CBSE Class X

Question 1:

Asexual reproduction takes place through budding in

(a) amoeba.

(b) yeast.

(c) plasmodium.

(d) leishmania.

Answer:

(b) Asexual reproduction takes place through budding in yeast.

Question 5:

If a woman is using a copper−T, will it help in protecting her from sexually

transmitted diseases?

Answer:

No. Using a copper-T will not provide a protection from sexually transmitted diseases,

as it does not prevent the entry of semen. It only prevents the implantation of the

embryo in the uterus.

Question 4:

How does the embryo get nourishment inside the mother’s body?

Answer:

The embryo develops inside the mother’s body for about nine months. Inside the

uterus, the outer tissue surrounding the embryo develops finger-like projections

called villi.

These villi are surrounded by uterine tissue and maternal blood. They provide a large

surface area for exchange of oxygen and nutrients. Also, there is a special tissue

called placenta, which is embedded in the uterine wall. The embryo receives the

oxygen and nutrients from the mother’s blood via the placenta. The waste materials

produced by the embryo are also removed through the placenta.

Question 3:

What are the changes seen in girls at the time of puberty?

Answer:

Secondary sexual characteristics in girls:

• Increase in breast size and darkening of skin of the nipples present at the tips of

   the breasts.

• Appearance of hair in the genital area.

• Appearance of hair in other areas of skin like underarms, face, hands, and legs.

• Increase in the size of uterus and ovary.

• Beginning of menstrual cycle.

• More secretion of oil from the skin, which results in the appearance of pimples.

Question 2:

What is the role of the seminal vesicles and the prostate gland?

Answer:

The secretions from seminal vesicles and prostate glands lubricate the sperms and

provide a fluid medium for easy transport of sperms. Their secretion also provides

nutrient in the form of fructose, calcium, and some enzymes.

Question 1:

How is the process of pollination different from fertilization?

Answer:

Pollination is the process of transfer of pollens from anther to stigma. It occurs with

the help of certain pollinators such as air, water, birds, or some insects.

Fertilization, on the other hand, is the fusion of the male and female gametes. It

occurs inside the ovule and leads to the formation of zygote.

Question 5:

Why is DNA copying an essential part of the process of reproduction?

Answer:

DNA (Deoxyribonucleic acid) copying is an essential part of reproduction as it passes

genetic information from parents to offspring. It determines the body design of an

individual. The reproducing cells produce a copy of their DNA through some chemical

reactions and result in two copies of DNA. The copying of DNA always takes place

along with the creation of additional cellular structure. This process is then followed

by division of a cell to form two cells.

Question 4:

Which of the following is a plant hormone?

(a) Insulin

(b) Thyroxin

(c) Oestrogen

(d) Cytokinin

Answer:

(d) Cytokinin is a plant hormone.

Question 3:

Can you think of reasons why more complex organisms cannot give rise to new

individuals through regeneration?

Answer:

Simple organisms such as Hydra and Planaria are capable of producing new indivi-

duals through the process of regeneration. The process of regeneration involves the

formation of new organisms from its body parts. Simple organisms can utilize this

method of reproduction as their entire body is made of similar kind of cells in which

any part of their body can be formed by growth and development.

However, complex organisms have organ-system level of organization. All the organ

systems of their body work together as an interconnected unit. They can regenerate

their lost body parts such as skin, muscles, blood, etc. However, they cannot give

rise to new individuals through regeneration.

Question 2:

How will an organism be benefited if it reproduces through spores?

Answer:

There are many advantages, if an organism reproduces through spores.

Advantages of spore formation:

• Large numbers of spores are produced in one sporangium.

• Spores are distributed easily by air to far-off places to avoid competition at one   

   place.

• Spores are covered by thick walls to prevent dehydration under unfavourable

   conditions.

Question 1:

How does binary fission differ from multiple fission?

Answer:

In binary fission, a single cell divides into two equal halves. Amoeba and

Bacteria divide by binary fission.

