7. How do Organisms Reproduce

DNA (Deoxyribonucleic Acid) :- DNA is present in chromosomes, chromosomes are present in nucleus and nucleus is present in a cell. The individuals produced by reproduction are similar to each other and their parents . This similarity occurs because of DNA. One of the basic events in reproduction is the creation of a DNA copy. Errors in DNA copying are a source of variations in populations of organisms.

Importance of variation : Variation ensures species can survive during unfavourable conditions.

Reproduction : The production of new organisms from the existing organisms of the same species is known as reproduction.

In the process of reproduction, the existing organisms are called parents and new organisms produced by them are called offspring.

Reproduction is essential for the survival of a species

Types/Mode of Reproductions:

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

Modes of Asexual Reproduction

1. Fission : Fission is a process by which a unicellular organism splits to form two or more daughter cells.

There are two types of fission

(i) Binary fission : In binary fission the cell splits into two daughter cells during cell division.

Ex. Bacteria, Protozoa, Amoeba, Leishmania

Binary fission in amoeba can take place in any plane while binary fission in leishmania (which cause kala-azar) take place in a definite orientation.

(ii) Multiple fission : In Multiple fission the cell splits into many daughter cells during cell division.

Ex. - Malarial parasite( Plasmodium)

2. Fragmentation : Fragmentation is a form of asexual reproduction in which an simple multi-cellular organism breaks into multiple fragments or smaller parts on maturation and these pieces or fragments grow into new organism.

Ex.- Spirogyra

3. Regeneration : The ability to give rise to new organism from the body parts of the parent organism is called regeneration.

Ex. - Hydra and Planaria

4. Budding : Budding is an asexual reproduction method in which a new organism develops from a bud of an existing organism.

Ex. - Yeast, Hydra

Budding : A bud develops as an outgrowth due to repeated cell division at one specific site of hydra. These buds develop into tiny individuals and when fully mature, detach from the parent body and become new independent individuals.

In Hydra, a bud develops 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 individuals.

5. Vegetative Propagation : Vegetative propagation is the asexual mode of reproduction in which any Vegetative parts of plant body like the root, stem and leaves develop into new plants under appropriate conditions.

Ex. - Root - Dahlia, Stem- Patoto Leaf - Bryophyllum

Advantages of vegetative propagation.

(i) The vegetative propagation is used in methods such as layering or grafting to grow many plants for agricultural purposes.

(ii) Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds.

(iii) Such methods also make possible the propagation of plants that have lost the capacity to produce seeds.

(iv)All plants produced by vegetative propagation are genetically similar enough to the parent plant to have all its characteristics.

(v) Spore Formation : In spore formation, the parent plant produce hundred of microscopic reproductive unit called spores. Spores are microscopic asexual reproductive unit which are covered by thick walls that protect them until they come into contact with moist surface. Under suitable conditions, these spores germinate to form a new plant.

Ex.- Rhizopus (fungus).

Rhizopus body is made up of thread like structures called hyphae.They are not reproductive parts. A sac-like structure at the tips of hyphae is called sporangium. Sporangium contain reproductive structures called spores which develop into new Rhizopus.

Sexual Reproduction : The process of production of new organism from two parents by using sex cells (called gametes) is called sexual reproduction.

The important features of sexual reproduction

(i) It involves two parents of different sexes.

(ii) Each parent produces different reproductive units called gametes.

(iii) The motile germcell is called the male gamete and the germ-cell containing the stored food is called the female gamete.

(iv) The gametes are haploid and are produced as a result of meiotic division.

(v) The fusion of two gametes (male and female) results in the formation of a single celled diploid zygote.

Sexual Reproduction in Flowering Plants.

Bisexual flowers : Plants that have both male (stamens) and female(pistil) reproductive organs in the same flower are known bisexual flowers. Ex.- Hibiscus, mustard

Unisexual flowers : Plants that have either male(stamens) or female(pistil) reproductive parts in a flower are known unisexual flowers. Ex.- Papaya, Watermelon.

The reproductive parts of angiosperms are located in the flower.

Different parts of flower

(i) Sepals (ii) petals (iii) stamens (iv) pistil.

