Lesson: How do Organisms Reproduce

Question: 1

Asexual reproduction takes place through budding in _____________.

(a) Amoeba.

(b) Yeast.

(d) Leishmania.

Solution:

(b)

Question: 2

Which of the following is not part of the female reproductive system in human beings?

(a) Ovary

(b) Uterus

(d) Fallopian tube

Solution:

(c)

Question: 3

The anther contains:

(a) Sepals.

(b) Ovules.

(d) Pollen grains.

Solution:

(d)

Question: 4

What are the advantages of sexual reproduction over asexual reproduction?

Solution:

Sexual reproduction produces more variations. The newly formed individual has characteristics of both parents. Thus, evolution of new and complex species is possible because of sexual reproduction.

Question: 5

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

Solution:

Functions of testis:

· Produce sperms

· Produce a hormone called testosterone, which brings secondary sexual characters in boys.

Question: 6

Why does menstruation occur?

Solution:

In each ovulation cycle, an egg is released from an ovary and transferred to the fallopian tube. At the same time, the uterus prepares itself to receive a fertilized egg. Thus, the inner lining of the uterus thickens and is supplied with blood to nourish the embryo. If the egg does not fertilize, the lining of the uterus breaks down slowly, and gets released out through the vagina in the form of bleeding with blood, mucus and the discarded egg. This release unwanted particles through the vagina is called menstruation.

Question: 7

Draw a labelled diagram of the longitudinal section of a flower.

Solution:

Question: 8

What are the different methods of contraception?

Solution:

· Natural method

· Barrier method

· Chemical method

· Implants and surgical method

Question: 9

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

Solution:

Unicellular organisms always reproduce by asexual methods, such as binary fission, budding, etc. Multicellular organisms use both asexual and sexual methods. Simple organisms follow asexual methods of reproduction and other multicellular organisms follow sexual methods of reproduction.

Question: 10

How does reproduction help in providing stability to the population of a species?

Solution:

Reproduction helps in providing stability to the population of a species by producing a new individual that resembles their parents.

Every species on Earth has to constantly adopt in order to survive. The natural cycle of birth and death, natural predators and vagaries of nature continue to remove a large section of the population of a particular species. So, living organisms reproduce to replenish the lost section of their population.

Question: 11

What could be the reasons for adopting contraceptive methods?

Solution:

Contraceptive methods are mainly adapted to:

(i) Prevent unwanted pregnancies

(ii) Control population rise or birth rate

(iii) Prevent the transfer of sexually transmitted diseases

Lesson: How do Organisms Reproduce

Question: 1

In the list of organisms given below, those that reproduce by asexual method are:

(i) Banana

(ii) Dog

(iii) Yeast

(iv) Amoeba

(a) (ii) and (iv)

(b) (i), (iii) and (iv)

(d) (ii), (iii) and (iv)

Solution:

(b)

Question: 2

In a flower, the parts that produce male and female gametes (germ cells) are:

(a) Stamen and anther

(b) Filament and stigma

d) Stamen and style

Solution:

(c)

Question: 3

Which of the following is the correct sequence of events of sexual reproduction in a flower?

(a) Pollination, fertilisation, seedling, embryo

(b) Seedling, embryo, fertilisation, pollination

(d) Embryo, seedling, pollination, fertilisation

Solution:

(c)

Question: 4

Offspring formed by asexual method of reproduction have greater similarity among themselves because:

(i) Asexual reproduction involves only one parent

(ii) Asexual reproduction does not involve gametes

(iii) Asexual reproduction occurs before sexual reproduction

(iv) Asexual reproduction occurs after sexual reproduction

(a) (i) and (ii)

(b) (i) and (iii)

(d) (iii) and (iv)

Solution:

(a)

Question: 5

Characters transmitted from parents to offspring are present in:

(a) Cytoplasm

(b) Ribosome

(d) Genes

Solution:

(d)

Question: 6

Characters that are transmitted from parents to offspring during reproduction show:

(a) Only similarities with parents

(b) Only variations with parents

(d) Neither similarities nor variations

Solution:

(c)

Question: 7

A feature of reproduction that is common to Amoeba, Spirogyra and Yeast is that:

(a) They reproduce asexually

(b) They are all unicellular

(d) They are all multicellular

Solution:

(a)

Question: 8

In Spirogyra, asexual reproduction takes place by:

(a) Breaking up of filaments into smaller bits

(b) Division of a cell into two cells

(d) Formation of young cells from older cells.

