SEE Science: Heredity

1. Mendel selected pea plant for his experiment, why?
Ans: He selected pea plant for his experiment due to the following reasons:
1. Pea plants can be cultivated easily and have a short life cycle. 
2. They produce a large number of offsprings. 
 
2. Write down the significance of Mendel's law.
Ans: The significances of Mendel's law are:
1. Hybrids with desired characteristics can be produced. 
2. The genotypes and phenotypes likely to be produced in successive generations can be predicted before the cross is made.
 
3. Define genotype.
Ans: Genotype is the gene composition of an individual, which determines the individual’s form, size, colour, behavior, etc.

4. Define monohybrid cross.
Ans: When only one unit character is involved in a cross, it is called monohybrid cross.

5. Define recessive character.
Ans: The suppressed character which does not express itself in the successive generation is known as recessive character.

6. Define dominant characters.
Ans: The characters which appear in successive generations are called dominant characters.

7. Define homozygotes.
Ans: The organisms having two similar genes for a particular character in a homozygous pair of chromosomes are known as homozygotes.

8. Define heterozygotes.
Ans: The organisms containing both dominant and recessive characters of an allelic pair are called heterozygotes.

9. Define alleles.
Ans: Two or more alternating forms of a gene are called alleles.

10. Define pure organisms.
Ans: Those organisms which have same phenotype and genotype are called pure organisms.

11. State law of dominance.
Ans: Law of dominance states that when a cross is made between a pair of pure contrasting characters, only one of them is able to express itself phenotypically while the other remains hidden in the F1 generation.

12. What is law of segregation?
Ans: Law of segregation states that the two members of a pair of factors separate during the formation of gametes.

13. Blue eyed offspring may be produced from brown eyed parents, why?
Ans: Blue-eyed offspring may be produced from brain eyed parents, if the brain eyed parents are (not pure) hybrid. In a hybrid, both the blue-eyed as well as brain eyed characters are present. The blue-eyed character is recessive which if expressed in the next generation, results in offsprings with blue eyes.

14. Define acquired characters.
Ans: The characters developed by the organisms themselves through their own effort are called acquired characters.

15. Define RNA.
Ans: RNA represents ribose nucleic acid, which acts as a genetic material in some lower organisms like viruses.

16. Define DNA.
Ans: DNA represents deoxyribose nucleic acid which is a small segment of the gene that carries the hereditary material.

17. Mendel selected pea plant for his experiment, why?
Ans: He selected pea plant for his experiment due to the following reasons:
1. Pea plants can be cultivated easily and have a short life cycle. 
2. They produce a large number of offsprings. 
 
18. Write down the significance of Mendel's law.
Ans: The significances of Mendel's law are:
1. Hybrids with desired characteristics can be produced. 
2. The genotypes and phenotypes likely to be produced in successive generations can be predicted before the cross is made.
 
19. Mendel could not succeed in his experiment, if he used frogs instead of pea plants?
Ans: It is because a frog reproduces by crossing only. Thus, purity of characters cannot be checked in them. Similarly, they lack a large number of contrasting pairs of characteristics that can be observed from outside.

20. Write any two applications of Mendel's law of inheritance?
Ans: The two applications of Mendel's law of inheritance are:
i. It gives a new idea about the new combination of hybrids. 
ii. New types of plant with new combinations can be formed. 
 
21. Can we apply Mendel's law in human beings too? State difficulties Mendel would have faced if he had carried his experiment on a human instead of plants.
Ans: Yes, Mendel's law can also be applied in human beings. The difficulties that he would have faced, if he had carried it on human are:
i. Human beings produce only one offspring at a time. So, it would be difficult to compare the characteristics in the same generations.
ii. If it had been in human, he would wait for many years.

22. Study the given diagram and answer the following questions.

 

Rr	Rr
Rr	rr

a. Which filial generation is shown in the given diagram?
b. Which law of Mendel does it support?
c. Write phenotype and genotype of the generation?
d. Write the characteristics of the parents.

Ans: 
a. F₂ generation is shown in the given diagram.
b. It supports the law of purity of gametes.
c. Phenotypic ratio = 3:1
   Genotypic ratio = 1:2:1
d. This shows the cross between pure red (RR) and pure white (rr). That is parents are pure red and pure white.