Stamen : Stamen is the male reproductive part and it produces pollen grains. The long part of stamen called the filament, and the terminal bilobed structure called the anther.

Pistil : Pistil is the female reproductive part of a flower. It is made of three parts.

1. Ovary : It contains ovules and each ovule has an egg cell.

2. Style : It is the middle part of pistil which helps in the attachment of stigma to the ovary.

3. stigma : It is the terminal part of pistil which helps in receiving the pollen grains during pollination.

Pollination : Transfer of pollen grains from the anther of the stamen to the stigma of a flower is called pollination .

This transfer of pollen from one flower to another is achieved by agents like wind, water or animals.

Self pollination : Transfer of pollen grains from the stamen of a flower to the stigma of same flower is called self pollination.

Cross pollination : Transfer of pollen grains from the stamen of a flower to the stigma of another flower is called cross pollination.

The pollen grain germinates on the stigma to produce a pollen tube. Pollen tube travels through the style to reach the ovary. The male germ-cell produced by pollen grain fuses with the female gamete present in the ovule. By fusion of the gametes form the zygote

Pollination

Fertilisation : fertilisation is the process of fusion of male germ cells with the female gametes.

After fertilisation, the zygote divides many times and forms an embryo within the ovule. The ovule develops a tough coat and converted into a seed. The seed contains the future plant or embryo which develops into a seedling under suitable conditions.

Germination : The process of development of the new plant from the embryo present inside the seed is called seed germination.

Reproduction in Human Beings

PUBERTY : The age at which 'sex hormones ' are produced and a boy or a girl becomes sexually mature is called puberty.

Changes in the boys during puberty:

(i) Thick hair growing in armpits and the genital area

(ii) The skin becomes oily and we might begin to develop pimples.

(iii) Growth of moustache, beard on face.

(iv) The voice begin to crack.

(v) Body becomes more muscular due to the development of muscles.

Changes in the girls during puberty:

(i) Thick hair growing in armpits and the genital area.

(ii) The breast size begins to increase and skin of the nipples begins to darken.

(iii) Menstruation starts in girls

(iv) The skin becomes oily and we might begin to develop pimples.

(v) Extra fat is deposited in various parts of the body like hips and thighs.

Secondary sexual characters : The physical characters which develop during puberty and distinguish a male from female are called secondary sexual characters.

Male Reproductive System

Testis : Testis are located outside the abdominal cavity in scrotum because sperm formation requires a lower temperature than the normal body temperature. The testes are responsible for making male sex hormone, (testosterone) and for generating sperm

Vas deferens: The vas deferens is a long, muscular tube that travels from the epididymis to just behind the bladder. The vas deferens transports mature sperm to the urethra.

Urethra : The urethra forms a common path for both the sperms and urine.

Prostate Gland and seminal Vesicle : Secretions of these glands make transport easier for the sperm. This fluid provides nutrition.

Female Reproductive System

Ovaries : Ovaries are the primary female sex organs that produce the female gamete (egg) and estrogen and progesterone hormones

Oviduct (fallopian tube) : It carries egg from ovary to uterus . It is the site of fertilisation.

Uterus : The two oviducts unite into an elastic bag-like structure known as the uterus. The growth and development of embryo takes place in uterus

Vagina : The uterus opens into the vagina through the cervix.

Fertilisation

The sperms enter through the vaginal passage during sexual intercourse. They travel upwards and reach the oviduct where they encounter the egg. Fertilization takes place in the fallopian tube.

The fertilised egg (zygote) starts dividing and form an embryo.

The embryo is implanted in the lining of the uterus. The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. This is a disc which is embedded in the uterine wall. Placenta forms finger - like projections called villi towards embryo .

Placenta helps in transporting glucose and oxygen from the mother to the embryo.

Placenta removes waste generated by the embryo by transferring it to the mother’s blood. The development of the child inside the mother's body takes approximately nine months in human .

Menstruation : The ovary releases one egg every month , the uterus also prepares itself every month to receive a fertilised egg . Thus , its lining becomes thick and spongy. If egg is not fertilised the lining slowly breaks and comes out through the vagina as blood and mucous. This cycle takes place roughly every month and is known as menstruation . It usually lasts for about two to eight days.

