Science, Maths CBSE / ICSE Worksheets , Mcq's : January 2017

1. In a flower, the parts that produce male and female gametes (germ cells) are

a. Stamen and anther

b. Filament and stigma

c. Anther and ovary

d. Stamen and style

Answer: (c) Anther and Ovary

2. Which of the following is the correct sequence of events of sexual reproduction in a flower?

a. Pollination, fertilisation, seedling, embryo

b. Seedling, embryo, fertilisation, pollination

c. Pollination, fertilisation, embryo, seedling

d. Embryo, seedling, pollination, fertilization

Answer: (c) Pollination, fertilization, embryo, seedling

3. Offspring formed by asexual method of reproduction have greater similarity among themselves because

i. Asexual reproduction involves only one parent

ii. Asexual reproduction does not involve gametes

iii. Asexual reproduction occurs before sexual reproduction

iv. Asexual reproduction occurs after sexual reproduction

e. (i) and (ii)

f. (i) and (iii)

g. (ii) and (iv)

h. (iii) and (iv)

Answer: (a) (i) and (ii)

Characters transmitted from parents to offspring are present in

. Cytoplasm

a. Ribosome

b. Golgi bodies

c. Genes

Answer: (d) Genes

Characters that are transmitted from parents to offspring during reproduction show

. Only similarities with parents

a. Only variations with parents

b. Both similarities and variations with parents

c. Neither similarities nor variations

Answer: (c) Both similarities and variations with parents

A feature of reproduction that is common to Amoeba, Spirogyra and Yeast is that

. They reproduce asexually

a. They are all unicellular

b. They reproduce only sexually

c. They are all multicellular

Answer: (a) They reproduce asexually

In Spirogyra, asexual reproduction takes place by

. Breaking up of filaments into smaller bits

a. Division of a cell into two cells

b. Division of a cell into many cells

c. Formation of young cells from older cells

Answer: (a) Breaking up of filaments into smaller bits

The ability of a cell to divide into several cells during reproduction in Plasmodium is called

. Budding

a. Reduction division

b. Binary fission

c. Multiple fission

Answer: (d) Multiple Fission

The number of chromosomes in parents and offsprings of a particular species remains constant due to

Doubling of chromosomes afZter zygote formation
Halving of chromosomes during gamete formation
Doubling of chromosomes after gamete formation
Halving of chromosomes after gamete formation

Answer: (b) Halving of chromosomes during gamete formation

In Rhizopus, tubular thread-like structures bearing sporangia at their tips are called

Filaments
Hyphae
Rhizoids
Roots

Answer: (b) Hyphae

Vegetative propagation refers to formation of new plants from

Stem, roots and flowers
Stem, roots and leaves
Stem, flowers and fruits
Stem, leaves and flowers

Answer: (b) Stem, roots and leaves

Factors responsible for the rapid spread of bread mould on slices of bread are

i. Large number of spores

ii. Availability of moisture and nutrients in bread

iii. Presence of tubular branched hyphae

iv. Formation of round shaped sporangia

e. (i) and (iii)

f. (ii) and (iv)

g. (i) and (ii)

h. (iii) and (iv)

Answer: (c) (i) and (ii)

Length of pollen tube depends on the distance between

. Pollen grain and upper surface of stigma

a. Pollen grain on upper surface of stigma and ovule

b. Pollen grain in anther and upper surface of stigma

c. Upper surface of stigma and lower part of style

Answer: (c) Pollen grain in anther and upper surface of stigma

Which of the following statements are true for flowers?

Flowers are always bisexual
They are the sexual reproductive organs
They are produced in all groups of plants
After fertilisation they give rise to fruits

e. (i) and (iv)

f. (ii) and (iii)

g. (i) and (iii)

h. (ii) and (iv)

Answer: (b) (ii) and (iv)

Which among the following statements are true for unisexual flowers?

. They possess both stamen and pistil

i. They possess either stamen or pistil

ii. They exhibit cross pollination

iii. Unisexual flowers possessing only stamens cannot produce fruits

d. (i) and (iv)

e. (ii), (iii) and (iv)

f. (iii) and (iv)

g. (i), (iii) and (iv)

Answer: (b) (ii), (iii) and (iv)

Which among the following statements are true for sexual reproduction in flowering plants?