Solution:

(a)

Question: 9

The ability of a cell to divide into several cells during reproduction in Plasmodium is called:

(a) Budding

(b) Reduction division

(d) Multiple fission

Solution:

(d)

Question 10

The correct sequence of reproductive stages seen in flowering plants is:

(a) Gametes, zygote, embryo, seedling

(b) Zygote, gametes, embryo, seedling

(d) Gametes, embryo, zygote, seedling

Solution:

(a)

Question: 11

The number of chromosomes in parents and offspring of a particular species remains constant due to:

(a) Doubling of chromosomes after zygote formation

(b) Halving of chromosomes during gamete formation

(d) Halving of chromosomes after gamete formation

Solution:

(b)

Question: 12

In Rhizopus, tubular thread-like structures bearing sporangia at their tips are called:

(a) Filaments

(b) Hyphae

(d) Roots

Solution:

(b)

Question: 13

Vegetative propagation refers to formation of new plants from:

(a) Stem, roots and flowers

(b) Stem, roots and leaves

(d) Stem, leaves and flowers

Solution:

(b)

Question: 14

Factors responsible for the rapid spread of bread mould on slices of bread are:

(i) Large number of spores

(ii) Availability of moisture and nutrients in bread

(iii) Presence of tubular branched hyphae

(iv) Formation of round shaped sporangia

(a) (i) and (iii)

(b) (ii) and iv)

(d) (iii) and (iv)

Solution:

(c)

Question: 15

Length of a pollen tube depends on the distance between:

(a) Pollen grain and upper surface of stigma

(b) Pollen grain on upper surface of stigma and ovule

(d) Upper surface of stigma and lower part of style

Solution:

(b)

Question: 16

Which of the following statements are true for flowers?

(i) Flowers are always bisexual

(ii) They are the sexual reproductive organs

(iii)They are produced in all groups of plants

(iv) After fertilisation, they give rise to fruits

(a) (i) and (iv)

(b) (ii) and (iii)

(d) (ii) and (iv)

Solution:

(d)

Question: 17

Which among the following statements are true for unisexual flowers?

(i) They possess both stamen and pistil

(ii) They possess either stamen or pistil

(iii) They exhibit cross pollination

(iv) Unisexual flowers possessing only stamens cannot produce fruits

(a) (i) and (iv)

(b) (ii), (iii) and (iv)

(d) (i), (iii) and (iv)

Solution:

(b)

Question: 18

Which among the following statements are true for sexual reproduction in flowering plants?

(i) It requires two types of gametes

(ii) Fertilisation is a compulsory event

(iii) It always results in formation of zygote

(iv) Offspring formed are clones

(a) (i) and (iv)

(b) (i), (ii) and (iv)

(d) (i), (ii) and (iv)

Solution:

(c)

Question 19

In the given figure, the parts A, B and C are sequentially:

(a) Cotyledon, plumule and radicle

(b) Plumule, radicle and cotyledon

(d) Radicle, cotyledon and plumule

Solution:

(c)

Question: 20

Offspring formed as a result of sexual reproduction exhibit more variations because:

(a) Sexual reproduction is a lengthy process

(b) Genetic material comes from two parents of the same species

(d) Genetic material comes from many parents

Solution:

(b)

Question: 21

Reproduction is essential for living organisms in order to:

(a) Keep individual organism alive

(b) Fulfil their energy requirement

(d) Continue the species generation after generation

Solution:

(d)

Question: 22

During adolescence, several changes occur in human body.

Mark one change associated with sexual maturation in boys:

(a) Loss of milk teeth

(b) Increase in height

(d) Weight gain

Solution:

(c)

Question: 23

In human females, an event that reflects onset of reproductive phase is:

(a) Growth of body

(b) Changes in hair pattern

(d) Menstruation

Solution:

(d)

Question: 24

In human males, testes lie in the scrotum, because it helps in the:

(a) Process of mating

(b) Formation of sperm

(d) All the above

Solution:

(b)

Question: 25

Which among the following is not the function of testes at puberty?