23. Describe Mendel's law of dominance with one example.
Ans: Mendel's law of dominance states that when a cross is made between a pair of pure contrasting characters, only one of them is able to express itself phenotypically while the other remains hidden in F1 generation. The character which is expressed is called dominant while the other which is not expressed or remains hidden is called recessive.
Example:
When a pure tall pea plant (TT) and pure dwarf pea plant (tt) is cross-pollinated, all the offspring are toy bird tall in the first filial generation. In this case, tallness appears by suppressing the dwarfness.
 
24. Define dihybrid cross.
Ans: When two unit characters are involved in a cross, it is called dihybrid cross.

25. Define hybrids.
Ans: Hybrids are those organisms which have different phenotype and genotype.

26. Define mutation.
Ans: The sudden and unexpected change from one generation to another generation is called mutation.

27. What is the law of independent assortment?
Ans: Law of independent assortment states that when two pairs of independent alleles are brought together in the hybrid (F1), they, at the time of gamete formation, segregate or assort independently at random and freely.

28. Define polyhybrid cross.
Ans: When more than two unit characters are involved in a cross, it is called a polyhybrid cross.

29. Differentiate between dominant character and recessive character.
Ans: 

Dominant character	Recessive character
1. Dominant character is expressed by hybrid.	1. The recessive character is not expressed by hybrid.
2. It is not suppressed by the other character.	2. It is suppressed by the other character.

30. Define mutants and mutagens.
Ans: The organisms in which mutation occur, are called mutants. The cause of mutation is called mutagen. Example: X -rays, gamma rays, chemicals, etc.

31. What will be the results of crossing black hybrid masses and pure white mouse if black colour is dominant character? Insert in table.
Ans: The genotype for black hybrid mouse is Bb. The genotype for pure white mouse is bb. 
The cross between them is shown as:

Gametes	B	b
b	Bb	bb
b	Bb	bb

It results two hybrid black and two pure white coloured mouse.

32. How is hybrid produced? Explain with an example.
Ans: When cross is made between two parents having pure contrasting pair of characteristics then, hybrid is produced. For example, when a pure tall plant is crossed with pure dwarf plant then in it generation, hybrid tall is produced. i e.


33. Draw the result of crossing between tall and dwarf pea plant up to second filial generations.
Ans: Here,
TT represents tallness and it represents dwarfness.

TT = Pure tall
Tt = Hybrid tall
tt = Pure dwarf
Phenotypic ratio = 3:1
Genotypic ratio = 1:2:1

34. Show the genotype and phenotype of the offspring produced by crossing drosophila with long wings and short wings up to second filial generations.
Ans: The genotype for long-winged drosophila is LL.
The genotype for short-winged drosophila is ll.

Genotypic ratio = 1:2:1
Phenotypic ratio = 3:1

35. Every living beings reproduces its own kind of offspring, why?

A hybrid tall pea (Tt) is crossed with dwarf (tt) plant to get F1 generation, what will be the genotypic and phenotypic ratio in this case.

Ans: It is due to the presence of hereditary information in the chromosome of the gametes, which then passes into the zygote and finally to the offspring.
Hybrid tall pea plant = Tt
Dwarf pea plant = tt

Genotypic ratio = 1:1
Phenotypic ratio = 1:1

36. Write a name of sex linked disease seen only in male. Draw a chart to show first and second generation offspring obtained by crossing between black coloured mother (BB) and white coloured father bb. Also write phenotypic and genotypic ratio of second generation offspring.
Ans: Haemophilia is the sex-linked (X-linked) diseases that are seen only in the male.

BB = Pure black.
Bb = Hybrid black
bb = pure white
Genotypic ratio = 1:2:1
Phenotypic = 3:1

37. 

a. In humans, the gene for black skin colour (B) is dominant over the gene for white colour (b). Study the given chart and answer the following questions.

i. Write down the genotype and phenotype of the mother.
ii. What is the phenotypic and genotypic ratio of black and white complexion in the F2 generation?

b. State law of Segregation with an example.

