How do the Organisms Reproduce Class 10 Science Exam Questions

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Class 10 Science Exam Questions How do the Organisms Reproduce

Class 10 Science students should read and understand the important questions and answers provided below for How do the Organisms Reproduce which will help them to understand all important and difficult topics.

Very Short Answer:

Question. After examining a prepared slide under the high power of a compound microscope, a student concludes that the given slide shows the various stages of binary fission in a unicellular organism. Write two observations on the basis of which such a conclusion may be drawn. 
Answer : (a) The nucleus of mature cell seems elongated and a grove is formed in cell which divides the nucleus.
(b) A single parent divides to form two daughter cells. Constriction appears due to the division of cytoplasm.

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

Question. A student is viewing under a microscope a permanent slide showing various stages of asexual reproduction by budding in yeast. Draw diagram of what he observes in proper sequence.
Answer :

Question. List in proper sequence four steps of obtaining germinating dicot seeds.
Answer : (a) The root is formed when radicle of seed grows.
(b) The root grows downward into the soil and absorbs water and minerals from the soil.
(c) The shoot is formed from the upward growth of plumule.
(d) The green leaves are developed when shoot comes above the ground.

Question. When a cell reproduces, what happens to its DNA ?
Answer : During the process of reproduction, transmission of DNA from parents to offspring takes place. Before reproduction, DNA is replicated, which means two copies of DNA are produced. When the cell divides, the two copies are distributed equally between the two daughter cells so that similar amount and type of DNA is transferred from the parent cell to the daughter cells.
It maintains the consistency in the amount and type of DNA in the living organism of a particular species.

Question. Name the method by which spirogyra reproduces under favourable conditions. Is this method sexual or asexual ?
Answer : Under favourable conditions, spirogyra reproduces by fragmentation. This is an asexual method of reproduction.

Question. How does Planaria reproduce ? Is this method sexual or asexual ?
Answer : Planaria reproduces by the process of regeneration. It is a type of asexual reproduction in which planaria is cut into any number of pieces each piece grows into a new organism.

Question. Draw a labelled diagram in proper sequence to show budding in hydra.
Answer :

Question. What is the end product of double fertilisation ?
Answer : In double fertilisation one of the male gametes fuse with egg cell to form a zygote whereas the other male gamete fuses with two polar nuclei to form primary endosperm that provides nourishment to the growing embryo.

Question. Newly formed DNA copies may not be identical at times. Give one reason.
Answer : During the process of replication of DNA, most of the base sequences in the new copies are identical to those in the parent DNA. However, some changes can occur either due to mutation or due to minor errors during replication process. Thus, the newly formed DNA copies may not be identical at times.

Question. How does Plasmodium reproduce. Is this method sexual or asexual ?
Answer : Plasmodium reproduces by a process known as multiple fission. Multiple fission is a type of asexual reproduction in which a single parent cell divides into several daughter individuals. In this process, the parent nucleus divides several times into a number of daughter nuclei. Later the cytoplasm divides into as many pieces as the number of nuclei and each piece surrounds each nucleus. Each uninucleated piece develops an outer membrane and finally the parent cell divides into several uninucleate individuals.

Question. Name the agents which bring about cross pollination.
Answer : Insects, wind, water, animals etc., are the agents which bring about cross pollination.

Question. Explain : (a) IUCD (b) STDs
Answer : (a) IUCD—Intra Uterine Contraceptive Devices.
(b) STDs —Sexually Transmitted Diseases.

Question. How does the chemical method help in preventing pregnancy ?
Answer : Chemical methods prevent the ovaries from releasing the egg hence no fertilisation can occur thus preventing pregnancy.

Question. Draw diagrams showing reproduction in yeast in proper sequence. 
Answer :

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

Question. Draw a labelled diagram to show that particular stage of binary fission in Amoeba in which its nucleus elongates and a constriction appears in its cell membrane.
Answer :

Question. Why is vegetative propagation practiced for growing types of plants ?
Answer : Vegetative propagation practiced for growing types of plants because :
(a) The plants which cannot produce seeds or produce non-viable seeds also can be easily propagated by this method.
(b) It is a very easy, quick and cheapest method of propagation.
(c) Seedless plants can be produced by vegetative propagation.
(d) Flowers and fruits are produced in very short time.
(e) Parental features are preserved.

Question. Draw a diagram showing different parts of an embryo of gram seed and label them.
Answer :

Question. List any four modes of asexual reproduction.
Answer : Fission, fragmentation, regeneration, budding, vegetative propagation, spore formation etc., are the modes of asexual reproduction.

Question. Describe briefly how regeneration is carried out in Planaria.
Answer : When the body of Planaria by any means is cut into two or more number of pieces. Each piece contains specialised cells. These cells proliferate and make large number of cells. From this mass of cells different cells undergo changes to become various cell types and tissues finally developing into new organism.

Question. Name the organs producing sperms and ova respectively in humans.
Answer : Testis produces sperms and ovary produces ova.

Question. Name the method by which Planaria reproduce under favourable conditions. Is this method sexual or asexual?
Answer : Regeneration. Asexual

Question. Name the method by which Spirogyra reproduce under favourable conditions. Is this method sexual or asexual?
Answer : Fragmentation. Asexual

Question. Name the method by which Plasmodium reproduce under favourable conditions. Is this method sexual or asexual?
Answer : Multiple Fission. Asexual

Question. You have to perform the experiment, ‘‘To identify the different parts of an embryo of a gram seed.’’ Describe the procedure that you would follow.
Answer : (a) Soak a few seeds of gram or Bengal gram and leave them overnight.
(b) Drain the excess water.
(c) Cover the seeds with a wet cloth and leave them for a day.
(d) Cut open the seed carefully and observe the different parts.

Question. Name two ways of vegetative propagation practiced by gardeners.
Answer : Cutting and grafting.

Question. Regeneration is not possible in all types of animals. Why? 
Answer : Regeneration is carried by specialised cells. The organisms which have those cells only can show regeneration.

Question. Why is sexual reproduction considered to be superior to asexual reproduction is terms of evolution?
Answer : Sexual mode of reproduction is a source of variation (in a population of organisms) which ensures survival of the species.

Question. Malarial parasite divides into many daughter individuals simultaneously through multiple fission.
State an advantage the parasite gets because of this type of reproduction.
Answer : a. Progeny is identical like parent and in large number.
b. Single individual can reproduce.

Question. What is the effect of DNA copying which is not perfectly accurate on the reproduction process?
Answer : Leads to variation/ evolution.

Question. When a cell reproduces, what happens to its DNA?
Answer : Its DNA first doubles up followed by its equal and accurate division between two daughter cells.

Question. List two functions of ovary of human female reproductive system.
Answer :  In human female, ovary contains thousands of eggs.
One egg is produced every month one of the ovaries. 
Ovary also secretes estrogens hormone for development of sexual characteristics at puberty.

Question. a. What is the location of the following:
(i) DNA in a cell (ii) Gene
b. Expand DNA.
Answer : 
a. (i) Nucleus. (ii) Located on the chromosomes.
b. Deoxyribo Nucleic Acid.

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

Question. How can pregnancy be prevented surgically?
Answer : Pregnancy can be prevented surgically by adopting:
a. Vasectomy: When vas deferens in males are blocked surgically, sperm transfer will be prevented.
b. Tubectomy: When fallopian tubes are blocked,eggs will not be able to reach the uterus.

Question. “Variations” are seen in the organisms. State the two main causes of variation.
Answer :  Variations are caused by:
a. Change in the genetic material, i.e., DNA at the time of DNA copying.
b. Environmental factors viz., light, temperature, nutrition, wind and water supply, etc.
c. Mutations.

Question. Define the following processes of asexual reproduction:
a. Spore formation
b. Regeneration
c. Multiple fission
Answer : 
a. Reproduction seen in organisms by formation of spores.
b. Organisms are cut into any number of pieces and each piece grows into a complete organism.
c. Unicellular organisms divide into many daughter cells simultaneously.

Question. What happens when the following situations are initiated:
a. A Planaria is cut into three different pieces.
b. Leaf of the Bryophyllum with notches falls on the soil.
c. Testosterone is released in the male reproductive system.
Answer : a. Each piece grows into a complete organism.
b. Develops into new plants.
c. Changes occurs in the appearance at the time of puberty.

Question. Draw labelled diagrams to illustrate budding in Hydra.
Answer : 
a. In sexual reproduction, fusion of male and female gametes takes place, these germ-cells/gametes contain half the number of chromosomes and by the fusion of these gametes the zygote is formed with full set of chromosomes.
b. When male and female gametes fuse at the time of fertilization, it restores the original number of chromosomes (of the parent), ensuring the stability of species.

Question. “The chromosomal number of the sexually producing parents and their offspring is the same.” Justify this statement.
Answer : a. DNA copying is essential for formation of addition cellular apparatus, so that when DNA copies separate, each cell gets its own cellular apparatus.
b. The process of DNA copying results in variation each time. As a result, the DNA copies generated will be similar, but may not be identical to the original.

Question. Define variation in relation to a species. Why is variation beneficial to the species?
Answer : Variation means certain changes which occur in sexually reproducing organisms because of errors in DNA copying. Variations are beneficial for species because they given survival advantage even in the adverse environmental conditions.

