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Reproductive process is not essential for an individual. But it is very necessary for the continuity of the species. Reproduction performs following functions:
(i) In the process of reproduction one generation of living organisms produces the next generation i.e., parents produce offspring like themselves. Thus, this process preserves a species and maintains continuity of the race.
(ii) Reproduction is also the means of increasing the population of a species.
(iii) Reproduction plays an important role in evolution by transmitting favourable variation from parents to offspring.
The information for inheritance of features from parents to the next generation is in the form of DNA molecules. DNA found in chromosomes in the nucleus of the cells has the information for making proteins which lead to body design of an organism. Different proteins lead to altered body designs. Thus to ensure similar body design the DNA needs to be copied in reproduction.
Organisms which reproduce by:
(i) Budding: Hydra and Yeast.
(ii) Fragmentation: Spirogyra and flatworm.
(iii) Spore formation: Bacteria, Mucor, Fern of Moss.
Different types of asexual reproduction are:
(i) Fission: An individual divides and gives rise to offsprings. e.g., Amoeba.
(ii) Budding: An individual gives rise to a bulb-like projection called bud. This bud on separation from the body of the parent becomes a new individual. e.g., Hydra.
(iii) Fragmentation: An individual breaks into pieces and each piece grown into new individual e.g., Spirogyra.
(iv) Spore formation: An organism produces spores which in favourable conditions give rise to new individuals e.g., Mucor.
(v) Vegetative propagation: A part of the plant body give rise to new individual plant e.g,. in rose stem cutting gives rise to a new rose plant.
(i) Binary fission: It is found in unicellular animals like Amoeba, Paramoecium, Euglena, etc. After attaining an optimum size the adult individual undergoes a simple division into two daughters of equal size. It consists of division of the nucleus followed by cleavage of cytoplasm into equal parts, each having a daughter nucleus. Binary fission can occur in any place in Amoeba. It is longitudinal in Euglena and transverse in Paramoecium. The organisms undergoing binary fission are almost immortal since they never grow old but divide to form two young offspring after attaining the adult size.
(ii) Multiple fission: The mode of asexual reproduction is found in unicellular animals or protozoans, e.g., Amoeba, Plasmodium, Monocystis. The nucleus of the parent cell undergoes repeated divisions to produce a number of daughter nuclei. The cytoplasm cleaves around each nucleus simultaneously to form a number of daughter cells or individual inside a parent cell. Ultimately, under favourable conditions parent cell membrane ruptures and many daughter cells are released.
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Advantages of vegetative reproduction are:
(i) This is a very useful method of multiplying plants which do not produce seeds l;ike banana and oranges.
(ii) This is a more easy and quicker method of propagation than from the conventional method using eds. For example, Lilies produce flowers within one or two year when grown vegetatively. They produce flowers in 4—7 years (from germination to flower) when grown by seeds.
(iii) Vegetative propagation methods are useful in preservation of the desired parental characters in the offspringswhile plants produced by seeds show variations.
It is considered better to grow a rose from cutting or vegetative propagation method rather than from seeds because:
1. It is the only method of reproduction in seedless plants like rose.
2. It produces a new plant in a short span of time.. It is a short cut method for rapid multiplication.
3. It helps to preserve the type of character that a plant breeder desires in the particular rose plant.
4. It is an easy and economical method for the multiplication of ornamental plants like rose.
In vegetative propagation only one parent is involved and there is no combination or fusion of two different cells as in sexual reproduction, thus there is no variations and the plants propagated vegetatively are usually like their parents.
Vegetative propagation in the following plants:
(i) In sweet potato, the roots bear adventitious buds. These buds develop into new individual under favourable conditions.
(ii) In case of mint (Pudina), plant, the branches grow for some distances from the parent plant on the ground. These branches after travelling some distance give rise a cluster of adventitious roots below into the ground and a tuft of leaves above. These branches are called suckers in case of mint plant. On breaking from the parent plant, each branch gives rise a new individual plant.
The technique of culturing tissue on a nutrient medium and aseptic condition in laboratories is called tissue culture. Tissue culture technique is widely used in raising new plants. In this technique, a small piece of tissue is cut from a plant. This tissue is placed on a nutrient medium under suitable conditions. The tissue grows into an unorganised mass called callus. In the second stage, a portion of this callus is placed in another medium, which induces differentiation in the cells of the callus. As a result plantlets are produced. These plantlets are transplanted in pots or soil and new plants are raised. This technique is successfully applied to raise new plants of orchids, chrysanthemum, asparagus and other plants.
Tissue culture;
(A) A piece of tissue placed on a nutritive medium.
(B) Tissue grows into a callus.
(C) A piece of callus grown on another medium where cell differentiation occurs.
(D) Plantlets develop from the piece of callus.
Following are the three methods of vegetatitive propagation which are commonly used by man. For growing garden plants: (i) Grafting (ii) Cutting and (iii) Layering.
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Binary fission |
Multiple fission |
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(a) The cell divides into two producing two daughter individuals. (b) Nucleus and cytoplasm divide simultaneously. |
(a) The cell nucleus divides many times within the cyst to produce many daughter nuclei.
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Vegetative propagation is practiced for growing some types of plants because:
(a) It is the only method of reproduction in seedless plants like banana, orange etc.
(b) The plants produced by this method can bear flowers and fruits earlier than those that are produced by seeds.
(c) It is a short cut method for rapid multiplication.
(d) This method helps to produce genetically similar plants which have all the characteristics of the parent plant.
(e) It is very easy and economical method for the multiplication of ornamental plants.
After pollination and fertilization following changes occur in a flower:
(i) The petals, stamens, style and stigma of the flower fall off.
(ii) Sepals dry up and hold the ovary.
(iii) The ovules confined in the ovary develop into seeds.
(iv) The ovary develops into fruit. Sometimes the ovary wall may harden as in poppy. Sometimes ovary wall becomes fleshy and succulent as in tomato or plums.
Name of the organ – Testis.
Function:
(i) Formation of sperms.
(ii) Secretion male hormone called Testosterone.
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Male reproductive organs: Reproductive system of male human body consists of the following organs:
(a) Testes (Sex glands): There is a pair of oval testes present in the scrotum.
(b) Epididymis: It is the portion which is closely attached to the posterior side of each testes. It receives and stores the sperms produced by the testes.
(c) Vas deferens: From each epididymus a tube of whitish colour arises. The tube is known as vas deferens. The sperms pass through it.
