How do the Organisms Reproduce Class 10 Science Important Questions

Please refer to Chapter 8 How do the Organisms Reproduce Class 10 Science Important Questions with solutions provided below. These questions and answers have been provided for Class 10 Science based on the latest syllabus and examination guidelines issued by CBSE, NCERT, and KVS. Students should learn these problem solutions as it will help them to gain more marks in examinations. We have provided Important Questions for Class 10 Science for all chapters in your book. These Board exam questions have been designed by expert teachers of Standard 10.

Class 10 Science Important Questions How do the Organisms Reproduce Chapter 8

Very Short Answer:

Question. What are those organisms called which bear both sex organs in the same individual. Give one example of such organism.
Answer : Bisexual. For example: earthworm, leech, starfish, hibiscus, mustard. (Any one)

Question. Where is DNA found in a cell?
Answer : Genes/Chromosomes.

Question. What happens if egg is not fertilized?
Answer : If fertilization does not occur then menstruation occurs, i.e., blood and mucus comes out through the vagina.

Question. Differentiate between pollen grain and ovule.
Answer : Pollen grains contain male gametes and ovules contains female gametes in plants.

Question. How can the chromosomes be identified?
Answer : Chromosomes can be seen as thread like structure when cell is dividing.

Question. Give an advantage of vegetative propagation.
Answer : Vegetative propagation can be practised for growing such plants which usually do not produce seeds or produce non-viable seeds.

Question. Why is temperature of scrotal sac 2°C less than the body temperature?
Answer : Because testes require temperature 2°C less than the body temperature for the production of sperms.

Question. Differentiate between germination and fertilization,
Answer : Germination: Development of embryo into a seedling.
Fertilization: Fusion of male and female gametes.

Question. Name the life process of an organism that helps in the growth of its population.
Answer : Reproduction.

Question. List two functions performed by testis in human beings.
Answer :
a. Testis produce sperms.
b. Produces male sex hormone, testosterone.

Question. Name the causative organism of the disease “Kalaazar” and its mode of asexual reproduction.
Answer : Leishmania, Binary fission.

Question. Name two simple organisms having the ability of regeneration.
Answer : Planaria/hydra/earthworm (any two).

Question. Give the respective scientific terms used for studying:
a. The mechanism by which variations are created and inherited and
b. The development of new type of organisms from the existing ones.
Answer :
a. Heredity
b. Fission.

Question. What is reproduction?
Answer : Reproduction is the process of producing individuals of its own kind.

Question. What is the advantage of reproducing through spores?
Answer : In the form of cyst, spore with a cell wall can survive in adverse conditions.
They can be easily dispersed through wind as they are more in number and light in weight.

Question. Name the type of cells which undergo regeneration.
Answer : Regenerative cells can proliferate and make large number of cells.

Question. What are sexually transmitted diseases? Name an STD which damages the immune system of human body.
Answer : a. Diseases that spread through the sexual contact.
b. AIDS

Question. Organisms have a varied body design. Name the property which gives the basic difference in body design.
Answer : Errors in DNA copying (variations).

Question. How does the embryo gets nourishment from the mother?
Answer : Through placenta.

Question. Why does the lining of uterus become thick and spongy every month?
Answer : To receive and nurture the growing embryo, lining of uterus become thick and spongy.

Question: When a cell reproduces, what happens to its DNA? 
Answer: When a cell reproduces, DNA replication occurs which forms two similar copies of DNA. 

Question: Name the life process of an organism that helps in the growth of its population. generation.
Answer: Reproduction is a life process that helps in multiplication of an organism and growth of its population.

Question: Newly formed DNA copies may not be identical at times. Give one reason.
Answer: When a cell reproduces, DNA replication occurs which results in formation of two similar copies of DNA. The process of copying the DNA have some variations each time. As a result, the DNA copies produced are similar to each other but may not identical sometimes. 

Question: What is DNA ? 
Answer: DNA (deoxyribonucleic acid) is a polymer made up of large number of nucleotide units. It carries genetic information from generation to generation.

