a type of reproduction in unicellular organisms ? Give one reason.
Answer:
Yes, because it results in the formation of two daughter cells, that is, it results in the production of more individuals of the organism.

Question 21.
What is a clone ? Why do offsprings formed by asexual reproduction exhibit remarkable similarity ?
Answer:
Clone refers to offspring of an organism formed by asexual method of reproduction. Since they possess exact copies of the DNA of their parent, clones exhibit remarkable similarity.

Question 22.
Explain how offspring and parents of organisms reproducing sexually have the same number of chromosomes ?
Answer:
Reduction division (meiosis) during gamete formation halves the chromosome number in both male and female gametes. Since these two gametes fuse during fertilisation, the original number of chromosomes (as in the parent) is restored in the offspring.

Question 23.
Colonies of yeast fail to multiply in water, but multiply in sugar solution. Give one reason for this.
Answer:
Sugar provides energy for sustaining all life activities in yeasts. In water, it fails to reproduce because of inadequate energy in its cells.

Question 24.
Why does bread mould grow profusely on a moist slice of bread rather than on a dry slice of bread ?
Answer:
The spores of bread mould need favourable conditions like moist surface to germinate and produce new plants. A dry slice of bread does not provide suitable condition for the bread mould to grow.

Question 25.
Give two reasons for the appearance of variations among the progeny formed by sexual reproduction.
Answer:
(a) Sexual reproduction involves two parents with different sets of characters.
(b) The gene combinations are different in gametes.

Question 26.
Would a Planaria cut vertically into two halves regenerate into two individuals ? Complete figures D and E by indicating the regenerated regions.

Answer:
Yes, shaded parts in figures D and E represent the regenerated halves.

Question 27.
From the internet, gather information about the chromosome numbers of five animals and five plants. Correlate the number with the size of organism and answer the following questions.
(a) Do larger organisms have more number of chromosomes/cells ?
(b) Can organism with fewer chromosomes reproduce more easily than organisms with more number of chromosomes ?
(c) More the number of chromosomes/cells greater is the DNA content. Justify.
Answer:
(a) No, there is no relationship between size of organism and its chromosome number.
(b) No, process of reproduction follows a common pattern and is not dependent on the number of chromosomes.
(c) Yes, since the major component of chromosome is DNA. If there are more chromosomes in a cell, the quantity of DNA will also be more.

Question 28.
In tobacco plant, the male gametes have twenty four chromosomes.
What is the number of chromosomes in the female gamete ?
What is the number of chromosomes in the zygote ?
Answer:
Number of chromosomes in female gamete is 24.
Number of chromosomes in zygote is 48.

Question 29.
Why cannot fertilisation take place in flowers if pollination does not occur ?
Answer:
It is necessary that first the pollen grains from the anther of stamen should be carried to the stigma of carpel for the male gamete to be able to combine with the female gamete. That is why pollination is a necessary event to combine with the female gamete. That is why pollination is a necessary event to occur before fertilisation to take place.

Question 30.
As the chromosomes number of zygote, embryonal cells and adult of a particular organism always constant? How is the constancy maintained in these three stages?
Answer:
Yes, the constancy is maintained because cells in all these three structures undergo only mitotic divisions.

Question 31.
Where is the zygote located in the flower after fertilization ?
Answer:
Zygote is located inside the ovule which is present in the ovary.

Question 32.
Reproduction is linked to stability of population of a species. Justify the statement.
Answer:
In reproduction, DNA passes from one generation to the next. Copying of a DNA takes place with consistency but with minor variations. This consistency leads to stability of species.

Question 33.
How are general growth and sexual maturation different from each other?
Answer:
General growth of the individual refers to the increase in the height, weight, change in shape etc. Sexual maturation, however involves specific changes in the body of the organism reflected at puberty, e.g. cracking of voice, maturation of gonads, growth of body hairs, development of breasts in female etc.