(d) Seminal vesicle: The epididymus is connected by the seminal vesicle by vas deferens. The seminal vesicle are a pair of small lobulated sacs situated at the base of urinary bladder above the prostrate gland. They join each other to form ejaculatory duct. Seminal vesicles secrete a viscous fluid which forms most of the part of semen. It also lubricates the passage through which the sperms travel. This fluid also protects the sperms from the acids normally present in the urethra and female reproductive duct.
(e) Prostrate Gland: It is a bilobed glandular mass embracing the urethra. In man two prostrate glands fuse to form only one. It produces prostatic fluid which is discharged into urethra through more than two dozen fine ducts. There is more secretion during sexual act when they are forcefully ejected by contraction of muscular and elastic tissues.
(f) Urethra: It is a tube starting or arising at the urinary bladder. It passes through the copulatory organ (penis) to the tip of the glands penis. The urethra of male functions both for the passage of sperms and urine.
(g) Penis: The penis is the copulatory organ of male for the transfer of the sperms to the female reproductive tract.
Reproductive system in human male
The female reproductive organs consists of the following:
(1) A pair of ovaries, (2) Fallopian tubes, (3) Uterus, (4) Vagina, (5) Vulva.
(a) Ovaries: The paired ovaries lie on either side of the uterus or lower part of the abdominal cavity. The functions of the ovary are to produce eggs (ova) and hormones notably Estrogens and Progesterone.
(b) Fallopian tubes (Oviducts): These are the two tubes attached to the uterus one on either side. Each tube is about 10-12 cm in length. The fallopian tube-provides for the eggs (ova) to pass into the uterus by ciliary action. It is the site fertilization.
(c) Uterus (Womb): It is a pear shaped hollow muscular organ situated between the urinary bladder and the rectum. It receives the fallopian tubes on either side of uterus and is capable of undergoing great enlargement. Uterus contains developing young and expels it by muscular contraction at birth. It is the site of development of young one.
(d) Vagina: It is a short, wide collapsible muscular tube that connects cervical canal at the upper end with the external genitalia at the lower end. Vagina internally lined by a much folded epithelial layer. The functions of vagina are to receive penis and its ejaculated semen; to act as lower part of birth canal and to act as duct for menstrual flow.
(e) Vulva (External Genitalis): Vulva or the female external genitalis consist of pubis (monsveneris), labia majora, labia minora clitoris, urinary meatus, vaginal orifice and Bartholin’s glands. 
Human female reproductive system
Uterus provides:
(i) suitable place for the implantation of fertilized ovum the zygote.
(ii) nutrition for the development of foetus and
(iii) contributes in the formation of placenta.
(iv) maintenance the mentrual cycle.2
After fertilization:
(i) Ovum forms zygote which fixes itself into the wall of uterus and starts to develop as an embryo. The embryo tissues and mother’s uterus wall tissue form placenta which is the vital connection between foetus and the mother.
(ii) Menstruation and ovulation do not take place during pregnancy. However, they are resumed after the birth of the child.
Menstruation is the cyclic changes in the uterus and ovary. During this period, the ovary and uterus undergo a cycle of change every 28 days. After ovulation if ovum is not fertilized the menstruation occurs. If ovum is fertilized the menstruation cycle stops till the birth of the child. The menstruation consists of the following stages:
(i) Menstruation (3-7 days): During this period bleedings takes place and uterus lining, blood vessels shed off as blood and mucus.
(ii) Ovulation: The ovary releases one ovum after 10-12 days of menstruation. During this period the uterine wall prepares itself to receive the ovum.
(iii) The ovum reaches the Fallopian tube on the 14th day and waits up to 16th day for the sperm cell. If it does not meet the sperm it starts degenerating.
(iv) At the end of the 28th day, this ovum is rejected alongwith the uterus lining i.e., menstruation occurs.
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Menstruation |
Menopause |
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1. It is the discharge of blood and portions of endometrium of uterus. It lasts for 3 to 5 days. Beginning of menstruation indicates the beginning of next menstrual cycle. |
1. It is the cessation of menstruation, i.e., menstrual cycle. Generally, it occurs after the age of 45-50 years. This indicates the end of the fertility phase in a woman. |
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Egg |
Sperm |
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1. Eggs are produced in female reproductive organs and are the female gametes. 2. Eggs are non–motile and bigger in size. |
2. Sperms are motile and smaller in size. |
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Internal fertilisation |
External fertilisation |
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The sperms are injected inside the body of the female and fertilisation of the ovum takes place inside the body of the female. Example: Mammals, insects, spider |
Both male and female organisms shed their gametes in the medium (water) and the ovum is fertilised outside the body of the female. |
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Umbilical cord |
Placenta' |
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It is flexible cord like structure connecting the foetus to the placenta. It contains the blood vessels which carry blood to and fro between foetus and the placenta. |
The region where outer covering of the embryo develops contact with the tissues of the uterus of the mother is the placenta. Finger like projections (villi) of the embryo and the tissues of the uterus in which they are embedded constitute the placenta. Placenta helps the foetus to derive nourishment and oxygen from the body of the mother and helps in elimination of waste material. |
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Function of male urethra |
Function of female urethra |
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Male urethra forms the common passage for urine and semen. |
Female urethra is a passage only for urine. |
Role of hormones secreted by the gonads are to:
(i) regulate the formation of sperm and ovum (gametogenesis).
(ii) maintain the structure and function of accessory sex organs.
(iii) help in developing secondary sex characters such deepening of voice, growth facial hair in males; development of mammary glands in females.
The methods used for regulation of child birth are:
(i) Barrier Method: In this method physical devices like condom, cervical caps and diaphragm are used to prevent sperms to reach up to the ovum.
(ii) Chemical Method: In this method specific drugs are used by females. These drugs may be (a) oral pills or (b) vaginal pills. Oral pills mainly contain hormones and are called oral contraceptives.
(iii) Intrauterine Contraceptive Devices (IUCDs): IUCD like Copper-T is placed safely in the uterus by a skilled doctor. IUCDs prevent implantation of the fertilized ovum inside the uterus.
(iv) Surgical Method: This method is applicable to both male and female. In males, a small portion of vas deferens and the fallopian tube in female is surgically removed or ligated (tied). It is known as vasectomy in males which prevents release of sperms from the testes. In females, it is called tubectomy.