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

Question: Name the part of Bryophyllum where the buds are produced for vegetative propagation.
Answer: Bryophyllum propagates vegetatively by the buds produced at the margins of leaves.

Question: How does Plasmodium reproduce. Is this method sexual or asexual?
Answer: Plasmodium reproduces through multiple fission method. In this method, the parent
organism splits to form many new organisms at the same time. This is an asexual method of reproduction.

Question: What happens when a mature Spirogyra filament attains considerable length?
Answer: When a mature Spirogyra filament attains considerable length it simply breaks into two or more fragments and each fragment then grows into a new Spirogyra.

Question: What happens when a Planaria gets cut into two pieces? 
Answer: When Planaria is cut into two pieces then each piece grows into a complete organism. This is known as regeneration.

Question: Name two simple organisms having the ability of regeneration.
Answer: Hydra and Planaria are two organisms thathave the ability to regenerate

Short Answer:  1

Question: List four advantages of vegetative propagation.
Answer: The following are the advantages of vegetative propagation :
(i) THe characters of the parent plants are preserved hence a good variety produced can be propagated by vegetative means.
(ii) THe plants, which do not produce viable seeds or produce very few seeds, can be reproduced by this method, for example, banana, potato, grapes, sugarcane, rose, orange, etc.
(iii) It is an easier, quicker and cheaper method of propagation.
(iv) It is easier to get rid of pathogen from any part of plant by vegetative propagation.

Question: Write two differences between binary fission and multiple fission in a tabular form.
Answer: Differences between binary fission and multiple fission are as follows:

Question: List four modes of asexual reproduction other than fission in the living organisms.
Answer: The four modes of asexual reproduction other than fission in living organisms are :
(i) budding
(ii) spore formation
(iii) regeneration and
(iv) fragmentation. 

Question: Draw labelled diagrams to illustrate budding in Hydra.
Answer: The given diagram illustrates budding in Hydra:

Question: How do Plasmodium and Leishmania reproduce? Write one difierence in their mode of reproduction. 
Answer: Plasmodium and Leishmania reproduce by the process of fission: which is asexual mode of reproduction. Plasmodium reproduces by multiple fission:. About 1000 daughter cells are produced by the multiple fission: of a Plasmodium. Leishmania reproduces by the process of binary fission:. In Leishmania, the splitting of parent cell takes place in a deffnite plane (longitudinally) with respect to flagellum at its end to produce two daughter cells.

Question: List four modes of asexual reproduction.
Answer: The four modes of asexual reproduction are :
(i) binaryfission, (ii) budding
(iii) regeneration and
(iv) vegetative propagation.

Question: Define multiple fission. Give its one example.
Answer: Multiplefission is an asexual mode of reproduction in which the parent organism splits to form many new organisms at the same time. Multiple fission occurs in Plasmodium.

Question: Name an organism which reproduces by spore formation. List three conditions favourable for spores to germinate and grow. 
Answer: Rhizopus reproduce by the method of spore formation.
The three conditions favourable for spores to germinate and grow are moisture, suitable temperature and food (nutrition).

Question: List two advantages of vegetative reproduction practised in case of an orange plant.
Answer: The two advantages of vegetative propagation practised in case of an orange plant are :
(i) The new plants produced by vegetative propagation will be exactly like the parent plant. Therefore, any desirable features of the parent plant will be replicated in the new plants.
(ii) The orange plants that have lost the capacity to produce seeds, can also be propagated.

Question: List two advantages of practising vegetative propagation in plants. Select two plants raised by this method from the list given below : Banana, Gram, Pea, Rose, Tomato, Wheat
Answer: Two advantages of the vegetative propagation of plants are :
(i) Any desirable features of the parent plant can be replicated in the new plants.
(ii) Flowers and fruits can be grown in a shorter time as compared to the plants grown from seeds. The two plants raised by this method are banana and rose.