Reproduction How Life Continues Important Questions

Long Answer Type Questions

Question 1.
(a) Draw a longitudinal section of a flower and label the following parts :
(i) Part that produces pollen grain.
(ii) Part that transfers male gametes to the female gametes.
(iii) Part that is sticky to trap the pollen grain.
(iv) Part that develops into a fruit.
(b) Differentiate between pollination and fertilisation.
Answer:
(a) See fig.
(b)

Pollination	Fertilisation
1. It is the transfer of pollen grains from the anther of stamens to the stigma of a carpel through any agency.	1. It is defined as the fusion of a male gamete (sperm) with a female gamete (an ovum or egg) to form a zygote during sexual reproduction.
2. It involves external agencies like air, water, insects (bees and butterflies) birds, man etc.	2. It doesn’t involve any external  agencies but it involves certain enzymes and stimulation without which sperms can’t fused with ovum.

Question 2.
(a) Write the functions of the following parts in human female reproductive system :
(i) Ovary,
(ii) Oviduct,
(iii) Uterus.
(b) Write the structure and function of placenta.
Answer:
(a)

1. Ovary: Production of ova and sex hormones.
2. Oviduct: Site of fertilization.
3. Uterus: Keeps the foetus till complete development.

(b) Placenta: A special tissue embedded in the uterus wall with the help of which human embryo gets nutrition from mother’s blood.
Functions:

1. To provide large surface area for glucose and 02 to pass through mother’s blood to the embryo.
2. The metabolic waste generated by embryo is removed through placenta into mother’s blood.

Question 3.
Differentiate between external fertilisation and internal fertilisation. Give two examples of animals for each.
Answer:

Feature	External Fertilisation	Internal Fertilisation
Where it occurs	Outside the body of the female, usually in water	Inside the body of the female
Number of eggs laid	Very large numbers (hundreds to thousands) to compensate for low survival rate	Fewer eggs; each embryo has a higher chance of survival
Survival of young ones	Low — eggs/embryos are exposed and often eaten by predators or destroyed by water currents	Moderate to High – embryo is protected inside the mother’s body or in a yolk-rich egg
Examples	Fish, Frog	Lizard, Bird, Humans (mammals)

Question 4.
Describe three methods of vegetative propagation used in agriculture, with one example for each.
Answer:
1. Cutting: A healthy shoot cutting is taken from a plant, its lower leaves are removed, and it is inserted into moist soil at an angle of 45-60°. The cutting develops roots and grows into a new plant.
Example: Rose, money plant, sugarcane.

2. Grafting: A stem piece (scion) from one plant (Plant B with desirable fruit quality) is inserted into a slit made on the rooted stem (stock) of another plant (Plant A). The wound is wrapped to allow healing. The scion grows using the root system of Plant A.
Example: Mango, apple – used to develop high-yielding fruit varieties.

3. Layering: A flexible, thin twig of a plant is bent and the middle portion is buried in soil while still attached to the parent plant. The buried portion develops roots within 10-15 days. Once roots develop, the twig is cut from the parent and grows as a new plant.
Example: Lemon, jasmine.

Question 5.
Compare asexual and sexual reproduction under the following aspects: definition, number of parents, type of cell division, genetic variation in offspring, advantages, and examples.
Answer:

Asexual Reproduction		Sexual Reproduction
Definition	A single parent produces offspring without the formation and fusion of gametes	Two parents (male and female) contribute gametes that fuse to form a new individual
Number of parents	One	Two (in most cases)
Type of cell division	Mitosis – produces genetically identical daughter cells	Meiosis – reduces chromosome number by half to form gametes
Genetic variation	Absent – offspring are genetically identical to the parent (clones)	Present – offspring inherit a unique mix of characters from both parents, creating variation
Advantages	Fast, energy-efficient, useful when environment is stable and population growth is needed quickly	Creates genetic variation; helps species adapt to changing environments and evolve over time
Examples	Budding in Hydra and yeast; spore formation in Rhizopus; vegetative propagation (cutting, grafting) in plants	Pollination and fertilisation in flowering plants; internal fertilisation in humans, reptiles, and birds; external fertilisation in frogs and fish

Question 6.
Why are budding, fragmentation and regeneration all considered as asexual types of reproduction ? With neat diagrams explain the process of regeneration in Planaria.
Answer:
Budding, fragmentation and regeneration are considered as asexual types of reproduction because all of them involve only one parent and gametes are not involved in reproduction.