(i) formation of germ cells

(ii) secretion of testosterone

(iii) development of placenta

(iv) secretion of estrogen

(a) (i) and (ii)

(b) (ii) and (iii)

(d) (i) and (iv)

Solution:

(c)

Question: 26

The correct sequence of organs in a male reproductive system for transport of sperms is:

(a) Testis → Vas deferens → Urethra

(b) Testis → Ureter → Urethra

(d) Testis → Vas deferens → Ureter

Solution:

(a)

Question: 27

Which among the following diseases is not sexually transmitted?

(a) Syphilis

(b) Hepatitis

(d) Gonorrhoea

Solution:

(b)

Question: 28

In a bisexual flower in spite of young stamens being removed artificially, the flower produces fruit.

Provide a suitable explanation for the above situation.

Solution:

A flower produces fruit when the process of pollination and fertilisation take place. In absence of stamens, cross pollination can take place to facilitate fertilisation and formation of fruit.

Question: 29

Can you consider cell division as a type of reproduction in unicellular organism? Give one reason.

Solution:

Yes, because cell division results in the formation of two daughter cells, that is, it results in the production of more individuals of that organism.

Question: 30

What is a clone? Why do offspring formed by asexual reproduction exhibit remarkable similarity?

Solution:

An exact copy of something is called a clone. An offspring of an organism formed by asexual method of reproduction possess exact copies of the DNA of their parent. Hence, the offspring formed after asexual reproduction exhibit remarkable similarity.

Question: 31

Explain how, offspring and parents of organisms reproducing sexually have the same number of chromosomes?

Solution:

Gamete formation is the first step in sexual reproduction. Reduction division (meiosis) during gamete formation halves the chromosome number in both male and female gametes. When these two gametes fuse during fertilisation, the original number of chromosomes (as in the parent) becomes equal in the offspring. Therefore, the offspring and parents of organisms reproducing sexually have the same number of chromosomes.

Question: 32

Colonies of yeast fail to multiply in water, but multiply in sugar solution.

Give one reason for this.

Solution:

For all life processes, an organism requires nutrition.

Yeast gets inadequate nutrition in water which prevents its multiplication. On the other hand, yeast gets all the energy required for sustaining all life activities including reproductions in a sugar solution. Thus, colonies of yeast fail to multiply in water, but multiply in sugar solution.

Question: 33

Why does bread mould grow profusely on a moist slice of bread rather than on a dry slice of bread?

Solution:

Moisture is an important factor for the growth of hyphae. When compared to a dry slice of bread, the moist slice of bread offers much needed water to the spores of the bread mould. Hence, bread mould grows profusely on a moist slice of bread.

Question: 34

Give two reasons for the appearance of variations among the progeny formed by sexual reproduction.1

Solution:

The reasons for the appearance of variations among the progeny formed by sexual reproduction are:

(a) Gene proof of a progeny is contributed by two parents with different sets of characters

(b) The gene combinations are different in both male and female gametes.

Question: 35

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

Solution:

Yes, shaded part in Figures D and E represent the regenerated halves.

Question: 36

From the internet, gather information about the number of chromosomes present in five animals and five plants.

Correlate the number of chromosomes 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?

Solution:

(a) No, there is no relationship between size of an organism and its chromosome number.

(b) No, the process of reproduction is not dependent on the number of chromosomes. It depends on various factors like availability of nutrients, water, conductive environment and suitable mate.

(c) Yes, the major component of chromosome is DNA. If there are more chromosomes in a cell, the quantity of DNA will also be more.

Question: 37

In a tobacco plant, a male gamete has twenty-four chromosomes.

What is the number of chromosomes in a female gamete?

What is the number of chromosomes in the zygote?

Solution:

Number of chromosomes in a female gamete is 24.

Number of chromosomes in zygote is 48.

Question: 38

Why fertilisation cannot take place in flowers, if pollination does not occur?

Solution:

Fertilisation requires both male and female gametes. This can happen only when pollen grains are transferred to the stigma through any means of pollination. Hence, fertilization cannot take place in flowers if pollination does not occur.

Question: 39

Is the chromosome number of a zygote, an embryonal cell and an adult of a particular organism always constant?

How is the constancy maintained in these three stages?

Solution:

Yes, the chromosome number of a zygote, an embryonal cell and an adult of a particular organism is always constant.

The constancy is maintained because cells in all these three structural phases undergo only mitotic divisions.