Question. Why do we need to adopt contraceptive measures?
Answer :
a. Contraceptive measures are needed to be adopted to prevent unwanted pregnancies.
b. To prevent sexually transmitted diseases.
c. Spacing between children.
d. For sound health of a mother.

Question: Name the causative agent of the disease ‘‘Kalaazar’’ and its mode of asexual reproduction.
Answer: Causative agent of the disease Kala-azar is Leishmania. It reproduces asexually by binary fission.

Question: List two functions of ovary of human female reproductive system.
Answer: Two functions of ovary of human female are:
(i) production of female gametes i.e., ova
(ii) secretion of female hormones i.e., estrogen and progesterone.

Question: What are all organisms called which bear both the sex organs in the same individual. Give one example of such organism.
Answer: Organisms which bear both male and female sex organs in the same individual are called bisexual. For example, Hibiscus.

Question: List two unisexual flowers. 
Answer: Flowers of papaya and cucumber are unisexual.

Question: Name the parts of a bisexual flower that are not directly involved in reproduction.
Answer: Calyx and corolla are parts of a flower that are not directly involved in reproduction.

Question: Name the largest cell present in human body.
Answer: Ovum is the largest cell present in human body.

Question:No two individuals are absolutely alike in a population. Why?
Answer: No two individuals are absolutely alike in a population because sexual reproduction promotes diversity of characters in the offsprings by providing genetic variation.

Question: Why is ferilisation not possible without pollination? 
Answer: The process of pollination (in plants) ensures that male gametes bearing structure called pollen comes in contact with the female reproductive structure of the plant. Once the male and female gametes are in close vicinity, they fuse and fertilisation is accomplished. Hence, fertilisation cannot take place without pollination.

Question: Identify and write the male reproductive parts from the list of different parts of a flower given below: Stigma, Sepal, Anther, Petal, Ovule, Filament
Answer: The male reproductive parts that are present in a flower from given list are:
(i) anther and (ii) filament.

Short Answer:  1

Question: What is the role of seminal vesicles and prostate gland?
Answer: These are the accessory glands associated with the male reproductive system. Seminal vesicles and prostrate gland secrete a fluid which makes the transport of sperms easier and also provides nourishment to the sperms. This fluid together with the sperms is called the semen.

Question: Draw a well labelled diagram of a dicot seed (gram seed).
Answer:

Question: What does the male and female reproductive system consists of?
Answer: The male reproductive system in human beings consists of testes which produce sperms, vas deferens, seminal vesicles, prostrate gland, urethra and penis.
The female reproductive system consists of a pair of ovaries, fallopian tube, uterus and vagina.

Question: State the changes that occur in human males and females at puberty.
Answer: Puberty is the state of sexual maturiy in humans. The changes that take place in males during puberty are growth of hair on the body, appearance of beard and moustache and the voice becomes hoarse. Females show development of breasts, and beginning of menstruation.

Question: What is ‘reproduction’? Mention the importance of DNA copying in reproduction.
Answer: Reproduction is the process by which the existing organisms produce their own kind.
DNA copying during reproduction is important for the transfer of parental characters to the offspring.

Question: Mention the information source of making proteins in the cell. What is the basic event in
reproduction?
Answer: Cellular DNA is the information source of making proteins in the cell.
The basic event in reproduction is copying of DNA so that the cells can further divide.

Question: (a) In human body what is the role of
(i) Seminal vesicles
(iii) Prostrate glands.
(b) List two functions performed by testes in human beings.
Answer: (a) Seminal vesicles: Produce a fluid which makes the transport of sperms easy.
Prostate glands: Produces a fluid which keeps sperms floating in it and provides nourishment.
(b) Two functions of testes:
(i) They secrete hormone: testosterone responsible for the male characteristics.
(ii) It helps in the formation of sperms.

Question: (a) Draw a diagram showing longitudinal section of a flower and label on it:
stigma, ovary, anther, filament.
(b) How is the process of pollination different from fertilisation?
Answer: (a)

Question: (a) Explain the terms:
(i) Implantation (ii) Placenta
(b) What is the average duration of human pregnancy?
Answer: (a) (i) Implantation: The zygote when fixes itself on the inner thick wall of uterus for further development is called implantation.
(ii) Placenta: It is the special tissue in the form of a disc which is embedded in the uterus wall. It provides large surface area for glucose and oxygen to pass from mother to the embryo. The waste generated by the embryo also passes into the mother’s blood through this placenta
(b) It takes nine months for the human pregnancy.

Question: Name the following:
(i) Name two plants that cannot produce seeds.
(ii) An organism that reproduces by budding and regeneration.
(iii) An organism that grows by multiple fission
(iv) One unisexual flower.
Answer: (i) Bryophyllum, Banana
(ii) Hydra
(iii) Paramecium
(iv) Maize flower

Question: Give one term for the following:
(a) Beginning of menstrual cycle
(b) Release of ovum from the ovary
(c) Fusion of male and female eggs
(d) Prevention of unwanted pregnancy
(e) Time for development of offspring in female human.
Answer: (a) Menstruation
(b) Ovulation
(c) Fertilisation
(d) Contraception
(e) Nine months

Question: List two preparations shown every month by the uterus in anticipation of pregnancy in humans.
Answer: The two preparation shown every month by the uterus in anticipation of pregnancy in human are:
(i) the wall of uterus becomes thick to receive the fertilised egg and
(ii) the uterine wall is richly supplied with blood to nourish the growing embryo.

Question: “The chromosomal number of the sexually producing parents and their offspring is the same”. Justify this statement. 
Answer: In sexual reproduction, two gametes, male and female, combines together to form a new cell ‘zygote’. The reproductive cells or gametes contain only half the amount of DNA as compared to the non-reproductive cells of an organism. So, when a male gamete combines with a female gamete during sexual reproduction, then the new cell ‘zygote’ will have the normal amount of DNA. For example, the human sperm has 23 chromosome and the human egg has also 23 chromosomes. So when a sperm and an egg fuse together during fertilisation, then the zygote formed will have 23 + 23 = 46 chromosomes, which is the normal number of chromosomes in humans.

Question: State one genetically different feature between sperms and eggs of humans. What is its consequence? 
Answer: A sperm may have X or Y chromosomes whereas egg have X chromosomes. The consequence of this is that sperm decides the sex of the child because eggs contribute only X chromosome while sperms contribute either X or Y chromosomes to the offspring. Therefore, if a child inherits X chromosome from her father, will be a girl and the one that inherit Y chromosome will be a boy.

Question: List the parts of human male reproductive system which contribute fluid to the semen. State two advantages semen offers to the sperms. 
Answer: The secretion of male accessory reproductive glands i.e., seminal vesicles, prostate gland and Cowper’s glands contribute fluid to the semen. The two advantages that semen offers to the sperms are :
(i) it provides nutrition to the sperm and
(ii) it also activates the sperms and make their transport easier into the vagina of female during sexual act.

Question: Explain the terms:
(i) Implantation of zygote
Answer: (i) Implantation of zygote refers to the process of attachment of the blastocyst on the inner wall of the uterus. It occurs on 7th day after fertilisation and is controlled by estrogen and progesterone hormones.

Question: Explain giving one example of each, the unisexual and the bisexual flowers.
Answer: (i) Unisexual flowers : These flowers contain either stamens (male reproductive part) or carpel (female reproductive part). Example: Papaya, watermelon.
(ii) Bisexual flower : The flower is said to be bisexual when both male and females parts i.e., stamens and carpels, are present on the same flower. Example : Hibiscus, mustard.

Question: Describe the role of Fallopian tubes in the female reproductive system. flower. Example : Hibiscus, mustard.
Answer: Fallopian tubes are a pair of elongated, ciliated, muscular and tubular structures extending from close to ovaries to uterus. It is the site of fertilisation and helps in the conduction of ovum or zygote towards uterus by ciliary action and peristalsis.

Question: State the role of placenta in the development of embryo.
Answer: Placenta is a physiological connection between an embryo and uterine wall of the mother through which nutrients and other useful substances enter into fetus from mother’s blood and waste products like urea and carbon dioxide are expelled into mother’s blood from fetus.

Question: Draw a diagram of the longitudinal section of a flower and label on it (i) stigma and (ii)ovary. 
Answer: The labelled diagram of L.S. of flower is as follows: 

Question: Describe the role of the following in human beings.
(i) Seminal vesicles
(ii) Prostate gland 
Answer: (i) Seminal vesicles are one pair of sac like structures near the base of bladder. Seminal fluid is a watery alkaline fluid that contains nutrients (fructose) which serve as a source of energy for the sperm. Each seminal vesicle releases its contents into the ejaculatory duct during ejaculation.
(ii) Prostate gland is a single large gland that surrounds urethra. It secretes a slightly acidic, milky fluid that forms 25% of volume of semen. Secretion of prostate gland nourishes the sperms and helps in its mobility.

