Lakhmir Singh Manjit Kaur Class 10 Biology 3rd Chapter “How Do Organisms Reproduce” solution

Lakhmir Singh and Manjit Kaur Biology solution: “How Do Organisms Reproduce” Chapter 3. Here you get easy solutions of Lakhmir Singh and Manjit Kaur Biology solution Chapter 3. Here we have given Chapter 3 all solution of Class 10. Its help you to complete your homework.

Board – CBSE
Text Book – Biology
Class – 10
Chapter – 03

Lakhmir Singh Manjit Kaur Class 10 Biology 3rd Chapter Solution (1st Part)

Very short Answer Type Questions

1.) Which life process ensures that a plant or animal species will not disappear from this earth?

ANS-Reproduction is the one type of process that gives surety of plant of animal species will not disappear from the earth.

2.) What is the name of the reproductive process ( a) which involves two parents? (b) Which involves only one parent?

ANS-

a) Two parents are involved in sexual reproduction where male and female both genders needed.

b) Only one parent responsible for next generation is mainly occur in the asexual reproduction.

3.) State whether the following statement is true or false: Spores produced by the bread mould plant are actually its seeds.

ANS- false

4.) Most of the plants reproduce by sexual method. Name the two plants which can reproduce sexually.

ANS-Ferns and mosses are two plants which reproduce their progeny by asexually.

5.) Which type of reproduction:

(a) Involves gametes?

(b) Does not involve gametes?

ANS-

(a) Sexual reproduction involves male and female gametes.

(b) Asexual reproduction happened by single parents hence gametes does not involved in this reproduction.

6.) State whether human beings reproduce by sexual method or asexual method.

ANS-reproduction in human being occurs due to gametes involved in it. Male gamete testes and female gamete ovaries are take part to reproduce next generation hence it known to be sexual method.

7.) (a) Name two animals which reproduce sexually

(b) Name two animals which reproduce asexually.

ANS-(a) human being, pig

(b) Spirogyra, amoeba

8.) Name one organism which reproduces by spore formation.

ANS-mushroom develops spores for reproduction.

9.) Name the method by which Paramecium reproduces. Is this method sexual or asexual?

ANS-Paramecium produces its next generation by binary fission which is asexual method.

10.) Name two plants:

(a) Which can be grown from their broken stems?

(b) Which can be grown from their leaves?

ANS-

(a) Bryophyllum, money plant

(b) Bryophyllum, Begonia

11.) Name the asexual method of reproduction in yeast.

ANS- Yeast develops buds for asexual reproduction which is known as budding.

12.) Name the asexual method of reproduction in (a) Hydra, and (b) Plasmodium.

ANS-

(a) Budding (hydra develops buds which attach to parent body)

(b) Multiple fission

13.) What is the name of asexual reproduction method in:

(i) Spirogyraand (ii) Leishmania?

ANS-

(i) Fragmentation (ii) Binary fission

14.) Name the artificial propagation method used for the propagation of (a) rose plants, and apple trees.

ANS-a) Cutting (b) Grafting

15.) Which artificial propagation method is used for the production of jasmine plants?

ANS- Layering method is used for the production of jasmine plants.

16.) Name the natural method by which strawberry plants are propagated.

ANS-Strawberry plants are propagated naturally by layering method.

17.) Name two plants which are propagated by layering method.

ANS-Jasmine, Strawberry plants

18.) Name two plants which are propagated by cuttings method.

ANS-Two plants which propagated by cutting method are rose, hibiscus.

19.) Write down the different methods of asexual reproduction.

ANS-

(ii) Budding. (iii) Spore formation. (iv) Regeneration (v) Fragmentation (vi) fission

20.) Why budding, fragmentation and regeneration, all are considered to be asexual type of reproduction?

ANS- Budding, fragmentation and regeneration are considered as asexual types because (i) those organisms reproduce their progeny from single parent

(ii) Gamete formation and fertilization cannot occur in their body.

Short Answer Type Questions

22.) (a) What is the basic difference between asexual reproduction and sexual reproduction?

