Please refer to below Exam Question for Class 10 Science Chapter 8 How do the Organisms Reproduce. These questions and answers have been prepared by expert Class 10 Science teachers based on the latest NCERT Book for Class 10 Science and examination guidelines issued by CBSE, NCERT, and KVS. We have provided Class 10 Science exam questions for all chapters in your textbooks. You will be able to easily learn problems and solutions which are expected to come in the upcoming class tests and exams for standard 10th.

Chapter 8 How do the Organisms Reproduce Class 10 Science Exam Question

All questions and answers provided below for Exam Question Class 10 Science Chapter 8 How do the Organisms Reproduce are very important and should be revised daily.

Exam Question Class 10 Science Chapter 8 How do the Organisms Reproduce

Very Short Answer Type Questions:

Question: Give an example each of unisexual and bisexual flowers.
Answer: An example of unisexual flower is Papaya, water melon (write any one) and of bisexual
flower is Hibiscus, mustard (write any one).

Question: “Cell division is a type of reproduction in unicellular organism”. justify.
Answer: Cell division is a type of reproduction in unicellular organisms because by means of cell division the unicellular organisms produce daughter cells which develop into neworganisms.

Question: What is the effect of DNA copying which is not perfectly accurate on the reproduction process?
Answer : DNA copying is not perfectly accurate and the resultant errors are a source of variations in populations of organisms.

Question: List any four modes of asexual reproduction.
Answer : Four modes of asexual reproduction are—Binary fission in Amoeba, Fragmentation in Spirogyra, Regeneration in Planaria and Budding in Hydra.

Question: Mention the mode of reproduction used by(a) Amoeba (b) Planaria.
Answer : Mode of reproduction used by
(a) Amoeba is Binary fission.
(b) Planaria is Regeneration.

Question: What is meant by asexual reproduction? List its any two different forms.
Answer : Asexual reproduction is the process of producing new organism from a single parent without the involvement of sex cells. Fission and fragmentation are two different forms of asexual reproduction.

Question: Name an organism which reproduces by spore formation. List three conditions favourable for spores to germinate and grow.
Answer : Rhizopus reproduces by spore formation. Conditions favourable for spore formation are:
(i) Cool place, (ii) Moist place and (iii) Dark place.

Question: Name the information source of making proteins in the cell. State two basic events in reproduction.
Answer : The DNA in the cell nucleus is the information source of making proteins.
The two basic events in reproduction are:
(i) Creation of a DNA copy,
(ii) Additional cellular apparatus by the cell involved in the process.

Question: List the parts of human male reproductive system which contribute fluid to the semen. State two advantages semen offers to the sperms.
Answer : Prostate glands and seminal vesicles add fluid in the vas deferens. This makes transportation of sperms easier and also provides nutrition to the sperms.

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

Question: Name the method by which Spirogyra reproduces under favourable conditions. Is this method sexual or asexual?
Answer: The method by which Spirogyra reproduces under favourable conditions is Fragmentation.
This is an asexual mode of reproduction.

Question: Name the organs producing sperms and ova respectively in humAnswer:
Answer: The organ producing sperms in humans is Testes and that producing ova in humans is Ovary.

Question. Why do organisms look similar?
Answer: Organisms look similar because the blue prints of their body designs are similar.

Question. Name the common passage of urine and sperm.
Answer: Urethra

Question. What is sperm?
Answer: Sperm is a male germ cell

Question. What are the parts of a sperm?
Answer: Head (contain genetic material ) and a tail ( helps in movement)

Question. Name the smaller motile germ cell of human being.
Answer: Male gamete (Sperm)

Question. What are the two types of pollination?
Answer: Self-pollination and cross pollination

Question. Which part of sperm possesses genetic material?
Answer: Head of sperm possess genetic material

Question. What is stamen?
Answer: Male reproductive organ of a flower

Question What are the agents of pollination?
Answer: Wind, water and insects

Question. How can we control population?
Answer: By using contraceptive methods

Question: List two unisexual flowers.
Answer: Water melon, Papaya

Question: Name a unicellular organism which reproduces by multiple fission.
Answer: Plasmodium is a unicellular organism which reproduce by multiple fission.

Question: Name the part of Bryophyllum where the buds are produced for vegetative propagation.
Answer: Leaf 

Question: What is meant by the term regeneration?
Answer: Regeneration: The process of getting back a full organism from its body parts is called regeneration. The simple animals like Hydra and Planaria shows regeneration, i.e. if Hydra or Planaria somehow get cut into a number of pieces, then each body part can grow into a new complete organism. How is it possible in some organisms, new individual organisms form from their body parts if they are cut into parts

Question: Name one organism which reproduces by:
(a) multiple fission
(b) binary fission 
Answer: Types of fission Name of Organism
1. Multiple fissionPlasmodium, yeast
2. Binary fissionAmoeba, Paramecium

Question. Why is vegetative propagation practised for growing some types of plants? 
                                                                     or
Why is vegetative propagation practiced for growing some types of plant? List two plants which are grown by this method.
Answer : Advantages of vegetative propagation:
a. The plants bear flowers and fruits earlier than those propagated sexually.
b. Plants have lost capacity to form seeds hence they are propagated vegetatively. Such plants are genetically similar to parent plants and have all their characters.

Question. What is the function of copper-T used by some women? What is its effect?
Answer : Copper-T prevents pregnancy as it prevents implantation in the uterus. It can cause side effect due to irritation of the uterus.

Question. Leaves of Bryophyllum fallen on the ground produce new plants. Why?
Answer : Leaves of Bryophyllum bears adventi¬tious buds/plantlets in the notches along the leaf margin. When the buds fall on the soil they develop into new plant under favourable condi-tions.

Question. Differentiate between self-pollination and crosspollination.
Answer :

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

Question. What are the functions of the following in male reproductive system?
a. Seminal vesicles
b. Prostate gland
Answer : a. In human males, seminal vesicles store sperms temporarily before ejaculation.
b. Both seminal vesicles and prostate gland add their secretions so that the sperms remain in a fluid which makes their transport easier and also this fluid provides nutrition.

Question. Label any four parts.
Answer :  

1. Stigma 2. Anther 3. Style 4. Filament 5. Petal
6. Ovary 7. Sepal (any four)

Question. Draw a labelled diagram of
a. Regeneration in Planaria
b. Budding in Hydra
or
Explain budding in Hydra with the help of labelled diagrams only.
Answer : 

Question. What does the diagram given below correctly illustrate? Give reason in support of your answer.

Answer : Binary fission in Amoeba. The splitting of the two cells during division in Amoeba can take place in any plane.