Reproductive Health

Reproductive Health includes sexual health and satisfying sexual life and a healthy capability to reproduce.

Sexually transmitted desease. Diseases that spread through the sexual contact are called sexually transmitted diseases .

Ex.- AIDS (Acquired Immuno Deficiency syndrome)

Gonorrhoea

Syphilis

Using a condom during sex helps to prevent transmission of these diseases.

Birth Control

(i) Barrier methods: Physical devices such as condoms used by men and diaphragms (caps) used by women act as a mechanical barrier and prevent sperm from meeting the ovum.

(ii) Chemical Method : In the chemical methods of preventing pregnancy, the females use oral pills. Oral pills change the hormonal balance of the body so that eggs are not released. they can cause side-effects too.

(iii) Loop or the copper-T /Intrauterine Contraceptive Device (IUCD) : Copper-T is placed in the uterus to prevent pregnancy . It can cause side effect due to irritation of the uterus.

(iv) Surgical method : Vasectomy in males and Tubectomy in females are surgical methods of prevent pregnancy. In both cases fertilisation not take place.

Organisms have a varied body design. Name the property which gives the basic difference in body design.
Errors in DNA copying (variations).
When a cell reproduces, what happens to its DNA?
When a cell reproduces,its DNA is copied and passed to the offspring.
Name the method by which Plasmodium reproduce under favourable conditions.
Multiple Fission.
Name two simple organisms having the ability of regeneration.
Planaria and hydra
Name the life process of an organism that helps in the growth of its population.
Reproduction.
Name the method by which Spirogyra reproduce under favourable conditions.
Fragmentation.
Mention any four ways of asexual reproduction.
(i) Fission (ii) Budding (iii)Spore formation (iv)Fragmentation (v) Regeneration
Name the method by which Planaria reproduce under favourable conditions.
Regeneration.
Name the causative organism of the disease “Kalaazar” and its mode of asexual reproduction.
Leishmania, Mode of asexual reproduction- Binary fission.
Name the type of cells which undergo regeneration.
Specialised cells or Regenerative cells
How does the embryo gets nourishment from the mother?
Through placenta
Mention one function of vagina
The sperms enter through the vaginal passage during sexual intercourse.
Write the full form of AIDS
Acquired Immuno Deficiency syndrome
What is meant by DNA copying?
A process in which a DNA molecule produces two similar copies of itself in a reproducing cell through chemical reaction is a called DNA copying.
(i) What is the location of the following: (a) DNA in a cell (b) Gene
(ii) Expand DNA.
(i) (a) DNA located in Nucleus. (b) Gene located on the chromosomes.
(ii) Deoxyribo Nucleic Acid.
What is the effect of DNA copying, which is not perfectly accurate, on the reproduction process?
DNA copying which is not perfectly accurate leads to more variations in the offspring.
What is the advantage of reproducing through spores?
Spores are covered by thick walls that protect them until they come into contact with moist surface.
What is reproduction?
The production of new organisms from the existing organisms of the same species is known as reproduction.
‘Regeneration is not reproduction’. Justify this statement with reason.
Regeneration is not the same as reproduction, since most organisms would not normally depend on being cut up to be able to reproduce.
Regeneration is not possible in all types of animals. Why?
Regeneration is carried out by specialised cells. Therefore, regeneration occurs only in those organisms which have these cells.
Mention the endocrine and exocrine function of testes.
Endocrine function: Secretion of male hormone (testosterone).
Exocrine function: formation of male gametes (sperms).
Mention the function of prostate gland and seminal vesicles.
Secretion of prostate gland and and seminal vesicles make transport easier for the sperm and provides nutrition.
Why are the testes located outside the abdominal cavity?
Testis are located outside the abdominal cavity in scrotum because sperm formation requires a lower temperature than the normal body temperature.
List two functions performed by testis in human beings.
(i) Production of sperms.
(ii) Secration of male sex hormone, testosterone.
Why is temperature of scrotal sac 2°C less than the body temperature?
Because testes require temperature 2°C less than the body temperature for the production of sperms.
Write the function of Uterus s in human female reproductive system
(i) Implantation of zygote or embryo.
(ii) Nutrition (nourishment) of the developing embryo.
List two functions of ovary of human female reproductive system.
(i) Production of the female gamete (egg)
(ii) Secretion of estrogen and progesterone hormones
Mention the functions of fallopian tube in the human female reproductive system.