Question: Name one sexually transmitted disease each caused due to bacterial infection and viral infection. How can these be prevented?
Answer: Gonorrhoea is a sexually transmitted disease caused by bacterium Neisseria gonorrhoeae. AIDS (Acquired immunodeficiency syndrome) is a sexually transmitted disease caused by HIV (Human immunodeficiency virus). These sexually transmitted disease can be prevented by following monogamy and by using male or female condoms during sexual act.

Question: List any two differences between pollination and fertilisation. 
Answer: Differences between pollination and fertilisation are as follows 

Short Answer:  II 

Question: Deffine reproduction. How does it helps in providing stability to the population of species? 
Answer: The production of new organisms by the existing organisms of the same species is known as reproduction. It is linked to the stability of population of a species. DNA replication during reproduction ensures transfer of specific characters or body design features that is essential for an individual of a population to live and use that particular niche. Some variations present in a few individuals of population caused due to reproduction also help in their survival at changing niches.

Question: What is the effect of DNA copying, which is not perfectly accurate, on the reproduction process? How does the amount of DNA remain constant through each new generation is a combination of DNA copies of two individuals? 
Answer: In the process of reproduction, if DNA copying is not perfectly accurate, variation occurs.These in turn may allow few individuals of a population to survive in an altered niche and becomes the basis of evolution and over time. Such variations are useful for the survival of species.
The combination of DNA copies of two individuals (male and female) occurs during
sexual reproduction. Reduction division (meiosis) during gamete formation halves the chromosome number in both male and female gametes. Since these two gametes fuse during fertilisation, the original number of chromosomes (as in the parent) is restored in the offspring. By this way the amount of DNA remains constant in each new generation.

Question: What is DNA copying? State its importance.
Answer: DNA copying is the production of similar copies of DNA present in a cell using various
chemical reactions. DNA copying is essential for reproduction through which the organisms pass on their body features to their off springs. Moreover, minor alternations during the process of DNA copying result in the production of variations. Such variations are useful for the survival of species over time.

Question: Name the reproductive parts of an angiosperm. Where are these parts located? Explain in brief the structure of its female reproductive parts.
Answer: The reproductive organs of an angiosperm are stamen (male reproductive part) and carpel/pistil (female reproductive part).These are located in the flowers of an angiospermic plant.
The given diagram shows the structure of female reproductive part of aflower.

A carpel is made of three parts : stigma, style and ovary. The top part of carpel is called stigma.
Stigma is for receiving the pollen grains during pollination. Stigma is sticky so that pollen can stick to it. The middle part of carpel is called style.
Style is a tube which connects stigma to the ovary. The swollen part at the bottom of a carpel is called ovary. The ovary contains ovules. Ovules contain the female gametes or female sex cells (egg) of the plant. There are usually many ovules in the ovary. Each ovule contains only one female gamete of the plant.

Question: 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.
Answer: The four methods of birth control which deliberately prevent fertilisation in humans are:
(i) Barrier method- These are physical devices to prevent the entry of sperm in the female e.g.,condoms.
(ii) Chemical method – It involves the use of oral pills that check ovulation. These are mainly hormonal preparations and contain estrogen and progesterone.
(iii) Intrauterine contraception device- These devices are implemented into uterus, e.g., copper – T, to prevent fertilisation.
(iv) Surgical methods : These methods involves removal of a small portion of vas deferens in males or Fallopian tube in females to prevent fertilisation.
Contraception prevents frequent pregnancies and sexually transmitted diseases thus supports good health and prosperity of a family.

Question: (a) Mention the role of the following organs of human male reproductive system.
(i) Testis (ii) Scrotum (iii) Vas deferens (iv) Prostate gland
(b) What are the two roles of testosterone?
Answer: (a) (i) Testis :The two testes in male are the sites where male gametes, i.e., sperms are formed. Testes also produce the male sex hormone called testosterone.
(ii) Scrotum :The scrotum is a pouch of skin that lie outside abdominal cavity. The two testes lie in respective scrotal sacs. The scrotum acts as a thermoregulator and provides an optimal temperature for the formation of sperms.
(iii) Vas deferens : This a straight tube, about 40 cm long, which carries the sperms to the seminal vesicles, where mucus and a watery alkaline fiuid containing fructose, mix with the sperms.
(iv) Prostate gland : It is a single large gland that surrounds the urethra and produces a milky, slightly acidic secretion. Secretion of prostate gland nourishes and activates the sperm to swim.
(b) Two roles of testosterone are :
(i) It plays a key role in development of male secondary sex organs such as prostate, etc.
(ii) It promotes the secondary sexual characteristics in males such as increased muscle and bone mass, growth of body hair, etc. 

Question: What are sexually transmitted diseases? List two examples each of diseases caused due to (i) bacterial infection and (ii) viral infection. Which device or devices may be used to prevent the spread of such diseases?
Answer: The diseases that are spread by sexual contact with an infected person are called sexually transmitted disease (STDs).
(i) Bacterial infection causes Gonorrhoea, Syphilis.
(ii) Viral infection causes AIDS, Genital herpes. STDs can be prevented by using male and female condoms.

Question: List four points of significance of reproductive health in a society. Name any two areas related to reproductive health which have improved over the past 50 years in our country.

Answer: The general awareness regarding reproductive health in a society is significant as :
(i) maintenance of personal hygiene among youngsters and proper knowledge of their reproductive parts helps them adjust with the physical changes and cope with emotional disturbance .
(ii) reproductively healthy society must be free from the curse of child marriage which begets many complications at the level of individual and society both.
(iii) proper care of expecting mothers, monitoring their health after child birth and care of new born help in building a healthy society.
(iv) married couples aware of contraceptive methods lead a better married life as they are capable of avoiding unwanted pregnancies and have negligible chances of contracting sexually transmitted diseases. In past 50 years various areas related to reproductive health have been launched which have improved
the reproductive health of our society in following ways : Two of them are :
(i) reduced mortality rate of mother and infant
(ii) birth control due to easily available contraceptive and reduced STDs cases.

Question: List six specific characteristics of sexual reproduction. 
Answer: Six specific characteristic of sexual reproduction are as follows:
(i) Two different sexes, i.e., male and female are involved in this process.
(ii) Sexual reproduction involves formation of special sex cells called gametes.
(iii) Fusion of gametes or fertilisation takes place in the body of female (internal fertilisation) or outside (external fertilisation).
(iv) Off springs inherit traits from both parents (heredity) and also show some new traits of their own (variation), hence they are not clones of the parents.
(v) Variations in sexually reproducing organisms arises on account of crossing over during meiotic division during gamete formation.
(vi) It plays a prominent role in origin of new species as it leads to variations which accumulate over a period of time and get carried to successive generations.

Question: What is placenta? Explain its function in humans.
Answer: Placenta is an intimate connection between fetus and uterine wall of the mother to exchange the materials. It is a disc shaped structure embedded in the uterine wall. It contains villi on embryo’s side and blood spaces towards mother’s side. Blood spaces surround villi. Placenta performs the following functions :
(i) All nutritive elements from maternal blood pass into the fetus through it.
(ii) Placental helps in respiration i.e., supply of oxygen and removal of CO₂ from fetus to maternal blood.
(iii) Fetal excretory products diffuse out into maternal blood through placenta and are excreted by mother.
(iv) Placenta also secretes hormone. 

Question: Write one main difierence between asexual and sexual mode of reproduction. Which
species is likely to have comparatively better chances of survival – the one reproducing
asexually or the one reproducing sexually? Justify your answer.
Answer: Difference between asexual and sexual mode of reproduction is as follows :

Species reproducing sexually have a better chance of survival as variation occurs only during the sexual reproduction. Variations are necessary for evolution and to increase chances of survival in changed environmental conditions.

Question: Why is DNA copying an essential part of the process of reproduction? What are the advantages of sexual reproduction over asexual reproduction?
Answer: DNA copying is an essential part of the process of reproduction as it results in passing of nearly same genetic information from parents to the offsprings. DNA replication also ensures that same number of chromosomes are passed from parents to offspring.
Advantages of sexual reproduction over asexual reproduction is that sexual reproduction provides variations which is a major factor for evolution that helps in survival of species in changing environment. 

Question: Write names of those parts of a flower which serve the same function as the following do in the animals
(i) testis
(ii) sperm
(iii) ovary
(iv) egg. 
Answer: The parts of a flower which serve the same function as following do in the animals are
(i) testis – anther of stamen
(ii) sperm – pollen
(iii) ovary – ovary of pistil
(iv) egg – female germ cell present in ovule. 

Question: Draw a diagram of the longitudinal section of a flower exhibiting germination of pollen on stigma and label (i) ovary, (ii) male germ-cell,(iii) female germ-cell and (iv) ovule on it.
Answer: The diagram of the longitudinal section of flower is follows:

Question: On the notice board of ultrasound clinics it is generally stated. “Here prenatal sex determination and disclosure of sex (boy or girl before birth) of fetus is not done. It is prohibited and punishable under law.”
(a) List two advantages of imposing ban on prenatal sex determination.
(b) What can students do to educate the society about the following?
(i) The ill-effects of indiscriminate female feticide.
(ii) Adopting small family norms.
Answer: (a) The two advantages of imposing ban on prenatal sex determination are
(i) check on female feticide
(ii) improving sex ratio in the country.
(b) Students should educate the society as that 
(i) female feticide is reducing the number of girls drastically in some societies. For a healthy society, the male-female sex ratio must be maintained at almost the same level. Due to reckless female feticide, the male-female child sex ratio is declining at an alarming rate in some sections of our society.
(ii) Children in a small family can be provided with all the resources from education, good amenities like food, clothing and healthy life style.
As the family grows larger, the resources should be shared with increased number of member. Having fewer children also keeps the mother in good health. 