. It requires two types of gametes

i. Fertilisation is a compulsory event

ii. It always results in formation of zygote

iii. Offspring formed are clones

d. (i) and (iv)

e. (i), (ii) and (iv)

f. (i), (ii) and (iii)

g. (ii), (iii) and (iv)

Answer:(c) (i), (ii) and (iii)

Offspring formed as a result of sexual reproduction exhibit more variations because

. Sexual reproduction is a lengthy process

a. Genetic material comes from two parents of the same species

b. Genetic material comes from two parents of different species

c. Genetic material comes from many parents

Answer: (b) Genetic material comes from two parents of the same species

Reproduction is essential for living organisms in order to

. Keep the individual organism alive

a. Fulfill their energy requirement

b. Maintain growth

c. Continue the species generation after generation

Answer: (d) Continue the species generation after generation

During adolescence, several changes occur in the human body. Mark one change associated with sexual maturation in boys

. Loss of milk teeth

a. Increase in height

b. Cracking of voice

c. Weight gain

Answer: (c) Cracking of voice

In human females, an event that reflects onset of reproductive phase is

. Growth of body

a. Changes in hair pattern

b. Change in voice

c. Menstruation

Answer: (d) Menstruation

In human males, the testes lie in the scrotum, because it helps in the

Process of mating
Formation of sperm
Easy transfer of gametes
All the above

Answer: (b) Formation of sperm

Which among the following is not the function of testes at puberty?

i. Formation of germ cells

ii. Secretion of testosterone

iii. Development of placenta

iv. Secretion of estrogen

e. (i) and (ii)

f. (ii) and (iii)

g. (iii) and (iv)

h. (i) and (iv)

Answer: (c) (iii) and (iv)

The correct sequence of organs in the male reproductive system for transport of sperms is

. Testis → vas deferens → urethra

a. Testis → ureter → urethra

b. Testis → urethra → ureter

c. Testis → vas deferens → ureter

Answer: (a) Testis → vas deferens → urethra

Which among the following diseases is not sexually transmitted?

. Syphillis

a. Hepatitis

b. HIV – AIDS

c. Gonorrhoea

Answer: (b) Hepatitis

28. In a bisexual flower inspite of the young stamens being removed artificially, the flower produces fruit. Provide a suitable explanation for the above situation.

Answer: For a flower to produce fruits, it is necessary that pollination and fertilization take place. In the absence of stamens; as given here; cross pollination must have taken place to facilitate fertilization. The cross fertilization could be assisted by human or by some other agent of fertilization. This would have led to production of fruit.

29. Can you consider cell division as a type of reproduction in unicellular organism? Give one reason.

Answer: Unicellular organisms reproduce asexually and often do that by binary fission. Binary fission is similar to mitosis; in which two daughter cells are produced after cell division. Hence, cell division can be considered as a type of reproduction in unicellular organisms.

30. What is a clone? Why do offsprings formed by asexual reproduction exhibit remarkable similarity?

Answer: An exact copy of something is called a clone. During sexual reproduction, all the traits in an offspring are similar to the traits in the parent. Due to this, offspring formed after sexual reproduction exhibit remarkable similarity.

31. Explain how, offspring and parents of organisms reproducing sexually have the same number of chromosomes?

Answer: Gamete formation is the first step in sexual reproduction. Number of chromosomes is halved during gamete formation. As a result, the number of chromosomes in gamete is half the number of chromosomes in somatic cells. When male and female gametes fuse during fertilization, the number of chromosomes becomes equal to that in somatic cells. This explains how, offspring and parents of organisms reproducing sexually have the same number of chromosomes.

32. Colonies of yeast fail to multiply in water, but multiply in sugar solution. Give one reason for this.

Answer: Answer: When the colony of yeast is in water, it does not get nutrition; because water does not have nutrients. Sugar, on the other hand, provides nutrition. Once the yeast gets nutrition, it grows and begins producing buds. That is why, colonies of yeast fail to multiply in water, but multiply in sugar solution.

33. Why does bread mould grow profusely on a moist slice of bread rather than on a dry slice of bread?

Answer: Water is necessary for all metabolic activities. On the moist bread the spores of bread mold get the much needed water; which is not available on the dry bread. Hence, bread mould grows profusely on a moist slice of bread rather than on a dry slice of bread.

34. Give two reasons for the appearance of variations among the progeny formed by sexual reproduction.

Answer: The first and foremost reason for the appearance of variations among the progeny formed by sexual reproduction is, gene pool of the progeny is contributed by two different individuals. The second reason is that variations also happen during DNA replication before cell division.

35. Would a Planaria cut vertically into two halves regenerate into two individuals? Complete Figure ‘D’ and ‘E’ by indicating the regenerated regions.

Answer:

36. From the internet, gather information about the chromosome numbers of five animals and five plants. Correlate the number with the size of organism and answer the following questions.

(a) Do larger organisms have more number of chromosomes/cells?

(b) Can organism with fewer chromosomes reproduce more easily than organisms with more number of chromosomes?