(b) Which of the following organisms reproduce by sexual method and which by asexual method? Amoeba, Cats, Humans, Hydra, Birds

ANS- (a)

ASEXUAL REPRODUCTION	SEXUAL REPRODUCTION
1. Asexual reproduction generally occurs in lower organisms where new progeny produce by only one parent.	1. Sexual reproduction generally occurs in higher organisms (exceptional cases are there) where progeny produce by two parents.
2. In this reproduction, when progeny grows completely then it seems exact like a parent.	2. When progeny grows completely (at the adult stage) it seems to different than parent. Because it born with both types of characters.
3. Budding, multiple fission, spore formation, is the type of asexual reproduction.	3. in this reproduction two different sex gametes taking part to produce new progeny.
4. In this reproduction no any sex gamete takes part.	4. example- human being reproduces its progeny. For that male gametes and female gametes takes part to fertilization.
5. example-amoeba shows binary fission to reproduce new amoeba.

(b)

(i) Sexual Method: Cats, Humans, birds

(ii) Asexual method: Amoeba, Hydra

23.) (a) What is meant by regeneration? Name two animals which can regenerate fully from their cut body parts. (b) Explain why, more complex multicellular organisms cannot give to new organisms through regeneration.

ANS-

(a) When cut body part can regenerate its full body which is nothing but whole organism is newly born, that is known as regeneration. Example-Planaria and Hydra

(b) Many multicellular organisms like human beings are made up of very complex system. This complex system made body function with the help of very specific cells, organ, and organ system.Such complication cannot allow regenerating whole body when cut happens. Any specific organ and their cells is cut by anybody then it cannot grow because specific cells are gone and they cannot develop artificially. Hence complex Multi cellular organisms cannot be reproduced from their cut body parts by the process of regeneration.

24.) Explain vegetative propagation with the help of two examples. List two advantages of vegetative propagation.

ANS-new plants can grow with the help old plant parts this is we called vegetative propagation. Stems, roots leaves like body part take part in vegetative propagation where it happens asexually.

Example: Potato plant with tuber generates new plant.

Vegetative propagation:-

(i) Plant grow faster hence it less time consuming.

(ii) it grows naturally.

(iii) do not require special care.

25.) (a) What us meant by the term ‘artificial propagation of plants’?

(b) Name three common methods which are used for the artificial propagation of plants

(c) Name two plants which are usually propagated by artificial propagation methods. Name the method of artificial propagation used in each case.

ANS-

a) Artificial propagation-artificially means man made( not naturally) method which observed in many plants where they grows from another plant parts.

(b) Methods involved in artificial propagation of plants.

(i) Cutting

(ii) Layering

(iii) Grafting

(c)

(i) example of banana plant-new banana plants are grow by cutting

(ii) Grafting method-grafting method is used for apple tree.

26.) Describe the layering method for the artificial propagation of plants. Illustrate your answer with the help of a labeled diagram. Name any five plants which are propagated by the layering method.

ANS- Layering is the artificial propagation method in which the new plant can develop by

This method. Below diagram shows layering method in the jasmine.

For this method, we have to buried branch of plant into soil such way that the tip of branch is should be above from the ground level. After some days branch is getting automatically separate from parent body and develops as a new plant. This is asexual method of reproduction which generally seen in strawberry, guava etc.

27.) (a) What is meant by the term ‘fission’ as used in biology?

(b) How does binary fission differ from multiple fission?

(c) Name one organism which reproduces by binary fission and another which reproduces by multiple fission.

(d) State whether the above named organisms are animals or plants.

ANS-

(a) Fission means the splits up body part which is generally found in amoeba where its body getting spitted into two parts and forms new amoeba.

(b)

Binary fission	Multiple fission
1.Parent body get splits into two parts where only two organisms are observed	1. parent body get splits up into multiple part where the multiple organism are newly born
2.it is happened in normal condition	2. it is happened in unfavorable condition
3. example-amoeba	Example- plasmodium

(d) Amoeba and plasmodium both are animals not plants.

28.) (a) Can you consider cell division as a type of reproduction in unicellular organisms? Give reason.

(b) What is a clone? Why offspring do’s formed by asexual reproduction exhibit remarkable similarity?