Question: Write two examples each of sexually transmitted diseases causes by (i) virus, (ii) bacteria. Explain how the transmission of such diseases be prevented?
Answer: The infectious (communicable) diseases, which are spread from an infected person to a healthy person by sexual contact, are called sexually transmitted diseases.
Sexually transmitted diseases caused by virus are : AIDS (Acquired Immune deficiency Syndrome)
and genital warts while caused by bacteria are gonorrhoea and syphilis. Preventive measures for the diseases are:
(i) educating people in high risk groups.
(ii) mutually faithful monogamous relationship.
(iii) avoiding prostitution, multipartner sex and homosexuality.
(iv) using condoms, etc. 

Question: Name the two reproductive parts of a bisexual flower which contain the germ cells.
State the location and function of its female reproductive part.
Answer: The two reproductive parts of a bisexual flower which contain the germ cells are carpel (female reproductive part) and stamen (male reproductive part). Carpel is situated in the centre of the flower as a flask-shaped structure. A carpel is made up of three parts–stigma, style and ovary. The distal part of a carpel is called stigma. Stigma is responsible for receiving pollen during pollination. Style is an elongated tubular structure which connects stigma with ovary. The basal swollen part of carpel is ovary. Ovary bears several ovules. After fertilisation ovules form seeds and ovary forms the fruit.

Question: What does HIV stands for? Is AIDS an infectious disease? List any four modes of spreading AIDS. 
Answer: HIV stands for Human Immunodeficiency Virus. Yes, AIDS is an infectious disease. It is transmitted sexually or through exposure to contaminated blood.
Four modes of spreading AIDS are :
(i) unprotected sex with an infected partner
(ii) use of contaminated needle and syringes
(iii) use of contaminated razors for shaving
(iv) transfusion of infected blood or blood products.

Question: What is AIDS? Which microbe is responsible for AIDS infection? State one mode of transmission of this disease. Explain in brief one measure for prevention of AIDS.
Answer: AIDS is an infectious viral disease which weakens the immune system of human body and generally leads to death. It is caused by a retrovirus called HIV (Human Immunodeficiency Virus). AIDS can be transmitted by having sexual contact with an infected person. Use of condoms which are physical barriers can reduce the risk of a sexual exposure to HIV. 

Question: Expand AIDS. List any four methods of prevention (control) of AIDS.
Answer: AIDS is expanded as Acquired Immunode deficiency Syndrome. Four methods of prevention
or control of AIDS are :
(i) use of sterilised needles and syrings for injecting drugs or vaccine
(ii) to avoid sex with multiple partners
(iii) use of condoms during intercourse
(iv) avoid use of contaminated razor in barber shop. 

Long Answer:

Question: (a) ‘‘Use of a condom is beneficial for both the sexes involved in a sexual act.’’ Justify this statement giving two reasons.
(b) How do oral contraceptive help in avoiding pregnancies ?
(c) What is sex selective abortion ? How does it affect a healthy society ? (State any one consequence)
Answer : (a) Using condom for the penis during sex helps to prevent transmission of many of infections to some extent. The sexual act always has the potential to lead to pregnancy. Pregnancy will make major demands on the body and the mind of the woman, and if she is not ready for it, her health will be adversely affected. Therefore, many ways have been devised to avoid pregnancy.
Condoms on the penis or similar coverings worn in the vagina can serve this purpose. Another category of contraceptives acts 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.
However, since they change hormonal balances,
they can cause side-effects too. Contraception to avoid pregnancy can be achieved by the use of condoms. Thus, use of condoms is beneficial for both the sexes involved in a sexual act.
(b) Oral contraceptives act by changing the hormonal balance of the body so that eggs are not released and fertilisation cannot occur. Thus, in this way they help in avoiding the pregnancies.
(c) Sex-selective abortion of female foetuses involves surgical removal of unwanted pregnancies with female foetus. These may be misused by people who do not want a particular child. For a healthy society, the female-male sex ratio must be maintained due to the reckless female foeticides, child sex ratio is declining at an alarming rate in some sections of our society, although prenatal sex determination has been prohibited by law in order to protect the abortion of the female foetus.

Question: (a) Name the organ that produces sperms as well as secretes a hormone in human males. Name the hormone it secretes and write its functions.
(b) Name the parts of the human female reproductive system where fertilisation occurs.
(c) Explain how the developing embryo gets nourishment inside the mother’s body.
Answer : (a) The organ that produces sperms as well as secretes male hormones is testis. The hormone secreted by it is testosterone. Its important functions are as follows :
(i) It stimulates sperm production.
(ii) It stimulates the development of secondary sexual characters in males like growth of facial hairs, low pitch voice, etc.
(iii) It involves the development, maturation and functioning of male accessory sex organs like vas deferens and seminal vesicles.
(b) In human females reproductive system, the process of fertilisation takes place in one of the fallopian tubes.
(c) The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta.
Placenta is a vascular membranous organ that connects the developing foetus to the uterine wall of the mother. It contains villi on the embryo’s side of the tissue. This provides a large surface area for glucose and oxygen to pass from mother to the embryo. The placenta draws nourishment and oxygen, which it supplies to the foetus, from the maternal circulation. In turn, the placenta receives carbon dioxide and wastes of fetal metabolism and discharges them into the maternal circulation for disposal.

Question: (a) Draw a diagram showing germination of pollen on stigma of a flower and mark on it the following organs/parts :
(i) Pollen Grain (ii) Pollen tube
(iii) Stigma (iv) Female germ cell
(b) State the significance of pollen tube.
(c) Name the parts of flower that develop after fertilisation into
(i) Seed (ii) Fruit
Answer : 

(b) The pollen tube of most seed plants acts as a passage way. It transports sperm cells from the pollen grain, from the stigma (in flowering plants) to the ovules at the base of the pistil.
(c) After fertilisation, the zygote divides several times to form an embryo within the ovule.
(i) The ovule develops a tough coat and is gradually converted into a seed.
(ii) The ovary grows rapidly and ripens to form a fruit.

Question: Define pollination. Explain the different types of pollination. List two agents of pollination ? How does suitable pollination lead to fertilization ? 
Answer : Pollination is the transfer of pollen from the anther of the stamen to the stigma of the pistil with the help of air, water and insects.
Types of pollination :
(a) Self pollination : Transfer of pollen grain from the anther to the stigma of the same flower.
(b) Cross pollination : Transfer of pollen grain from the anther of one flower to the stigma of other flower of the same species.
Two agents of pollination are air, water, insects winds etc.
When correct species of pollen grain lands on the stigma it results in some chemical response from the ovary that causes the growth of pollen tube from pollen grain. The pollen grain slides down the pollen tube and enters the ovary where it meets the egg. This process is called as fertilization and leads to the formation of zygote.

Question: (a) Write the functions of each of the following parts in a human female reproductive system :
(i) Ovary, (ii) Uterus, (iii) Fallopian tube.
(b) Write the structure and functions of placenta in a human female.
Answer :
(a) (i) Functions of the Ovary :
1. It produces female gametes (ova).
2. It secretes female sex hormones.
(ii) Functions of Uterus :
1. It supports and nourishes the developing foetus.
2. It expands according to the growth of the baby.
(iii) Functions of Fallopian tubes :
1. They carry eggs from the ovary to the uterus.
2. They act as the site for fertilisation.
(b) Placenta is the connecting link between the mother’s body and the baby. It is a disc embedded in the uterine wall. This special tissue contains villi on the embryo’s side of the tissue. The mother’s end of placenta has blood spaces, which surrounds the villi. Placenta functions as a site of exchange of materials between the blood of mother to the baby. The developing embryo generates certain waste substances that are also removed through placenta. Thus, the placenta serves as the nutritive, respiratory and excretory organ of the foetus.

Question: With the help of suitable diagrams explain the various steps of budding in Hydra.
Answer : Budding is a form of asexual reproduction and is the process of production of new individual from an outgrowth called bud formed on the parent body. Regenerative cells present in Hydra are used for budding. Due to repeated mitotic divisions an outgrowth called bud develops from the parent body which enlarges in size and finally develops into a small hydra. After attaining suitable maturity the offspring get detached from the parent body and become an independent individual.

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

(b) What is contraception ? List three advantages of adopting contraceptive measures.
Answer : (a) The parts of the female Reproductive system are as follows :
1. Fallopian tube or Oviduct
2. Ovary 3. Uterus
4. Cervix 5. Vagina
(b) Contraception is the method by which a female inhibits fertilization and hence prevents pregnancy.
The three advantages of contraception are :
(i) It makes the people more aware about the concept of family planning keeping population under control.
(ii) It educates the people about Sexually Transmitted Diseases and ways to avoid it.
(iii) It helps the female to space children.
(iv) It reduces the risk of unwanted pregnancies.