Answer: Number of chromosomes in somatic cells of some organisms:

Organism	No. of Chromosomes
Human	46
Hare	48
Elephant	48
Cow	60
Dog	78
Kingfisher	132

(Ref: http://en.wikipedia.org/wiki/Chromosome#Number_of_chromosomes_in_various_organisms Accessed on 8th April 2013.)

Answer: (a) Number of chromosomes and size of an organism has no relationship. A smaller organism may have more chromosomes than a larger organism. The above table also shows number of chromosomes in kingfisher is significantly greater than that in dog; although kingfisher is much smaller in size.

Answer: (b) Ability to reproduce depends on a variety of factors; like availability of nutrients, water, conducive environment and suitable mate. Number of chromosomes has no bearing on the ease by which an organism reproduces.

Answer: (c) Chromosomes are composed of DNA. More chromosomes means, there will be more DNA. Hence, this statement is justified.

37. In tobacco plant, the male gametes have twenty four chromosomes. What is the number of chromosomes in the female gamete? What is the number of chromosomes in the zygote?

Answer: Answer: The number of chromosomes in the female gamete would be same as that in the male gamete, i.e. 24. The number of chromosomes in the zygote would be double the number in a gamete and hence it would be 48.

38. Why cannot fertilisation take place in flowers if pollination does not occur?

Answer: Answer: For fertilization to occur, it is necessary that the male gamete reaches the female gamete. This can only happen when the pollen grains are transferred to the stigma through any means of pollination. So, fertilization cannot take place in flowers if pollination does not occur.

39. Is the chromosome number of zygote, embryonal cells and adult of a particular organism always constant? How is the constancy maintained in these three stages?

Answer: Answer: The answer to the first part of this question is a definite yes. Meiosis is the cell division which happens during gametogenesis, i.e. during gamete formation. This results in number of chromosomes getting halved in gametes. When fertilization happens, the number of chromosomes becomes equal to that in somatic cells. After that, mitosis takes place during rest of the stages of life. And thus, the constancy of chromosomal number is maintained in all the three stages as mentioned in this question.

40. Where is the z

ygote located in the flower after fertilization?

Answer: After fertilization, zygote is located in the ovary.

41. Reproduction is linked to stability of population of a species. Justify the statement.

Answer: Answer: Every species has to constantly struggle for its survival. Natural predators and vagaries of nature keep on removing a large section of the population of a particular species. Moreover, the natural cycle of life and death also removes a section of the population. Reproduction is a way to replenish the lost section of population. Thus, it can be said that reproduction is linked to the stability of population of a species.

42. How are general growth and sexual maturation different from each other?

Answer: Answer: General growth and sexual maturation are different from each other in many senses. General growth is all about attaining physical maturity in which the organism undergoes through various stages to become an adult. Once the physical growth is complete, it lays the foundation for sexual maturity. Sexual maturity is related to preparing the body for physical and psychological responsibilities related to reproduction.

43. Trace the path of sperm during ejaculation and mention the gland and their functions associated with the male reproductive system.

Answer: The path of sperm during ejaculation is as follows:

Vas deferens → Seminal Vesicle → Urethra

Glands associated with the male reproductive system and their functions are as follows:

Testis: Secretes the hormone testosterone.
Prostate gland: Makes the medium of semen alkaline
Seminal vesicle: Adds fluid content to the semen
Cowper’s gland: The secretion of this gland lubricates the urethra before ejaculation and neutralizes the acidic traces of urine in the urethra

44. What changes are observed in the uterus if fertilisation does not occur?

Answer: The uterus prepares during every ovulation cycle in anticipation of a possible pregnancy. The lining of the uterus thickens so that it can give support to the developing embryo. When fertilization does not occur, this lining disintegrates because it is no longer required. The fragments of the lining are shed along with blood and the discarded egg; through the vagina. The discharge of discarded tissues is called menstrual flow and the process is called menstruation. What changes are observed in the uterus subsequent to implantation of young embryo?

Answer: Once the zygote is implanted in the uterine wall, several changes take place in the uterus. The uterine lining thickens so that it can give support to the growing embryo. It is richly supplied with blood so that it can provide nourishment to the embryo.

46. What are the benefits of using mechanical barriers during sexual act?

Answer: Mechanical barriers during sexual act provide two benefits. The first benefit is avoidance of unwanted pregnancy and the second benefit is prevention of sexually transmitted diseases.

47. In the given figure, label the parts and mention their functions

Production of egg
Site of fertilization
Site of implantation
Entry of the sperms

Answer:

48. What would be the ratio of chromosome number between an egg and its zygote? How is the sperm genetically different from the egg?

Answer: The ratio of chromosome number between and egg and its zygote is 1 : 2. Sperm and eggs are genetically different in terms of the nature of the 23rd chromosome. The 23rd chromosome is a Y chromosome in sperm, while it is an X chromosome in egg.