Ans: a.
i. Write down the genotype and phenotype of the mother.
The genotype of the mother = bb
The phenotype of the father = white coloured skin
ii. What is the phenotypic and genotypic ratio of black and white complexion in F2 generation?
Phenotypic ratio and white complexion is 1:1
The genotypic ratio of black and white complexion is also 1:1.

b. State law of Segregation with an example.

Mendel's law of segregation states that the hybrid obtained in F1 generation contain two contrasting characteristics i.e. dominant and recessive. Those characteristics remain together for a long period of time in hybrids but do not mix with each other and separate or segregate at the time of gamete formation so that each gamete gets only one characteristic, either dominant or recessive characteristics. Example: When a cross is made between pure red-flowered and pure white has red parents which are shown in the chart below.

38. Define continuous variation.
Ans: The gradual change from one generation to another generation is called continuous generation.

39. Differentiate between monohybrid and dihybrid cross.
Ans: 

Monohybrid cross	Dihybrid cross
1. Only one unit character is involved in a cross.	1. Two unit character is involved in a cross.
2. A cross between pure tall and pure dwarf pea plant.	2. A cross between a tall pea plant with red flower and dwarf plant with a white flower.

40. Write any two differences between phonotype and genotype.
Ans: 

Phenotype	Genotype
1. It is the external appearance of an organism.	1. It is the genetic makeup of an organism.
2. It can be known/identified through direct observation.	2. It cannot be known through direct observation.

41. Write any two differences between variation and mutation?
Ans: 

Variation	Mutation
1. The structural differences that provide individuality to eachmember of a species are calledvariation.	1.  A sudden inheritable change in the genetic materials of an organism is called mutation.
2. It is also called continuous variation	2. It is also called discontinuous variation

42. Differentiate between environmental variation and genetic variation.
Ans: 

Genetic variation	Environmental variation
1. This is acquired by the organism due to changes in the chromosomes or genes.	This is acquired by the organism due to the influence of the environment.
2. It is inheritable.	2. It is non-inheritable.

43. When black and brown dogs are crossed, all the dogs at F1 generation are found to black. Give reasons of not forming brain dogs. Also, give a chart to show the cross.
Ans: In this particular cross, black colour is dominated and the brown is the recessive character. According to Mendel's first law that is the law of dominance only one character is expressed in the offspring while the other remains in expressed or recessive. Here, also the black colour being dominant, it is expressed in the F1 generation. So, all the dogs of F1 generation are found to be black.
Showing the above information in the chart,
Black= BB
Brown= bb

All of the offspring of F1 generation are (hybrid) black. (Bb)







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SEE Science: Asexual And Sexual Reproduction

1. Differentiate between sexual and asexual reproduction. 
Ans: 

Sexual reproduction	Sexual reproduction
1. Both the parents i.e. male and female are involved.	1. Only one parent is involved. Variation does not occur.
2. A variation occurs which resultsin the formation of new species.	2. A variation occurs which resultsin the formation of same species.

2. The offspring produced by asexual and sexual reproduction process are dissimilar, why?
Ans: In asexual reproduction, crossing over does not take place and gametes are not involved. So, offspring produced by asexual reproduction are genetically identical to the parent. But in the case of sexual reproduction, crossing over takes place during the formation of gametes which results in the variation in the offsprings. 

3. Define sexual reproduction.
Ans: The reproduction which takes place by the fusion of male gamete and female gamete is called sexual reproduction.

4. Define multiple fission.
Ans: The process in which one parent body divides into more than two daughter organisms under unfavourable condition is called multiple fission.

5. Define binary fission.
Ans: The process in which one parent body divides into only two daughter organisms during the favourable condition is called binary fission.

6. Define vegetative propagation.
Ans: The process in which the vegetative parts of plants such as roots, stem and leaves take part in the formation of new plants is called vegetative propagation.

7. What is fertilization?
Ans: The process of fusion of male and female gametes is called fertilization.

8. What is external fertilization?
Ans: The fertilization which takes place outside the body of female is called external fertilization.

9. What is internal fertilization?
Ans: The fertilization which takes place inside the body of female is called internal fertilization.