The __________ in the nucleus is the information source for making____________
DNA
,proteins.
cell division
, fissionbacteria
,protozoans
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layering
,cutting/grafting
asexual reproduction
Transfer of _______ from stamen to stigma of same or any other flower of same species is termed ________.
pollen grain
,pollination
cross pollination
wind
,water
,animals
germ cells
,deliver
,fertilisation
lower temperature
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Two methods of reproduction found in lower organisms are
(i) Fission–Amoeba.
(ii) Spore formation–Moulds.
Gestation: The development of foetus inside the uterus till birth is called gestation.
Parturition: On completion of gestation the action or process of giving birth to offspring is called parturition.
(i) AIDS stands for Acquired Immuno Deficiency Syndrome.
(ii) HIV stands for Human Immunodeficiency Virus.
D.
fallopian tube (oviduct)D.
All of theseD.
all of these
The different methodsof contraception are:
(i) Barrier method: In this method physical devices like condom, cervical caps and diaphragm are used to prevent sperms to reach up to the ovum.
(ii) Chemical method: In this method specific drugs are used by females like oral pills. Oral pills mainly contain hormones and are called oral contraceptives.
(iii) Intrauterine Contraceptive Devices (IUCDs): IUCD like Copper-T is placed safely in the uterus by a skilled doctor. IUCDs prevent implantation of the fertilized ovum inside the uterus.
(iv) Surgical method: This method is applicable to both male and female. In males, a small portion of vas deferens and the fallopian tube in female is surgically removed or ligated (tied). It is known as vasectomy in males which prevents release of sperms from the testes. In females, it is called tubectomy.
The modes for reproduction in unicellular oganisms are:
(i) Binary fission: In this the parent undergoes a simple division into two daughters of equal size. It consists of division of the nucleus followed by cleavage of cytoplasm into equal parts, each having a daughter nucleus. Beg- amoeba.
(ii) Multiple fission: Tthe parent divides into many daughter cells simultaneously. eg in plasmodium.
The modes of reproduction in multicellular organisms are:
(i) Regeneration: The organism gives rise to new individual organisms from cut or broken body parts. eg in Hydra.
(ii) Fragmentation: The mature Spirogyra (an alga) breaks into two or more pieces (fragments). Each fragment grows into new individual. The process is called Fragmentation.
(iii) Sexual Reproduction: This is the mode which involves male and female gametes which fuse to from the zygote.
Name those parts of the flower which serve the same function as the following do in the animals:
(i) testis (ii) ovary (iii) eggs (iv) sperms
List two functions performed by the testis in human beings.
Two functions performed by the testis in human beings are:
i) It produces the male hormone, which is responsible for the secondary sexual changes in males.
ii) It produces sperms, required for fertilisation.
Explain budding in hydra with the help of labelled diagrams only.
Budding involves the formation of a new individual from a protrusion called bud. Budding is a process commonly seen in plants, yeasts and lower-level animals such as hydra.
In Hydra, the cells divide rapidly at a specific site and develop as an outgrowth called bud which 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 individuals.
List any four methods of contraception used by humans. How does their use have a direct effect on the health and prosperity of a family?
Four methods of contraception that used by humans are:
(i) Natural method in which the sexual act is avoided from the 10th day to the 17th day of the menstrual cycle.
(ii) Use of condoms.
(iii) Oral contraceptive method such as i-pill.
(iv) Contraceptive devices, such as a loop and a Copper-T rod.
The following are the effects of contraception on the health and prosperity of a family:
(i) It helps in preventing unwanted pregnancies.
(ii) It prevents the chances of frequent pregnancies, which, otherwise, affect the health of females.
(iii) It helps in family planning by controlling the number of children in a family.
(iv) It also reduces the chances of transmission of sexually transmitted diseases such as AIDS.
Write the functions of the following in human female reproductive system: Ovary, oviduct, uterus. How does the embryo get nourishment inside the mother's body? Explain in brief.
Functions of the Ovary
It produces female gametes (ova) or egg.
It secretes female sex hormones that is progesterone.
Functions of the Oviduct
Fertilization takes place here.
It carries egg from the ovary to the womb.
Functions of the Uterus
It prepares itself every month to receive and nurture
the growing embryo.
It expands according to the growth of the baby.
The embryo develops inside the mother’s body for about nine months. Inside the uterus, the outer tissue surrounding the embryo develops finger-like projections called villi. These villi are surrounded by uterine tissue and maternal blood. They provide a large surface area for the exchange of oxygen and nutrients. There is a special tissue called placenta embedded in the uterine wall. The embryo receives the oxygen and nutrients from the mother’s blood via the placenta. The waste material produced by the embryo is removed through the placenta.
A student identified the various parts of an embryo of a gram seed and listed them as given below:
(I) Testa
(II) Plumule
(III) Radicle
(IV) Cotyledon
(V) Tegmen
Out of these the actual parts of the embryo are
I, II, III
II, III, IV
III, IV, V
II, IV, V
B.
II, III, IV
The correct option is B.
Actual parts of the embryo of a gram seed are plumule, radicle and cotyledon. Testa and tegmen are the parts of the seed coat.
Name the type of asexual reproduction in which two individuals are formed from a single parent and the parental identity is lost. Draw the initial and the final stages of this type of reproduction. State the event with which this reproduction starts.
Binary fission is the type of reproduction in which two individuals are formed from a single parent. In the process, the identity of the parent is lost.
This type of reproduction starts with karyokinesis ( a division of nucleus).
List four advantages of vegetative propagation.
Vegetative propagation is an asexual mode of reproduction.
Advantages of vegetative propagation:
Only one parent is required, which eliminates the need for special mechanisms (pollination).
All plants produced are genetically similar enough to the parent plant to have all its characteristics hence genetic characteristic of the parent plant can be preserved.
Plants that do not produce seeds can be propagated by this method. For example Sugar-cane, Potato, etc.
Vegetative propagation is a cheaper, easier and rapid method of propagation in plants than growing them from their seeds.
Draw diagrams to explain the regeneration that takes place in each of the body parts of planaria when its body is cut into pieces. Name any other organism in which a similar process can be observed.
The figure below shows the step-by-step process of regeneration in planaria.
Planaria has the amazing capacity to regenerate its lost body part. When it is cut horizontally, separating the head from the tail, the part with tail regenerates the lost head and the part with head regenerates the lost tail. This process is known as regeneration.
Hydra uses the method of regeneration for its propagation.List any four methods of contraception used by humans. How does their use have a direct effect on the health and prosperity of a family?
The following are the four methods of contraception used by humans:
(i) Natural method in which sexual act is avoided from day 10th to day 17th of the menstrual cycle.