(i) It carries egg from ovary to uterus .
(ii) It is the site of fertilisation.
Why does the lining of uterus become thick and spongy every month?
To receive and nurture the growing embryo (fertilised egg), lining of uterus become thick and spongy.
Differentiate between pollen grain and ovule.
Pollen grains contain male gametes and ovules contains female gametes in plants.
What happens if egg is not fertilized?
If egg is not fertilised the lining slowly breaks and comes out through the vagina as blood and mucous. This is known as menstruation.
What is the function of copper-T used by some women? What is its effect?
Copper-T prevents pregnancy . It can cause side effect due to irritation of the uterus.
List two functions of ovary of human female reproductive system.
(i) Production of the female gamete (egg)
(ii) Secretion of estrogen and progesterone hormones.
List any two reasons why the Government has banned prenatal sex determination by law.
(i) It promots sex-selective abortion/female foeticide
(ii) It affects male female ratio in society
“Variations” are seen in the organisms. State the two main causes of variation.
Variations are caused by:
(i) Change in the genetic material at the time of DNA copying.
(ii) Mutations.
(i) State the role of DNA in the cell nucleus,
The DNA in the cell nucleus is the information source for making proteins.
(iii) What will be the after effect if the information of the DNA is changed.
If the information of the DNA is changed, different proteins will be made. Different proteins will lead to variation in the organism.
Leaves of Bryophyllum fallen on the ground produce new plants. Why?
The leaves of Bryophyllum have notches on their margins, which produce buds. When these leaves fall on the soil , the buds develop into a new plant by process of vegetative reproduction, under favourable conditions.
How do organisms reproduced by fission? Write names of any two organisms which reproduce by this method.
Fission is a process by which a unicellular organism splits to form two or more daughter cells.
Ex.- Bacteria, Amoeba.
State two differences between male and female gametes. ( sperms and eggs)
(i) Male gamete is smaller in size while female gamete is larger in size.
(ii) Male gamete is motile while female gamete is non-motile and contains stored food.
Differentiate between germination and fertilization.
Fertilisation is the process of fusion of male germ cells with the female gametes while germination is the process of development of the new plant from the embryo present inside the seed.
Define the Menstruation
If egg is not fertilised the lining of uterus slowly breaks and comes out through the vagina as blood and mucous. This cycle takes place roughly every month and is known as menstruation .
Name one sexually transmitted disease each caused due to bacterial infection and viral infection. How can they be prevented?
Bacterial infections - Syphilis, Gonorrhoea.
Viral infections - AIDS
Using a condom during sex helps to prevent transmission of these diseases.
What kind of contraceptive methods prevents STDs and how?
Barrier method prevent STDs.
By this method there is no direct contact of genital organs of male and female and thus it prevents transmission of any infection.
What are sexually transmitted diseases? Name an STD which damages the immune system of human body.
Diseases that spread through the sexual contact are called sexually transmitted diseases .
AIDS damages the immune system of human body.
How can pregnancy be prevented surgically?
(i) Vasectomy : The vas deferens of male is blocked to prevent sperm transfer
(ii) Tubectomy: The fallopian tube of female is blocked to prevent egg to reach uterus.
Give two examples each of the following:
(i) Agents of pollination
Wind, water or animals
(ii) Physical changes on puberty that are common to both boys and girls.
Thick hair growing in armpits and the genital area.
The skin becomes oily and we might begin to develop pimples.
Define variation in relation to a species. Why is variation beneficial to the species?
Variation refers to the differences in the characters or traits among the individuals of a species, caused by errors in DNA copying
Variations are beneficial to species because they provide a survival advantage to the species under adverse conditions.
Explain how do organisms create an exact copy of themselves.
DNA copies are made during the cell division. To build the copies of DNA the cells use biochemical reactions. This creates two copies of the DNA in a reproducing cell. Additional cellular apparatus along with the DNA copies are separated and so a cell divides to give rise to two cells.
Why is binary fission different from fragmentation.
(i) In binary fission, a parent cell splits into two daughter cells while in fragmentation organisms breaks into multiple parts which grow into new organism.