Question: 40

Where is the zygote located in a flower after fertilization?

Solution:

After fertilization, zygote is located, inside the ovule present inside the ovary.

Question: 41

Reproduction is linked to stability of population, of a species.

Justify the statement.

Solution:

Every species on Earth has to constantly struggle for its survival. The natural cycle of birth and death, natural predators and vagaries of nature will continue to remove a large section of population of a particular species. So, living organisms reproduce to replenish the lost section of their population. Thus, reproduction helps in providing stability to the population of a species by producing new individuals that resembles their parents.

Question: 42

How are general growth and sexual maturation different from each other?

Solution:

General growth refers to the growth, where body parts become larger. Examples: Increase in height, weight gain, changes in shape and size of the body.

Sexual maturation: These are certain changes that occur when one attains a certain age. In human beings, this starts at an early age, $—$ teenage years. These changes are signs of one gaining more sexual maturity like the ability to reproduce. Examples: Cracking of voice, new hair patterns, development of breast in females etc.

Question: 43

Trace the path of sperms during ejaculation and mention the gland and their functions associated with the male reproductive system.

Solution:

Sperms come out from testes into the vas deferens, and then passes through urethra before ejaculation.

The secretion from seminal vesicles adds fluid content to the semen, which lubricates the sperms and provides a fluid medium for easy transport of sperms.

The prostate gland makes the medium of semen alkaline.

Question: 44

What changes are observed in the uterus if fertilisation does not occur?

Solution:

The thick and spongy lining of the uterus slowly breaks and comes out along with blood, mucus, and the discarded egg.

Question: 45

What changes are observed in the uterus subsequent to implantation of young embryo?

Solution:

Once the zygote is implanted in a uterine wall, the uterine wall thickens. So that it gives support to the growing embryo. It is richly supplied with blood to provide nourishment to the embryo. A special tissue called placenta develops and it connects the embryo to the uterine wall to provide nutrients and oxygen to the embryo.

Question: 46

What are the benefits of using mechanical barriers during sexual act?

Solution:

Benefits of using mechanical barriers:

a) It prevents sperms from reaching the egg. Thus, it helps avoiding unwanted pregnancy.

b) A condom on a penis or similar covering worn in a vagina, and used as mechanical barriers also prevents transfer of sexually transmitted diseases.

Question: 47

In the given figure label the parts and mention their functions:

(a) Production of egg

(b) Site of fertilisation

(d) Entry of the sperms

a) Ovary (production of egg)

b) Oviduct (site of fertilisation)

c) Uterus (site of implantation)

d) Vagina (entry of the sperms)

Question: 48

What would be the ratio of chromosome number between an egg and its zygote? How is the sperm genetically different from the egg?

Solution:

The ratio is 1:2. Sperms are genetically different from an egg in a way that it contains either X or Y chromosome whereas an egg always carries X chromosome.

Question: 49

Why are budding, fragmentation and regeneration considered as asexual types of reproduction?

With a neat diagram explain the process of regeneration in a Planarian.

Solution:

Budding, fragmentation and regeneration are considered as asexual types of reproduction because only one parent carries out the process of reproduction and gamete formation does not happen during this mode of reproduction.

The following diagram shows the regeneration in a Planarian:

When the body of a Planarian is cut off into several parts, each part regenerates its complimentary part to develop a new individual.

Question: 50

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

Solution:

Asexual Reproduction	Sexual Reproduction
Involves only one parent	Often involves two parents
Gametes are not produced	Gametes are produced
No fertilisation and zygote formation	Fertilisaton and zygote formation is observed.

Reason for variations in offspring produced by sexual reproduction:

During sexual reproduction, two sets of genes are contributed by different parents. This brings different sets of characters in the offspring.

Question: 51

Distinguish between pollination and fertilisation.

Mention the site and product of fertilisation in a flower.

Draw a neat, labelled diagram of a pistil showing pollen tube growth and its entry into an ovule.

Solution:

Pollination: Transfer of pollen grains from anther to stigma is termed as pollination. It is a physical process in which pollen grains move due to certain physical factors such as air, water, birds or some insects.

Fertilisation: Fusion of male and female gametes is termed fertilization. The site of fertilisation is ovule. The product of fertilisation is zygote.

The following diagram shows fertilisation in a plant:

Question: 52

Distinguish between a gamete and zygote.