ANS-

(a) Yes, whenever the cell division occurs cell can produce another cell or we say one cell give birth to another cell so there is total two daughter cell observed hence this process is consider in the reproduction.

(b) Clone means new species produced by single parent by asexual reproduction. Those species physically and genetically similar with the parent.

DNA plays vital role in in reproduction in which DNA can replicate with the purpose of new offspring formation and specify their characters. Replication of DNA is happened due to various biochemical reactions. In asexual reproduction only one parent is responsible for next generation. Whenever the DNA does there replication in the nucleus at that time slight variation occurs in new (copied) DNA. Hence DNA is not exact same but is remarkably similar.

29.) (a) The yeast cells fail to multiply in water but they multiply rapidly in sugar solution. Give one reason for it

(b) Why does bread mould grow profusely on a moist slice of bread but not on a dry slice of bread?

ANS-

(a) Energy is must for reproduction because new species is getting born through this process. In the sugar solution, yeast get energy but it does not get energy from water hence it not shows reproduction in sugar solution.

(b) Mould mostly grow on wet bread because moist bread gives it favorable condition for grow also bread provides nutrient to them. But if bread is dry then it does not grow due to lack of favorable condition.

30.) (a) What is tuber? Name one stem tuber and one root tuber?

(b) What is the name of the organ of propagation present in a tuber?

(c) Name on commonly used vegetable which is propagated by using tubers.

ANS-

(a) A tuber is stem which is generally grown inside the soil. Tuber is looks like swollen.

Stem tuber-Potato

Root tuber- Sweet potato

(b) Buds

31.) (a) What is meant by vegetative propagation?

(b) Vegetative propagation involves the growth and development of ‘ something’ present in the old part of the plant to form a new plant. What is this ‘something’?

(c) Why do green grass plants spring up in dry fields on their own after the rains?

ANS-(a) new plants can grow with the help old plant parts such type of process we called vegetative propagation. Stems, roots leaves like body part take part in vegetative propagation where it happens asexually. For example, the tuber of potato, rhizome grows on ginger.

(b) Buds

(c) The dry stem which present in the field have buds like projection.it is in inactive state without water. When rain falls that time due to water it get active and new grass plant grows. That is the way green grass plants springs up in dry fields on their own after the rain fall.

32.) (a) Explain how, new Bryophyllum plants can be produced from the leaves of the old plant? Illustrate your answer with help of a labeled diagram.

(b) How can you grow money plant by vegetative propagation?

ANS-

a) Bryophyllum can be reproduced by vegetative propagation by using either a piece of its stem or leaves. The leaves of a Bryophyllum plant have special buds in their margins which may get detached from the leaves, fall to the ground and then grow to produce a new plant.

(b) Stem of money plant dipped into water for few days. Only that stem should dip which has at least one leaf. New roots can develop below the stem and tip of stem further grow in upward direction.

Long Answer Type Questions

34.) (a) What is meant by reproduction?

(b) What are the two general methods of reproduction in organisms?

(c) How does an Amoeba reproduce? Describe the process of reproduction in Amoeba with the help of labelled diagrams of different stages in its reproduction process.

(d) What is the name of the process by which Amoeba reproduces?

(e) Name two organisms which reproduce by the same sexual process as that of Amoeba.

ANS-

(a) The production of new organisms from the other organisms (parent organism) is called reproduction. From the reproduction we get next generation of the parent species.

(b)Sexual reproduction ( from two parents) and asexual reproduction( from one parents) is the two methods of reproduction.

(c) Amoeba shows binary fission which is type of asexual reproduction where the amoeba splits up into two parts and those parts can develop as a individual amoeba.In this reproduction nucleus of amoeba get splits into two parts gradually cytoplasm also splits and makes cover around nucleus such a way two individual amoeba forms.

In above diagram a) nucleus starts to split up

b) Two individual nucleus present in the amoeba

c) Gradually cytoplasm also splits up

d) Two daughter cell of amoeba is been born

35.) (a) What is the difference between the two asexual methods Of reproduction: fission and fragmentation?

(b) Name the organism which reproduces by fission and another which reproduces by fragmentation.