Question: (a) Write the functions of the following parts in human female reproductive system :
(i) Ovary
(ii) Fallopian tube
(iii) Uterus
(b) Describe the structure and functions of placenta.
Answer : (a) (i) Ovary : Produces female gamete or ovum and Produces oestrogen or female sex hormones
(ii) Fallopian tube : Carries ovum from ovary to the uterus and acts as the site of fertilization.
(iii) Uterus : Site for implantation and nourishment of the future embryo.
(b) Structure of placenta : Placenta is a disc like structure embedded in the uterine wall. It has villi on the embryo’s side and blood species on the mother’s side which surround the villi. Function of placenta :
(i) Transports oxygen and nutrition from the mother’s blood to the embryo.
(ii) Removes the excretory substances from embryo into the mother’s blood.

Question: What is vegetative propagation ? Describe various methods of vegetative propagation.
Answer : The growth of new plants from vegetative parts of the plant like roots, stem, leaves other than the seeds is called vegetative propagation. Various methods of vegetative propagation are :
(a) Cutting : Small piece of plant part like roots, stem or leaves is cut and is used for propagation.
Examples : Rose, china-rose, sugarcane etc.
(b) Layering : It is the process where roots are induced when a stem comes in contact with the ground.
Examples : Grapevine, jasmine, litchi, mango etc.
(c) Grafting : It is a process of joining a part of a living plant like stem or bud to another plant and they grow as one plant. Examples : Lime, lemon etc.
(d) Propagation by plant tissue culture : In this method plant cells are cultured in an artificial culture
media, where a cell divides into undifferentiated mass of cells called callus which is transferred to different nutrient medium to grow into plantlets.
All the above methods are artificial method of vegetative propagation.
In natural methods of vegetative propagation underground roots [Root tubers of Dahlia] or underground stems [bulbs of onions, rhizomes of ginger] or adventitious buds on leaves [Bryophyllum] grow into new plants. 

Question: Give one example each of unisexual and bisexual flowers. Differentiate between the two types of pollination that occur in flowers. What happens when a pollen lands on a suitable stigma ? Write about the events that occur till the seed formation in the ovary.
Answer : Unisexual flower : Papaya or Water-melon or any other
Bisexual flower : Hibiscus or Rose.
Self pollination : The pollen grains are transferred from the anther to the stigma of the same flower or to the flower of the same plant.
Cross pollination : The pollen grains are transferred from the anther to the stigma of a flower of a different plant.
After pollen lands on a suitable stigma, a pollen tube grows out of pollen grain and travels through the style to reach the ovary. The male germ cell fuses with the female germ cell to form a zygote.
Zygote divides several times to form an embryo within the ovule.
The ovule develops tough coat and gradually gets converted into a seed.

Question: Study the below diagram and answer the following :
(a) Label the parts A, B, C and D.
(b) Which parts represent the male and female reproductive part respectively.
(c) What is the function of the parts labelled A and D ?
(d) What do you mean by pollination and explain the different types of pollination ?

Answer : (a) A – Petals; B – Stamens; C – Pistil; D – Sepals
(b) Part B [Stamens] represent male reproductive part and part C [Pistil] represent female reproductive part of a flower.
(c) The main function of petal is to attract insects for pollination so they are large, showy and brightly coloured. The main function of sepal is to protect the stamens and pistils.
(d) Pollination is the process of transfer of pollen grains from anther to the stigma of the carpel by various pollinating agents like wind, insects etc.
There are two types of pollination :
(i) Self-pollination : The transfer of pollen grains from anther of a flower to stigma of the same flower or different flower but in same plant is called self pollination.
(ii) Cross pollination : The transfer of pollen grains from anther of flower of one plant to stigma of another flower of different plant but of same species is called cross pollination.

Question: Draw a well labelled diagram of the female reproductive system in humans.
Answer:

Question: State the functions of the following:
(a) testis (b) ovaries (c) vas deferens (d) stamen (e) pistil
Ans. (a) Testis: Form the male gametes the sperms and secrete the male sex hormone testosterone
(b) Ovaries: Form the female gamete ovum or the egg cell and secrete the female sex hormones estrogen and progesterone.
(c) Vas deferens: Transport the sperms from the testis to the exterior.
(d) Stamen: Form the pollen grains in flowers. The pollen grains bear the male gametes.
(e) Pistil: The ovary forms the egg and the stigma helps in attracting the pollen grains for fertilisation.

Question: Illustrate the following with the help of a suitable diagrams:
(i) Regeneration in Planaria
(ii) Budding in Hydra
Answer: (i) Regeneration in Planaria

Planaria: If it is divided into 3 parts a, b and c, each part grows as a new individual

(ii) Budding in Hydra

Question: Illustrate the following with the help of suitable diagram
(i) Binary fission in Amoeba
(ii) Leaf of Bryophyllum with buds 
Answer: (i) Binary fission in Amoeba
(ii) Bryophyllum leaf

Question: Explain why variations are observed in the off springs of sexually reproducing organisms? 
Answer: Sexual reproduction involves fusion of male and female gametes coming from male and female parents. Variations occur due to
(i) fusion of gametes which come from two different and sexually distinct individuals and (ii) meiosis which occurs during gametogenesis and create a new combination of genes. It plays a prominent role in the origin of new species and leads to variations required for evolution. Therefore, off springs of sexually reproducing organisms show variation.

Question: (a) Give an example of a bisexual flower.
(b) Draw a longitudinal section of a pistil showing the germination of pollen grains. Label the following parts:
(i) Stigma (ii) Male germ cell (iii) Female germ cell (iv) Ovary (v) Style (vi) Pollen tube
Answer: (a) Hibiscus is an example of a bisexual flower.
(b) Diagrammatic representation of pistil showing germination is as follows:

Question: (a) Give one example each of unisexual and bisexual flower.
(b) Mention the changes a flower undergoes afer fertilisation.
(c) How does the amount of DNA remain constant though each new generation is a combination of DNA copies of two individuals. 
Answer: (a) Unisexual flowers bear organs of only one sex, i.e., either stamen or pistil, e.g., papaya.
Bisexual flowers contain both stamen and pistil,e.g., Hibiscus.
(b) After fertilisation, the fertilised egg (or zygote) divides several times to from an embryo within the ovule. the ovule develops a tough coat around it and is gradually converted into a seed.the ovary of flower develops and becomes a fruit (with seeds inside it). The other parts of flower like sepals, petals, stamens ,stigma and style dry up and fall off. Only the ovary is left behind. So, at the place on plant where we had a flower originally, we now have a fruit (which is the ovary of the flower containing seeds). A fruit protects the seeds.
(c) The amount of DNA remain constant in each new generation because of formation of haploid gametes. Gametes are 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. So, when a male gamete combines with a female gamete during sexual reproduction, then the new cell ‘zygote’ will have the normal amount of DNA. For example, the human sperm has 23 chromosomes and the human egg (or ovum) has also 23 chromosomes. So, when a sperm and an egg fuse together during fertilisation, then the zygote formed will have 23 + 23 = 46 chromosomes, which is the normal number of chromosomes.

Question: (a) Draw a sectional view of human female reproductive system and label that part where
(i) eggs develop
(ii) fertilisation take place
(iii) fertilised egg gets implanted
(b) Describe, in brief, the changes that uterus undergoes
(i) to receive the zygote
(ii) if zygote is not formed. 
Answer: (a)The sectional view of human female reproductive system is as follows: 

(i) Ovary is the part where eggs develop.
(ii) Fallopian tube is the part where fertilisation takes place.
(iii) Uterus is the part where fertilised egg gets implanted.
(b) (i) When the ovum (or egg) is fertilised in the oviduct, then a zygote is formed. The uterus prepares itself every month to receive a zygote.
The inner lining of uterus becomes thick and spongy with lot of blood capillaries in it. This would be required for nourishment and further development of embryo.
(ii) If a sperm is not available at the time of ovulation, then fertilisation of ovum does not take place. Since the ovum (or egg) is not fertilised, so the thick and soft uterus lining having lot of blood capillaries in it is not required. The unfertilised ovum dies within a day and the uterus lining also breaks down. The breakdown and removal of the inner, thick and soft lining of the uterus along with its blood vessels in the form of vaginal bleeding is called menstrual flow or menstruation. 

Question:(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.
Answer: (a) A represents stigma. It receives the pollen grains from the anther of stamen. Stigma is sticky so that pollen can stick to it so that fertilisation can occur. B represents pollen tube. Pollen tube acts as a conduit to transport the male gamete cells from the pollen grain at stigma to the ovules at the base of the carpel for the process of fertilisation. C represent female germ cell. Female germ cell fertilise with male germ cells to forms zygote which develops
into an embryo within the ovule. Ovule converts into a seed that gives rise a new individual.
(b) Role of Gamete : Gametes are the reproductive cells involved in sexual reproduction having half of the chromosome. Gametes carry variations generated during its formation (meiosis). A male gamete and a female gamete fuses to form zygote.
Role of Zygote :The fusion of male gamete with female gamete forms a zygote during sexual reproduction. Zygote has normal number of chromosomes and new combinations of variation that express in new generation.The zygote undergoes repeated mitotic divisions to form the embryo which has the potential to form a complete individual.