10. What is pollination?
Ans: The transfer of pollen grains from anther to stigma is called pollination.

11. What is self-pollination?
Ans: The transfer of pollen grains from anther to stigma within the same flower without any agent is called self-pollination.

12. What is cross-pollination?
Ans: The transfer of pollen grains from the anther of one flower to the sigma of another flower is called cross-pollination.

13. What is budding?
Ans: The process in which an outgrowth or bud is produced from the parent body is called budding.

14. What is regeneration?
Ans: The process in which a parent body breaks into two or more fragments and each fragment develops into a new individual is called regeneration.

15. What is grafting?
Ans: The process by which a new plant can be grown by inserting a branch or stem of a plant on another plant body is called grafting.

16. Define ovum.
Ans: Ovum is a female gamete produced in female sex organ after meiosis.

17. Define sperm.
Ans: Sperm is a male gamete produced in male sex organ after meiosis.

18. Define isogametes.
Ans: Isogametes are those gametes which do not differentiate into male and female by structure but work as opposite sex cells.

19. Define zygote.
Ans: Zygote is a fertilized ovum having diploid number of chromosomes.

20. Define fragmentation.
Ans: The process in which a multicellular organism breaks into two or more daughter organisms is called fragmentation.

21. Define unisexual organisms.
Ans: The organisms in which male and female reproductive organs are found in separate individuals are called unisexual organisms.

22. Define bisexual organisms.
Ans: The organisms in which male and female reproductive organs are found in the same individual are called bisexual organisms.

23. Define double fertilization.
Ans: The process in which two male gametes fuse with different female nuclei in the embryo sac is called double fertilization.

24. What is the major characteristic of a sexual reproduction?

25. Name the type of reproduction in Bryophyllum and Planeria.
Ans: Bryophyllum reproduces through leaves i.e vegetative propagation. Planeria reproduces through regeneration.

26. What is tissue Culture?
Ans: It is a modern technique of producing new plants from a small piece of plant tissue (explant) in a culture medium.

27. Differentiate between Scion and Stock.
Ans: 

Stock	Scion
1. The plant whose root system is taken is called stock.	1. The plant whose shoot system is taken is called Scion.
2. A stock is selected for its adaptabilities like strength and absorbing system.	2. A Scion is selected for good quality of fruits and flowers.

28. 

Study the given diagram and answer the following questions. 

a. What type of reproduction is shown in the diagram? 
b. Write the name of A and B.
c. Name any two organisms in which such phenomenon occurs.

Ans: a. The diagram shows the asexual reproduction ie. Sporulation.
b. A is sporangium.
    B is spore.
c. This type of reproduction occurs in Mucor and Mushroom. 
 
29. How does the reproduction occur in higher animals?
Ans: In case of higher animals, sexes are separated. Both male and females are involved in reproduction. So, the reproduction is sexual reproduction. The male produces sperm cells and female produces the egg cells during male and female gametes fuses to form a zygote. 


30. Bee farming was done in a village along with the cultivation of mustard. But all the bees died in one particular year and the production of mustard also decreased, why did that happen?
Ans: Bees are the pollinators i e. they help in transferring the pollen grains from anther to stigma of the same or different mustard plants. Such process helps in the reproduction which ultimately increases the production of mustard. But when all the bees died, the pollination was decreased that resulted the decrease in the production of mustard. 

 31. A new rose plant is grown by planting a piece of its stem in the soil. What type of reproduction is it? Why is such type of reproduction more beneficial ?
Ans: This type of reproduction is called vegetative propagation by stem (Asexual reproduction).
Such type of reproduction is more beneficial due to the following reasons:
1. A large number of plants can be propagated in as short period of time. 
2. The plants which do not produce viable seeds like a rose, sugarcane, potato, etc. can easily be produced by this method. 
 
32. Cross-pollination is considered to be superior to self-pollination, why?
Ans: The hybrids (organisms) provided as a result of cross-pollination are more healthy, vigorous and generally better adapted in the environment in which they live. Therefore, cross-pollination is considered to be superior to self-pollination. 

33. What is reproduction?
Ans: Reproduction is a biological process by which living organisms produce individual of their own kind.