(c) What is meant by multiple fission? Name one organism which reproduces by the process of multiple fission.

(d) Describe the process of reproduction in Hydra with the help of labeled diagrams. What is the name of the process of reproduction?

(e) Name one unicellular organism which reproduces by the same asexual process as Hydra.

ANS-

(a)

Fission

(i) in this asexual reproduction body shows fission where it splits up into two or more parts and automatically new organisms can form.

(ii)When body splits into two parts that we called binary fission example- amoeba.

When body splits into multiple parts then that type of fission is known as multiple fission. Example- Plasmodium

(iii) fission is happens in unicellular organism.

(iv) Diagram:

Fragmentation

(i) in this asexual reproduction body breaks and form fragment and they are gradually develops as new species

(ii) example- spirogyra

(iii) It happens in multicellular organisms. Example: Spirogyra.

(iv) Diagram:

(b) Amoeba is splits into two parts with their nucleus hence we called it shows binary fission

Spirogyramakes fragment and develops as new individual hence we called this method is fragmentation.

(c) multiple fission is one type of asexual reproduction where the organisms splits (fission) into multiple organism and it mainly seen in the Plasmodium.

(d) Hydra shows budding which is one type of asexual reproduction. In this reproduction parent hydra give birth to new hydra such way which shown in below diagram

a) parent hydra present
b) one type of outgrowth develops on hydra which we called bud
c) in this diagram that new buds are looks like small hydra because its tentacles and mouth is develops in proper their structure
d) New hydra detached from parent body and further it grows individually.

(e) Yeast is reproducing asexually like hydra.

36.) (a) Name the method by which bread mould (Rhizopus fungus) reproduces. Is this method sexual or asexual?

(b) What is yeast? Describe the process of reproduction in yeast with the help of labeled diagrams.

(c) Name a tiny fresh-water animal which reproduces by the same method as that of yeast? What is this method known as?

(d) Name two marine organisms which reproduce by the same method as yeast but form colonies.

ANS-

(a) Rhizopus and fungus shows asexual reproduction by forming Spores that get burst out results, the formation of new species.

(b) Yeast reproduces by showing special type of asexual reproduction called budding.it is non-green, small, unicellular organism. New bud develop on cell wall of yeast while this process nucleus shifted towardsthe bud develop some of thenucleic material remain as it is in the parent yeast. Buds grows gradually thenfurther it get separate from the parent body and new yeast is born.

(d) Sponge and corals.

37.) (a) What is meant by ‘grafting’ as a means of propagation in plants?

(b) Define ‘stock’ and ‘scion’.

(c) Describe the grafting method for artificial propagation of plants with the help of labeled diagram.

(d) Name two fruit trees which are usually propagated by grafting method.

(e) State two advantages of grafting method of artificial propagation of plants.

(f) What is the difference between cuttings method and grafting method for artificial propagation of plants?

ANS-

a) Grafting – it is artificial propagation method where two different plants are taken. For that artificial process we have to cut stems of two different plants and join together then it grows as a single plant that whole process is known as grafting method.

(b) In grafting method we have to take two stems one with roots called stock and another one is without roots called scion.

(c) In grafting method we have to take two stems one with roots and another one is without roots which we called stock and scion respectively. These both stem cut by diagonally and stick together with the help of cloth. Their gap heels gradually and they became a one plant.

(e) Advantages of grafting method:

(i) in grafting method two different plants takes part that is why two characters is seen in one plant, results the production and productivity of plant increases.(ii) It helps to take production of varieties of seedless fruits.

(f)

Cutting

(i) cutting is the method where plant part is cut by using sharp knife .From that remain part, whole new plant can grow.

(ii) New plant contains same character like its parent plant.

(iii) example- hibiscus

Grafting

(i) in this method stem of different plants joined and they grow as a single plant.

(ii) New plant is originated from the two different plants hence it shows both characters.

(iii) Example –apple, peach, apricot.

38.) (a) What is tissue culture?

(b) Name any four types of ornamental plants which are being produced by tissue culture technique.

(c) What is the importance of DNA copying in reproduction? Explain with an example.