Question: Deffine the terms pollination and fertilisation. Draw a diagram of a pistil showing pollen tube growth into the ovule and label the following: pollen grain, male gamete, female gamete, ovary.
Answer: The process of transfer of pollen grains from the anther of aflower to the stigma of the same flower or another flower is known as pollination.
Fertilisation is the fusion of male gamete with the female gamete (or egg). Diagrammatic representation of pistil showing germination is as follows:

Question: Distinguish between unisexual and bisexual flowers giving one example of each. Draw a diagram showing process of germination of pollen grains on stigma and label the following parts :
(i) Female germ cell (ii) Male germ cell (iii) Ovary 
Answer: The flowers which contain only one sex organ, either stamens or carpels are called unisexual flowers. E.g., flowers of papaya and watermelon whereas the flowers which contain both the sex organs, stamens as well as carpel, are called bisexual flowers, e.g., flowers of Hibiscus and mustard. The given diagram showing germination of pollen on stigma.

Question: What is binary fission: in organisms? With the help of suitable diagrams, describe the mode of reproduction in Amoeba.
Answer: Binary fission is the division of adult parental body into two nearly equal daughter cells. It is the simplest and most common method of asexual
reproduction found in protistan protozoans i.e. Amoeba, Paramecium, etc.
Amoeba reproduces by binary fission by dividing its body into two parts. When the Amoeba cell has reached its maximum size of growth, then first the
nucleus of Amoeba lengthens and divides into two parts. After that the cytoplasm of Amoeba divides to form two smaller Amoeba (called daughter
amoebae). Diagrammatic representation of binaryfission in Amoeba is as follows :

Question: State in brief the changes that take place in a fertilised egg(zygote) till birth of the child in the human female reproductive system. What happens to the egg when it is not fertilised?
Answer: When the ovum (or egg) is fertilised inthe oviduct, then a zygote is formed. The zygote divides rapidly by mitosis as it moves down slowly in the oviduct and forms a ball of cells.This hollow ball of cells, called an embryo sinks into the soft and thick lining of the uterus and gets embedded in it. e embedding of embryo in the thick lining of the uterus is called implantation.
After implantation, a disc-like special tissue develops between the uterus wall (called uterine wall) and the embryo (or fetus), which is called placenta.The fetus is connected to placenta in mother’s body through umbilical cord. It is through the placenta that all the requirements of the developing fetus like nutrition, respiration and excretion, etc., are met from the mother’s body.
The time period from the fertilisation upto the birth of the baby is called gestation.The average gestation period in humans (or the average during of human pregnancy) is about nine months. During the gestation period, the fetus grows to become a baby. Birth begins when the strong muscles in the walls of the uterus start to contract rhythmically. The rhythmic contraction of uterus muscles gradually pushes the baby out of the mother’s baby through vagina and a baby is born.
If, a sperm is not available at the time of ovulation, then fertilisation of ovum (or egg) does not take place. Since the ovum (or egg) is not fertilised, so the thick and soft uterus lining having lot of blood capillaries in it is not required.The unfertilised ovum dies within a day and the uterus lining also breaks down.The breakdown and removal of the inner, thick and soft lining of the uterus alongwith its blood vessels is called menstrual flow or menstruation.

SHORT ANSWER TYPE QUESTIONS

Question. (a) Budding, fragmentation and regeneration, all are considered as asexual mode of reproduction. Why ?
(b) With the help of neat diagrams, explain the process of regeneration in Planaria.
Answer : (a) Budding, fragmentation and regeneration are considered as asexual mode of reproduction because only one parent is involved no sex cells are involved.
(b) Regeneration in planaria.

The process of getting back a full organism from its body parts is called regeneration. Planaria reproduces by this method in which if the body of Planaria somehow gets cut into a number of pieces, then each body piece can regenerate into a complete Planaria by growing all the missing parts.

Question. What is carpel ? Write the function of its various parts.
Answer : The flask-shaped organ in the centre of a flower is called carpel. It is also called as female reproductive organ of the plant.
It is made up of three parts :
(a) Stigma (b) Style (c) Ovary.
(a) Stigma is the top part of carpel and is sticky. So, it receives the pollen from the anther of stamen.
(b) Style connects stigma to ovary and acts as the passage for the growth of pollen tube.
(c) Ovary contains female gametes of the plant and helps in reproduction it is the site of fertilisation.

Question. Distinguish between pollination and fertilisation. Mention the site and the product of fertilisation in a flower.
Answer : (a) The transfer of pollen grains from anther of a stamen to the stigma of a carpel is called pollination whereas fertilisation is the process when the male gamete present in pollen grain joins the female gamete present in ovule.
(b) Pollination is an external mechanism whereas fertilisation is an internal mechanism which takes place inside the flower.
Site of fertilisation in flower is ovary. Product of fertilisation in flower is zygote.

Question. Reproduction is one of the most important characteristics of living beings. Give three reasons in support of the statement.
Answer : Reproduction is an energy consuming process which is not essential for the survival of an individual. But it is highly essential for all the living beings because of the following reasons :
(a) Reproduction helps in increasing the number of members of a population.
(b) By replacing the dead members with the new ones, it minimises the risk of extinction of a species.
(c) It brings about variations in species, thus, leading to their evolution.

Question. What is vegetative propagation ? State two advantages and two disadvantages of this method.
Answer : Vegetative propagation is a mode of asexual reproduction in which new plants are obtained from vegetative parts of the plants such as shoots or stem for the propagation of new plants.
Two advantages of vegetative propagation are :
(a) Plants which do not produce seeds are propagated by this method.
(b) Vegetative propagation is a cheaper, easier and rapid method of propagation in plants than growing plants from their seeds. Plants grow very slowly and take 4 to 7 years to develop flowers when grown with their seeds.
Two disadvantages of vegetative propagation are :
(a) As there is no genetic variation, there is no chance of development of new and better varieties.
(b) The vegetatively propagated plants are more prone to diseases that are specific to the species.

Question. List three techniques that have been developed to prevent pregnancy. Which one of these techniques is not meant for males ? How does the use of these techniques have a direct impact on the health and prosperity of a family ?
Answer : Three techniques that have been developed to prevent pregnancy are :
(a) Mechanical Methods : Include condoms, diaphragm, IUCDs, etc.
(b) Chemical Methods : Include oral contraceptive pills, spermicide.
(c) Surgical Method : Includes vasectomy and tubectomy.
The chemical methods are not meant for males.
The use of such contraceptive methods have various benefits, such as :
(a) Large size of families have a negative impact on the economic status of the family.
(b) Having pregnancies at quick successions reduces mother’s health and vitality. Use of contraceptive devices thus, effects the maternal health status.
(c) Some contraceptive devices (such as condoms) are also helpful in preventing sexually transmitted diseases.

Question. Describe reproduction by spores in Rhizopus.
Answer : Rhizopus is a fungus that reproduces by spore formation. The fungal hyphae gives rise to a globular structure known as sporangium. The sporangium gives rise to several spores by repetitive division of its nucleus. Each nucleus gets surrounded by a part of cytoplasm and thus develops into a spore. These spores then mature inside the sporangium. Once they are fully mature, the sporangium bursts to release these spores in the environment. Since, the spores disperse through air, they can land on various sites. These sites may be favourable or unfavourable. During unfavourable conditions, these spores are protected by a tough coat. Once favourable conditions return, they germinate and grow into new hyphae.

Question. What happens when :
(a) Accidently, Planaria gets cut into many pieces ?
(b) Bryophyllum leaf falls on the wet soil ?
(c) On maturation sporangia of Rhizopus bursts ?
Answer : (a) When planaria gets cut into many pieces, it will undergo a process known as regeneration due to which each piece will grow into a new Planaria organism.
(b) When bryophyllum leaf falls on the wet soil, the buds that are produced in the notches along the leaf will develop into new plants by the process known as vegetative propagation.
(c) When the sporangia of rhizopus bursts on maturation, the spores present inside it spread in the open environment. Then, with the help of different agents, they are carried to different places and when they land on a favourable surface, they start growing and produce new organism.

Question. List the two types of reproduction. Which one of the two is responsible for bringing in more variations in its progeny and how ?
Answer : Reproduction methods are of two types : Sexual and Asexual. Out of these, sexual reproduction brings more variation in organisms. In sexual reproduction fusion of male and female gametes from different organisms occurs. Since the fusion of gametes come from two different individuals, the offsprings exhibit more diversity of characters. Also during gamete formation, meiosis occurs which brings new combinations of genes. Both these factors lead to more variations in the progeny.

Question. State the changes that take place in the uterus when :
(a) Implantation of embryo has occurred.
(b) Female gamete/egg is not fertilised.
Answer : (a) When implantation has occured in uterus of the mother, the inner lining of the uterus thickens and is richly supplied with the blood vessels to provide nourishment to the growing embryo.
(b) If the egg is not fertilised, it lives for about one day. Since, the thickened uterus lining is no more required, it will slowly breakdown and comes out through the vagina as blood and mucous known as menstruation which lasts for about two to eight days.