Regeneration in Planaria:
If the individual body of the planaria are cut or broken up into many pieces, many of these pieces grow into separate individuals.

Question 7.
Write two points of difference between asexual and sexual types of reproduction. Describe why variations are observed in the offspring formed by sexual reproduction.
Answer:

Asexual Reproduction	Sexual Reproduction
1. Involves only one parent	1. Often involves two parents
2. Gametes are not produced.	2. Gametes produced.
3. No fertilisation and zygote formation	3. Fertilisation and zygote formation is observed.
4. Meiosis does not occur at anytime during reproduction.	4. Meiosis occurs at the time of gamete formation.

During sexual reproduction two types of gametes fuse. Although the gametes contain the same number of chromosomes, their DNA is not identical. This situation generates variations among the offsprings.

Question 8.
Distinguish between pollination and fertilisation. Mention the site and product of fertilisation in a flower.
Draw a neat, labelled diagram of pistil showing pollen tube growth and its entry into the ovule.
Answer:
The process or mechanism of transfer of pollen grains from the anther to the stigma is termed as pollination.

The fusion of male and female gametes giving rise to zygote is termed as fertilisation. The site of fertilisation is ovule. The product of fertilisation is zygote.

Question 9.
Distinguish between a gamete and zygote. Explain their roles in sexual reproduction.
Answer:
Difference between Gamete and Zygote :

Gamete	Zygote
1. Nature : It is sex or germ cell that takes part in fertilisation.	1. It is a product of fertilization.
2. Types : There are two types of gametes, male and female.	2. Zygote is of one type.
3. Chromosome number : A gamete has haploid or 1 n chromosome number.	3. Zygote has diploid or 2n chromosome number.
4. Characteristics : A gamete carries characteristics of only one parent.	4. It carries characteristics of both the parents
5. Generation : Gamete is the last cell of its generation.	5. It is the first cell of new generation.

Role of Gamete : Gamete is sex or germ cell which is specialized to take part in sexual reproduction. There are two types of gametes, male and female. Each of them carries one set of chromosomes which are randomly obtained from its parent. Fusion of male gamete with a female gamete produces a zygote.
Role of Zygote : It is the first cell of new generation. Zygote develops into embryo that later forms the new individual.

Question 10.
Draw the diagram of a flower and label the four whorls. Write the names of gamete producing organs in the flower.
Answer:
See Fig.
Male gamete forming part—anther/stamen
Female gamete forming part—pistil/ovary/ovule.

Question 11.
What is placenta ? Mention its role during pregnancy.
Answer:
Placenta: Placenta is the physiological connection between the embryo and the uterine wall of mother. This is a disc-shaped structure embedded in the uterine wall. The foetus part of placenta is formed of villi which lie embedded in maternal blood spaces.
Role of placenta:
(a) It provides nutrition and oxygen to the foetus from mother’s blood.
(b) It removes carbon dioxide and nitrogenous wastes from the blood of foetus.
(c) Produces hormone progesterone for maintaining pregnancy.

Question 12.
What are various ways to avoid pregnancy ? Elaborate any one method.
Answer:
The different methods of contraception are:
(i) Mechanical barrier methods
(ii) Chemical methods
(iii) Surgical methods

(i) Mechanical Barrier Method: In this method condoms on penis by male and a covering in the vagina are used by females. These devices prevent the sperms from meeting the ovum by acting as a barrier between them.

(ii) Chemical Methods: In this type of method two types of pills are used by the females.
(a) Oral pills: This pills acts by changing the hormonal balance of the body so that eggs are not released and fertilisation cannot occur.
(b) Vaginal pills: This pills contains the chemicals called spermicides which kills the sperms.