Question. What is the main difference between sperms and eggs of human? Write the importance of this difference?
Answer : Sperms are motile and are produced in . large numbers by a male. Egg are non-motile and only one is produced at a time by the female.
Sperms are motile as they have to travel up to egg for fertilization. It becomes zygote, remains protected inside female’s body and gives rise to foetus and baby.

Short Answer Type Questions:

Question: (A) What provides nutrition to human sperms? State the genetic constitution of a sperm.
(B) mention the chromosome pair present in zygote which determines the sex of (i) a female child, and (ii) a male child.
Answer: (A) The secretions of seminal vesicles and prostrate gland provide nutrition to the
sperms. The genetic constitution of a human sperm is DNA (Deoxy ribo nucleic acid). The head of the sperm cell contains the male’s genetic information in the form of DNAthat is passed on to the next generation.
Sex chromosomes in males is XY so sperms produced either have X or Y chromosomes.
(B) Chromosome pair present in zygote which determines the sex of:
(i) a female child– XX
(ii) a male child–XY.

Question: (i) What is fertilisation? Distinguish between external fertilisation and internal fertilisation.
(ii) What is the site of fertilisation in human beings?
Answer.
(i) Fertilisation 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.

Question: Define the term pollination. Differentiate between self pollination and cross pollination. What is the significance of pollination?
Answer: Pollination: The transfer of pollen grains from the anthero of a stamen to the stigma of a carpel is called. Pollination: It is done by various agents like wind, water, insects like bees and butterflies, birds etc.
Pollination can occur in two ways:
(i) self pollination
(ii) cross Pollination
Differences between self pollination and cross pollination.
Significance of Pollination: Fertilization takes place after pollination. When a pollen grain falls on the stigma of the carpel, it bursts open and a pollen tube starts growing downwards through a style towards the female gamete in the ovary.
Pollination is a very important part of the life cycle of plants.
It leads to production of fruits and seeds.

Question: Can you consider cell division as a type of reproduction in unicellular organisms? Give one reason.
Answer: Unicellular organisms reproduce by asexual reproduction, which is a simple division of parent cell into two daughter cells. Now, these two daughter cells grow into mature organisms.
Hence, cell division can be considered as the mode of reproduction in single celled organisms as it results in the production of more individuals of the organism.

Question: Differentiate between ‘self-pollination’ and ‘cross-pollination’. Describe double fertilisation in plants.
Answer.

During fertilisation in plants, the following events take place:
(i) One of the male gamete fuses with the female gamete present in the embryo sac.
(ii) The other male gamete fuses with the two polar nuclei in the embryo sac.
The first fusion product gives rise to the zygote while the second one forms the endosperm.
The process of two fusions occurring in the embryo sac is called double fertilisation.

Question: 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: A bisexual flower has both male and female reproductive organs. It consists of both stamen (male reproductive part) and carpel (female reproductivepart). If in a bisexual flower, stamens are removed artificially and carpel remains intact in the flower, then, cross- pollination may occur in this flower, leading to the formation of fruit. The pollens from another flower of the same kind land on the stigma of this flower and fertilisation takes place and hence produces a fruit.

Question: What is vegetative propagation? Write the names of any two plants grown by this method.
Answer: Vegetative propagation is a method of asexual reproduction in some higher plants in which a new plant develops from the vegetative parts of a plant such as root, stem or leaf.
Two plants grown by this method are:
(1) Dahlia, sweet potato from roots.
(2) Ginger, potato, onion are grown from stem.
(3) Bryophyllum grown from leaf.
(4) Grapes grown by cutting.
(5) Guava grown by layering.
(6) Lemon grown by Grafting

Question: Illustrate the following with the help of suitable diagrams:
(i) Binary Fission in Amoeba.
(ii) Leaf of Bryophyllum with buds.
Answer.

Question: Give two reasons for the appearance of variations among the progeny formed by sexual reproduction.
Answer: Progeny formed as a result of sexual reproduction shows variations because:
(1) Sexual reproduction involves combining of DNA from two different individuals.
(2) The gene combination is different in gametes. The genetic material is exchanged between chromosomes before the formation of zygote, i.e., deoxyri- bonucleic acid (DNA) exchange in the chromosome. The combination of two sets of chromo-somes, one set from each parent during zygote formation, leads to variation within a species.

Question: Explain the process of budding in yeast by drawing labelled diagrams of different stages of the process in a correct sequence.
Answer: Diagram showing budding in yeast: 

Question: Illustrate the following with the help of suitable diagrams:
(i) Spore formation in Rhizopus.
(ii) Multiple fission in Plasmodium.
Answer.

Question: In a tobacco plant, the male gametes have 24 chromosomes. What is the number of chromosomes in the female gamete? What is the number of chromosomes in the zygote?
Answer: Male and female gametes of a species have the same number of chromosomes. Hence, the number of chromosome in the female gamete of tobacco plants is 24. Zygote is formed by the fusion of male and female gametes, so it will have 48 chromosomes.
The number of chromosomes in the female gamete is 24.
The number of chromosomes in zygote is 48.

Question: Give an example each of unisexual and bisexual flowers.
Answer: An example of unisexual flower is Papaya, water melon (write any one) and of bisexual flower is Hibiscus, mustard (write any one).

Question: (a) Name the parts labelled A, B, C, D and E.

(b) Where do the following functions occur?
(i) Production of an egg
(ii) Fertilisation
(iii) Implantation of zygote.
(c) What happens to the lining of uterus:
(i) before release of a fertilised egg?
(ii) if no fertilisation occurs?
Answer: (a)
A – Oviduct or Fallopian tube;
B – Ovary;
C – Uterus;
D – Cervix;
E – Vagina.
(b) (i) Ovaries; (ii) Fallopian tube;
(iii) Lining of the uterus.
(c) (i) The lining of uterus becomes
(ii) The lining of uterus slowly breaks and comes out through the vagina as blood and mucous, if no fertilisation occurs.

Question: From the Internet, gather information about the chromosome numbers of five animals and five plants. Correlate the number with the size of the organism and answer the following questions:
(A) Do larger organisms have more number of chromosomes/cells?
(B) Can organisms with fewer chromosomes reproduce more easily than organisms with more number of chromosomes?
(C) The more the number of chromosomes/cells the greater the DNA content. justify.
Answer: This table shows the number of chromosomes present in some important animals and plants:
(A) Number of chromosomes is not related to the size of an organisms. In the given table, we can see that even though a Kingfisher is smaller in size than a dog, the number of chromosomes is more in a Kingfisher.
(B) Ease of reproduction is not dependent on the number of chromosomes present. It depends on other factors like availability of water, nutrients, suitable mate and favorable environment.
(C) Yes, since the major component of chromosome is DNA, Chromosomes are made up of DNA. If chromosomes are more, this implies DNA will be more.