Explain their roles in sexual reproduction.

Solution:

Gamete: It is a sex or germ cell that takes part in fertilization. There are two types of gametes $—$ male and female.

Zygote: The fertilisation of male and female gametes leads to the formation of zygotes. It is the first cell of a new generation.

Role of gamete in sexual reproduction:

Gamete formation results in halving of number of chromosomes. This is necessary to maintain the number of chromosomes in an organism that reproduces sexually.

Role of zygote in sexual reproduction:

Zygote formation makes the number of chromosome equal to the somatic cells. Further, it is the zygote which undergoes mitosis to develop into an embryo and subsequently into a new individual.

Question: 53

Draw diagram of a flower and label the four whorls.

Write the names of gamete producing organs in a flower.

Solution:

Male gamete forming part: anther/stamen

Female gamete forming part: pistil/ovary/ovule

Question: 54

What is placenta? Mention its role during pregnancy?

Solution:

Placenta is a tissue that connects embryo to the uterine wall. It is a disc-like structure which is embedded in the uterine wall. Placenta contains villi on the embryo’s side of the tissue, and blood spaces on mother’s side surrounding the villi. Placenta works as a channel between the mother and the embryo and provides nutrients and oxygen to the embryo. This also provides a large surface from mother to the embryo and waste products from embryo to mother.

Question: 55

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

Solution:

The various ways to avoid pregnancy are:

(i) Mechanical barriers

(ii) Drugs (as pills)

(iii) Loop or copper T

(iv) Surgical method

Copper-T: Copper-T is in the shape of ‘T’ and is made of copper. Copper-T makes a barrier at the opening of the fallopian tubes in the uterus and thus prevents sperms from entering the fallopian tubes and prevents fertilization.

Question: 56

How does fertilisation take place? Fertilisation occurs once in a month. Comment.

Solution:

During the ovulation cycle, one egg is released by either of the two ovaries and it reaches the fallopian tube. During sexual intercourse, sperms enter through the vaginal passage. Sperms are highly active and mobile and thus move up through cervix into the uterus. From there, it reaches the fallopian tube. Millions of sperms are released into the vagina at one time, but only one sperm encounters the egg in the fallopian tube and fertilization takes place.

Since only one egg is released in a single ovulation cycle and ovulation cycle happens once in a month, therefore, fertilisation occurs once in a month.

Question: 57

Reproduction is essentially a phenomenon that is not for survival of an individual but for the stability of a species. Justify.

Solution:

All organisms on Earth need energy for survival and growth. This energy is obtained from life processes such as nutrition and respiration. Compared to these life processes, reproduction needs a lot of energy. Reproduction helps in the production of new individuals of its own kind. During reproduction, genetic material is transferred from one generation to the next through DNA copying, with high constancy and considerable variations. Variations are important for maintaining features that allow an organism to survive in the changing environment. Therefore, reproduction is essential for the stability of a species and for the survival of an individual.

Question: 58

Describe sexually transmitted diseases and mention different ways to prevent them.

Solution:

A disease that can be transmitted through sexual contact is called sexually transmitted disease or STD. This includes bacterial infections such as gonorrhoea and syphilis and viral infections like HIV.

Some of the ways to prevent STDs are as follows:

• Being faithful to one’s life partner.

• Avoiding sexual contact with unknown person.

• Using condom during sexual intercourse.

• Maintaining personal hygiene.

Lesson: How do Organisms Reproduce?

Question: 1

What is the importance of DNA copying in reproduction?

Solution:

Chromosome contains information in DNA for inheritance of features from parent to next generation. For an organism to produce its own kind, it becomes necessary that the offspring should get DNA that is similar to the parents. DNA replication is a way through which a cell makes additional copies of DNA so that they can be transferred to the next generation. So, DNA copying is an essential part of the process of reproduction.

Question: 2

Why is variation beneficial to the species but not necessarily for an individual?

Solution:

Variations are beneficial to a species as variations help the species to adapt according to changes in external environment. So, whenever there is a change in external environment, species ensure required changes to ensure continuity of its life.

However, these variations may not happen in all organisms of the same species.