(iii) Surgical methods:
(a) In males, a small portion of the sperm duct i.e., vas deferens is removed by surgical operation and both the cut ends are tied properly. This prevents the transfer of sperm. This is called vasectomy.
(b) In females, a small portion of the fallopian tubes i.e., oviducts is removed by surgical operation and cut ends are tied. This will not allow the egg to reach the uterus. This surgical procedure carried out in females is tubectomy.

Question 13.
How does fertilisation take place? Fertilisation occurs once in a month. Comment.
Answer:
In humans, the sperms made in testes are introduced into the vagina of woman through penis. Sperms move up through cervix into the uterus. From uterus, the sperms pass into oviducts. One of the oviducts contain an ovum released by the ovary during ovulation. Here, only one sperm fuses with the ovum in the oviduct to form a zygote. This is called fertilisation.
The ovary releases only one mature egg every month during a menstrual cycle (around 14th day). Therefore, fertilisation can occur only once in a month.

Question 14.
State the function(s) of the following organs in human reproductive system :
(a) Testes
(b) Ovary
(c) Fallopian tube
(d) Prostate and seminal vesicles
Answer:
(a) Testes: Testes produce sperms and hormone (Testosterone hormone). Testosterone brings about changes in appearance of boys at the time of puberty.

(b) Ovary: Ovaries produce female gamete (ovum or egg) and secrete female hormones (estrogen and progesterone). One egg is produced every month alternately by one of the ovaries.

(c) Fallopian tube : The egg is carried from the ovary to womb/uterus through fallopian tube.

(d) Prostate and seminal vesicles :
Prostate: The secretions of these glands keeps the sperm active and mobile. It secretes alkaline fluid comprising up to a third of semen volume and assists sperm motility.
Seminal vesicles: It secretes alkaline secretions which lower the pH of the semen and provide nourishment. It also stores sperms in some lower vertebrates and invertebrates (earthworm, insects).

Question 15.
Describe sexually transmitted diseases and mention the ways to prevent them.
Answer:
Sexually Transmitted Diseases: The common diseases are syphilis and gonorrhoea. Syphilis is characterised by sores around the anus, vagina, penis, lips, fingers, nipples, etc. In the later stages it results in fever and skin rashes. If untreated, it can result in insanity, heart damage or blindness. Gonorrhoea is characterised by yellow discharge from urethra and burning sensation while passing urine. In females it affects the uterus and the fallopian tubes. It can result in sterility.

Both syphilis and gonorrhoea are extremely infectious diseases. They spread through sexual contact. Indulging in unsafe and promiscous, a (of a person) having frequent and diverse sexual relationships, esp. transitent ones, b (of sexual relationships of this kind) sexual activities increases the risk of infection. Both diseases can be cured by antibiotics.

AIDS: It is the most serious and challenging health problem confronting the world today. It is also a sexually transmitted disease. AIDS stands for Acquired Immuno Deficiency Syndrome. It is caused by human immuno deficiency virus (HTV). It spreads through transfer of bodily fluids such as blood and semen. Thus the main causes are unprotected sexual activities, use of infected needles or transfusion of infected blood. The virus affects the immune system of the body by inactivating the white blood cells. This results in loss of resistance against infections. It is a fatal disease.

Class 9 Science Reproduction How Life Continues Important Questions

Case-Study Based Questions

Question 1.
Read the case study given below and answer the following questions.
The sexual act always has the potential to lead to pregnancy. Pregnancy will make major demands on the body and the mind of the woman, and if she is not ready for it, her health will be adversely affected. Therefore, many ways have been devised to avoid pregnancy.

(i) What are the different methods to prevent pregnancy?
Answer:
Uses of contraceptive such as condoms, pills, copper -T and surgical methods.

(ii) What are the surgical methods to prevent pregnancy?
Answer:
Tubectomy in females and vasecotomy in males.

(iii) Why the female sex ratio is declining day by day?
Answer:
Due to female foeticides by doing illegal sex selective abortion of female foetuses.

(iv) Which contraceptive methods have large side effects?
Answer:
Oral pills and by changing the hormonal balance leads to high side effect.

(v) Why should one have the knowledge about sexual act and the disease causing by it?
Answer:
To stay healthy and free free from sexually transmitted disease one should be aware of the disease cause by bacteria and viruses such as gonorrhoea, syphilis and HIV- AIDS.