Question: (a) Draw a diagram showing germination of pollen on stigma of a flower.
(b) Label pollen grain, male germ- cells, pollen tube and female germ-cell in the above diagram.
(c) How is zygote formed?
Answer. (a) and (b)

(c) Zygote is formed when male gamete, Le. sperm fuses with female gamete, i.e. ovum.

Question: Trace the path of sperm during ejaculation and mention the gland and their functions associated with the male reproductive system.
Answer: Sperms are produced in testes and move from Testes to Vas deferens. Ducts of seminal vesicle and prostate gland combine with Vas deferens to form liquid mixture (consisting of sperm) joins the urethra and gets ejaculated.
The path of sperm during ejaculation is as follows:
Vas deferens → Seminal vesicle → Urethra Glands associated with the male reproductive system and their functions are as follows:
(1) Seminal vesicles: The secretion of seminal vesicle provides a fluid medium for the movement of sperms.
(2) Prostate glands: The secretion of prostate gland produces a fluid which keeps sperms floating in it and provides nourishment.
(3) Testes: It secretes the hormone testosterone. Along the path of the vas deferens, glands like the prostate and the seminal vesicles add their secretions, so that the sperms are now in a fluid which makes their transport easier and this fluid also provides nutrition.

Question: What changes are observed in the uterus if fertilisation does not occur?
Answer: In female, ovary produces one egg every month. 
The uterus also prepares itself to receive a fertilised egg. So, the wall of uterus becomes thick and spongy containing lots of blood capillaries. If egg gets fertilised with sperm, then fertilised egg gets attached with uterus wall and gets nourishment from it. In case, egg is not fertilised, then this lining is no onger needed. The inner lining of uterus breaks down and comes out in the form of blood and mucous through the vagina. This cycle occurs every month and is called menstruation. It usually lasts for about 2 to 8 days.

Question: Draw a labelled diagram to show that particular stage of binary fission in Amoeba in which its nucleus elongates and a constriction appears in its cell membrane.
Answer: Labelled diagram showing the stage in binary fission of amoeba in which its nucleus elongates and a constriction appears in its cell membrane is drawn below:  

Question: A student is given a permanent slide showing binary fission in Amoeba. Write two steps to focus the slide under microscope. Draw diagram and label the parts.
Answer: Steps to focus the slide under microscope:
(i) Move the stage down to its lowest position.
(ii) Place the glass slide onto the stage.
(iii) Select the lowest power objective lens.
(iv) Turn the focus know slowly until the cells are not seen.
(v) There is a proper management of light.

Binary fission in Amoeba.

Question: Draw a diagram showing the different parts of an embryo of gram seed and label them.
Answer: A diagram showing the different parts of an embryo of a gram seed is drawn below:

Question: What would be the ratio of chromosome numbers between an egg and a zygote? How is the sperm genetically different from the egg?
Answer: The ratio of chromosome numbers between egg and its zygote is 1:2.
Both sperm and eg g contain half number of chromosome, i.e., 23 chromosomes. Sperm is genetically different from the egg in the way that it contains either X or Y chromosome, whereas an egg always contains an X chromosome.

Question: List any four modes of asexual reproduction.
Answer: The four modes of asexual reproduction are:
(1) Fission
(2) Fragmentation
(3) Regeneration
(4) Budding
(5) Vegetative Propagation
(6) Spore formation.

Question: What is the effect of DNA copying which is not perfectly accurate in the reproductive process?
Answer: The effect of DNA copying in reproductive process is that the characteristics of the parent organisms are transmitted to its offspring and at the same time some variations are also produced in the offspring. The importance of variations in organisms is that these help the species of various organisms to survive and flourish even in adverse environment.

Question: Is the chromosome number of zygote, embryonal cells and adult of a particular
organism always constant? How is the constancy maintained in these three stages?
Answer: Yes, zygote, embryonic cell and adult of a particular organism always have constant chromosome number.
Sexual reproduction includes gamete formation through meiosis and fertilization. Meiosis reduces the number of chromosomes to half in male and female gametes. This reduced chromosome number is then restored to normal during fertilization of male and female gametes. This is how; constant chromosome number is maintained in sexually reproducing organisms. Growth and development of zygote into embryonic cell and then into adult one takes place by mitosis (equatorial cell division) which produce the daughter cells carrying same chromosome number as that of parent cell.

Question: Why is reproduction so essential in living organisms?
Answer: Reproductio n is essential for the survival of a species on Earth. Living organisms produce more organisms of their kind to maintain their species on Earth. The process of reproduction ensures the continuity of life on Earth. It also
leads to the evolution of the species in the long run.

Question: Akshaya was very inquisitive in nature and used to ask a number of questions from his mother. One day he saw a beautiful hibiscus flower and ite various parts. He asked his mother to explain all the parts of a flower.
Answer the question on the basis of your understanding of the given information and
the related studied concepts.
Draw longitudinal section of a bisexual flower and label the following parts on it and write function of any two parts:
(a) Anther (b) Ovary
(c) Stigma (d) Style
Answer: Longitudinal section of a bisexual flower 

Functions of parts of a bisexual flower:
(a) Anther: Anther produces pollen grains i.e. male sex cells.
Explanation/Related Theory: The male reproductive part of a flower is known as
stamen and consists of filament and anther.
(b) Ovary: The ovary contains ovules, which develop into seeds upon fertilization the ovary matures into a fruit.
(c) Stigma: It is that part where pollen lands and then transferred to the carpel.
(d) Style: The style is the stalk that supports stigma and connects it to ovary. Pollen tube travels in the style to deliver sperm cells to the egg.
Explanation: A carpel is a female reproductive organ in a flower. It is composed of an ovary, a style and a stigma. 

Question: How will an organism benefit if it reproduces through spores?
Answer: The reproduction by spores takes place in
plants. Spores are protected by covered coat. It helps spores to survive under unfavourable conditions such as lack of food and water.
When the conditions become favourable, then spores can grow to produce new plants.
Thus, we can say that reproduction by spores benefits the plants by surviving under adverse conditions. The spores help these plants to live forever on Earth.

Question: Answer the following:
(A) Name any 2 plants that reproduce by grafting.
(B) List any two benefits to an organism that reproduces through spores.
Answer: (A) Two plants that reproduce by grafting are apple and peach.

Question: How is reproduction in leishmania different from that in plasmodium, even though both  are unicellular?
Answer: Leishmania undergoes binary fission, whereas plasmodium reproduces through multiple fission.

Question: Students were asked to observe the permanent slides showing different stages of budding in yeast under high power of a microscope.
(A) Which adjustment screw (coarse/fine) were you asked to move to focus the slides?
(B) Draw three diagrams in correct sequence showing budding in yeast.
Answer: Fine 

Question: Explain how DNA copying is an essential part of the process of reproduction? What are the advantages of sexual reproduction over asexual reproduction?
Answer: DNA copying is an essential part of the process of reproduction because it makes possible the transmission of genetic information from parents to offspring in the next generation.
DNA contains information for the inheritance of characteristics from the parents to the next generation.