(d) How does reproduction help in providing stability to population of species?

(e) Why is variation during reproduction beneficial to the species but not necessarily for the individual?

ANS-

(a) New plant can grow in suitable growth medium. For that tissue of parent plant removed from the tip and then it grow in the specific medium, results we get new plant which we called tissue culture.

(b) Orchids, dahlia, carnation, chrysanthemum.

(c)(i) chromosomes are always found in the nucleus which contains DNA. Many proteins amino acids present on DNA which specify the particular characters of species. When the DNA copy happens in the nucleus at that time special type of character is made in offspring because every reproduction is starts from nucleus and DNA replication.

(ii) Replication of DNA is happened due to various biochemical reactions. Whenever the DNA does there replication in the nucleus at that time, slight variation occurs in new (copied) DNA. Hence,DNA copying develops a similar character in between parent and offspring (but not exactly same character) results, we experiences variation in two species.

Example: 1) Offspring’s produced by sexually reproduction shows many variations from parents because in sexual reproduction two different species takes part hence their DNA inherited their own characters in their new progeny.

2) Organisms which reproduces asexually, such organisms shows slight difference in DNA with parents.

(d) DNA is the main part of nucleus which responsible for reproduction and variation happens in the parent to progeny. Many adverse conditions affect the species population but reproduction with variation, sustain their population and develop stability. Whenever the DNA does there replication in the nucleus at that time, slight variation occurs in new (copied) DNA. Through variation new species born with new feature, which can easily tackles those adverse conditions.

(e) Variation helps to species for sustain population and develops stability in them.Variation in species can fight adverse condition.

Variation happens in the species reasons-When drastic change found in the environment that time DNA modify some features itself that get inherited to progeny. Sometime during replication DNA codes get change and variation happens.

Whenever the adverse condition happens, many species might bedie and they became a extinct or endangered species. From those, if any individual is born with variations have chances to survive in this adverse condition and it reproduces its progeny again. So, ultimately whole species population can’t destroy by Tran’s environments.

Example: many years ago in London, white moth species get extinct due to pollution (it looks white and due to pollutions trees became a dark so they easily

Captured by predators) but after many years variation occurs and their appearance change to greyish such a way they do not get extinct completely.

39.) (a) What is a ‘cutting’ in respect of plants for propagation purposes?

(b) What care should be taken while making a cutting from a plant?

(c) Describe the cuttings method for artificial propagation of plants. Illustrate your answer with the help of a labeled diagram.

(d) Name any two plants which are usually propagated by cuttings method.

ANS-

(a) A small part of the plant cut by a sharp knife is called cutting.

(b) Parent plant which we have to cut that always should be with bud. And we have to cut the plant, such a way that there is remains bud on body.

(c)In the cutting method we have to choose that plant which have bud And also cut plant such a way that the bud is remains on plant body. Bud is responsible for new plant.

In the below diagram

a) Plant can cut by the sharp knife (bud is present in the bottom)

b) Small limb is grow from the site of bud

c) New plant form.

(d) Rose and Bougainvillea.

2nd Part Solution

Very short type questions

1.) Where is a plant sex organ located?

ANS-flower is the plant part where the sex organ located.

2.) What is the function of a flower?

ANS- male and female gametes located in the flower So it is responsible for fertilization occurs in both gametes with forming new seeds for the reproduction.

3.) What are the reproductive organs in a flower?

ANS- Stamen and carpel.

4.) What is the name of: (a) male part of a flower (b) female part of a flower?

ANS-

(a) Stamen.

(b) Carpel.

5.) What is the name of a female organ of a flower (other than carpel)?

ANS- Pistil.

6.) What is the other name of sex cells?

ANS-Gametes is the name of sex cells.

7.) What is the name of sex cells (other than gametes)?

ANS- Germ cells

8.) Name the male and female gametes in animal.

ANS-

Male gamete -sperm

Female gamete -ovum

9.) Where is the male gamete formed; (i) in humans (ii) in flowering plants

ANS-

(i) Testes

(ii) Anther

10.) Where is the female gamete formed(i) in humans (ii) in flowering plants

ANS-

(i) Ovary.