(ii) Barrier method in which condoms are used as protection.
(iii) Oral contraceptives like tablets or drugs that prevent the release of eggs, thus preventing fertilisation.
(iv) Implants and surgical methods: Contraceptive devices such as the loop or copper-T are placed in the uterus to prevent pregnancy. Some surgical methods like vasectomy and tubectomy.
Effects of contraception on the health and prosperity of a family:
(i) It helps in preventing unwanted pregnancies.
(ii) It prevents the chances of frequent pregnancies, which otherwise affect the health of females.
(iii) It helps in family planning by controlling the number of children in a family, thus reducing the chances of poverty.
(iv) It also reduces the chances of transmission of sexually transmitted diseases such as AIDS.
In this way, birth control methods play an important role in the health and prosperity of a family.
(a) Give one example each of a unisexual and a bisexual flower.
(b) Mention the changes a flower undergoes after fertilization.
c) How does the amount of DNA remain constant though each new generation is a combination of DNA copies of two individuals?
(a) Unisexual flowers are those flowers which contain either stamen (male reproductory part) or pistil ( female reproductory part). For example Cucumber, pumpkin, water melon, papaya, etc.
Bisexual flowers are those flowers which have both stamen and pistil in the same flower. For example- Hibiscus, rose, lily, etc.
b) A flower undergoes certain changes after fertilization. the zygote divides several times to form an embryo within the ovule. The ovule develops a tough coat and is gradually converted into a seed. The ovary grows rapidly and ripens to form a fruit. The petals, sepals, stamens, style and stigma may fall off.
c) Deoxyribonucleic acid (DNA) copying is the process by which the DNA is copied and the genetic information is passed from parents to offspring. The reproducing cells produce a copy of their DNA through process of replication and result in the formation of copy of DNA from an existing one. In this way, the amount of DNA remains constant through each new generation.
Name the respective part of human female reproductive system:
(i) that produces eggs,
ii) where the fusion of eggs and sperm takes place, and
iii) where zygote gets implanted.
b) Describe in brief what happens to the zygote after it gets implanted.
a) i) Ovary produces egg in females.
ii) Fusion of eggs and sperm takes place in the fallopian tube.
iii) Zygote gets implanted in the uterus of the female reproductive system.
The diagram below shows Female reproductive system.
b) The zygote formed after fertilization in the fallopian tube is implanted in the uterus. It divides repeatedly to form a mass of cells known as embryo. This embryo gets attached to the inner layer of the uterine cavity, i.e., endometrium. It thickens every month and is supplied with blood to nourish the embryo. Soon it gets covered by rapidly dividing uterine cells. This leads to pregnancy. Within a span of some months, the embryo starts developing limbs and begins to resemble a miniature being. When all parts of the embryo can be recognized, it becomes a foetus. The mother gives birth to the baby when the foetus fully develops.
Study the following diagrams showing various stages of binary fission in Amoeba:
The correct sequence of these diagrams should be:
I, IV, III,II, V
I, III, IV, II, V
I, II, IV, III, V
I, II, III, IV, V
B.
I, III, IV, II, V
The correct option is B.
The nucleus of the parent cell elongates and divides initially during binary fission a constriction starts appearing on the cell membrane. It starts widening and finally divides the parent cell into two almost equal halves (daughter cells). The daughter cells are identical to the parent cell.
Identify the figures showing the process of budding in yeast.
I, II AND III
II, III AND IV
I, II AND IV
III, IV AND I
D.
III, IV AND I
The correct option is D.
A single cell develops a protrusion wherein the nucleus divides to give rise to two daughter nuclei, during the process of budding. One of the daughter nuclei migrates to the protrusion to form a bud. This bud then grows in size and may undergo budding while attached to the parent cell. So, a chain of cells is formed in the process of budding.
Write any two differences between binary fission and multiple fission in a tabular form as observed in cells of organisms.
Difference between binary fission and multiple fission are:
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Binary Fission |
Multiple fission |
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In binary fission, the single cell divides into halves that is into two. |
In multiple fission, a single cell divides into many daughter cells simultaneously. |
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Binary fission is of two types; along any plane or longitudinally. Example: Amoeba(along any plane), Leishmania (longitudinally) |
Multiple fission occurs along only one plane. Example: Plasmodium. |
Why is DNA copying an essential part of the process of reproduction?
DNA copying is an important process that ensures that when cell multiplies, through the mechanisms of mitosis or meiosis, equal amount of DNA (genetic material) passes in to the new cell. DNA is copied so that the amount of DNA remains constant in the daughter cells.
Explain how equal genetic contribution of male and female parents is ensured in the progeny.
All human beings have 23 pairs of chromosomes out of which 22 are autosomes and two chromosomes are sex chromosomes. Gametes are formed in the males and females by the process of meiosis and these gametes contain 23 chromosomes. The male gametes and female gametes are haploid and have 23 chromosomes. During fertilisation, the male and the female gametes fuse to form a zygote which is diploid and has 23 pairs of chromosomes. Thus both male and female show equal genetic contribution to the progeny
(a) List two sexually transmitted disease in each of the following cases:
(i) Bacterial infections
(ii) Viral infections
(b) How may the spread of such diseases be prevented?
Sexually transmitted disease in each of the following case is:
(i) Bacterial infections are Syphilis, Gonorrhoea.
(ii) Viral infections: AIDS, warts.
(b) Sexually transmitted disease can be prevented by using contraceptive measures like a condom, avoiding sex with multiple partners or infected person.
(a) What is fragmentation in organisms? Name a multicellular organism which reproduces by this method.
(b) What is regeneration in organism? Describe regeneration in Planaria with the help of a suitable diagram.
(a) Diagram of longitudinal section of flower is shown below:
(b) Male reproductive part of the flower is the stamen which consists of filaments and anthers.
The female reproductive part of the flower is the pistil that consists of stigma, style and ovary.
(a) What is fragmentation in organisms? Name a multicellular organism which reproduces by this method.
(b) What is regeneration in an organism? Describe regeneration in Planaria with the help of a suitable diagram.
(a) Fragmentation is a mode of asexual reproduction. Fragmentation is the process in certain multi-cellular organisms with relatively simple body organisation, the body of the organism simply breaks up into smaller pieces upon maturation and these pieces or fragments grow into new individuals. Example: Spirogyra.