Question: With the help of diagrams show the different stages of binary fission: in Amoeba.
Answer: Different stages of binaryfission in Amoeba are as follows:

Question: What is the main difference between sperms and eggs of humans? Write the importance of this difference. 
Answer: The main difference between sperms and eggs of humans is that a sperm has X or Y chromosome whereas egg has X chromosome. This helps in determination of the sex of a person and maintaining the genetic continuity in the organisms.

 Short Answer:  II 

Question: Reproduction is one of the most important characteristic of living beings. Give three reasons in support of the statement.
Answer: Reproduction is one of the most important characteristics of living beings because :
(i) it is essential for existence and continuity of a species.
(ii) it helps to pass genetic information to next generation.
(iii) it brings variations in next generation which is the basis for evolution.

Question: Write the full form of DNA. Name the part of the cell where it is located. Explain its role in the process of reproduction of the cell.
Answer: The full form of DNA is deoxyribonucleic acid. It is located in the nucleus of a cell in the form of chromosomes. It contains information for the inheritance of characteristics from the parents to the next generation. Copying of DNA is an essential part of the process of reproduction because its makes possible the transmission of characteristics of the parents to its offsprings in the next generation. At the time of replication two copies of DNA are formed. DNA copying is accompanied by creation of additional cellular apparatus and then DNA copies separate, each with its own cellular apparatus. Thus, a cell divides to form two daughter cells.

Question: Describe reproduction by spores in Rhizopus.
Answer: Fungus Rhizopus reproduces by spore formation. During the growth of Rhizopus, small rounded, bulb-like structures develop at the top of the erect hyphae. Such structures are called sporangia. Inside each sporangium, nucleus divides several times. Each nucleus gets surrounded by a little amount of cytoplasm to become spore.
Large number of spores are formed inside each sporangium. After sometime sporangium bursts and spores are released in the air. When these spores land on food or soil, under favourable conditions, they germinate into new individuals.

Question: What is vegetative propagation? State two advantages and two disadvantages of this method. 
Answer: Vegetative propagation is a type of asexual reproduction in which the plant parts other than seeds are used as a propagule. Advantages of vegetative propagation :
(i) Desirable character of the plant can be preserved through generation.
(ii) Seedless plants can be grown through this method.
Disadvantages of vegetative propagation :
(i) Plants produced by this method posses less vigour and are more prone to diseases.
(ii) Plants produced by this method show no genetic variation.

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 accidently gets cut into many pieces then its each piece grows into a complete organism. This is known as regeneration.
(b) When the Bryophyllum leaf falls on the wet soil, the buds present in the notches along the leaf margin develop into new plants.This is known as vegetative propagation.
(c) The sporangia of Rhizopus contain cells or spores that can eventually develop into new Rhizopus individuals when it bursts on maturation. 

Question: In the context of reproduction of species state the main difference between fission: and fragmentation. Also give one example of each. 
Answer: The main differences betweenfission and fragmentation are as follows:

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) When Planaria is cut into two pieces then
each piece grows into a complete organism.This is known as regeneration.
(b) When a mature Spirogyra filament attains a considerable length it breaks into small pieces called fragments. These fragments grow into new individuals and this mode of reproduction is called fragmentation.
(c) When a sporangium burst, large number of spores are released in the air. When these spores land on food or soil, under favourable conditions they germinate into new individuals.

Question: What is vegetative propagation? List with brief explanation three advantages of practising this process for growing some types of plants. Select two plants from the following which are grown by this process :
Banana, Wheat, Mustard, Jasmine, Gram
Answer: Vegetative propagation is an asexual method of reproduction in plants. In this method, new plants are obtained from the parts of old plants (like stems, roots and leaves), without the help of any reproductive organs.
Advantages of vegetative propagation are as follows:
(i) Vegetative propagation is usually used for the propagation of those plants which produce either very few seeds or do not produce viable seeds.
(ii) Seedless plants can be obtained by artificial vegetative propagation.
(iii) Grafting is a propagation method which is very useful for fruit trees and flowering
bushes. It enables to combine the most desirable characteristics of two plants.
(iv) Plants like rose, sugarcane, cactus, etc., can be rapidly propagated through stem cuttings as this method produces new plants from just one plant quickly without waiting forflowers and seeds.
Banana and jasmine are generally grown through vegetative propagation method.