(ii) Ovary.

11.) Name two animals which undergo external fertilization into animals which undergo internal fertilization.

ANS-

(i) External fertilization: Frog and toads

(ii) Internal fertilization: human being and cats

12.) Define sexual reproduction.

ANS- The reproduction which takes place with the help of two different sex gametes. These gametes produces special type of cells (male-sperms, female-ova) which combines and give birth to new progeny is called sexual reproduction.

13.) Do all organisms give birth to individuals like humans?

ANS- All organisms do not give birth to individuals like humans.

14.) Write the full form of the following as they occur in biology:

(i) STD. (ii) AIDS. (iii) HIV

ANS-

i) STD – Sexually Transmitted Diseases.

(ii) AIDS – Acquired Immune Deficiency Syndrome.

(iii) HIV – Human Immunodeficiency virus.

15.) What is the causative organism for the following diseases?

(i) Gonorrhea. (ii) Syphilis (iii) AIDS

ANS-

(i) Bacteria.

(ii) Bacteria.

(iii) Virus.

16.) What are the organs in humans which produce the gametes?

ANS-Testes is present in the male body

Ovaries present in the female body.

17.) (a) What are the male sex cells in humans called?

ANS-Spermsis the male sex cell.

(b) Name the organ which produces male sex cells.

ANS- Testes is the organ which produces sperm cell.

18.) (a) What are the female sex cells in humans called?

(b) Name the organ which produces female sex cells.

ANS-

(a) Ova or eggs

(b) Ovaries.

19.) Which part of the human body:(a) produces sperms(b) produces ova(c) passes sperm from man to woman.

ANS-

a) Testes is the male reproductive part which produces sperm.

(b) Ovaries is the female reproductive part who reproduces ova.

20.) (a) What do testes in a man produce? (b) What do the ovaries in a woman produce?

ANS-

a) Sperms.

(b) Ova (eggs)

21.) (a) Where in the human body does an ovum get fertilized?

(b) Where does a fertilized ovum develop into a baby in the human body?

ANS-

a) Oviduct (fallopian tube) is the tube like body part where the ovum get fertilized.

(b) After the fertilization baby get develop into uterus.

22.) Name the liquid that contains sperms?

ANS- Semen.

23.) What is the name of the process in which thickened uterus lining along with blood vessels is removed from the body of human female through vaginal bleeding?

ANS- Whenever fertilization is not takes place in the uterus that time inner linings of blood vessel is getting flow off (bleeding) through vagina is we called mensuration.

24.) (a) For how much time does menstruation last in human females (or women)?

(b) What is the frequency of menstrual cycle in human females (or women) ?

ANS-

(a) 3 to 5 days.

(b) after every 28 days (approx. 28 days).

Short Answer type Questions

26.) (a) What are gametes?

(b) In which sort of reproduction gametes involved

(c) What is formed when two gametes fuse?

(d) What is this act of fusion called?

ANS- (a) the cells which responsible for sexual reproduction are called gametes.

(b) Sexual reproduction is happened due to two different gametes (one is female gamete and another one is male gamete) taking part in fertilization.

27.) (a) Write the names of male sex hormone and female sex hormones

(b) What name is given to the fusion of sperm and ovum?

(c) Name the tissue through which the fetus gets all the requirements from the mothers’ body

ANS-(a) Testosterone is the male sex hormone whereas oestrogen and progesterone is the female sex hormones.

(b) When ovum and sperm met of fuses that phenomenon is known asFertilization.

28.) (a) Draw a neat sketch of the stamen of a flower. Mark in it filament and anther.

(b) Draw a neat sketch of the carpel of a flower. Mark in it stigma, style and ovary.

(c) What is made in anther and ovary of a flower?

ANS-(a)

(b)

29.) (a) Explain the terms self-pollination and cross pollination?

(b) How do the insects help in cross pollination?

(c) How is the process of pollination different from fertilization?

ANS-

(a)

The Fertilization takes place in same flower is called self-pollination where the pollen grain travelled from anther to stigma of flower and meting happens in between ovule and pollen grain at the same flower is called self-pollination.