(ii) Binary fission is mode of asexual reproduction in unicellular organisms whereas fragmentation is mode of asexual reproduction in simple multi-cellular organism.
Reproduction is one of the most important characteristics of the living beings. Give three reasons in support of your answer.
(i) Reproduction maintain the continuity and survival of a species.
(ii) Reproduction brings variation so that population may adapt better and evolution in species takes place.
(iii) Reproduction passes genetic information to the next generation.
Write scientific name for malarial parasite. How is fission in amoeba different from that of malarial parasite?
Scientific name of malarial parasite is plasmodium.
Amoeba reproduces by binary fission, where one cell splits into two daughter cells while plasmodium reproduces by multiple fission where one cell splits into many daughter cells.
Write difference between asexual and sexual mode of reproduction.
(i) Asexual reproduction involves only one parent whereas asexual reproduction involves two parents
(ii) Asexual reproduction does not involve genetic fusion while sexual reproduction involves fusion of male and female gametes to form a zygote.
Different between the fission of Leishmania and Plasmodium.
1. Leishmania reproduces by binary fission whereas plasmodium reproduces by multiple fission
(ii) In leishmania one cell splits into two daughter cells while in plasmodium one cell splits into many daughter cells.
What is fragmentation? Name a multicellular organism which reproduces by this method.
Fragmentation is a form of asexual reproduction in which an simple multi-cellular organism breaks into multiple fragments or smaller parts on maturation and these pieces or fragments grow into new organism.
Spirogyra is a multicellular organism which reproduces by this method.
Explain how Spirogyra reproduces.
Spirogyra reproduces by fragmentation. In this process spirogyra breaks up into smaller fragments upon maturation or pieces. Each fragment has an ability to reproduce itself. Therefore these fragments grow into new individuals.
Give the functions of following parts in flower : (i) Stigma (ii) Ovary (iii) Pollen tube
(i) Stigma :The stigma serves as a landing platform for pollen grains.
(ii) Ovary : Ovary has ovule (female germ cell) and forms fruit to protect of seeds.
(iii) Pollen tube : Pollen tube carries male gamete from stigma to ovule.
What happens to the following parts after fertilization? (i) ovum (ii) ovary (iii) ovule (iv) sepals and petals
(i) Ovum forms zygote
(ii) Ovary forms fruit
(iii) Ovule forms seed
(iv) Sepals and petals shrink and fall off
List changes observed in the body of a female during puberty.
(i) Thick hair growing in armpits and the genital area.
(ii) The breast size begins to increase and skin of the nipples begins to darken.
(iii) Menstruation starts in girls
(iv) The skin becomes oily and we might begin to develop pimples.
Describe in brief, the changes the uterus undergoes: (i) To receive the zygote (ii) If zygote is not formed.
(i) The uterus prepares itself every month to receive a fertilised egg . Therefore its lining becomes thick and spongy.
(ii)If zygote is not formed the lining of uterus slowly breaks and comes out through the vagina as blood and mucous.
Why do we need to adopt contraceptive measures?
1. To prevent unwanted pregnancies.
2. To control population rise or birth rate.
3. To prevent the transfer of sexually transmitted diseases.
4. Contraceptives helps space the timing of the births of the children.
List four steps in sexual reproduction.
Formation of gametes through meiosis.
Transfer of male gamete into the female body.
Fertilisation (fusion of male and female gametes)
Formation of offspring from zygote
Name the human male reproductive organ that produces sperms and also secretes a hormone. Write the functions of the secreted hormone.
Human male reproductive organ - Testis
Secreted male hormone - Testosterone.
Functions : (i) Development of secondary sexual characters.
(ii) Plays an important role in sperm production
Name the parts of the human female reproductive system where (i) Fertilization takes place, (ii) Implantation of the fertilized egg occurs. Explain how the embryo gets nourishment inside the mother’s body.
(i) fallopian tube/oviduct.
(ii) uterus.
The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. This is a disc which is embedded in the uterine wall.
Give reasons:
(i) Wind acts as a pollinating agent.
Because wind transfer of pollen grains from anther to stigma.
(ii) Variation is essential and beneficial to a species.
Variation helps in evolution and survival.
(iii) Use of condoms prevents pregnancy.
Condoms act as a mechanical barrier and prevent sperm from meeting the ovum.
A part of the male reproductive system is shown below. Study the diagram and answer the questions that follow.