Question 2.
Read the case study given below and answer the following questions.
The reproductive parts of angiosperms are located in the flower. You have already studied the different parts of a flower – sepals, petals, stamens and pistil. Stamens and pistil are the reproductive parts of a flower which contain the germ-cells.The flower may be unisexual (papaya, watermelon) when it contains either stamens or pistil or bisexual (Hibiscus, mustard) when it contains both stamens and pistil.

(i) What is the male reproductive parts of flower?
Answer:
Stamen is the male reproductive part of flower and it consist of anther and filament

(ii) What are the different part of pistil?
Answer:
Stigma, style and ovary.

(iii) What is pollination?
Answer:
The transfer of pollen grains from the stamen to the stigma of flower is called pollination.

(iv) Where does fertilization occur in flower?
Answer:
The fertilization takes place inside the ovule.

(v) What are the two types of pollination?
Answer:
Self pollination and cross pollination.

Self Assessment

Question 1.
During favourable conditions, Amoeba reproduces by
(a) multiple fission
(b) binary fission
(c) budding
(d) fragmentation

Question 2.
Bryophyllum can be propagated vegetatively by the
(a) stem
(b) leaf
(c) root
(d) flower

Question 3.
In a potato, vegetative propagation takes place by:
(a) root
(b) leaf
(c) stem tuber
(d) grafting

Question 4.
Vegetatively propagated plants
(a) do not bear roots
(b) do not bear buds
(c) are genetically similar
(d) are genetically dissimilar

Question 5.
Spirogyra reproduce by
(a) budding
(b) fragmentation
(c) regeneration
(d) fission

Question 6.
Mention the name of common passage meant for transporting urine and sperms in males.

Question 7.
What is the role of placenta ?

Question 8.
Where does fertilization occur in the female reproductive tract ?

Question 9.
Why is temperature of scrotal sac 2°C less than the body temperature ?

Question 10.
Define asexual reproduction.

Question 11.
Name the male gonads. What product do they produce ?

Question 12.
Name the female gonads. What product do they produce ?

Question 13.
Draw a diagram to show the germination of pollen on stigma and label the following parts :
(i) Ovary, (ii) Pollen tube.

Question 14.
List any two differences between pollination and fertilisation.

Question 15.
What are chromosomes ? Explain how in sexually reproducing organisms, the number of chromosomes in the progeny is maintained ?

Question 16.
List four categories of contraceptive methods. State in brief two advantages of adopting such preventive methods.

Question 17.
State the importance of chromosomal difference between sperms and eggs of humans.

Question 18.
List two advantages of growing grapes or banana plants through vegetative propagation.

Question 19.
Explain the process of regeneration in Planaria. How is this process different from reproduction?

Question 20.
What is placenta ? State its function in human female.

Question 21.
What is fertilisation ? Differentiate between external and internal fertilisation.

Question 22.
Draw a labelled diagram of a longitudinal section of pistil flower showing the germination of pollen on stigma.

Question 23.
List four methods of contraception used by humans. How does their use have a direct effect On health and prosperity of the family ?

Question 24.
Explain the process of regeneration of Planaria.

Question 25.
(a) Name the following :
(i) thread like non-reproductive structures present in Rhizopus.
(ii) ‘blobs’ that develop at the tops of the non-reproductive threads in Rhizopus.
(b) Explain the structure and the function of the structures released from the blobs in Rhizopus.

Question 26.
Describe briefly three methods of plant propagation which are commonly used for growing garden plants.

Question 27.
What is double fertilisation ? How does it is different from normal fertilisation ? After fertilisation name the part in each case which develops, (i) the fruits, (ii) the seeds.

Question 28.
Describe the human male reproductive system with the help of a labelled diagram.

Question 29.
Describe fertilisation in human female. What happens to the ovum, menstruation, after the fertilisation of the ovum ?

Question 30.
What is pollination ? How does it occur in plants ? How does pollination lead to fertilization ? Explain.

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