Question: Answer the following:
(a) What is a clone? Why do offspring formed by asexual reproduction exhibit remarkable similarity?
(b) Explain how offspring and parents of organisms reproducing sexually have the same number of chromosomes?
Answer: (a) The new organisms or offsprings produced by one parent through asexual reproduction are called clones. The clones possess exact copies of the DNA or genes of their parents and hence show remarkable similarity to the parent or one another. Asexual reproduction does not involve gamete formation by meiosis and fertilization of male and female gametes; the offspring are genetically similar to the single parent.
(b) Sexual reproduction includes gamete formation through meiosis and fertilization.
The gametes are special type of cells called reproductive cells which contain only half the amount of DNA or half the number of chromosomes as compared to the normal body cells of an organism. So, when a male gamete combines with a female gamete during sexual reproduction, then the new cell zygote will have the normal amount of DNA.
For example: Human sperm has 23 chromosomes and the human egg also has 23 chromosomes. So when a sperm and an egg fuse together, then the zygote formed will have 46 chromosomes.

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 is the type of asexual reproduction in which two individuals are formed from a single parent and the parental identity is lost.
The first step in binary fission is elongation and subsequent division of nucleus into two nuclei i.e., nuclear division.
In Binary Fission the identity of parental cell is lost. After fission parental cell called as daughter cell.
The process starts with elongation of nucleus.

Question: Answer the following:
(A) Rahul observes bread mould grow profusely on a moist slice of bread rather
than on a dry slice of bread. Explain the observation briefly.
(B) Colonies of yeast fail to multiply in water, but multiply in sugar solution. Give reason.
Answer: (A) The spores of bread mould need favourable conditions like moist surface to germinate.
Moisture is an important factor for the growth of hyphae of bread mould that contains spores. Therefore, moistened bread slice offers both moisture and nutrients to the bread mould, hence it grows profusely.
Dry slice of bread offers nutrients, but not moisture hence, hyphae fail to grow.
(b) The sugar solution provides the yeast with a food source and energy for sustaining all life activities in yeasts. So they can respire and therefore multiply. The water contains no food source, and thus does not provide nergy to the yeast cells to multiply.

Question: Rohan’s friend gifted him a beautiful plant. He lived it so much that he wanted to make more plants of the same kind. He asked his teacher how he can make more plants. The teacher explained the process of tissue culture.
In tissue culture, new plants are grown by separating cells from the growing tip of a lant. These cells are placed in an artificial medium. Where they divide rapidly to form a small group of cells which is called callus.
The callus is transferred to another medium containing hormones. After some time plantlets are seen which are then placed in the soil to have mature plants.
Based on the above case study, answer the following questions:
(A) Tissue culture is a type of asexual reproduction. justify.
(B) What are the advantages of growing plants by vegetables propagation?
Answer: (A) Tissue culture is a type of asexual reproduction as many plants can be grown from one parent and all the plants are also identical.
(B) Advantages of growing plants by vegetative propagation.
(1) The new plants produced are exactly like the parent plants.
(2) Plants which do not form viable seeds can be grown by this method
(3) This method is a rapid, cheaper and converient method for growing plants.
(4) Survival rate of new plants is it is upto 10􀊆 when raised by seeds.
Human male Reproductive System
(C) Testis is the human male reproductive organ that produces sperm and secrets a hormone.
The name of the hormone secreted is Testosterone.
Functions of hormone:
(1) It regulates development of secondary sexual characters.
(2) It regulates the formation, development and maturation of sperm.

Long Answer Type Questions:

Question: Describe in brief the role of (i) testis (ii) seminal vesicle, (iii) vas deferens, (iv) ureter and (v) prostate gland in human male reproductive system.
Answer :
Testis: Testes are oval shaped primary reproductive organs in men. The function of testes is to produce sperms and male sex hormone testosterone. The scrotum provides optimal temperature for the formation of sperms.
Seminal vesicle: Seminal vesicles are a pair of thin walled muscular elongated sac which secrete fluid for nourishment of sperms.
vas deferens: The sperms are carried by a long tube called vas deferens to organs called seminal vesicles where the sperms get nourishment and stored.
Ureter It is the tube that carries urine from kidney to the urinary bladder. In humans, there are two ureters, one attached to each kidney.
Prostate glands: Prostate glands produce a fluid which is released in the urethra along with secretion of seminal vesicles for nourishment and transportation of sperms.

Question: Explain vegetative propagation with the help of two examples. List two advantages of vegetative propagation.
Answer : In vegetative propagation, new plants are obtained from the parts of old plants like stems, roots and leaves, without the help of any reproductive organ.
There are two ways of vegetative propagation:
(a) Natural Vegetative Propagation, and
(b) Artificial Vegetative Propagation.
Natural vegetative propagation by leaves: The fleshy leaves of Bryophyllum bear adventitious buds in the notches along the leaf margin.
Grafting: In this method of reproduction, two plants of closely related varieties are joined together so that they live as one plant.
• The portion of a plant that is grafted on the other plant is called scion, and the plant in which grafting is performed is called the stock.
• This method is applied to improve variety of fruits like mango, apple, peas, citrus and guava. advantages of vegetative propagation are:
(i) Vegetative propagation is a cheaper, easier and more rapid method of propagation in plants than growing plants from their seeds.
(ii) Better quality of the plants can be maintained by this method.

Question: tate in brief the changes that take place in a fertilised egg (zygote) till birth of the child in the human female reproductive system. What happens to the egg when it is not fertilised?
Answer : The egg gets fertilised in the oviduct. The fertilised egg, the zygote gets implanted in the lining of the uterus and starts dividing. The uterus prepares itself every month to receive and nurture the growing embryo. The lining 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. The development of the child inside the mother’s body takes approximately nine months. On completion of 9 months, the child is born as a result of rhythmic contractions of the muscles in the uterus.
If the egg is not fertilised, the thick and nourishing lining of the uterus breaks and comes out through vagina as blood and mucous.

Question: (a) In the human body what is the role of
(i) seminal vesicles, and (ii) prostate gland?
(b) List two functions performed by testis in human beings.
Answer : (a) The role of seminal vesicles and the prostate gland are as follows:
(i) Seminal vesicles produce seminal plasma which is in the form of fluid makes the transport of sperms smooth.
(ii) Prostate gland secretes prostatic fluid that keeps the sperms alive and helps them to swim vigorously.
(b) Two functions performed by testis
in human beings are as follows:
(i) Formation of sperms takes place in testis.
(ii) They secrete the hormone testosterone which regulates the formation of sperms and brings changes in appearance of boys at the time of puberty.