(i)Two part have been incorrectly labelled. Identify them.
Testis, Penis.
(ii) Give the function of urethra.
Urethra serves as a common passage for both sperms and urine.
(iii) Which hormone is released by testis?
Testosterone.
Draw a diagram of the longitudinal section of a flower and label on it sepals, petal, ovary and stigma.
How does the amount of DNA remain constant though each new generation is a combination of DNA copies of two individuals?
The amount of DNA and number of chromosom is maintained in each generation by meiosis. During the formation of the germ-cell, due to meiosis the number of chromosomes and the amount of DNA in the germ-cell is halved. When two germ-cells combine during sexual reproduction to form a new individual the original number of chromosome and the amount of DNA gets restored in the offspring.
What is the importance of DNA copying in reproduction?
(i) It transmits the characteritics from parents to the next generation ( offspring )
(ii) Some variations are produced in the offsprings during reproduction by DNA copying which form the basis for evolution.
(iii) It maintains the body designs and features in different generations of the species.
Mention the two asexual methods by which hydra can reproduce. Explain briefly any one such method.
The two asexual methods by which hydra can reproduce.
(i) Budding (ii) Regeneration.
Budding : A bud develops as an outgrowth due to repeated cell division at one specific site of hydra. These buds develop into tiny individuals and when fully mature, detach from the parent body and become new independent individuals.
What are secondary sexual characters in humans? Name one such character of male and female.
The physical characters which develop during puberty and distinguish a male from female are called secondary sexual characters.
Secondary sexual characters of male are growth of moustache-beard, thick growth of hair on body, strong muscles and harsh voice. Secondary sexual characters of female are less hair on body, broad hips, development of breasts and soft voice.
Explain the process of fertilization in flowers.
After pollination pollen grain germinates on the stigma to produce a pollen tube. Pollen tube travels through the style to reach the ovary.
Here the male germ cell (carried by the pollen tube) fuses with the female germ cell present in the ovuleto form a zygote. Fusion of male germ cells with the female gametes is called fertilisation.
Differentiate between placenta and uterus.
(i) Placenta is a temporary organ attached to the uterine wall whereas uterus is a Permanentorgans of the female reproductive system
(ii) The embryo gets nutrition from the mother’s blood with the help of placenta whereas the growth and development of embryo takes place in uterus.
Name the type of asexual reproduction in: (i) Rhizopus (ii) Hydra (iii) Rose (iv) Yeast (v) Amoeba (vi) Bryophyllum
(i) Rhizopus - Spore formation
(ii) Hydra - Budding
(iii) Rose - Vegetative propagation by stem.
(iv) Yeast - Budding
(v) Amoeba - Binary fission.
(vi) Bryophyllum - Vegetative propagation.
Differentiate between unisexual and bisexual flower.
Unisexual flowers have either male(stamens) or female(pistil) reproductive parts in a flower are known unisexual flowers.
Ex.- Papaya, Watermelon.
Bisexual flowers have both male (stamens) and female(pistil) reproductive organs in the same flower .
Ex.- Hibiscus, mustard
Define reproduction. How does it help in providing stability to the population of species?
The production of new organisms from the existing organisms of the same species is known as reproduction.
Reproduction helps in providing stability to population of species by giving birth to new individuals. Organisms are produced in large numbers by the process of reproduction out of which only some survive and the surviving organisms take place of the members dying in the population hence maintaining stability.
Define the following processes of asexual reproduction: (i) Spore formation (ii) Regeneration (iii) Multiple fission
(i) Spore formation : In spore formation, the parent plant produce hundred of microscopic reproductive unit called spores. Under suitable conditions, these spores germinate to form a new plant.
(ii) Regeneration :The ability to give rise to new organism from the body parts of the parent organism is called regeneration.
(iii) Multiple fission : In multiple fission the cell splits into many daughter cells during cell division.
What is vegetative propagation? List two advantages of vegetative propagation.
Vegetative propagation is the asexual mode of reproduction in which any Vegetative parts of plant body like the root, stem and leaves develop into new plants under appropriate conditions.
Ex. - Root - Dahlia, Stem- Patoto Leaf - Bryophyllum
Advantages of vegetative propagation.
(i) The vegetative propagation is used in methods such as layering or grafting to grow many plants for agricultural purposes.
(ii) Plants raised by vegetative propagation bear flowers and fruits earlier than those produced from seeds.
(iii) Such methods also make possible the propagation of plants that have lost the capacity to produce seeds.
List any four differences between pollination and fertilization.