(b) Regeneration: Regeneration involves the capacity of an organism to give rise to an entire individual from a cut portion. This type of regeneration occurs in Planaria. When Planaria gets cut unintentionally, the cut fragments give rise to a new individual. Regeneration is carried out by specialised cells. These cells proliferate and make large numbers of cells. From this mass of cells, different cells undergo changes to become various cell types and tissues. The figure shows regeneration in planaria: 
A student was given two permanent slides, one of binary fission in amoeba and other of budding in yeast. He was asked to identify any one difference in the nucleus of the two. One such difference, he identified correctly was
Presence of one nucleus in amoeba, two in yeast cell and one in bud.
Presence of two nuclei in centrally constricted amoeba, one in yeast cell and one in its bud.
Presence of two distant nuclei in amoeba, one in yeast cell and two in bud.
Presence of a single nucleus each in amoeba, yeast cell and its attached bud.
B.
Presence of two nuclei in centrally constricted amoeba, one in yeast cell and one in its bud.
Presence of two nuclei in centrally constricted amoeba, one in yeast cell and one in its bud.
Binary fission is observed in which one of the following figures?
C.
Binary fission in Amoeba.
To determine the percentage of water absorbed by raisins, raisins are soaked in water for:
30 seconds
10 minutes
2 to 3 hours
24 hours
A.
30 seconds
C.
2 to 3 hours
(a) Explain the process of regeneration in Planaria. (b) How is regeneration different from reproduction?
Regeneration in Planaria
Regeneration is the process in Planaria, by which any part of the body if cut, is capable of developing into a complete organism. Regeneration is carried out by specialized cells. These cells proliferate and make large numbers of cells and from this mass of cells, different cells undergo changes to become various cell types and tissues. These changes take place in an organized sequence referred to as development and finally lead to the development of a complete organism.
b.
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Regeneration |
Reproduction |
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1. It is a type of asexual mode of reproduction in which only single parent is involved |
1. It includes both sexual and asexual mode of reproduction in which either single parent or both the parents are involved respectively. |
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2. This mode of reproduction depends on the fact that the organism needs to be cut in order to regenerate. |
2. This mode of reproduction is not dependent on cut. |
|
Example- Planaria |
Example- Sexual reproduction in humans |
Write two examples each of sexually transmitted diseases caused by (i) virus, (ii) bacteria. Explain how the transmission of such diseases be prevented?
Sexually transmitted diseases by virus- Warts and HIV-AIDS.
Sexually transmitted diseases by bacteria- Gonorrhoea and Syphilis.
The transmission of Sexually transmitted diseases can be prevented in the following ways:
• Using protection or condoms during sexual intercourse.
• Prohibiting the sharing of needles, syringes etc.
• Testing of blood before transfusion
(a) List three distinguishing features between sexual and asexual types of reproduction.
(b) Explain why variations are observed in the offspring of sexually reproducing organisms?
(a)
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Sexual Reproduction |
Asexual Reproduction |
||
|
1. |
It involves both the parent |
1. |
It involves only a single parent |
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2. |
It involves fusion of male and female gametes |
2. |
It does not involve fusion of gametes. The gamete of single parent undergoes division and gives rise to new a individual |
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3. |
It results in the introduction of variation in a population as newly formed organisms are not the exact copies of the parent |
3. |
It does not bring variation in a population as the newly formed organisms are identical to the parents |
(b) In case of sexual reproduction, variation is observed in the offspring due to the following reasons:
1. Two parents are involved, who are different from each other. One set of chromosomes comes from the male gamete and the other comes from the female gamete and the fusion of these two creates variations and produces a distinct individual.
2. The male and female gametes are formed by meiotic division which allows crossing over and recombination which further generates variation in the genes of offspring.
(a) Identify A, B and C in the given diagram and write their functions.
(b) Mention the role of gamete and zygote in sexually reproducing organisms.
In the diagram given above:
(a) A is the Stigma.
Function: The stigma is a sticky surface where the pollen lands and later germinates.
B is the Pollen tube.
Function: It carries the pollen from stigma to the egg cell in the ovary for fertilization.
C is the Egg cell.
Function: It fuses with the male gamete and leads to the formation of zygote.
(b) The gametes play an important role in the sexually reproducing organisms as they carry a genetic instructions that is a haploid set of chromosomes that the new organism needs to grow, develop and complete its life cycle.. These gametes upon fusion result in the formation of zygote, which develops into a new individual.
Zygote is the diploid cell formed by the fusion of male and female gametes during fertilization in sexual reproduction. Zygote is the first stage in the development process of an organism and it contains the complete set of genetic information of both the parents, essential for the growth of the new organism.
A student after observing a slide showing different stages of binary fission in Amoeba draws the following diagrams. However these diagrams are not in proper sequence:
The correct sequence is:
I, V, IV, III, II
I, III, IV, V, II
I, V, III, IV, II
I, IV, V, III, II
I, IV, V, III, II
E.
None of the above
The correct sequence should be I, II, III, IV, V.
Select the correct statements for the process of budding in yeast:
I. A bud arises from a particular region on a parent body.
II. A parent cell divides into two daughter cells, here the parental identity is lost.
III. Before detaching from the parent body a bud may form another bud.
IV. A bud when detaches from the parent body grows into a new individual.
I, II and III
II, III and IV
III, IV and I
IV, I and II
C.
III, IV and I
Budding is a type of asexual reproduction in which a new organism is formed from a bud of an existing organism. A small bud is formed at a specific position on the parent cell. The nucleus of parent cells splits and a part of it enters inside the newly formed bud. The bud develops into a new cell or daughter organism. The new organism remains attached to the parent organism till it gets matured. After attaining maturity it separates from the parent body.
In the figure, the parts marked A, B and C is sequentially: 
Plumule, Radicle and Cotyledon
Radicle, Plumule and Cotyledon
Plumule, Cotyledon and Radicle
Radicle, Cotyledon and Plumule
A.
Plumule, Radicle and Cotyledon
In the figure, the parts marked A, B, and C is Plumule, Radicle and Cotyledon respectively.
List two advantages of vegetative reproduction practiced in case of an orange plant.
Advantage of vegetative reproduction practiced in case on an orange plant is:
(i) Orange plant which has lost the capacity to produce viable seeds can be propagated by the method of vegetative reproduction.
(ii) All plants produced are genetically similar to parent plant and have all its characteristics.
How does growing embryo get nutrition from the mother's blood?
The embryo gets nutrition from the mother’s blood with the help of a tissue called placenta. Glucose and oxygen are passed from the mother to the embryo and the waste generated by embryo is also removed by transferring them to the mother’s blood by placenta.
