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
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
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)
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
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
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
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
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
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)
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
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)
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)
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)
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
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
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
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
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)
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
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
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?
(c) More the number of chromosomes/cells greater
is the DNA content. Justify.
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.