1. Pollination is the transfer of pollen grain from the anther to the stigma of flower. whereas fertilization is the fusion of male gamete with female gamete
2.Pollination is an external process whereas fertilization is internal process.
3. Pollination is a physical process whereas fertilization is a genetic and biochemical process.
4.Pollination occurs before fertilization whereas fertilization occurs after pollination
What is placenta? Mention the functions of placenta in the human female reproductive system.
Placenta is a disc of special tissue embedded in the uterine wall that develops during pregnancy.
Function of placenta:
(i) Placenta helps in transporting glucose and oxygen from the mother to the embryo.
(ii) Placenta removes waste generated by the embryo by transferring it to the mother’s blood.
Identify the organisms A, B and the mode of asexual reproduction exhibited by them.
A = Bryophyllum - Vegetative propagation.
B= Plasmodium - Multiple fission.
Draw a labelled diagram of (i) Regeneration in Planaria (ii) Budding in Hydra
Draw a labelled diagram of (i) Spore formation in Rhizopus (ii) Multiple fission in Plasmodium.
Draw a labelled diagram of (i) Binary fission in Amoeba (ii) leaf of Bryophyllum with buds.
In the diagram of human male reproductive system given below:
(i) Label parts A and B.
A - seminal vesicle,
B - prostate gland.
(ii) Name the hormone produced by organ “X’.
Testosterone
(iii) Mention the name of substances that are transported by tubes C and D.
C - sperms
D - sperms/semen and urine.
List three techniques to prevent pregnancy. Which of them is not meant for males? How does the use of such techniques have an impact on health and prosperity of a family?
Three techniques to prevent pregnancy:
(i) Barrier methods: — Use of condom.
(ii) Chemical Method : Use of oral pills by females.
(iii) Use of loop or the copper-T .
(iv) Surgical method : Vasectomy in males and Tubectomy in females.
Use of loop orcopper-T and chemical Method and is not meant for males
Effect on Health and Prosperity:
(i)Health of women is maintained
(ii) Parents can provide more attention and quality resources to children.
Differentiate between self-pollination and cross-pollination.
1. In self-pollination, pollen grains are transferred from the stamens of one flower to the stigma of the same flower, whereas in cross-pollination, pollen grains are transferred from the stamens of one flower to the stigma of another flower.
2. Self-pollination occurs in genetically same plants, whereas cross-pollination,occurs in genetically different plants of the same species.
3.self-pollination occurs either in the same flower or another flower of the same plant, whereas cross-pollination occurs between two flowers which are on different plants.
What happens when: (i) Testosterone is released in males.
Testosterone stimulates the development of secondary sexual characters
Testosterone plays an important role in sperm production
(ii) Pollen grain falls on the stigma of the flower.
When pollen grain falls on stigma, it germinates on stigma and produce pollen tube which travels through the style to reach the ovary
(iii) Egg fuses with sperm cell.
When egg fuses with sperm cell fertilization occurs and a zygote forms.
(iv) Planaria is cut into many pieces.
Each piece grows into a complete organis by regeneration
(v) Buds produced in the notches along the leaf margin of Bryophyllum fall on the soil
Buds develop into new plants by vegetative propagation
(vi) The sporangia of Rhizopus burst upon maturation.
When the sporangia of Rhizopus burst upon maturation, the spores spread out and under suitable conditions, these spores germinate to form a new plant.
Identify the following methods and giving one example of each:
(i) Process in which reproduction takes place by breaking up of parent into fragments.
Method - Fragmentation
Example - Spirogyra
(ii) Process of dividing of organisms into many cells simultaneously.
Method - Multiple fission
Example - Plasmodium
(iii) Process of reproduction by formation of bud on parent body.
Method - Budding
Example -Hydra
(iv) Process of reproduction by formation of spores.
Method - Spore formation
Example - Rhizopus
(v) Process used by multicellular organisms to reproduce by cutting into many pieces and each piece forms a new individual.
Method - Regeneration
Example - Planaria
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.
Significance of reproductive health in a society:
(i) It prevents the spread of various sexually transmitted diseases (STDs).
(ii) Better sex education and awareness help in maintaining the population and prevent the population explosion.
(iii) It helps in the prevention of unwanted and teen pregnancies.
(iv) Less maternal and child mortality rates due to better health-care services.
Or
(i) Prevention of sexually transmitted diseases.
(ii) To promote small family system.
(iii) Prevention of unwanted and teen pregnancies.
(iv)Less mortality among new-borns and maternal.
Over the last 50 years, reproductive health which have improved in the following areas:
(i) Family planning (ii)Less maternal mortality rates.
Identify A,B,C and D in the given diagram and write their names. b. What is pollination? Explain its significance of pollination'