Explain the meaning of sexually transmitted diseases (STDs). Give two examples of STDs each, caused due to
(i) bacterial infection and (ii) viral infection. State in brief how the spread of such diseases may be prevented.
Sexually Transmitted Diseases are infections that are commonly spread by sexual intercourse.
Examples of STDs spread because of
(i) Bacterial infection are - Gonorrhoea and Syphilis.
(ii) Viral infection are- AIDS and Warts.
The spread of such diseases may be prevented by the use of contraceptive methods such as condom.
Define the terms pollination and fertilization. Draw a diagram of a pistil showing pollen tube growth into the ovule and label the following:
Pollen grain, male gamete, female gamete, ovary.
Pollination is the process of the transfer of pollen grains from anther to stigma in plants. Fertilization refers to the fusion of male and female gamete to form a zygote.
Diagram of pistil showing formation of pollen tube
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.
. Testes: The testes are the male reproductive organs that are located outside the abdominal cavity within a pouch called scrotum. It produces sperms and also produce a hormone called testosterone, which brings about secondary sexual characters in boys.
2. Seminal vesicles: The seminal vesicles secretion makes the transport of the sperm easier and the fluid also provides nutrition.
3. Vas deferens: It carries sperm from the vasa efferentia to the urethra.
4. Ureter: When blood is filtered by the kidney, the waste material (urine) is passed on to urinary bladder via the ureters. The function of ureter is to carry urine from the kidney to the urinary bladder.
5. Prostate glands: It produces an alkaline fluid (prostatic fluid), which is a constituent of the semen. The prostatic fluid provides motility, longer survival period (neutralizes the acidic environment of the female reproductive tract) and protection to sperms.
After observing the prepared slides of binary fission in amoeba and budding in yeast following observations were reported:
(a) Single cells of amoeba and yeast were undergoing binary fission and budding respectively.
(B) Cytokinesis was observed in the yeast cell.
(C) Elongated nucleus was dividing to form two daughter nuclei in amoeba.
(D) A chain of buds were observed due to reproduction in amoeba.
The correct observation(s) is/are:
a and c
b only
c and d
d, a and c
A.
a and c
Both amoeba and yeast are unicellular organisms and undergo asexual reproduction. In Amoeba, a single cell divides to give rise to two identical daughter cells by the process of binary fission. In yeast, the cells reproduce by the process of budding.
A student after viewing a prepared slide illustrates the budding in yeast in the following order which is not correct:
b, c, d, e, a
b, e, d, c, a
b, d, e, c, a
b, d, c, e, a
D.
b, d, c, e, a
During budding in yeast, a single cell develops a protrusion wherein the nucleus divides to give rise to two daughter nuclei. One of the daughter nucleus migrates into the protrusion to form a bud. This bud then enlarges in size and may undergo budding while attached to the parent cell. Hence, budding results in a chain of cells.
A student has to observe a permanent slide of binary fission in amoeba. Find the correct sequence of steps given below for focusing the object under a microscope.
(a) Place the slide on the stage, look through the eye-piece and adjust the mirror to get proper illumination.
(b) Focus the slide sharp using fine adjustment screw
(c) Look through the eye-piece and raise the objective lens using coarse adjustment screw till the object is focused.
(d) Look through the eye-piece and move the slide till the object is visible.
d, c, b, a
a, b, d, c
a, d, c, b
a, c, d, b
C.
a, d, c, b
The correct order of steps is a, d, c, b.
After viewing different slides, a student draws following diagrams. Select the one which depicts binary fission in amoeba:
C.
During binary fission, a single cell gets divided into two equal and identical daughter cells.
Name the part of Bryophyllum where the buds are produced for vegetative propagation
The buds are produced at the margin of the leaves in Bryophyllum.
How do organisms, whether reproduced asexually or sexually maintain a constant chromosome number through several generations? Explain with the help of suitable example.
The chromosome number has to be maintained in all the organisms. For this the asexual and sexual reproduction maintain a constant chromosome number by adopting different methods.
In asexual reproduction the organisms divide the chromosome first and then the cells. For example in binary fission the chromosomes are replicated and then tranfered to the daughter cells.
In case of sxual reproduction, gametes are formed which are haploid in nature and then unite to restore the normal diploid condition . Thus , mainataining the chromosome number in the organism. For example in humans the male and the female gamete carry 23 chromosomes. They unite to form zygite which restores the normal 46 chromosome number in the offspring.
Name the parts A, B and C shown in the following diagram and state one function of each.
The given diagram represents
A - Anthers - A part of the the male reproductive organ of the flower.
Function - they produce pollen grains which are the male gametes of the flower.
B - Style - A part of the female reproductive organ of the flower.
Function - Connects the stigma to the ovary and allow the passage for the pollen and the pollen tube.
C - Ovary - The female reproductive organ of flower.
Function - Bears the ovules or the female gametes.
Suggest three contraceptive methods to control the size of human population, which is essential for the health and prosperity of a country. State the basic principle involved in each.
Oral pills - they change the hormone balance so that eggs are not
released and fertilisation cannot occur.
Barrier method - In this method the fertilisation is prevented by using barriers like condoms.
Surgical methods - In this method vas deferens and fallopian tubes are tied and blocked. so that the sperm transfer is blocked.
(a) Write the functions of the following parts in human female reproductive system:
(i) Ovary
(ii) Oviduct
(iii) Uterus
(b) Describe the structure and function of placenta.
(a) i . Ovary - They produce eggs or the female gamete. They also prodece the female hormone estrogen which brings about the development of secondary sexual characters in females.
(ii) Oviduct - Carries the mature egg to the uterus. The oviduct provide the place for fertilisation to occur.
(iii) Uterus - It nurturing the fertilized ovum that develops into the fetus and holding and supporting it till the baby is mature enough for birth.
(b) Placenta is a disc which is embedded in the uterine wall. It contains villi on the embryo’s side of the tissue. On the mother’s side are blood spaces, which surround the villi.
Th placenta provides a large surface area for glucose and oxygen to pass from the mother to the embryo. The waste substances generated by the foetus is removed by transferring them into the mother’s blood through the placenta.
What happens when a mature spirogyra filament attains considerable length?
When the mature filament of a spirogyra attains considerable length the filament breaks up into smaller fragments or pieces, and each fragment grows into a new filament/individual.
Define reproduction. How does it help in providing stability to the population of species?
Reproduction is the biological process by which new individual organisms – 'offspring' – are produced from their 'parents'. It is a ( biological) process by which new individuals of the same species are produced by the existing organisms.