Question: What is multiple fission:? How does it occur in an organism? Explain briefly. Name one organism which exhibits this type of reproduction.
Answer: Multiple fission refers to the process of asexual reproduction in which many individuals are formed from a single parent. This method of reproduction occurs in unfavourable conditions.
The unicellular organism develops a protective covering called cyst, over the cell. The nucleus of the cell divides repeatedly producing many nuclei. Later on, each nucleus is surrounded by small amount of cytoplasm and many daughter cells are produced within the cyst. When conditions are favourable the cyst breaks and small offsprings are liberated.This type of reproduction is seen in some protozoans, e.g.,malarial parasite (Plasmodium).

Question: Explain the term “regeneration” as used in relation to reproduction of organisms.Describe briefly how regeneration is carried out in multicellular organisms like Hydra.
Answer: The process of formation of entire organism from the body parts of a fully differentiated organism is called regeneration. It occurs by process of growth and development.
Simple animal like Hydra shows regeneration. When a small piece of Hydra breaks off it grows into complete new Hydra. During regeneration, the cells of cut body part of the organism divide rapidly to make a mass of cells. The cells here move to their proper places within the mass where they have to form different types of tissues. In this way complete organism is regenerated.

Question: (a) Name the following:
(i)Thread like non-reproductive structures present in Rhizopus.
(ii) ‘Blobs’ that develop at the tips of the nonreproductive threads in Rhizopus.
(b) Explain how these structures protect themselves and what is the function of the structures released from the ‘blobs’ in Rhizopus.
Answer: (a) (i)Thread like non-reproductive structures present in Rhizopus are called hyphae.
(ii) Blobs developing at the tip of hyphae are called sporangia which contain spores.
(b) The structures called spores are present in sporangia which can develop into new Rhizopus individuals. These spores are covered with thick walls that protect them until they come in contact with another moist surface and can begin to grow

Question: Explain the process of regeneration in Planaria. How is this process different from reproduction?
Answer: Planaria possesses great power of regeneration. 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. This is shown in following figure.

During the process of reproduction new organism is formed from the complete parent organism however, during fragmentation, a fragment of original parent body grows into new individual.

Question: On cutting the body of an organism into many pieces, it was observed that many of
these pieces developed as new individuals. Name the process and list two organisms in
which this process may be observed. Draw a schematic diagram to illustrate the changes that are likely to be observed during the development of new individuals in any one of the organisms named. 
Answer: On cutting the body of an organism into many pieces, each of these pieces develop as new individuals. This process is known as regeneration.
Hydra and Planaria are the organism in which this process may be observed. Following is the diagram show development of new individuals by regeneration of body parts of a parent Hydra.

Question: State the basic requirement for sexual reproduction. Write the importance of such reproductions in nature. 
Answer:The basic requirement for sexual reproduction is involvement of both sexes, i.e., male and female, to produce an offspring. It takes place by the combination of gametes which come from two different parents. The importance of sexual reproduction in nature are :
• Fusion of male and female gametes coming from two different and sexually distinct individuals, exhibit diversity of characters in offsprings.
• Meiosis during gametogenesis provides opportunities for new combination of genes, which leads to variation required for evolution and plays a prominent role in the origin of new species. Variations lead to the appearance of such characters, which fit to the changing environment, resulting in the survival of the species. 

Question: List any two steps involved in sexual reproduction and write its two advantage.
Answer: The two main steps involved in sexual reproduction are:
(i) formation of male and female gametes.
(ii) fusion of a male gamete with a female gamete to form a new cell called zygote by the process of fertilisation.
The two important advantages of sexual reproduction are:
(i) It promotes diversity of characters in the offsprings through genetic variations.
(ii) It plays an important role in continuous evolution of better organisms that may lead to the origin of new 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: Methods developed to prevent pregnancy are: 
(i) barrier method, i.e., use of condoms, diaphragm, etc.
(ii) chemical method, i.e., use of oral pills or vaginal pills.
(iii) surgical method, i.e., vasectomy and tubectomy. Out of these methods, chemical method is not meant for males.
Use of these techniques help to keep control over number of children in a family, which directly effects prosperity of a family. One of the most common reason for deterioration of women’s health is frequent conception and child bearing. Controlled chilbirth will directly affect women
health and this will indirectly affect the prosperity of family and nation.