For example, if the temperature of water increases suddenly, then most of the bacteria living in that water may die. A few bacteria that are more resistant to heat would be able to survive. However, in the absence of these variants, the entire species of bacteria would have been destroyed. Thus, these variants help in the survival of a particular species. However, all variations are not necessarily beneficial for an individual organism as not all individuals survive.

Question: 3

How does binary fission differ from multiple fission?

Solution:

In binary fission, a single cell divides into two equal halves.

Example: Amoeba and Bacteria divide by binary fission.

In multiple fission, a single cell divides into many daughter cells simultaneously. Example: Plasmodium divides by multiple fission.

Question: 4

How will an organism be benefited if it reproduces through spores?

Solution:

Advantages of spore formation:

· Large numbers of spores are produced in one sporangium.

· Spores can easily spread through water, air or animals and thus is good for the spread of an organism to more places.

· Spores are covered by thick walls to prevent dehydration under unfavourable conditions. So, a spore can remain dormant till favourable condition become available.

Question: 5

Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?

Solution:

The process of regeneration in simple organisms involves the formation of new organisms from its body parts. Simple organisms can utilize this method of reproduction as their entire body is made of similar kind of cells in which any part of their body can be formed by growth and development.

On the other hand, in complex organisms are made up of different tissues and organs each having different structures. These organ systems of a complex body, work together as an interconnected unit and perform different functions. Through regeneration, different organs can redevelop certain body parts such as muscles, blood, etc. but not new individuals.

Question: 6

Why is vegetative propagation practised for growing some types of plants?

Solution:

Vegetative propagation is practised for growing some types of plants for the following reasons.

a) It is useful to grow plants for which viable seeds are not formed or very few seeds are produced.

b) It is a rapid and cheaper method of propagation.

c) It helps to introduce plants in new areas where seed germination fails to produce mature plant due to changes in environmental factors and soil.

d) It is useful to develop different traits of a species of the same plant.

Question: 7

Why is DNA copying an essential part of the process of reproduction?

Solution:

Chromosome contains information in DNA for inheritance of features from parent to next generation. For an organism to produce its own kind, it becomes necessary that the offspring should get DNA similar to their parents. DNA replication is a way through which a cell makes additional copies of DNA so that they can be transferred to the next generation. So, DNA copying is an essential part of the process of reproduction.

Question: 8

How is the process of pollination different from fertilisation?

Solution:

Pollination: Transfer of pollen grains from the anther to the stigma is termed pollination. It is a physical process in which pollen grains move due to certain physical factors such as air, water, birds or some insects.

Fertilisation: Fusion of male and female gametes is termed fertilization. The site of fertilisation is ovule. The product of fertilization is zygote.

Question: 9

What is the role of the seminal vesicles and the prostate gland?

Solution:

The secretion from seminal vesicles adds fluid content to the semen, which lubricates the sperms and provide a fluid medium for easy transport of sperms.

The prostate gland makes the medium of semen alkaline.

Question: 10

What are the changes seen in girls at the time of puberty?

Solution:

Changes seen in girls at the time of puberty are as follows:

· Voice becomes thin

· Increase in breast size

· Hair growth under armpit and in pubic area

· Beginning of menstrual cycle

· Increase in the size of uterus and ovary

Question: 11

How does an embryo get nourishment inside a mother’s body?

Solution:

After fertilization, a zygote is implanted in the uterine wall. The lining of the uterine wall thickens to give support to the growing embryo. It is richly supplied with blood to provide nourishment to the growing embryo. A special tissue called placenta develops and connects the embryo to the uterine wall to provide nutrients and oxygen to the embryo. Placenta contains villi on the embryo’s side of the tissue, and blood spaces on mother’s side surrounding the villi. This provides a large surface from mother to the embryo and waste products from embryo to mother.

Question: 12

If a woman is using a copper-T, will it help in protecting her from sexually transmitted diseases?

Solution:

No. Copper-T will not prevent the contact of body fluids. Therefore, it will not protect her from sexually transmitted diseases.

Questions

Q1	Name two types of asexual reproduction.

Q2	What are the special spore-bearing organs in moulds called?

Q3	What is the transfer of pollen grains from the anthers of the stamens to the stigma of a carpel called?

Q4	What is another name for sex cells?

Q5	Name the process by which an entire adult forms from an amputated fragment of a planaria.

Q6	Name the male reproductive part of a flower.

Q7	What are the two main types of reproduction in living organisms?