Question: Differentiate between pollination and fertilisation. What is cross-pollination? State
any two carriers (agents) that carry out this process.
Answer: Differences between pollination and fertilization:  

Cross pollination is the transfer of pollen grains from the anther of a flower to the stigma of another flower.
Two agents or carriers that carry out cross pollination are wind, water, insects, animals.

Question: What is regeneration? Give one example of an organism that shows this process
and one organism that does not. Why does regeneration not occur in the latter?

Answer: Regeneration is the ability of many fully differentiated organisms to give rise to new individual organisms from their body parts, if the individual is somehow cut or broken up into many pieces.
Planaria is an example of organism that has the ability to regenerate.
Rhizopus is an example of an organism that does not show regeneration.
Regeneration is carried out by specialized cells which proliferate and make large number of cells. From this mass of cells, different cells undergo changes to form different cell types and tissues. As such specialized cells are not present in Rhizopus, regeneration does not occur in Rhizopus.

Question: 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  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. Due to lot of variations,sexual reproduction allows species to change to more advanced forms from one generation to the next and speed up evolution.

Question: Draw a diagram of longitudinal section of a bisexual flower and label the following:
Ovary, anther, style, stigma, filament Identify from these the female reproductive
organs and state one function of each.
Answer: Diagram of longitudinal section of a bisexual flower is drawn below:

The female reproductive organs are ovary, style and stigma. Their functions are mentioned below:
Ovary: It is the swollen bottom part of the pistil and contains ovules which has the female gamete, the egg cell.
Style: A pollen tube grows out of the pollen grain and travels through the style, which is the middle part of the pistil, to reach the ovary.
Stigma: It is the terminal part of the pistil and may be sticky and on which the pollen grains are deposited.

Question: (A) List two reasons of using contraceptive methods by married couples.
(B) Write in proper sequence the process going on in the different organs of the reproductive system of a human female starting from the time of egg production to childbirth. 
Answer: (A) Married couples use contraceptive methods:
(1) To avoid unwanted pregnancy
(2) To have proper time gap between two children.
(3) To limit the number of children in the family.
(4) To prevent transmission of many of sexually transmitted diseases. 
(B) In human female reproductive system, there are two ovaries. One egg is produced every month by one of the ovaries during ovulation:
(1) The ovum egg goes into the oviduct or fallopian tube.
(2) The sperms released by the human male during copulation or mating are deposited at the top of the vagina close to the cervix of uterus. The sperms
travel through the uterus to the top of fallopian tube.
(3) The fertilization of the ovum or egg takes place in the oviduct and a zygote is formed.
(4) The zygote divides rapidly as it moves down slowly in the oviduct and forms a hollow ball of hundreds of cells called embryo. The close attachment
of embryo to the uterine wall is called implantation.
(5) After implantation, a number of development changes takes place in embryo as well as in the wall of uterus. When body features are seen clearly, the developing embryo is called foetus.
(6) A disc-like special tissue develops between the uterine wall and the foetus which is called placenta. The exchange of nutrients, oxygen and waste products between the embryo and the mother takes place through the placenta.
(7) The time period from the fertilization up to the birth of baby is called gestation.
The average gestation period in humans is about nine months or 40 weeks or 280 days from the first day of the last menstruation.
(8) The rhythmic contraction of uterus muscles gradually pushes the baby out of the mother’s body through vagina which is called parturition. This is how a child is born.

Question: List two observations on the basis of which it  ay be concluded that the given slide shows binary fission in Amoeba.
Answer: Two observations on the basis of which student  concluded that given process is binary fission in amoeba:
(1) Elongation and subsequent division of nucleus into two nuclei.
(2) Appearance of constriction in cell membrane and division of cytoplasm into two.

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

Importance of gametes and zygote in sexual reproduction:
Gametes are the reproductive cells which actually take part in sexual fertilisation. The gametes are carriers of the genetic material from one generation to the other and also help in the maintenance of the chromosome number of a species. The two fusing gametes possess characters of their parents in their DNA. Fertilisation brings characters of both the parents into one zygote cell.
Zygote is the name given to the cell produced by fertilisation of male and female gametes in sexual reproduction. It represents the first cell of the next generation which subsequently grows into a new individual and carries genetic information from both the parents involved.
It is divided repeatedly to give rise to a new individual. Gametes are a product of meiosis and hence carry half the chromosome number as that of parent cells. This chromosome number is restored during fertilisation and zygote formation. Hence, gamete and zygote are the two phases of sexually reproducing organisms that help maintain a constant chromosome number in each species.

Question: mrs. Seghal’s family was very happy after the birth of their second child. Her friend, mrs. Raman, suggested her to undergo tubectomy.
(A) What is tubectomy?
(B) Why do you think mrs. Raman gave her such a suggestion?
(C) Can tubectomy prevent the spread of sexually transmitted diseases?
(D) Give reason for your answer. Why is there a need of adopting contraceptive methods?
Answer: (A) Tubectomy is a surgical method of birth control in females. In females, a small portion of the oviducts is removed by surgical operation and the cut ends are tied.
This prevents the ovum or egg from entering into the oviducts. This prevents fertilization, which prevents the pregnancy.
(B) Mrs Raman gave advice for tubectomy to Mrs Sehgal because she knows that a small family is a happy family. If a couple has only two children, it can provide good food, clothes, and education to each child.
This will keep parents as well as children happy. Mrs Raman also knows that having fewer children also keeps the mother in good health.
(C) No, tubectomy does not prevent the spread of sexually transmitted diseases.
(D) Since, there will be no physical barrier during sexual contact, there is every chance of a person (with tubectomy) getting infected with sexual transmitted diseases during sexual contact with an infected person.
The need of adopting contraceptive methods is to avoid getting infected with sexually transmitted disease and for birth control. These are also used to avoid unwanted pregnancy.

Question: Based on the given diagram answer the questions given below:

(A) Label the parts A, B, C and D.
(B) Name the hormone secreted by testis and mention its role.
(C) State the functions of B and C in the process of reproduction.
Answer: Copy the figure and Label
(A) A—Ureter
B—Seminal vesicle
C—Urethra
D—Vas deferens
(B) Hormone secreted by testis: Testosterone Role of testosterone: It brings about changes in appearance seen in boys at the time of puberty (secondary sexual characteristics).
(C) Functions of B (Seminal vesicle): Along the path of vas deference, seminal vesicle along with prostrate gland add their secretions which make the transport of sperms easier and this fluid provides nutrition to sperms.
The transport of sperms easier and this fluid provides nutrition to sperms.
Functions of C (Urethra): Urethra carries urine from the bladder and sperms through vas deference through the penis.