Binary fission in Amoeba

In multiple fission, a single cell divides into many daughter cells simultaneously.

Amoeba and Plasmodium divide by multiple fission.

Multiple fission in Plasmodium

Question 2:

Why is variation beneficial to the species but not necessarily for the individual?

Answer:

Variations are beneficial to the species than individual because sometimes for a

species, the environmental conditions change so drastically that their survival

becomes difficult. For example, if the temperature of water increases suddenly,

then most of the bacteria living in that water would die. Only few variants that

are resistant to heat would be able to survive. However, if these variants were

not there, then the entire species of bacteria would have been destroyed. Thus,

these variants help in the survival of the species.However, all variations are not

necessarily beneficial for the individual organisms.

Question 1:

What is the importance of DNA copying in reproduction?

Answer:

DNA (Deoxyribonucleic acid) is the genetic material found in the chromosomes,

which are present in the nucleus of a cell. The DNA is the information site for

making proteins and each specific type of protein leads to a specific type of body

design.

Thus, it is the DNA molecule that determines the body design of an individual.

Therefore, it can be concluded that it is the DNA that gets transferred from

parents to offsprings and makes them look similar.

Question 12:

What is the difference between the manner in which movement takes place in a

sensitive plant and the movement in our legs?

Answer:

Question 11:

Compare and contrast nervous and hormonal mechanisms for control and coordination

in animals.

Answer:

Question 10:

How are involuntary actions and reflex actions different from each other?

Answer:

Involuntary actions cannot be consciously controlled. For example, we cannot

consciously control the movement of food in the alimentary canal. These actions

are however directly under the control of the brain. On the other hand, the reflex

actions such as closing of eyes immediately when bright light is focused show

sudden response and do not involve any thinking. This means that unlike involuntary

actions, the reflex actions are not under the control of brain.

Question 9:

What is the need for a system of control and coordination in an organism?

Answer:

The maintenance of the body functions in response to changes in the body by

working together of various integrated body systems is known as coordination.

All the movements that occur in response to stimuli are carefully coordinated

and controlled. In animals, the control and coordination movements are provided

by nervous and muscular systems. The nervous system sends messages to and

away from the brain. The spinal cord plays an important role in the relay of

messages. In the absence of this system of control and coordination, our body

will not be able to function properly. For example, when we accidentally touch

a hot utensil, we immediately withdraw our hand. In the absence of nerve

transmission, we will not withdraw our hand and may get burnt.

Question 8:

How does chemical coordination occur in plants?

Answer:

In animals, control and coordination occur with the help of nervous system. However,

plants do not have a nervous system.

Plants respond to stimuli by showing movements. The growth, development, and

responses to the environment in plants is controlled and coordinated by a special

class of chemical substances known as hormones. These hormones are produced in

one part of the plant body and are translocated to other needy parts. For example,

a hormone produced in roots is translocated to other parts when required. The five

major types of phytohormone are auxins, gibberellins, cytokinins, abscisic acid, and

ethylene. These phytohormones are either growth promoters (such as auxins,

gibberellins, cytokinins,and ethylene) or growth inhibitors such as abscisic acid.

Question 7:

Which signals will get disrupted in case of a spinal cord injury?

Answer:

The reflex arc connections between the input and output nerves meet in a bundle

in the spinal cord. In fact, nerves from all over the body meet in a bundle in the

spinal cord on their way to the brain. In case of any injury to the spinal cord, the

signals coming from the nerves as well as the signals coming to the receptors will

be disrupted.

Question 6:

What are the changes seen in girls at the time of puberty?

Answer:

Secondary sexual characteristics in girls:

• Increase in breast size and darkening of skin of the nipples present at the tips of 

   the breasts.

• Appearance of hair in the genital area.

• Appearance of hair in other areas of skin like underarms, face, hands, and legs.

• Increase in the size of uterus and ovary.

• Beginning of menstrual cycle.

• More secretion of oil from the skin, which results in the appearance of pimples.