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) Implantation is the close attachment of the blastocyst (young multicellular embryo) to the uterine wall. It is followed by a number of developmental changes in the thickened wall of uterus. An intimate connection between the fetal membrane and the uterine wall called placenta is formed. This is a disc which is embedded in the uterine wall. The placenta serves as the nutritive, respiratory and excretory organ of the fetus.
(b) As the ovary releases one egg every month, the uterus also prepares itself, every month to receive fertilised egg by making its lining thick and spongy to nourish the embryo if fertilisation had taken place. When the female gamete/egg is not fertilised, this lining is not needed any longer.
So, the lining slowly breaks and comes out through vagina as blood and mucus.This cycle takes place every month and is known as menstrual cycle.

Question: How do organisms, whether reproduced asexually or sexually maintain a constant chromosome number through several generations? Explain with the help of suitable example. 
Answer: In organisms reproducing asexually, only single parent is involved in reproduction. Therefore, amount of DNA remains same from parent to offspring. For example in Amoeba, whole organism divides into two daughter individuals by binary fission. erefore, amount of DNA remain constant.
In organisms reproducing sexually. Reproduction take place with the help 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: 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.
Answer: Three contraceptive methods which can help control human population are:
(i) Condoms : It is a mechanical barrier which does not allow sperms and ovum to meet hence prevents fertilisation. Condoms are made of thin rubber/latex sheath used to cover the penis in the male and vagina/cervix in female just before coitus (intercourse) so that the ejaculated semen is not released in the female reproductive tract.
(ii) Intrauterine devices (IUDs) : These are devices inserted by doctors or expert nurses in the uterus through vagina. These are presently available as non-medicated IUDs, copper releasing IUDs (CuT, etc.) and hormone releasing IUDs. They increase phagocytosis of sperms within uterus and suppress sperm motility and its fertilising capacity.
They also make uterus unsuitable for implantation and cervix hostile to sperms.
(iii) Oral pills : Oral pills contain progesterone alone or a combination of progestogen and estrogen. They inhibit ovulation and make uterus unsuitable for implantation, hence prevent fertilisation. 

Question: Name the parts A, B and C shown in the following diagram and state one function of each.

Answer: In the given figure part A is anther, part B is style and part C is ovule.
 Anther(A) is a part of male reproductive organ of flower called stamen. Large number of pollen
grains are formed inside anther. Style (B) and ovule (C) are parts of female reproductive organ of flower called carpel / pistil. Style is a long conducting tube which gives the passage to pollen tube carrying male gametes so that it reaches ovary which contains one or more ovules. Ovules contain female gamete or egg. On fertilisation ovary converts into fruit and ovules give rise to seeds. 

Question: What is meant by pollination? Name and differentiate between the two modes of pollination in flowering plants.
Answer: The process of transfer of pollen grains from anther of a flower to the stigma of the same flower or another flower of the same species is known as pollination.The two modes of pollination are self pollination and cross pollination. Differences between self pollination and cross pollination are:

Question: What is sexual reproduction? List its four significances. 
Answer: Sexual reproduction is the process of production of offspring by the fusion of male and female gametes. Here haploid gametes fuse to form diploid zygote which develop into a mature organism. Significances of sexual reproduction are as follows:
(i) Sexual reproduction gives rise to genetic variations because of genetic recombination that takes place during fusion of gametes.
(ii) Progenies arising through sexual reproduction sometimes show better combination of traits and get better adapted to their surroundings.
(iii) Genetic recombination, interaction, etc. during sexual reproduction provide vigour and vitality to the offspring.
(iv) Variations in genes play an important role in evolution