Reproduction is the only means to ensure the continuity of a species. By reproduction, organisms produce a large number of new individuals out of which several get perished and only some survive. These surviving organisms replace the naturally dying members of the population. Hence the population as a whole is not affected and remains stable. Moreover, in certain modes of reproduction like the sexual mode variations are incorporated which help the species to adapt better to the environment and results in evolution too.
Explain the term 'Regeneration' as used in relation to reproduction of organisms. Describe briefly how regeneration is carried out in multicellular organisms like Hydra.
Regeneration is the ability of an organism to give rise to a new organism/ individual from their body parts.
Regeneration in hydra-
i. When the body of hydra by any means is cut into a number of pieces
ii. Each piece contains specialised cells
iii. Regeneration is carried out by specialised cells. These cells proliferate and make large numbers of cells.
iv. From this mass of cells, different cells undergo changes to become various cell types and tissues.
v. These changes take place in an organised sequence referred to as development which finally leads to the development of a new organism.
List two reasons for the appearance of variations among the progeny formed by sexual reproduction.
Two reasons for the appearance of variations among the progeny formed by sexual reproduction are :
i) Involvement of two different individuals - Since two individuals that is the male and female are involved therefore there will be more number of variation. The offspring acquires half genetic material from the father and half from the mother. So, the combination of various traits results in the variation in the offspring due to which the offspring is different from both the parents.
ii) Crossing over is the process in which the DNA is exchanged between the homologous chromosomes during meiosis.This causes variations in the cells.
(i) Name the part marked 'A' in the diagram.
(ii) How does 'A' reaches part 'B'?
(iii) State the importance of the part 'C'.
(iv) What happens to the part marked 'D' after fertilisation is over?
i) A - pollen/pollen grain
ii) The pollen (A) reaches the Stigma (B) by the process of pollination. The agents of pollination such as wind, water, insects carry the pollen grains from the anther to the stigma.
iii) Pollen tube (C) helps male gamete to reach egg (ovule).
iv) D - Egg forms the zygote on combining with the sperm by the process of fertilisation.
What is placenta? Describe its structure. State its functions in case of a pregnant human female.
Placenta is a special tissue that forms a connection between the foetus and the mother. It is a disc embedded in the uterine wall, it contains villi on the embryo’s side of the tissue while there are blood spaces on the Mother's side, which surround the villi.
Function of placenta
The placenta acts as a respiratory and excretory surface.
i. It provides a large surface area for glucose and oxygen to pass from the mother to
the embryo.
ii. It also helps to remove the waste substances generated by the foetus by transferring them into the mother’s blood.
A student is observing a permanent slide showing sequentially the different stages of asexual reproduction taking place in yeast. Name this process and draw diagrams of what he observes, in a proper sequence.
The yeast reproduces by the process of budding. 
List six specific characteristics of sexual reproduction.
Characteristics of sexual reproduction:
(i) Sexual reproduction takes place by the combination of special reproductive cells called sex cells.
(ii) It usually involves two parents male and female.
(iii) It involves the formation of gametes followed by the fusion of the gametes.
(iv) It is comparatively slower as compared to asexual reproduction.
(v) Meiosis and mitosis occur during gamete formation, while mitosis takes place during the development of the zygote.
(vi) Variations appear because of a new combination of genes during crossing over.
List four points of significance of reproductive health in a society. Name any two areas related to the reproductive health which have improved over the past 50 years in our country.
The significance of reproductive health in a society:
(a) It prevents the spread of various sexually transmitted diseases such as AIDS, syphilis etc.
(b) Good reproductive health ensures that the offsprings produced are healthy and have better chances of survival.
(c) Better sex education and awareness help to maintain the population and prevent the population explosion.
(d) It helps to avoid unwanted and teen pregnancies.
The areas in which reproductive health have improved over the past 50 years. include
(a) Family planning: Better family planning has led to the reduction in family size.
(b) Decreased mortality rate of the mother and infant because of better health care facilities and post natal care.
(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.
(a) Leydig cells of testes produce sperms and secrete a hormone called testosterone.
The function of testosterone is to control the development of male sex organs and secondary male features such as a deeper voice, moustache, beard and more body hair .
(b)
i. Fertilisation takes place in the oviduct or fallopian tubes.
ii. Implantation of the fertilised egg occurs in the uterus.
The foetus gets its nourishment from the special tissue called placenta. After implantation, a disc-like special tissue called placenta develops between
the uterus wall and the embryo. The placenta helps in the exchange of nutrients,
oxygen and waste products between the embryo and the mother. Thus, it
provides nourishment to the growing embryo
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.
(A) A fine screw is used to focus the slides of budding in yeast under high power of a microscope.
(B) Sequence showing budding in yeast:
Write one difference between asexual and sexual mode of reproduction. Which species is likely to have better chances of survival - the one reproducing asexually or the one reproducing sexually? Justify your answer.
The difference between asexual and sexual reproduction is that in asexual reproduction only one parent is involved, whereas in the sexual mode of reproduction two parents are involved.
The organisms reproducing sexually have better chances of survival because it incorporates variations and promotes diversity of characters in an offspring due to combinations of genes and thus the offsprings are better adapted to the environment and therefore have better chances of survival.
What is the effect of DNA copying, which is not perfectly accurate, on the reproduction process? How does the amount of DNA remain constant though each new generation in a combination of DNA copies of two individuals?
The not so perfect DNA copying produces variation in the reproduction process. The variation may be useful or harmful, The useful selection is selected by nature whereas, the harmful ones are discarded.
The amount of DNA remains constant because meiosis in the cells produces gametes. The gametes are a special type of cells called reproductive cells which contain only half the amount of DNA as compared to the normal body cells of an organism. The gametes combine during the process of fertilisation and restore the original chromosomal number and thus maintain a constant amount of DNA through each generation.
(a) Name the parts labelled as A, B, C and D in the diagram given below:
(b) What is pollination? State its significance.
(c) How does fertilisation occur in flowers? Name the parts of the flower that develop into (i) seed, and (ii) fruit after fertilisation.
(a)
A - Pollen grain
B - Pollen tube
C - Ovary
D - Female germ cell
(b) Pollination is the process of transfer of pollen grains from anther to stigma of the flower.
Significance of pollination: Pollination is a significant event because it precedes fertilization. It brings the two types of gametes closer for the process of fertilization.
Pollination like cross pollination introduces variations in the plants due to mixing of
different genes which increases adaptability towards environment .