34. Name any four method of asexual reproduction.
Ans: The four method of asexual reproduction are:
1. Fission
2. Budding
3. Sporulation
4.Vegetative propagation

35. Which parts change into seed and fruits after fertilization?
Ans: The ovule changes into seed and ovary change into fruit.

36. Define fertilization.
Ans: The process of fusion of nuclei of male and female gamete to form a zygote is called fertilization.

37. Write a significance of sexual reproduction.
Ans: Sexual reproduction gives variation which helps in the evolution.

38. There would not be varieties of plants and animals in the world if there was no sexual reproduction. Justify.
Ans: Sexual reproduction involves the fusion of chromosomes in the nuclei of gametes more precisely; it involves the transmission of favourable variation from generation to generation which causes evolution. Due to this many types/variation of plants and animals are present in the world. 

39. Differentiate between self pollination and cross pollination?
Ans:

Self pollination	Cross pollination
1. It is the process of transfer of pollen grain from another to the stigma of the same flower.	1. It is the process of transfer of pollen grains from the anther of the flower to the stigma of another flower in the same plant or different plant of the same species.
2. It does not bring variation In offsprings.	2. It brings variation in offsprings.

40. Write two differences between internal fertilization and external fertilization. 
Ans: 

Internal fertilization	External fertilization
1. It takes place inside the female body.	1. It takes place outside the female body.
2. It takes place in lower vertebrates such as Pisces and amphibians.	2. It takes place in higher vertebrates such as reptiles,  aves and mammals.

41. Double fertilization occurs in higher angiosperms. Justify.
Ans: In the higher angiosperms two pairs of nuclei fuse in them out of the two pollen grains, one of them fuses with egg nucleus to form embryo while the other (pollen grains) fuses with the secondary nucleus to form endosperm. So, double fertilization occurs in higher angiosperms. 

42. Reproduction is advantageous to living beings, why?
Ans: Reproduction is necessary for the preservation and more in a population of a species. Reproduction is any means of preserving the species as it maintains the population. Species would be extinct once they die if there was no such process i e. Reproduction. Therefore, it is advantageous to living beings for the preparation/continuation of the generation. 

43. Write down the significance of asexual reproduction?
Ans: 1. It produces new individual having exactly identical qualities as that of parent. 
2. It is faster, cheaper and easier method of reproduction.
3. It is useful method of reproduction for the plants which do not produce viable seeds.
4. Off springs produced by this method get ready for further reproduction fast.
 
44. What is meant by triple fission? Draw a well labelled diagram showing fertilization in angiosperm.
Ans: In the flavering plants, during fertilization the male gamete fuses with the diploid secondary nucleus. The secondary nucleus is the fusion product of two polar nuclei and forms the endosperm nucleus. This process is called triple fusion. 
OR
The process or by which endosperm nucleus is formed by the fusion of male gamete with the diploid secondary nucleus is called triple fusion. 


45. Define budding.
Ans: Budding is the method of asexual reproduction which takes place by the formation of bud.

46. Write the name of any two plants which reproduce by vegetative propagation.
Ans: Sugarcane and Rose reproduce by vegetative propagation.

47. Name any two artificial method of vegetative propagation.
Ans: Grafting and layering are an artificial method of vegetative propagation.

48. Write one advantage of artificial vegetative propagation.
Ans: Artificial vegetative propagation is a cheaper, easier and faster method of propagation of plants.

49. What is grafting?
Ans: It is the artificial method of vegetative propagation in which two branches of different plants of closely related varieties are joined together.

50. "Vegetative propagation is beneficial to the farmers." Give any two reasons to justify this statement. 
Ans: Vegetative propagation is beneficial to farmers because of the following reasons. 
1. A large number of plants can be propagated easily and cheaply within a short period of time. 
2. The plants like a rose, sugarcane, potato, etc. which does not produce viable seeds can easily be produced by this method. 

 51. Sugarcane is planted by cutting into pieces. What type of reproduction is it? Give three reasons for applying this method in sugarcane. 
Ans: It is a type of asexual reproduction i.e. Vegetative propagation.