Question: 49. Why are budding, fragmentation and regeneration all considered as asexual types of reproduction? With neat diagrams explain the process of regeneration in Planaria.

Answer: Budding, fragmentation and regeneration are considered as asexual types of reproduction because gamete formation does not happen during these modes of reproduction and a single parent carries out the process of reproduction.

The following figure shows regeneration in planaria:

When the body of planaria is cut off into several part, each part regenerates its complementary part to develop into a new individual.

Q: 50. Write two points of difference between asexual and sexual types of reproduction. Describe why variations are observed in the offspring formed by sexual reproduction.

Answer: Two points of difference between asexual and sexual reproduction are as follows:

A single parent is involved in asexual reproduction, while two parents are involved in sexual reproduction.
Meiosis does not happen in asexual reproduction, while meiosis happens in sexual reproduction during gamete formation.

Reason of variations in offspring produced by sexual reproduction: Two sets of genes are contributed by different parents, which bring different sets of characters in the offspring.

Q: 51. Distinguish between pollination and fertilisation. Mention the site and product of fertilisation in a flower. Draw a neat, labelled diagram of a pistil showing pollen tube growth and its entry into the ovule.

Answer: Difference between pollination and fertilization: Transfer of pollen grains from anther to stigma is called pollination. On the other hand, fusion of male and female gametes is called fertilization. Pollination is a physical process in which movement of pollen grains are attained by certain physical factors. Fertilization is a biological process. Ovary is the site of fertilization and embryo is the product of fertilization.

The following figure shows fertilization in plant:

Q: 52. Distinguish between a gamete and zygote. Explain their roles in sexual reproduction.

Answer: Gamete is formed as a result of meiosis in gametogenetic cells. Zygote is formed after fusion two different kinds of gametes. Different types of gametes are formed by different parents. Zygote is formed in the female reproductive part only.

Role of gamete in sexual reproduction: Gamete formation results in halving of number of chromosomes which is necessary to maintain the number of chromosomes in an organism which reproduces sexually.

Role of zygote in sexual reproduction: Zygote formation makes the number of chromosome equal to the somatic cells. Further, it is the zygote which undergoes mitosis to develop into an embryo and subsequently into a new individual.

Q: 53. Draw the diagram of a flower and label the four whorls. Write the names of gamete producing organs in the flower.

Answer: The gamete producing organs in the flower are: anther and ovary.

Q: 54. What is placenta? Mention its role during pregnancy?

Answer: It is a issue which is attached with the embryo and the uterine wall. It is a disc-like structure which is embedded in the uterine wall. On the embryo’s side of the tissue lie the villi and on the mother’s side lie blood spaces. The blood spaces surround the villi. The placenta works as a channel between the mother and the embryo. Nutrients and oxygen are supplied to the embryo through this. Additionally, excretory products from the embryo are removed through the placenta.

Q: 55. What are various ways to avoid pregnancy? Elaborate any one method.

Answer: There are various methods to avoid pregnancy. The physical barrier methods prevent the entry of sperm into the uterus. The hormonal pills prevent transfer of egg to the uterus. Copper-T is a method which prevents entry of sperms in the fallopian tube and thus prevents fertilization. Surgical methods are permanent methods to stop the chances of pregnancy.

Copper-T: Copper-T is in the shape of ‘T’ and is made of copper. Copper is known to have contraceptive properties. Moreover, copper-T makes a barrier in the at the opening of the fallopian tubes in the uterus and thus prevents sperms from entering the fallopian tubes to prevent fertilization.

Question: 56. How does fertilisation take place? Fertilisation occurs once in a month. Comment.

Answer: During the ovulation cycle; one egg is released by either of the ovaries. The egg reaches the fallopian tube. The sperm enters the vagina during mating. From there, it enters the uterus through cervix and reaches fallopian tube. Numerous sperms reach the fallopian tube but only one sperm is required for fertilization.

Since only one egg is released in a single ovulation cycle and ovulation cycle happens once in a month, so fertilization occurs once in a month.

Question: 57. Describe sexually transmitted diseases and mention the ways to prevent them.

Answer: A disease which can be transmitted through sexual contact is called sexually transmitted disease or STD. Lack of hygiene is usually a major factor in providing conditions for spread of STDs. But unprotected sex with multiple and unknown partners is the biggest reason for the spread of STDs. Some of the ways to prevent STDs are as follows:

Being faithful to one’s life partner.
Avoiding sexual contact with unknown person.
Using condom during sexual intercourse.
Maintaining personal hygiene.

Science, Maths CBSE / ICSE Worksheets , Mcq's

Tuesday, January 3, 2017

Reproduction class 10 Question Answers part 3