Question: What are the functions of testis in the human male reproductive system? Why are these located outside the abdominal cavity? Who is responsible for bringing about changes in appearance seen in boys at the time of puberty? 
Answer: Testes, in human males, are the primary reproductive organs. They are the site of sperm formation. The testes also produce male sex hormone testosterone. Testes are located outside the abdominal cavity because sperm formation requires a lower temperature than normal body temperature.The temperature of the testes in the scrotum is about 2–2.5°C lower than normal body temperature.This temperature is ideal for sperm formation and development. Hormone testosterone brings about the development of secondary sexual character during puberty in boys like growth of facial hair, deepening of voice, growth of scrotum and penis, accumulation of muscle mass, etc., and also regulates formation of sperms.

Long Answer:

Question: With the help of diagrams explain the process of budding in Hydra and fission in Amoeba.
Answer:

Question: What are the various artificial methods of vegetative propagation in plants?
Answer: The various artificial methods of vegetative propagation in plants are:
(a) Cutting: In this any part of the plant like the stem root or leaf is cut and buried in the soil which gives rise to a new plant as in rose, guava, grapes etc.,
(b) Layering: In plants like jasmine and strawberry a branch from the plant is brought down too the ground and covered with damp soil. After few days new roots are formed and the branch is cut from the main plant.
(c) Grafting: In this the stem of a plant is given a cut and the other plant is fixed (with its stem) in it e.g., sugarcane, roses, grapes are grown for agricultural purposes.
(d) By Roots: Plants like sweet potato show the growth of more plants from a root.
(e) Stem: Plants like potato, ginger, onion, they show growth from their stems.
(f) By Buds: Plant like Bryophyllum and potato grow small buds on them and a growth of new plant takes place.

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

(ii) Multiple fission in Plasmodium

Question:(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.
Answer: (a) Fragmentation is the mode of reproduction in which parent body breaks into two or more fragments and each fragment develops into a new individual. It is a method of reproduction in many filamentous algae, mycelial fungi and thalloid bryophytes, e.g., Spirogyra. The given figure shows the process of fragmentation in Spirogyra.

(b) Regeneration may be deffned as the ability of an organism to regenerates lost part of the body which have been removed as by injury or autotomy.
Many fully differentiated organisms use this ability as a mode of reproduction and give rise to new individual organisms from their body parts. It is common in Hydra, Planaria, etc.The process of regeneration in Planaria is described in the figure given below

Question: (a) What is spore formation?
(b) Draw a diagram showing spore formation in Rhizopus.
(c) List two advantages for organisms to reproduce themselves through spores.
Answer: (a) Spore formation is the process of formation of microscopic reproductive structures called spores.These spores when detaches from the parent gives rise to a new individual. Reproduction by the formation of spores is a common method of asexual reproduction in some bacteria and most of the fungi.
(b) Following figure shows the process of spore formation in Rhizopus 

(c) Two advantages to spore producing organism are as follows:
(i) Spores help organism to survive harsh environmental conditions as spores are covered by thick walls which protect them until they come in contact with moist surface and germinate.
(ii) Spores are generally very small and light. Therefore, it ensures easy dispersal by wind, water and animal.  

Question: (a) Write the functions of each of the following parts in a human female reproductive system.
(i) Ovary
(ii) Uterus
(iii) Fallopian tube
Answer:(a) (i)The ovaries in female are primary sex organs (or female gonads) which perform the dual function – production of female gametes (eggs or ova) and secretion of female sex hormones (estrogen and progesterone).
(ii) Uterus is a single, pear-shaped, highly muscular, hollow structure present in the pelvic cavity, lying between urinary bladder and rectum.
If fertilisation takes place, the embryo gets implanted to the wall of uterus and grows there until birth. Development of foetus occurs inside uterus, hence it is also called womb.
(iii) Oviducts or Fallopian tube are paired tubes originating near to the ovaries of their respective sides and extend upto uterus. The terminal part of Fallopian tube is funnel-shaped with fingerlike projections called fimbriae lying near ovary. Fimbriae pick up the ovum released from ovary and push it into Fallopian tube. Fertilisation also takes place in the oviduct. 