A - pollen grain; B - stigma; C - Pollen tube, D - Female germ cell.
Pollination : Transfer of pollen grains from the anther of the stamen to the stigma of a flower is called pollination .
Significance of pollination - Process of pollination leads to fertilization as it brings the male and female gametes together for fusion.
Draw a sectional view of human female reproductive system and label the part where:
(i) Eggs develop - Ovary
(ii) Fertilization takes place- Oviduct or fallopian tube
(iii) Fertilized eggs get implanted. -Uterus
If egg is not fertilised the lining of uterus slowly breaks and comes out through the vagina as blood and mucous. This cycle takes place roughly every month and is known as menstruation.
How does vegetative propagation occur in nature? Explain with four different examples.
Vegetative propagation is the asexual mode of reproduction in which any Vegetative parts of plant body like the root, stem and leaves develop into new plants without human interference under appropriate conditions.
Examples
(I)The leaves of Bryophyllum have notches on their margins, which produce buds. When these leaves fall on the soil, the buds develop into a new plant.
(ii) Potato contains tubers Inside stem which have eyes or nods.
These eyes or nodes develop into a new plant.
(iii) A swollen part is present in onion stem which is called bulb. This bulb develops into a new plant.
(iv)The roots of sweet potatoes produce shoots or buds . These buds grow into a new plant.
Differentiate between:
(i) Pollen tube and Style
Pollen tube :The pollen tube grows out from pollen grain which carries the male gamete from the stigma to the ovules
Style : Style is a part of carpel/pistil which joins the stigma to the ovary.
(ii) Fragmentation and regeneration
Fragmentation : In fragmentation an simple multi-cellular organism breaks into multiple fragments on maturation and these fragments grow into new organism
regeneration : Regeneration is the ability to give rise to new organism from the body parts of the parent organism
(iii) Bud of Hydra and bud of Bryophyllum
Bud of Hydra : The bud of Hydra prosduce at the budding zone
Bud of Bryophyllum : the bud of Bryophyllum produces on the leaf.
The bud of hydra is an outgrowth due to repeated cell division while the bud of Bryophyllum is the plantlet on its leaf.
(iv) Vegetative propagation and spore formation.
Vegetative propagation : In vegetative propagation a new plant are obtained from part of old plant ( root, stem and leaves) without help of reproductive part under appropriate conditions.
Spore formation : In spore formation, the parent plant produce hundred of microscopic reproductive unit called spores. Spores are microscopic asexual reproductive unit which are covered by thick walls. Under suitable conditions, these spores germinate to form a new plant.
Explain the structure of the female reproductive system of humans.
Female Reproductive System consists of ovaries, fallopian tubes, uterus and vagina.
(i) Ovaries : Ovaries are the primary female sex organs that produce the female gamete (egg) and estrogen and progesterone hormones
(ii) Oviduct (fallopian tube) : It carries egg from ovary to uterus . It is the site of fertilisation.
(iii) Uterus : The two oviducts unite into an elastic bag-like structure known as the uterus. The growth and development of embryo takes place in uterus
(iv) Vagina : The uterus opens into the vagina through the cervix.

7. How do Organisms Reproduce

Post a Comment

Contact Form