In this method pollen grains of anther of one flower plant enters into ova (egg) of another flower plant is called cross pollination.

(b) Insects are always wandered from one plant to another plant for the searching of food. many insects, bees suck a nectar from one flower plant, that time pollen grain get stick over the body ( because of moisten skin). Whenever they go to another plant for sucking nectar, those pollen grains (which present on body of insects) from anther get entered in stigma of flower (which is grown on another plant). Such a way fertilization occurs called cross pollination.

(c)

Pollination

Fertillization

1.This process is occurs in only plant.

2 in this process pollen get transfer from anther to stigma of flower.

3. in this pollination process pollen grain and egg of flower takes part.

1.This process occurs in plant as well animals

2.in this process two gametes, one of male and another one is female gametes get fuses together and form zygote.

3. in this process male gamete ( pollen grain, testes) and female gamete ova takes part.

30.) (a) Explain the term fertilization.

(b) Give some examples of different modes of fertilization in nature.

(c) What type of fertilization takes place in fish and birds?

ANS-

(a) Male and female gamete is fuse together and forms zygote. Which happens in sexual reproduction is called fertilization.

(b) Internal and external fertilization.

(c)(i) in case of fish fertilization occurs outside the female body-External fertilization.

(ii) In case of bird fertilization occurs in the female body-Internal fertilization.

31.) (a) What are the male and female gonads in human beings? Mention their functions.

(b) State the advantages of sexual reproduction over asexual reproduction.

ANS-

(a)

Male

Gonad name- testes

Function of testes-1. Testes is the male sex organ

Which produces sperm also it makes male hormone called testosterone

Female

Gonad name- ovary

Function of ovary- ovary is the female sex organs which contain ova or egg and it made hormones called estrogen and progesterone.

(b) Advantages of sexual reproduction over asexual reproduction:

(i) sexual reproduction happens in two different sex organs. Hence DNA comes in progeny from two parents that is the reason; offspring is born with variation whereas in asexual reproduction variation is not found that much because only one parent is responsible.

(ii) Variation is the main reason which is responsible for evolution happens in the environment. So the animals which shows sexual reproduction get evolved during adverse condition developed in environment ( like so hot, so cool) and they survive.

But organisms which shows asexual reproduction they doesn’t get evolved due to lack of variation and it will extinct if adverse climatic conditions developed in environment.

32.) Describe the various steps involved in the sexual reproduction in animals. Draw labeled diagrams to show the fertilization of ovum or egg by a sperm to form a zygote.

ANS-

The sexual reproduction happens in animals by below way

(i) MALE -male sex organ called testes which produces sperm cell. It is mobile in nature and its body part known as head and tail. (B diagram of sperm)

FEMALE-ovary is the female sex organ which produces ova. Its oval shape cell.(diagram).

(iii)sperm is produced from testes and it enters to female body through vagina then in fuses with the ova this process is called as fertilization. After the fertilization zygote get forms in the female uterus.

(iv) Zygote is further divides into multiple cells and lastly, it converts into baby.

34.) (a) Write the various steps involved in the sexual reproduction in plants.

(b) Name two plants which reproduce by sexual reproduction method and two plants which reproduce by asexual reproduction methods.

ANS-(a) The sexual reproduction in plants takes place in the following steps:

(i) The male sex organ of flower called stamen which made the male gametes whereas female sex organ in plant called carpel. These gametes present in pollen grain and ova respectively

(ii) due to wind, insects, water or by self-pollination pollen grain transfer to stigma.

(iii) after the contact of male and female gametes fertilization occurs.

(iv) The fertilized egg cells grows inside the ovules which known as seeds.

(v) by germination process new plant get grow from the seed site.

(b) Sexual reproduction: Hibiscus and sunflower plant;

Asexual reproduction: Ferns and mosses.

35.) (a) What type of plants reproduces by sexual reproduction method?

(b) What is a seed? What are the parts of a seed? Explain with the help of a labeled diagram.

ANS-(a) Flowering plants contains male and female sex gametes which is responsible for seed formation and ultimately new plant get birth.

(b) A seed is the reproductive unit of a plant which is responsible for germination process where the new plant get form.