Question: Give reasons:
(A) Blocking of vas deferens prevents pregnancy.
(B) Wind acts as a pollinating agent.
(C) Can of condoms prevents pregnancy.
(D) Blocking of fallopian tubes prevents pregnancy.
Answer: (A) Blocking of vas deferens is a surgical method of birth control in males. A small portion of the vas deferens is removed by surgical operation and both the cut ends are tied properly. This prevents sperms from ejaculating during sexual contact and prevents pregnancy.
(B) The blowing wind carries pollen grains from one flower to another flower and helps in cross-pollination.
(C) Condom prevents sperms from fertilizing the ovum by acting as a barrier between them.
(D) In females, a small portion of the fallopian tube is removed by surgical operation and the cut ends are tied. This prevents the ovum from travelling further into the fallopian tube.
As a result, the sperm never meets the ovum during sexual contact and the chances of pregnancy become nil.

Question: (A) Name the mode of reproduction of the following organisms and state the important feature of each mode :
(i) Planaria
(ii) Hydra
(iii) Rhizopus
(B) We can develop new plants from the leaves of Bryophyllum. Comment.
(C) List two advantages of vegetative propagation over other modes of reproduction.
Answer: (A) Mode of reproduction in:
(1) Planaria: Regeneration Regeneration is carried out by specialised cells. Planaria if somehow gets cut into three pieces, after sometime, each cut piece of body of planaria grows into new planaria.

Explanation: Most organisms would not normally depend on being cut up to be able to reproduce. Regeneration is carried out by specialized cells which divide and make large number of cells.
From this mass of cells, different cells undergo changes to become various cell types and tissues. These different tissues form different organs and body parts. This is referred as growth and development.
(2) Hydra: Hydra reproduces by two modes:
(i) Regeneration
(ii) Budding
Budding is a method of asexual reproduction. Hydra reproduces by budding and uses regenerative cells for budding.
Explanation: A bud is formed as an outgrowth due to repeated cell division at one specific site. This bud developed into a small hydra by forming mouth and tentacles. And finally the tiny new hydra detaches itself from the body of parent hydra and lives as a separate organism.
(3) Rhizopus: Spore formation. In spore formation, the parent plant produces hundreds of microscopic reproductive units called spores.

Spore formation in Rhizopus Explanation: Whenever a spore falls on the substratum (where conditions are conductive less moist and warm conditions), it forms thread like projections called hyphae and thin stems having knob like structures called sporangia which contain spores. When the spore case bursts, the tiny spores are dispersed in air.
(B) The surface of leaves of Bryophyllum has notches. The buds are produced in these notches along the margin of leaf. These buds get detached from the leaves, fall to the ground and then grow to produce new plants.

(C) Advantages of vegetative propagation:
(i) Plants can bear flower and fruits earlier than those produced from seeds.
(ii) Plants such as banana, orange, rose and jasmine that donot produce viable seeds can be propagated.
(iii) All the plants produced are genetically similar and have all the characteristics as those of parent plant.

Question: (A) What is puberty?
(B) Describe in brief the functions of the following parts in the human male reproductive system:
(i) Testes
(ii) Seminal vesicle
(iii) Vas deferens
(iv) Urethra
(C) Why are testes located outside the abdominal cavity?
(D) State how sperms move towards the female germ cell.
Answer: (A) Puberty: Puberty is the age at which the reproductive organs become functional, reproductive organs (gonads) start producing gametes and sex hormones and the boys and girls become sexually mature.
(B) Functions of various parts in the human male reproductive system.
(i) Testes: The testes are male gonads. Its functions are:
Regulate the formation of male gametes i.e. sperms To produce male sex hormone i.e. testosterone.
(ii) Seminal vesicle: The secretions of seminal vesicles (along with prostrate gland).
provide nutrition to the sperms make the transport of sperms easier
(iii) Vas deferens: The sperms formed in testes are carried through vas deferens to urethra.
(iv) Urethra: Urethra serves as a common passage for both the sperms and urine.
(C) Testes are located outside the abdominal cavity in scrotum in human male reproductive system because sperm formation requires a lower temperature than body temperature.
(D) Sperms formed in the testes moves towards vas deferens which unites with a tube coming from urinary bladder. Along the path of vas deferens, prostrate and seminal vesicle glands add their secretions which makes it easier for the sperms to move by penis into the vagina of females where they can meet the female germ cell in the fallopian tube.

Question: Draw a neat diagram showing fertilisation in a flower and label (a) Pollen tube, (b) male
germ cell and (c) Female germ cell, on it.   
Explain the process of fertilisation in a flower.
What happens to the (i) ovary and (ii) ovule after fertilisation?
Answer:

Fertilization in a flower plant Process of fertilization in a flower During the process of pollination pollen grains land on the stigma of the carpel. Pollen grains form pollen tubes and one of the pollen tubes grows into the stigma, passes through the style and enters the ovary and finally to embryosac through an opening called micropyle.
Two non-motile male gametes (male germ cells) are formed in the pollen tube during its growth through the style.
Pollen tube releases two male gametes into the embryosac.
The mature embryosac consist of an egg apparatus having one haploid egg (Female germ cell, two synergids and two polar nuclei).
During the process of fertilization, one male gamete fuses with the female germ cell (egg) to form the diploid zygote. The process is called fertilization or syngamy. The zygote finally develops into embryo.
The other male gamete fuses with two polar nuclei and this process is called triple fusion.
In the ovary two fusions take place so this process is called double fertilization.
After fertilization
(i) The ovary grows rapidly and ripens to form a fruit.
(ii) The ovule develops a tough coat and is gradually converted to seed.
At the same time, the petals, sepals, stamens, style and stigma may strive and fall off.

Question: (A) Identify the modes of asexual reproduction in each of the following organisms:
(i) Hydra
(ii) Planaria
(iii) Amoeba
(iv) Spirogyra
(v) Rhizopus
(B) List three advantages of vegetative propagation.
(C) Why can fertilisation not take place in flowers if pollination does not occur?
Answer: (A) Modes of reproduction in:
(i) Hydra—Regeneration or budding
(ii) Planaria—Regeneration
(iii) Amobea—Binary fission
(iv) Spirogyra—Fragmentation
(v) Rhizopus—Spore formation
(B) Advantages of vegetative propagation
(i) Plants can bear flowers and fruits earlier than those produced from seeds.
(ii) All the plants produced are genetically similar and have all the characteristics
as those of parent plant.
(iii) Plants such as banana, orange, rose jasmine etc. that do not produce viable seeds can be propagated.
(iv) Desirable traits of fruits and flowers can be maintained.
(v) It is a cheaper, rapid and convenient method for growing plants.
(vi) Plants can easily be introduced in new areas by this method. (Any three)
(C) Fertilization cannot take place in flowers if pollination does not occur because for the male gamete to be able to combine with the female gamete, it is necessary that the pollen grains from the anther of stamen should be carried to the stigma of carpel.
The transfer of pollen grains from the anther of a stamen to the stigma of a carpel is called pollination.