Q8	How does hydra reproduce?

Q9	What are the various man-made methods of artificial propagation?

Q10	Define fertilization.

Q11	What is germination?

Q12	Which period is referred to as the gestation period?

Q13	Name four STDs.

Q14	Name the female sex hormones that cause changes in girls.

Q15	Differentiate between asexual and sexual reproduction. What are the advantages of sexual reproduction?

Q16	What are the advantages of vegetative propagation?

Q17	What is menstruation?

Q18	Describe the reproductive system in human beings.

Q19	Why is reproduction essential for a species? How do variations help genera to evolve?

Q20

What are the various reasons for the adoption of birth control procedures? What are those?

Questions

Q1	Name two types of asexual reproduction.

A1	Binary fission and fragmentation are the two types of asexual reproduction.

Q2	What are the special spore-bearing organs in moulds called?

A2	The special spore-bearing organs in moulds are called sporangia.

Q3	What is the transfer of pollen grains from the anthers of the stamens to the stigma of a carpel called?

A3	The transfer of pollen grains from the anthers of the stamens to the stigma of a carpel called pollination.

Q4	What is another name for sex cells?

A4	Another name for sex cells is gametes.

Q5	Name the process by which an entire adult forms from an amputated fragment of a planaria.

A5	The process by which an entire adult forms from an amputated fragment of a planaria is known as regeneration.

Q6	Name the male reproductive part of a flower.

A6	Stamen is the male reproductive part of a flower.

Q7	What are the two main types of reproduction in living organisms?

A7	Asexual and sexual are the two main types of reproduction in living organisms.

Q8	How does hydra reproduce?

A8	Hydra multiplies by budding under favourable conditions. 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 mature, detach from the parent body and become new independent individual.

Q9	What are the various man-made methods of artificial propagation?

A9	The various man-made methods of artificial propagation are cutting, layering and grafting.

Q10	Define fertilization.

A10	The fusion of male and female gametes producing zygote is called fertilization.

Q11	What is germination?

A11	Germination is the process which involves the emergence of a plant from the seed when proper temperature, humidity and sunlight are provided.

Q12	Which period is referred to as the gestation period?

A12	The period during which the embryo development takes place in the uterus is called gestation period. The development of the child inside the mother’s body takes around nine months.

Q13	Name four STDs.

A13	Some sexually transmitted diseases or STDs are AIDS (Acquired Immune Deficiency Syndrome), gonorrhea, syphilis and genital herpes.

Q14	Name the female sex hormones that cause changes in girls.

A14	Oestrogen and progesterone are the female sex hormones that cause changes in girls.

Q15	Differentiate between asexual and sexual reproduction. What are the advantages of sexual reproduction?

A15

Differences between asexual and sexual reproduction are:

Asexual Reproduction	Sexual Reproduction
It is uniparental, that means only one parent is involved to form an offspring.	It is generally biparental, that means two parents, one male and one female are involved to give rise to an offspring
It does not involve formation and fusion of gametes and undergoes only mitotic divisions.	It involves meiosis during formation and fusion of gametes.
It does not lead to variations.	It gives rise to variations.
It generally occurs in unicellular organisms, plants and sponges, like hydra.	It occurs in higher animals which are multicellular and well developed.
The offspring are genetically similar to parents and are exact replicas of parents, and so can be called clones.	The offspring are genetically different from the parents and are not exact replicas.
This way leads to rapid production of large number of young ones.	This way is of less rapid increase in number.

Advantages of sexual reproduction:

→ Sexual reproduction is beneficial to organisms in fluctuating physical environments.

→ In sexual reproduction, more variation is ensured, leading to the advantage of survival of more species

in a population due to increase in their efficiency.

→ The newly formed individual inherits characteristics of both the parents.

→ Variations are more likely in sexual mode than in asexual one because in asexual reproduction, DNA

has to perform inside the inherited cellular apparatus.

Q16	What are the advantages of vegetative propagation?

A16

The advantages of vegetative propagation are as follows:

(a) It is much simple and unproblematic, cost effective, a quicker method comparedto sexual reproduction.

(b) Plants which produce non-viable seeds or too few seeds or have altogether lost the ability to produce

seeds too can be made to reproduce through vegetative propagation, to produce another plant.

the features of the parent plant.

Q17	What is menstruation?