Question. State the basic requirement for sexual reproduction.
Write the importance of such reproduction in nature.
Answer : The basic requirements for sexual reproduction to take place is the involvement of two parents and fusion of their haploid gametes. In the sexual reproduction, a new individual is formed which is diploid in nature, the gametes, one from the male parent and the other from the female parent. Since, the new individual formed is diploid in nature, the gametes must be formed by meiosis, so that chromosome number can be reduced to half. When fusion of gametes occurs, the nuclei of these two gametes fuse and the chromosome number is then restored to normal. The zygote, thus, formed is diploid in nature.
Importance of sexual reproduction :
(a) Sexual reproduction involves fusion of male and female gametes from both the parents, thus results in genetic variations in the offsprings.
(b) Sexual reproduction promotes diversity of characters in offsprings by providing genetic variations.
(c) These genetic variations, thus lead to evolution of species as well as allow the organisms to become better adapted in the changing environment.

Question. Draw in sequence (showing the four stages), the process of binary fission in amoeba.
Answer : Binary fission is an asexual mode of reproduction in amoeba where a single parent cell divides into two daughter cells and each daughter cell receives a copy of genetic material.

Question. List any four steps involved in sexual reproduction and write its two advantages ?
Answer : The steps involved in sexual reproduction are as follows :
(a) Formation of gametes through meiosis.
(b) Transfer of male gametes into the female body.
(c) Fertilisation (fusion of male and female gametes).
(d) Post fertilisation changes.
Advantages of sexual reproduction :
(a) It is a source of genetic variation among individuals of a population.
(b) It gives rise to individuals that are more adapted to the environment.

Question. What is the importance of DNA copying in reproduction ?
Answer : DNA copying is necessary as parents transmit their characters to offsprings through DNA. Due to this the offsprings resemble some of the features with their parents. But DNA copying also produces some variations in the offsprings that helps them to adapt to the changing environment.

Question. How will an organism be benefited if it reproduces through spores ?
Answer : An organism can be benefited if it reproduces through spores by following ways :
(a) Spores are covered with thick walls which protect them from adverse environmental conditions like drought, high temperature etc. So, they can survive even in these conditions.
(b) They are very light, small and can be easily dispersed through wind, water, animals and on getting favourable conditions they germinate and give rise to new individuals.
(c) This mode of reproduction is simple and faster.
(d) Large numbers of spores are produced at one time within a sporangium.

Question. What could be the reasons for adopting contraceptive method ?
Answer : The reasons for adopting contraceptive method are :
(a) Preventing unwanted pregnancies to control population growth.
(b) It protects from sexually transmitted diseases like AIDS, Syphillis etc.
(c) Proper health of mother and child can be maintained by preventing frequent pregnancies.
(d) Sufficient gap between the off springs, which ensures the proper health of the mother and child.

Question. Name the following parts :
(a) The organ where foetus develop during gestation period.
(b) A funnel like structure near the posterior end of ovary.
(c) Technical term given to the stalk of the flower.
(d) Three parts of carpel.
Answer : (a) Uterus (b) Fallopian tube
(c) Pedicel (d) Stigma, style, ovary

Question. Draw a labelled diagram of the longitudinal section of a flower.
Answer :

Question. Distinguish between a gamete and zygote ?
Answer :

Question. How does binary fission differ from multiple fission ?
Answer :

Question. Name the three parts A, B and C of the flower shown in the figure and state one function of each.

Answer :
A → Anther : Produces pollen or male gamete.
B → Style : Carries the pollen to the ovary.
C → Ovary : Produces ovules or female gamete.

Question. What are acquired traits ? Why are these traits generally not inherited over generations ? Explain.
Answer : Characters that a person acquires during one’s life time are known as acquired characters or traits. These traits generally are not inherited over generations because these changes do not occur in the reproductive tissues.
Changes in the non-reproductive tissues are not passed on to the DNA of the germ cells and therefore not inherited by the next generation.

Question. List any four advantages of vegetative propagation.
Answer : (a) Plants raised by vegetative propagation bear fruits and flowers earlier than those raised by seeds.
(b) Such methods also make possible the propagation of seedless plants.
(c) Used for raising genetically similar progeny or clones.
(d) A rare variety can be propagated by this method while maintaining the quality.

Question. The teacher explained in the class that reproduction is the process by which organisms increase their population. Manoj wanted to know more about the reproductive health. Therefore, the teacher also explained in the class about the diseases that can be transmitted, if proper care is not taken.
(a) Why is the increasing human population a cause of concern for all of us ?
(b) Name two diseases that can be sexually transmitted.
Answer : (a) Increasing human population is a causes of concern for all of us because natural resources are limited, and it would be difficult to sustain a large population on limited resources.
(b) HIV-AIDS, syphilis, gonorrhoea, warts can be sexually transmitted.

Question. What is asexual reproduction ? Write the process of budding in Hydra.
Answer : Asexual reproduction is the mode of reproduction used by single celled organisms. A bud develops as an outgrowth due to repeated cell division of reproductive cells at one specific site. These buds develop into tiny individuals, and when they fully mature, they detach from the parent body as new independent individuals. This is the process of budding in Hydra.

Question. (a) Write the functions of the following parts of human male reproductive system :
(i) Testes (ii) Vas deferens
(iii) Urethra (iv) Prostate
(b) List any two common pubertal changes that appear in human males.
Answer : (a) (i) Testes – Formation of sperm, germ cells and secretion of testosterone.
(ii) Vas deferens – Delivery of sperms from testis to urethra.
(iii) Urethra – Ejaculation of sperms.
(iv) Prostate – Its secretions nourishes the sperms.
(b) Thick hair growth on the face, voice begins to crack, hair growth in armpits are the common pubertal changes that appear in human males.

Question. What is vegetative propagation ? List its any four advantages.
Answer : Vegetative propagation is the process where plant parts roots, stems and leaves are used to develop new plants.
Four advantages of vegetative propagation are :
(a) Plants can bear flowers and fruits earlier than those produced from seeds.
(b) Plants that have lost the capacity to produce viable seeds can be grown.
(c) Plants grown are genetically similar or clones of the parent plant.
(d) Economical, quick and easy method of reproduction.

Question. List and explain briefly any three methods of contraception.
Answer : Three methods of contraception are :
(a) Barrier method or mechanical method : Condom, diaphragm are used to prevent the meeting of sperms and ova.
(b) Chemical method or oral pills : Changes the hormonal balance of the female so that the eggs are not released.
(c) Surgical method : To block the vas deferens in males, vasectomy or the fallopian tube (oviduct) in females, tubectomy, thus to prevent the transfer of sperms or egg and hence no fertilization takes place.
(d) Intra Uterine Contraceptive Devices IUCDs :
Loop or the Copper-T is placed in the uterus; to prevent pregnancy.
(e) Natural methods : To avoid copulation around the time of ovulation.

Question. What is reproduction ? Explain two advantages of sexual reproduction over asexual reproduction.
Answer : Reproduction is the biological process by which new individuals of the same species are produced by the existing organisms.
Advantages of sexual reproduction over asexual reproduction are :
(a) Leads to stability of population of species. 
(b) Results in variations useful for the survival of species over time.

Question. Write the functions of the following parts of human female reproductive system :
(a) Ovary, (b) Fallopian tubes, (c) Uterus.
Answer : (a) Ovary : Produces egg or female gamete, female sex hormone or estrogen.
(b) Fallopian tube : Transfer of ovum to the uterus, and is the site for fertilization.
(c) Uterus : Site of implantation of zygote and for the development of embryo.

Question. What is regeneration ? Give one example of an organism that shows this process and one organism that does not. Why does regeneration not occur in the latter ?
Answer : Regeneration is the ability of organisms to give rise to new individual organisms from their body parts.
Example : Planaria / Hydra; Amoeba, Rhizopus, does not show regeneration because it is carried out by specialised cells which are not present in nonregenerating organisms.

Question. State briefly the changes that take place in a fertilized egg till birth of the child in the human female reproductive system. What happens to the egg when it is not fertilized ?
Answer : Changes that take place in fertilized egg till birth of the child in the human female reproductive system are :
(a) Zygote or fertilized egg starts dividing.
(b) Implantation of zygote in the inner uterine wall.
(c) Embryo starts growing with the help of the placenta which results in the development of the child.
(d) Birth of a child as a result of rhythmic contraction of the muscles in the uterus. 
(e) When egg is not fertilized, the inner lining of the uterus slowly breaks and comes out through the vagina as blood and mucous (Menstruation).

Question. Name the two types of mammalian gametes. How are these different from each other ? Name the type of reproduction they are involved in. Write the advantage of this type of reproduction.
Answer : Two types of mammalian gametes are sperms and ova. Sperm is motile and is produced by male gamete whereas ova is non-motile and is produced by female gamete. Sexual reproduction is involved in it and its advantage is it generates more variations.

Question What is contraception ? Name any two methods. How does the use of these methods have a direct effect on the health and prosperity of a family ? State any three points. 
Answer : Contraception is any method which prevents conception or pregnancy. Barrier method, chemical method, surgical method.
Effect of these methods are :
(a) Health of women (mother) is maintained.
(b) Parents can give more attention to their children or family.
(c) More resources may be made available for improvement of standard of living.