Plumule, radical and cotyledon are the major parts of seeds.

37.) (a) What is gestation period ? How much is the gestation period in humans?

(c) Name one sexually transmitted disease for which no definite cure has been found so far. What is the causative organism of this disease?

ANS-

(a) gestation period means the time period between fertilization (occurs in ova and sperm) and birth of baby. it is generally 9 months period.

(c) AIDS is the disease which no definite cure has been found so far. It is caused by special type of virus called HIV (human Immunodeficiency Virus).

45.) Explain how, offspring’s and parents of organisms reproducing sexually have the same number of chromosomes.

ANS-. Meiosis is responsible for reduction of chromosome number. During meiosis chromosomes number get reduces in the half at the formation of gametes in the parent body. Such way half of chromosomes from male gamete and another half from female gamete which incorporated in offspring through fertilization (gamete fusion). So, when the male and female gametes fuse together that time fertilization occurs through which original number of chromosomes comes as it is in the offspring.

47.) (a) What would be the ratio of chromosomes number between an egg and its zygote?

(b) Distinguish between gamete and a zygote.

ANS-

(a) Egg contain 24 chromosomes and zygote contain 48 chromosomes hence ration is 1:2

(b)

Gametes

Zygote

1. gametes is term related to germ cells or we called sex cells

2. Two types of gametes mainly found. Male gamete name sperm and female gamete name egg.

3. Gametes are responsible fertilization happens.

4. Gametes contain 24 chromosomes.

1. Zygote is nothing but initial stage of baby.

2. Zygote is formed after fertilization when two sex gametes fuse together.

3. Zygote contains 48 chromosomes.

52.) People who die from AIDS are not killed by the virus itself. Explain.

ANS- AIDS cause by HIV. It is virus which contains proteins which easily affects to our white blood cells (fighter cells). So due to attack of virus, immune system getting weak hence any infection can easily experience by body. That is the reason people who suffers from AIDS are not killed by the virus itself.

Long Answer Type Questions

54.)

(a) What is meant by unisexual flowers and bisexual flowers? Give two examples of each.

(b) What is pollination? How does pollination occur?

(c) Describe the process of fertilization in a flower with the help of labeled diagrams.

(d) What changes take place in the flower after fertilization which leads to formation of seeds and fruit?

ANS-

(a) Unisexual flower contain only one sex organ. This flower is born with either stamen or carpel. Such type of flowers shows fertilization in different-different flowers from which one is contain carpel and another one contain anther .example-papaya, watermelon

Bisexual plant contain both sex organ like carpel and anther, these both part present in one flower. So, in that plant fertilization happens in single flower example-Hibiscus, Mustard

(b) Pollination= pollen grain transferred from anther to stigma of carpel called pollination.

Self-pollination and cross pollination is the type of pollination which happens with the help of insects, bees, birds, wind, water etc.

Fertilization occurs in plant when pollen grain fuses with ovule which is female reproductive cell.

When pollen grains falls on the stigma of carpel that time it travels through style of carpel, where it goes towards the female gametes in the ovary. Male gametes moves down through pollen tube and get burst out. That gamete (which burst already) fuses with the ovule and fertilization occurs.

(d) When fertilized egg transform into embryo that time ovary get develops as tough coat and slowly it convert into seed so,all fertilized ovules converts into seeds. After the seed formation, flower modifies into fruit because remaining part like sepals, petals, stigma, stamens are fall off and only ovary which left became fruit which grow around the seed.

55.) (a) Draw a neat diagram of a flower showing its various parts. In this diagram mark stem, receptacle, sepals, petals, stamen and carpel.

(b) What name is given to (i) all the petals of a flower, and (ii) all the sepals of a flower?

(c) What are (i) stamen, and (ii) carpel in a flower?

(d) What is the other name of carpel of a flower?

(e) What is the name of yellow powdery substance present in the anther of a flower?

ANS-(a)

(b) (i) Corolla (ii) Calyx

(ii) Carpel is the female reproductive part of plant.

(d) Pistil is the other name of carpel.

(e) Yellow powdery substance which present on anther called pollen grain.

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