A17

Menstruation is a feature which is unique to humans and some primates.

In the females, during each ovulation cycle, the uterus grooms itself in expectancy of a possible pregnancy. Due to this, the uterine wall develops an additional lining. When the egg is not fertilized, along with the egg, the additional lining in the uterine wall too break up. The fragments of disintegrated tissues are shed along with blood. This is observed in the form of bleeding through the vagina which can last from 4 to 6 days. The whole order of events during an ovulation cycle is called menstrual cycle. The bleeding which occurs for a few days is called menstruation. The first menstrual flow is called menarche and the last menstrual flow (which happens at the age of late 40s in females) is called menopause.

Q18	Describe the reproductive system in human beings.

A18

The male reproductive system in human beings is composed of following parts:

Scrotum, a skin pouch contains a pair of testes suspended outside the body, below the abdominal cavity, in order to maintain the temperature of testes, which should ideally be below the body temperature, necessary for most favourable condition for sperm production. Testes primarily serves the function of production of male gamete called sperm and also manufactures the male hormone testosterone, which is liable for developing certain secondary sexual characters in boys.

The tube which carries sperms to the seminal vesicle, where sperms are stored, is the vas deferens. Secretions from the seminal vesicle and prostate gland add up to make the semen.

Penis is a muscular organ which performs the genitor-urinary functions. The urethra works as the common passage for urine as well as for sperm emission.

The female reproductive system in human beings is composed of the following parts:

A pear-shaped hollow muscular organ called uterus is where the embryo gets implanted and develops into a new-born baby. The wall of the uterus provides protection and nutrition to the growing foetus.

A fallopian tube comes out from each side at the top of the uterus and end in finger-like structures called fimbriae. Fertilization takes place in the fallopian tube.

There are two ovaries; one nears each fallopian tube respectively. Ovary produces the eggs or the female gametes. When the female child is still in the womb, all the eggs are produced by the ovary. One egg matures in each ovulation cycle and is released from the ovary. The egg is trapped by the fimbriae and passed on to the fallopian tube.

The cervix, which is the mouth of the uterus, opens into the vagina which is a muscular tube-like organ which acts as the passageway for the sperms and also as the canal during the child birth.

Q19	Why is reproduction essential for a species? How do variations help genera to evolve?

A19

Reproduction is essential for species in order to increase their numbers otherwise it will be wiped out.This is the only way for a living being to prolong its lineage. Apart from being important for a particular individual, reproduction is also important for the whole ecosystem. Reproduction helps in sustaining a proper balance among various biotic constituents of the ecosystem. Moreover, reproduction also aids in evolution because variations come through reproduction, over a number of generations. In sexual reproduction, the offspring obtains sets of genes from two different individuals. This leads to subtle variation through successive generations. Variations are better for a species rather than an individual because the variations facilitate the organism to survive adeptly in varying settings of natural environments. When these variations are passed to many organisms of same species it helps the new species to originate, as variations occur in their DNA which is the genetic material and controls total metabolism.

Q20	What are the various reasons for the adoption of birth control procedures? What are those?

A20

Birth control procedures are mainly adopted because of the following reasons:

• to stay away from unwanted pregnancies

• To control population rise

• To prevent the transfer of sexually transmitted diseases.

The contraceptive methods can be broadly divided into the following types:

• Natural method: It is regarded that not having sex is a natural method of birth control, It means keeping away from the chances of meeting of sperms and ovum, by stay away from the sexual act.

• Barrier method: In this method, the fertilization of ovum and sperm is barred physically with the help of barriers by preventing sperm from entering the uterus. . Condoms are barriers, available for both males and females, made of thin rubber, that are used to cover penis in males and vagina in females.

• Oral contraceptives: In this method, tablets or drugs are taken orally, which contain small hormonal doses that change the hormonal balance of the body so that eggs are not released and thus fertilisation cannot occur.

Implants and surgical methods: Contraceptive devices such as the loop or copper-T are placed in uterus to avoid pregnancy. Some surgical sterilizations can also be used to block the gamete transfer. It includes the blocking of vas deferens to prevent the transportation of sperms. Similarly, fallopian tubes of the female can be blocked so that the egg will not get through to the uterus. Surgery can also be used to prevent for removal of unwanted pregnancies.

How do Organisms Reproduce cbsc class 10th F

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