Question. What happens when
(a) Planaria gets cut into two pieces ?
(b) A mature spirogyra filament attains considerable length ?
(c) On maturation sporangia burst ?
Answer : (a) Each piece regenerates into a new planaria when planaria gets cut into two pieces.
(b) Its filaments breaks into smaller pieces or fragments and each fragment gives rise to a new filament.
(c) It releases spores which germinate into new mycelium in moist conditions.

Question. What is puberty?
Answer : Puberty is the age at which the gametes start forming in the male and female human beings. At this age boys and girls become sexually mature.

Question. What changes occur in the flower after fertilisation?
Answer : After fertilisation the flower withers. The sepals and the petals dry up, the ovary converts into fruit, the ovule forms the seed and the zygote forms the embryo which is enclosed in the seed.

Question. What is regeneration? Name two organisms that can reproduce by regeneration.
Answer : Many fully differentiated organisms have the ability to give rise to new organisms from their body parts by being cut or broken into many pieces. This is known as regeneration. All organisms do not have the capacity to reproduce by regeneration.
Hydra and Planaria can reproduce by the process of regeneration.

Question. State the functions of the human male and female sex hormones.
Answer : The human male sex hormone testosterone regulates the formation of the male gamete, the sperms and brings about changes in appearance seen in boys at the time of puberty.
The human female sex hormone estrogen brings about the changes occurring in girls at puberty and progesterone controls the uterus changes occurring during the menstrual cycle and also helps in maintaining the pregnancy.

Question. What happens when the egg is fertilised?
Answer : When the egg is fertilised zygote is formed, it starts dividing and gets implanted in the lining of the uterus.

Question. What is menstruation? Why does it occur?
Answer : Menstruation is the process of breakdown and removal of the inner lining of the uterus along with the blood vessels in the form of vaginal bleeding. This happens after every 28 days if the egg is not fertilised. This takes place in human females and in some primates.

Question. What is ‘reproduction’? Mention the importance of DNA copying in reproduction.
Answer : Reproduction is the process by which the existing organisms produce their own kind. 
DNA copying during reproduction is important for the transfer of parental characters to the offspring.

Question. Name the agents of pollination.
Answer : The agents that bring about pollination are wind, water, birds and insects.

Question. What is the role of seminal vesicles and prostate gland?
Answer : These are the accessory glands associated with the male reproductive system. Seminal vesicles and prostrate gland secrete a fluid which makes the transport of sperms easier and also provides nourishment to the sperms. This fluid together with the sperms is called the semen.

Question. Name the following:
(i) Name two plants that cannot produce seeds.
(ii) An organism that reproduces by budding and regeneration.
(iii) An organism that grows by multiple fission
(iv) One unisexual flower.
Answer : (i) Bryophyllum, Banana (ii) Hydra (iii) Paramecium (iv) Maize flower

Question. What is fragmentation?
Answer : Fragmentation is the method of breaking up of an organism into smaller pieces or fragments which grow into new organisms as in algae Spirogyra.

Question. Draw a well labelled diagram of a dicot seed (gram seed).
Answer :  

Question. Device an experiment to show germination of gram seed.
Answer : (a) Soak a few seeds of Bengal gram (chana) and keep them overnight.
(b) Drain the excess water and cover the seeds with a wet cloth and leave them for a day. Make sure that the seeds do not become dry.
(c) Cut open the seeds carefully and observe the different parts.
(d) Compare your observations with the figure above that shows the germination of gram seed and see if you can identify all the parts.

Question. What does the male and female reproductive system consists of?
Answer : The male reproductive system in human beings consists of testes which produce sperms, vas deferens, seminal vesicles, prostrate gland, urethra and penis.The female reproductive system consists of a pair of ovaries, fallopian tube, uterus and vagina.

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

(B) Differences between modes of reproduction in unicellular and multicellular organisms:  (Table 196)

Question. (A) What are Sexually Transmitted Diseases (STD)? List two viral and two bacterial STDs.
(B) What is contraception? List three reasons for adopting contraceptive methods.
Answer : (A) The diseases that can be transmitted from an infected person to a healthy person through the sexual act are known as Sexually Transmitted Diseases.
(1) Two viral STDs are HIV-AIDS and warts.
(2) Two bacterial STDs are gonorrhoea and syphilis.

(B) Contraception: These are the techniques which have been developed to prevent and manage pregnancy.
Advantages of adopting contraceptive methods:
(1) Avoiding frequent and unwanted pregnancy.
(2) Keeping population and hence birth rate under control.
(3) Helps in keeping proper gap between two pregnancies.
(4) Helps in preventing the spread of sexually transmitted diseases.
(4) Helps in improving the reproductive health of women.
(Any 3 of 5 points can be written to get full marks)

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

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

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

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

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

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

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

The female reproductive organs are ovary, style and stigma. Their functions are mentioned below:

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

Question. (a) Draw and explain the sectional view of human male reproductive system and label the parts.
(b) Reproduction is not an essential life process that is needed for survival of individual but for the stability of species.
justify.
Answer : (a) Human male reproductive system. It consists of the folowing parts:

(1) A pair of testis
(i) located outside abdominal carety.
(ii) produce male gametes i.e., sperms.
(iii) secrete male hormone testosterone.

(2) A pair of vas deferens (spermduct)
(i) thick walled tube emerges from each epdidymis.
(ii) carry sperms and join with urethra.

(3) Urethra
(i) common passage for sperms and urine.
(ii) carries berms to penis which opens out side the body.

(4) Penis
(ii) a muscular and erectile copulatory organ.
(ii) passes sperms from man’s body into the vagina in the woman’s body during mating.
(􀇨) Acessory reproductive glands
(i) Serminal vesicles, prostrate gland, cowper’s glands.
(ii) Secretions of these glands provide
nutrition to sperms and also make their further transport easier.
(b) Reproduction is not an essential life process like nutrition, respirations or excretion.
During reproduction.
(i) To, maintain existence living beings produce their copies in large numbers.
(ii) Reproduction introduces variations in the offspring and helps in transfer of these variations into their offspring so reproduction plays a key role in maintaining viability of species and
evolution.

Question. How do variations arise in organisms? ‘‘Variation is useful for the survival of species justify this statement with the help of an example.
Answer : Variations arise in organisms during creation of DNA copy which is the basic event in reproduction. Cells use chemical reactions to build copies of their DNA but this process of copying the DNA will have some variations due to which the DNA copies will be similar but not identical to the original. Variations which are favourable increase the chances of survival of the species. If an organism can withstand a higher temperature, then the variation goes on accumulating in its future generations. Hence, these organisms can survive sudden rise in the temperature. This ensures the survival of the species. But other organisms (variants) without this variation may not survive due to sudden rise in temperature. So, variation is beneficial to the species, but not necessarily for individual.

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

Question. Give one example each of unisexual and bisexual flowers. Differentiate between the two types of pollination that occur in flowers. What happens when a pollen lands on a suitable stigma? Write about the events that occur till the seed formation in the ovary.
Answer : An example of unisexual flower is Papaya, water melon (write any one) and of bisexual flower is Hibiscus, mustard (write any one). Differences between the two types of pollination that occurs in plants, namely, self pollination and cross-pollination is given below:   (Table 199)

Following events take place when a pollen lands on a suitable stigma:
(1) Pollen grains which are deposited on the stigma form tubes called pollen tubes.
(2) One pollen tube grows through the style and reaches the ovary where the ovules are located.
(3) The pollen tube normally enters the ovule through a small opening called micropyle.
(4) Inside the ovule, the pollen tube releases two male gametes into the embryosac which contains the egg.
(5) Fertilization of male and female gametes takes place inside the embryosac.
(6) After fertilization, the zygote divides several times to form an embryo within the ovule.
(7) The ovule develops a tough coat and is gradually converted into a seed, which contains the food store.
(8) The ovary grows rapidly and ripens to form a fruit.

Question. (A) Write the functions of the following parts in human female reproductive system:
(i) Ovary
(ii) Fallopian tube
(iii) Uterus
(B) Describe the structure and functions of placenta. 
Answer : (A) Function of following parts in human female reproductive system is given below:
(1) Ovary: Ovaries are the female primary reproductive organs which perform dual functions of production of female gamete or ovum and the secretion of female sex hormones, estrogen and progesterone.
(2) Fallopian tube: These are a pair of long convoluted tubes that carry ova or eggs from the ovary to the uterus and is also the site of fertilization of the ovum.
(3) Uterus: It is a hollow, pear-shaped organ within which the embryo develops after implantation. After fertilization has taken place, the embryo moves down to reach the uterus and gets attached to its thickened wall.
(B) Structure and functions of placenta: Structure:
(1) It is a special disc like tissue which develops between uterine wall and the embryo after implantation.
(2) It contains villi on the embryo’s side of the tissue and blood spaces surrounding the villi on the mother’s side.
Functions:
(1) It is through the placenta that all the development needs of the foetus are met from the mother’s body.
(2) It provides a large surface area for glucose and oxygen to pass from the mother to the embryo.
(3) The waste substances generated by the developing embryo is also removed through the placenta.

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