Question: What is menstruation? Why does itoccur? 
Answer: Menstruation is the cyclic discharge of blood along with endometrial lining of the uterus and unfertilised egg in women. It last for 3-5 days. After the release of egg in the females, the uterine lining becomes thickened for the implantation of fertilised egg or zygote. In the absence of fertilisation, the egg along with endometrial lining is expelled out of the body in the form of menstruation. 

Question: List in tabular form the two differences between asexual and sexual mode of reproduction. Name and explain with the help of labelled diagram the process by which Hydra reproduces asexually.
Answer:Differences between asexual and sexual forms of reproduction are following. 

Hydra is simple multicellular animal. It reproduces asexually by the process of budding. In Hydra first a small outgrowth called ‘bud’ is formed on the side of its body by the repeated mitotic divisions of its cells.This bud then grows gradually to form a small Hydra by developing a mouth a tentacles.
Finally, the tiny new Hydra detaches itself from the body of parent and lives as a separate organism. In this way, the parent Hydra produce a new Hydra.The following figure shows Hydra reproducing by the method of budding.

Question. What are chromosomes? Explain how the number of chromosomes in the progeny is maintained in sexually reproducing organisms.
Answer : Chromosomes are thread-like structures located inside the nucleus of animal and plant cells. Each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA).
During the process of formation of germ cells in sexually reproducing organisms, meiosis cell division takes place in the reproductive organs,due to which the male and female germ cells
or gametes will have half the number of chromosomes as compared to their parent cells.
When fertilisation takes place by the fusion 

of the two germ cells, the normal number of chromosomes and DNA content is thus restored in the progeny. So, the progeny will have the same number of chromosomes as its parents.

Question. (A) Name a sexually transmitted disease and a method to avoid it.
(B) Draw a neat diagram of human male reproductive system and label the parts performing the following functions:
(i) Production of sperms
(ii) Gland which provides fluid
(iii) Provides low temperature for the formation of sperms
(iv) Common passage for sperm and urine 
(C) Name the human male reproductive organ that produces sperm and secretes a hormone. What is the name the hormone secreted and state its function.
Answer : (A) A disease which can be transmitted through sexual contact is called sexually transmitted disease or STD. This includes warts or syphilis or HIV-AIDS. They can be prevented
by using condoms during sexual intercourse.
(B) The parts of human male reproductive system performing the following functions: 

Human Male Reproductive System
(i) Production of sperms: Testis
(ii) Gland which provides fluid: Prostate gland (iii) Provides low temperature for the formation of sperms: Scrotum
(iv) Common passage for sperm and urine: Urethra

Question. (A) What is meant by fragmentation in organisms? Name a multicellular organism which reproduces by this method.
(B) How does regeneration take place? Why is this process not possible in all animals?
Answer : (A) The breaking up of the body of a simple multicellular organisms into two pieces on maturing, each of which subsequently grows to form a complex new organism is
called fragmentation.
Spirogyra simply breaks up into smaller pieces upon maturation. These pieces or fragments grow into new individuals. This happens without forming any gametes. 

Question. In our country the legally prescribed minimum age for marriage is 18 years for females and 21 years for males. Why is it essential to fix the minimum age for marriage? Give three reasons to Justify your answer. List three methods for preventing unwanted pregnancy.
Answer : Setting a minimum age of marriage are an important way to safeguard boys and girls from being married before they are ready (physically,mentally, sexually) methods for preventing unwanted pregnancy are:
(1) Chemical Method: Use of oral pills to change the hormonal balance of the female.
(2) Barrier Methods: Use of condoms, Diaphram, to prevent the meeting of sperm and ova.
(3) Surgical Methods: Block the vasdeferns in males (vasectomy) or oviduct in females (Tubectomy).
IUCs: Loop or copper T (CuT) placed in uterus, to prevent pregnancy.