The three reasons for applying this method in sugarcane are:
1. It is an easier, cheaper and rapid method of reproduction or propagation of plants. 
2. Sugarcane does not produce viable seed. 
3. To get, the same variety year after year. 
 
52. Write down three applications of tissue culture technique. 
Ans: The three applications of tissue culture techniques are:
1. For the production of valuable compounds like plants derived protein used as biopharmaceuticals.
2. To cross distantly related species so as to obtain the hybrid. 
3. To conserve rare or endangered plant species. 
 
53. 

Study the given diagram and answer the following questions.

                                        Figure (a).

                                       Figure (b)

                                       Figure (c).
a. Which one of them shows vegetative propagation? Name this method. 
b. What is the name of the animal shown in b? Name the method of reproduction shown in figure b and c?
c. Name the organism shown in c.
d. Name A and B. 

Ans:
a. Figure (a) shows vegetative propagation. This method is called whip grafting. 
b. It is amoeba. The method of reproduction shown by b is binary fission and by c is budding. 
c. It is yeast.
d. A is mother yeast.
    B is a bud. 
 
54. Differentiate between sexual and asexual reproduction. 
Ans: 

Sexual reproduction	Sexual reproduction
1. Both the parents i.e. male and female are involved.	1. Only one parent is involved. Variation does not occur.
2. A variation occurs which resultsin the formation of new species.	2. A variation occurs which resultsin the formation of same species.

55. The offspring produced by asexual and sexual reproduction process are dissimilar, why?
Ans: In asexual reproduction, crossing over does not take place and gametes are not involved. So, offspring produced by asexual reproduction are genetically identical to the parent. But in the case of sexual reproduction, crossing over takes place during the formation of gametes which results in the variation in the offsprings. 

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Class 9 Opt Maths: Area Of Triangle

Area of triangle

Area of Triangle

Let A(x1,y1), B(x2.y2) and C (x3.y3) be the vertices of a triangle. Draw ⊥$\perp$AL, BM and CN from the vertices A, B, and C respectively to the X-axis.

Then,
OL = x1 OM = x2 ON =x3
AL = y1 BM = y2 CN = y3
Here, LN = ON - OL = x3-x1
NM = OM - ON = x2-x3 and
LM = OM -OL = x2-x1
Now, Area ofΔABC is equal to
Area of trapezium ALNC + Area of trapezium CNMB - Area of trapezium ALMB.
= ½LN(AL+CN) + ½NM(CN+BM) - ½ LM(AL+BM)
= ½(x3-x1)(y1+y3)+½(x2-x3)(y3+y2)-½(x2-x1)(y1+y2)
= ½(x3y1+x3y3-x1y1-x1y3+x2y3+x2y2-x3y3-x3y2-x2y1-x2y2+x1y1+x1y2)
= ½(x1y2-x2y1+x2y3-x3y2+x3y1-x1y3)

Area of a Quadrilateral

Area of quadrilateral

Let A (x1,y1), B(x2,y2), C(x3,y3) and D (x4,y4)be the vertices of quadrilateral ABCD. Join AC. Then the diagonal AC divides the quadrilateral into two triangles ABC and ACD.
Now,
Area of quadrilateral ABCD = Area of △$\mathrm{△}$ABC + Area of △$\mathrm{△}$ACD.
□$◻$ABCD = ½∣∣∣x1y1x2y2x3y3x1y1∣∣
∣

$\left|\begin{array}{cccc}{x}_1& x_2& x_3& x_1\\ y_1& y_2& y_3& y_1\end{array}\right|$ + ½ ∣∣∣x1y1x3y3x4y4x1y1∣∣∣$\left|\begin{array}{cccc}{x}_1& x_3& x_4& x_1\\ y_1& y_3& y_4& y_1\end{array}\right|$
= ½ (x1y2-x2y1+x2y3-x3y2+x3y1-x1y3) + ½ (x1y3-x3y1+x3y4-x4y3+x4y1-x1y4)
= ½ (x1y2-x2y1+x2y3-x3y2+x3y4-x4y3+x4y1-x1y4)

Note: To find the area of a quadrilateral by using this formula, the vertices of quadrilateral should be taken in order. So it is better to plot the points roughty before applying the formula. Otherwise the result may be wrong.

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