Question: (a) List three different categories of contraception methods.
(b) Why has Government of India prohibited prenatal sex determination by law? State its benefits in the long run.
(c) Unsafe sexual act can lead to various infections. Name two bacterial and two viral infections caused due to unsafe sex. 5
Answer: (A) Three different categories of contraception methods are:
(1) Barrier methods
(2) Surgical methods
(3) Intrauterine Contraceptive Device (IUCD)
(4) Natural methods. 
Explanation: Contraception methods have been developed for birth control, to prevent
fertilization. The sexual act always has the potential to lead to pregnancy. If a woman is not ready for it, is will affect the health and mind of the women.
(B) Government of India has prohibited prenatal sex determination by law because it is misused by people who do not want a particular child and illegal sex-selective abortion of female foetuses is done.
Because of reckless female foeticides, child sex ratio is declining at an alarming rate in some sections of our society.
Benefits of prohibition of Prenatal sex determination Female foeticides will decline/ stop and female male ratio will be maintained.
Crime against females will decrease and would provide a healthier and safe environment for females.
Provide a healthier and safe environment for females.
There will be steady birth-rate in the society.
(C) Unsafe sexual act can lead to various infections.
Infections caused by bacteria:
(1) Gonorrhoea
(2) Syphilis
(3) Infections caused by virus:
(4) Warts
(5) HIV-AIDS

Question: (A) Identify the given diagram. Name the parts 1 to 5

(B) What is contraception? List three advantage of adopting contraceptive measure.
Answer: (A) The given diagram is the human female reproductive system.
Name of parts are given below:
(1) Fallopian tube/Oviduct
(2) Ovary
(3) Uterus
(4) Cervix
(5) Vagina
(B) Contraception: These are the techniques which have been developed to prevent and manage pregnancy.
Advantages of adopting contraceptive methods:
(1) Avoiding frequent and unwanted pregnancy
(2) Keeping population and hence birth rate under control
(3) Helps in keeping proper gap between two pregnancies.
(4) Helps in preventing the transfer of sexually transmitted diseases.

Question: (A) What are Sexually Transmitted Diseases (STD)? List two viral and two bacterial STDs.
(B) What is contraception? List three reasons for adopting contraceptive methods.
Answer: (A) The diseases that can be transmitted from an infected person to a healthy person through the sexual act are known as Sexually Transmitted Diseases.
(1) Two viral STDs are HIV-AIDS and warts.
(2) Two bacterial STDs are gonorrhoea and syphilis.
(B) Contraception: These are the techniques which have been developed to prevent and manage pregnancy.
Advantages of adopting contraceptive methods:
(1) Avoiding frequent and unwanted pregnancy.
(2) Keeping population and hence birth rate under control.
(3) Helps in keeping proper gap between two pregnancies.
(4) Helps in preventing the spread of sexually transmitted diseases.
(5) Helps in improving the reproductive health of women.

Question: (A) Define vegetative propagation. List its two methods.
(B) Why is this mode practised for growing some types of plants?
(C) Explain the process of budding in Hydra with the help of labelled diagrams.
Answer: (A) Vegetative propagation is a method of asexual reproduction in some higher plants in which a new plant develops from the vegetative parts of a plant such as root,stem or leaf.
Two methods are:
(1) From root as in Dahlia, sweet potato.
(2) From stem as in ginger, potato, onion.
(3) From leaf as in Bryophyllum
(4) Cutting as in grapes.
(5) Layering as in guava
(6) Grafting as in lemon

Question: (A) What is reproduction? List its two types.
(B) How are the modes of reproduction different in unicellular and multicellular organisms? 
Answer: (A) Reproduction is a biological process by which existing organisms produce new individuals of the same species.
The two types of Reproduction are:
(1) Asexual reproduction
(2) Sexual reproduction
(B) Differences between modes of reproduction in unicellular and multicellular organisms:

Question: A student is observing the temporary mount of a leaf peel under a microscope. Draw labelled diagram of the structure of stomata as seen under the microscope.
Answer: Structure of stomata as seen under a microscope:

Question. List four points of significance of reproductive health in a society. Name any two areas related to reproductive health which have improved over the past 50 years in our country. 
Answer :
Significance: prevent STDs, Advantage of small family,Less mortality among new borns, Reduces the cases of maternal mortality.
Areas which have improved:
(1) Family Planning,
(2) Decrease in STD cases (any other)

Question. (A) Name the human male reproductive organ that produces sperms and also secretes a hormone. Write the functions of the secreted hormone.
(B) Name the parts of the human female reproductive system where
(i) fertilisation takes place,
(ii) implantation of the fertilised egg occurs.
Explain how the embryo gets nourishment inside the mother’s body.

Answer :
(A) Testis: secrete male hormone – testosterone
Functions:
(i) formation of sperms,
(ii) development of secondary sexual characters.
(B) (i) fallopian tube / oviduct.
(ii) uterus.
(1) Placenta is a special disc like tissue embedded in the mother’s uterine wall and connected to the foetus / embryo.
(2) Placenta provides a large surface area for glucose and oxygen/ nutrients to pass from the mother’s blood to the embryo/ foetus.

Question. (A) Draw and explain the sectional view of human female reproductive system and label the parts.
(B) Why does menstruation occur?
Answer : (A) Human female reproductive system:
Female reproductive system consists of the following parts:

(1) A pair of Ovaries
(i) One on each side of uterus
(ii) Produce female sex cell (ovum/ova)
(iii) Secrete female hormones estrogen & progesterone

(2) Fallopian tube
(i) Exist in pairs, originating from uterus extending up to each ovary
(ii) Receives ovum from ovary

(3) Uterus
(ii) Pear-shaped muscular hollow structure
(ii) Foetus develops here
(4) Cervix
(i) Narrow lower part of uterus

(5) Vagina
(i) Tube like structure
(ii) Sperm discharge occurs here
(iii) Acts as birth canal
(B) When fertilization does not occur and embryo is not formed, the endometrium breaks down and bleeding start. This process ic alled menstruation.