Question. Draw neat diagram of human female reproductive system. Label oviduct and uterus on it. State the role of placenta. How the waste generated by the developing embryo removed?
Answer : 

Role of Placenta: Placenta is a special tissue connection between embryo and uterine wall.
It acts as an endocrine gland:
(1) It possess villi that increase the surface area for absorption of nutrients.
(2) Waste substances produced by embryo are removed through placenta into mother’s blood.
(3) Cocilitate passage of nutrition and oxygen to embryo from mother through blood.
The waste generated by the developing embryo removed through placenta into mother’s blood.

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 accidentally gets cut into many pieces, many of these pieces grow
into separate organisms. This is known as regeneration. Plauaria reproduces asexually by the method of regeneration. 

(B) When Bryophyllum leaf falls on wet soil, buds produced in the notches along the leaf margin develop into new plants. This is a form of vegetative propagation.   

(C) When sporangia of Rhizopus burst on maturation, the spores are released which develop into new Rhizopus individuals when they come in contact with a moist surface and begin to grow.   

Question. State the basic requirement for sexual reproduction? Write the importance of such reproductions in nature. 
Answer : The basic requirement for sexual reproduction is the involvement of two sexes, namely, male and female and incorporates a process of combining DNA from two different individuals during reproduction.
Importance of sexual reproduction:
(1) It promotes diversity and new combination of characters in the off springs.
(2) It leads to variations which helps the survival of species in extreme environmental conditions.
(3) It is necessary for evolution.
(4) It plays an important role in the origin of new species.
(Any 2 of 4 points can be written to get full marks)

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 a hormone in human males is testes.
Hormone secreted by testes is testosterone hormone.
Functions of testosterone hormone:
(1) Regulates formation of the male gametes, sperms.
(2) Develops secondary sexual
characteristics such as increased muscle and bone mass, deep voice and the growth of body and facial hair.
(3) Develops male reproductive tissues such as testes and prostate gland.

Question. What is sexual reproduction? List its four significances. 
Answer : Sexual-Reproduction: The Type of reproduction in which male gametes and female gametes fuse together to form zygote which change into embryo and new organism, is called sexual Reproduction.
Significance of Sexual Reproduction
(1) Increases genetic variations.
(2) Promotes diversity in offsprings.
(3) Play a role in origin of new species.
(4) Genetic variations leads to survival of the species.
(5) Variations play an important role in the process of evolution.

Question. What is vegetative propagation? List with brief explanation three advantages of practising this process for growing some types of plants.
Select two plants from the following which are grown by this process:
Banana, Wheat, Mustard, Jasmine, Gram.
Answer : Vegatative Propagation: It is the development of a new plant from the vegatative part like roots, stem and leaves of a plant.
Advantages of vegetative propagation are:
(1) Such plants can bear flower earlier than those produced from seeds.
(2) Allows propagation of plants that have lost capacity to produce seeds,
(3) All plants produced are genetically similar to the parent plant and hence have all its characters.
Banana and Jasmine are the two plants–

Question. (A) List four reasons for adopting contraceptive methods.
(B) If a woman is using Copper – T, will it help in protecting her from sexually transmitted diseases? Give reason in support of your answer. 
Answer : (A) Reasons for adopting contraceptive methods
(1) Population Control.
(2) Medical fitness or physical fitness.
(3) Stop to transmit sexually transmitted disease.
(B) Copper T helps to protect from unwanted pregnancy. Copper T does not help to protect from sexually transmitted diseases (STD) because it does not stop physical contact or semen to reach in vagina.

Question. (A) Fertilization is possible if ovulation has taken place during middle of menstrual cycle. Give reasons.
(B) List in tabular form two distinguishing features between a sperm and an ovum.
Answer : (A) Mature ovum is released from the ovary during ovulation which occurs in the middle of the menstrual cycle. The ovum travels to the fallopian tube of the female reproductive system. If mating takes place during this time. One of the millions sperms released will travel to the cervix of the uterus and fusion may take place.
(B) Distinguishing feature between a sperms and or ovum.