(c) Fertilisation in plants: In plants, pollination is followed by fertilisation. Once
the pollen grains are deposited on the stigma, they form pollen tubes. The pollen tubes grow through the ovules and reach the ovary where ovules are located. The pollen tube normally enters the ovule through a small opening called micropyle. Inside the ovule, the pollen tube releases two male gametes into the embryo sac.
The embryo sac of the ovule contains the egg. One male gamete fuses with the
egg. This fusion of male and female gamete is called syngamy and its product is
called zygote. The other male gamete fuse with two polar bodies and this
process is called triple fusion, where three nuclei are involved in the fusion
process, one male gamete and two polar nuclei. Thus, inside each embryo sac,
two fusions, syngamy and triple fusion, takes place. This mechanism of two
fusions occurring in an embryo sac is called double-fertilization.
After fertilization,
i. ovules develop into the seeds and
ii. ovary develops into the fruit.
Why is vegetative propagation practiced for growing some types of plant? List two plants which are grown by this method.
Vegetative propagation practised for growing some types of plant
i. Certain plants have lost the ability to produce seeds.
ii. To produce genetically similar plants.
Two plants which are grown by this method are:
i. Banana
ii. Rose
State the role of placenta in the development of embryo.
The placenta plays the following role in the development of embryo:
i. Provides oxygen and nutrients to your growing baby
ii.It moves waste products from your baby's blood and helps in excretion.
List and explain in brief three methods of contraception.
The three methods of contraception are:
i. Mechanical barrier - For example condoms on penis and similar covering on vagina serve to block the sperm and does not allow it to reach the egg.
ii. Pills - These act by changing the hormonal balance of the body so that eggs are not released and fertilisation cannot occur. These drugs commonly need to be taken orally as pills.They can cause side-effects.
iii. Contraceptive devices - Like the loop or the copper-T are placed in the uterus to prevent pregnancy. They too can cause side effects due to irritation of the uterus.
Distinguish between unisexual and bisexual flowers giving one example of each. Draw a diagram showing the process of germination of pollen grains stigma and label the following parts:
(a) Female Germ cell
(b) Male germ cell
(c) Ovary
| Unisexual flowers | Bisexual flowers |
| The flower has either male reproductive organs (stamens) or the female reproductive organs (pistil) | The flower has both the male reproductive organs (stamens) and the female reproductive organs (pistil) in a single flower. |
| eg papaya | eg hibiscus |
Draw a diagram of a human female reproductive system and label the part.
i. That produces eggs
ii. Where fusion of egg and sperm takes place.
iii. Where zygote is implanted.
What happens when the egg is not fertilised?
Human female reproductive system
If the event that egg is not fertilised, the egg lives for about one day. The uterus prepares itself every month to receive a fertilised egg since the ovary releases one egg every month.
As the implantation does not take place the thick lining is no longer required, thus 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.
List any, four reasons for vegetative propagation being practised in the growth of some type of plants.
Four reasons why vegetative propagation is practised in the growth of some type of plants are;
i. As some plants do not produce seeds.
ii. It is a cheaper, easier and a rapid method.
iii. To maintain the character and traits of certain plants. The plants produced by this method are genetically similar.
iv. Used in methods such as layering or grafting to grow many plants like sugarcane, roses, or grapes for agricultural purposes.
Describe the role of fallopian tubes in the female reproductive system.
The fallopian tube is responsible for carrying the egg to the uterus. The finger-like processes or fimbriae of the tube reach out into the pelvic cavity and picks up the released egg. The fallopian tubes are not only crucial for the transport of the egg from the ovary to the uterus, they are also the location where the sperm meets the egg cell and fertilises the egg.
What does HIV stand for? Is AIDS an infectious disease? List any four modes of spreading AIDS.
HIV stands for Human Immunodeficiency Virus. It is the virus responsible for the disease AIDS.
Yes, AIDS is an infectious disease.
The four modes of spreading AIDS are:
i. Sexual intercourse with an infected person.
ii. Use of infected needles or syringe.
iii. Transfusion of blood from an infected person to a healthy person.
iv. From a infected pregnant mother to the child during pregnancy, birth and breasfeeding.
The shape of yeast cell is
only spherical
only oval.
irregular.
both oval and spherical.
B.
only oval.
With the help of suitable diagrams, explain the various steps of budding in Hydra.
The hydra reproduces by the process of budding by the use of regenerative cells. It carries out the process in the follwoing steps:
i. A bud develops as an outgrowth due to repeated cell division at one
specific site.
ii. The buds develop into tiny individuals
iii. When fully mature, these buds detach from the parent body and become new independent individuals.
What is binary fission in organisms? With the help of suitable diagrams, describe the mode of reproduction in Amoeba.
Binary fission which means division in half. It is a kind of asexual reproduction. It is the most common form of reproduction in prokaryotes and occurs in some single-celled eukaryotes. After replicating its genetic material, the cell divides into two nearly equal sized daughter cells.
In unicellular organisms like Amoeba cell division, or fission, leads to the creation of new individuals. The parent cell simply splita into two equal halves during cell division. In organisms such as Amoeba, the splitting of the two cells during division can take place in any plane.
It takes place in the following steps
i. Parent cell enlarges and the nucleus develops constriction.
ii. The cytoplasm divided with the two nucleus.
iii. The cell divides into two.
You have been selected to talk on “ozone layer and its protection” in the school assembly on ‘Environment Day.’
(a) Why should ozone layer be protected to save the environment?
(b) List any two ways that you would stress in your talk to bring in awareness amongst your fellow friends that would also help in the protection of ozone layer as well as the environment.
Students in a school listened to the news read in the morning assembly that the mountain of garbage
in Delhi, suddenly exploded and various vehicles got buried under it. Several people were also injured
and there was traffic jam all around. In the brain- storming session, the teacher also discussed this issue and asked the students to find out a solution to the problem of garbage. Finally, they arrived at two main points - one is self-management of the garbage we produce and the second is to generate lee
garbage at the individual level.
(a) Suggest two measures to manage the garbage we produce.
(b) As an individual, what can we do to generate the least garbage ? Give two points.
(c) List two values the teacher instilled in his students in this episode.
(a) Garbage can be used to landfill and can be used for making fertilizers and manure.
(b) To reduce the garbage we should follow three 'R' rule such as Reuse, Recycle, Reduce.
(c) Value of environment and healthy life.
Management of the garbage we produce and learn to generate less garbage at an individual level.
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