Question. (A) What is the importance of DNA copying in reproduction?
(B) Draw a labelled diagram of the
longitudinal section of a flower.
Answer : (A) Importance of DNA copying in reproduction: Organisms look similar because their body designs are similar. Reproduction at its most basic level will involve making copies of the blueprints of body design.
The chromosomes in the nucleus of a cell contain information for inheritance of features from parents to next generation in the form of DNA (Deoxyribonucleic Acid) molecules. The DNA in the cell nucleus is the information source for making proteins and each specific type of protein leads to a specific type of body design. If the information is changed, different proteins will be made.
Different proteins will eventually lead to altered body designs. Therefore, it can be concluded that it is the DNA that gets transferred from parents to offspring and makes them look similar.
(B)

Question. (A) Write the names of those parts of flower which serve the same function as the following do in the animals.
(i) Testis (ii) Sperm
(iii) Ovary (iv) Egg
(B) Mention the changes a flower undergoes after fertilization.
(C) List two advantages of growing grapes or banana plants through vegetative propagation.
Answer : (A) Testis: Anther
In animals testis produces sperm whereas in plants anther produces pollen grains.
(B) Sperm: Pollen grains Sperm is male gamete in animals whereas pollen grain is male gamate in plants.(C) Ovary: Ovary
Ovary produces eggs in animals whereas ovary contains ovules in plants.
(D) Egg: Ovalouum
Embryo is formed when egg fuses with sperm after fertilization whereas ovalouum change/changes to zygote after the fusion of male gamete.
(E) Changes in a flower after fertilization:
(1) Zygote divides several times to forms an embryo within the ovule.
(2) The ovule develops a tough coat and changes into seed.
(3) Ovary grows rapidly and changes to form a fruit on ripening.
(4) Petals, sepals stamens, style and stigma may shrivel and fall off.
(F) Advantages of growing grapes or banana plants through vegetative propagation:
(1) Traits of parent plants are preserved.
(2) Grapes or banana plants donot produce viable seeds, vegetative propagation is advantageous.

Question. (A) What is the signification of reproductive health in a society?
(B) What is placenta? Explain its function is humAnswer : 
(C) How does the amount of DNA remain constant though each new generation is a combination of DNA copies of two individuals?
Answer : (A) Significance of reproductive helath in a society: (1) Individuals with good reproductive health produce better offsprings and they have better chances of survival.
(2) Knowledge of reproductive health prevents spread of sexually transmitted diseases.
(3) Unwanted pregnancies can be avoided.
(4) It helps to maintain the population and prevent population explosion.
(B) Placenta is a special tissue embedded in the uterine wall of female of contains villi on the embryo’s side of the tissue. The blood spaces are present on mother’s side and surround the villi.
Functions of placenta: The exchange of nutrients, oxygen and waste produce between the embryo and the mother takes place through the placenta.
(C) The essential part of reproduction is the DNA copying (formation of DNA copy).
Creation of additional cellular structure takes place along with the formation of a DNA copy. This process is followed by the division of a cell into two cells. So in this way, the amout of DNA remains constant through each new generation.

Question. Answer the following:
(A) What could be the reasons for adopting contraceptive methods?
(B) List three techniques that have been developed to prevent pregnancy. Which one of the technique is not meant for males.! Suggest one contraceptive technique which helps to prevent transmission of sexually transmitted disease. 
Answer : (A) Contraceptive methods are mainly adopted:
(1) To avoid unwanted pregnancies.
(2) To keep the population of a country under control.
(3) To limit the number of children a couple wants to have.
(4) To maintain adequate gap between two consecutive children.
(5) To prevent the transfer of sexually transmitted diseases.
(B) The techniques developed to prevent pregnancy are :
The various methods of contraception are described below:
(1) Mechanical barrier methods: Physicald evices such as condom, diaphragm and cervical caps which prevent the entry of sperm in the female genital tract during copulation are used.
(2) Surgical methods: A small protion of vas deferens in males and the fallopian tube in females is surgically removed or ligated (tied). It is called vasectomy in males and tubectomy in females.
(3) Chemical methods: Specific drugs are used by females which are of two types oral pills and vaginal pills. These pills change the hormonal balance of the body so that eggs are not released and fertilisation cannot take place.
(4) Intra uterine contraceptive devices (IUCD): IUCDs are placed in the uterus to prevent pregnancies. A copper-T is placed safely inside the uterus.

Question. (A) What is puberty?
(B) Describe in brief the functions of the following parts in the human male reproductive system:
(i) Testes
(ii) Seminal vesicle
(iii) Vas deferens
(iv) Urethra
(C) Why are testes located outside the abdominal cavity?
(D) State how sperms move towards the female germ cell. 
Answer : (A) Puberty: Puberty is the age at which the reproductive organs become functional, reproductive organs (gonads) start producing gametes and sex hormones and the boys and girls become sexually mature.
(B) Functions of various parts in the human male reproductive system.

(i) Testes: The testes are male gonads. Its functions are:
Regulate the formation of male gametes i.e. sperms To produce male sex hormone i.e. testosterone.
(ii) Seminal vesicle: The secretions of seminal vesicles (along with prostrate gland). provide nutrition to the sperms make the transport of sperms easier.
(iii) Vas deferens: The sperms formed in testes are carried through vas deferens to urethra.
(iv) Urethra: Urethra serves as a common passage for both the sperms and urine.
(C) Testes are located outside the abdominal cavity in scrotum in human male reproductive system because sperm formation requires a lower temperature than body temperature.
(D) Sperms formed in the testes moves towards vas deferens which unites with a tube coming from urinary bladder. Along the path of vas deferens, prostrate and seminal vesicle glands add their secretions which makes it easier for the sperms to move by penis into the vagina of females where they can meet the female germ cell in the fallopian tube.

Question. Angiosperms are commontry known as flowering plants. The flowering plants reproduce by sexual reproduction. The flowers enclose the reproductive organs’parts of a plant. Therefore, flowers are called the reproductive organs of plants. In most flowering plants like mustard, hibiscus etc.
The male and female reproductive parts are present in the same flower and these flowers are called bisexual flowers. There are other flowers in which either male or female organ is present as in papaya and watermelon and these flowers are called unisexual flowers.
(A) Identify a, b, c and d in the given diagram and write their names.
(B) What is pollination? Name the different types of pollination.
(C) Explain the process of fertilization in flowers.
Answer : (A) a represents the pollen grain b represents the pollen tube
c represents the ovary
d represents the female germ cell
(B) The transfer of pollen grains from the anther to the stigma of a flower is known as pollination. It is of two types:
Self-pollination: It is the transfer of pollen grains from the anther to the stigma of the same flower or another flower on the same plant.
Cross-pollination: It is the transfer of pollen grains from the anther to the stigma of the flower present on two different plants.
(C) Fertilisation occurs when the male gamete present in a pollen grain Joins with the female gamete or egg present in ovule.
When the pollen grain falls on the stigma of the carpel, it bursts open and grows a pollen tube downward through the style towards the female gamete in the ovary.
Here, zygote is formed which later grows into embryo. Zygote divides repeatedly to form an embryo within the ovule.
Ovule develops a thick coat and gradually forms seed. Ovary of flower develops and becomes a fruit.