Selina Textbook Solutions: Skin- The Jack of All Trades | Biology Class 9 ICSE PDF Download

 Page 1


Chapter 13. Skin- “The Jack of All Trades”
Exercise 1
Solution A.
1. (d) the skin will turn dry and rough
2. (b) Albinism, Leucoderma
3. (c) Skin
4. (b) Dermis
5. (d) Palm
Solution B.1.
Hypothalamus, a portion of the forebrain is the principal body heat regulating centre in 
our brain.
Solution B.2.
Modified sweat gland: Mammary gland 
Modified sebaceous gland: Ceruminous gland
Solution B.3.
Sebaceous glands
Solution C.1.
Functions of the mammalian skin other than those concerned with heat regulation:
1. Storage of food: Skin acts as a storehouse of energy by storing reserve food in 
the form of fat in the hypodermis.
2. Synthesis of Vitamin D: Skin has the ability to synthesize small quantity of 
Vitamin D in the presence of sunlight.
Solution C.2.
A peculiar roughness of the skin produced by cold or fear, in which the hair follicles 
become erect and form bumps on the skin is called goose flesh.
Goose flesh occurs when the muscles at the base of hair known as erectors or arrectors, 
contract. The erector muscles are obliquely placed between the hair follicle and the outer 
part of dermis. They are smooth muscles that are necessary to move the hair. The 
contraction of erector muscle pulls the hair vertical and depresses the epidermis, 
resulting in goose flesh.
Solution C.3.
Man is a warm-blooded mammal. Our body must maintain an average temperature of 
98.6 degree Fahrenheit to function properly. When we feel too hot or too cold, our 
Page 2


Chapter 13. Skin- “The Jack of All Trades”
Exercise 1
Solution A.
1. (d) the skin will turn dry and rough
2. (b) Albinism, Leucoderma
3. (c) Skin
4. (b) Dermis
5. (d) Palm
Solution B.1.
Hypothalamus, a portion of the forebrain is the principal body heat regulating centre in 
our brain.
Solution B.2.
Modified sweat gland: Mammary gland 
Modified sebaceous gland: Ceruminous gland
Solution B.3.
Sebaceous glands
Solution C.1.
Functions of the mammalian skin other than those concerned with heat regulation:
1. Storage of food: Skin acts as a storehouse of energy by storing reserve food in 
the form of fat in the hypodermis.
2. Synthesis of Vitamin D: Skin has the ability to synthesize small quantity of 
Vitamin D in the presence of sunlight.
Solution C.2.
A peculiar roughness of the skin produced by cold or fear, in which the hair follicles 
become erect and form bumps on the skin is called goose flesh.
Goose flesh occurs when the muscles at the base of hair known as erectors or arrectors, 
contract. The erector muscles are obliquely placed between the hair follicle and the outer 
part of dermis. They are smooth muscles that are necessary to move the hair. The 
contraction of erector muscle pulls the hair vertical and depresses the epidermis, 
resulting in goose flesh.
Solution C.3.
Man is a warm-blooded mammal. Our body must maintain an average temperature of 
98.6 degree Fahrenheit to function properly. When we feel too hot or too cold, our 
nervous system sends certain automatic and autonomic reflexes that help to keep us 
warm. In cold weather, the blood vessels get narrowed (vasoconstricted). Shivering 
occurs when our muscles expand and contract rapidly to produce extra body heat. The 
amount of heat produced is increased by increased metabolic rate and muscular activity, 
which occurs in the form of shivering. That is why, our body shivers and teeth chatter to 
protect from cold by generating more heat.
Solution C.4.
Leucoderma Albinism
Loss of skin pigmentation from 
smaller or larger patches at 
different regions of the body
Complete loss of pigmentation 
of the skin all over the body
Solution C.5.
Two glands found in the human skin are:
1. Ceruminous gland: It is a modified sebaceous gland found in the auditory canal. It 
secretes wax-like substance called ear wax.
2. Mammary gland: It is a modified sweat gland. It is related to reproductive 
hormones and pregnancy.
Solution C.6.
Fever and sickness or any kind of vigorous activity can lead to perspiration even in cold 
outside.
Solution D.1.
Epidermis Dermis
1. Stratum corneum: It is 
the outermost layer having 
layers of flattened dead cells 
made up of horny protein 
called keratin.
It consists of elastic fibres, 
blood vessels, nerves, etc.
2. Granular layer: It is very 
thin middle layer having two 
or three sublayers of flattened 
cells.
 
3. Malpighian layer: It is the 
innermost region of the 
epidermis. The cells can 
actively divide to produce new 
cells.
 
Solution D.2.
Page 3


Chapter 13. Skin- “The Jack of All Trades”
Exercise 1
Solution A.
1. (d) the skin will turn dry and rough
2. (b) Albinism, Leucoderma
3. (c) Skin
4. (b) Dermis
5. (d) Palm
Solution B.1.
Hypothalamus, a portion of the forebrain is the principal body heat regulating centre in 
our brain.
Solution B.2.
Modified sweat gland: Mammary gland 
Modified sebaceous gland: Ceruminous gland
Solution B.3.
Sebaceous glands
Solution C.1.
Functions of the mammalian skin other than those concerned with heat regulation:
1. Storage of food: Skin acts as a storehouse of energy by storing reserve food in 
the form of fat in the hypodermis.
2. Synthesis of Vitamin D: Skin has the ability to synthesize small quantity of 
Vitamin D in the presence of sunlight.
Solution C.2.
A peculiar roughness of the skin produced by cold or fear, in which the hair follicles 
become erect and form bumps on the skin is called goose flesh.
Goose flesh occurs when the muscles at the base of hair known as erectors or arrectors, 
contract. The erector muscles are obliquely placed between the hair follicle and the outer 
part of dermis. They are smooth muscles that are necessary to move the hair. The 
contraction of erector muscle pulls the hair vertical and depresses the epidermis, 
resulting in goose flesh.
Solution C.3.
Man is a warm-blooded mammal. Our body must maintain an average temperature of 
98.6 degree Fahrenheit to function properly. When we feel too hot or too cold, our 
nervous system sends certain automatic and autonomic reflexes that help to keep us 
warm. In cold weather, the blood vessels get narrowed (vasoconstricted). Shivering 
occurs when our muscles expand and contract rapidly to produce extra body heat. The 
amount of heat produced is increased by increased metabolic rate and muscular activity, 
which occurs in the form of shivering. That is why, our body shivers and teeth chatter to 
protect from cold by generating more heat.
Solution C.4.
Leucoderma Albinism
Loss of skin pigmentation from 
smaller or larger patches at 
different regions of the body
Complete loss of pigmentation 
of the skin all over the body
Solution C.5.
Two glands found in the human skin are:
1. Ceruminous gland: It is a modified sebaceous gland found in the auditory canal. It 
secretes wax-like substance called ear wax.
2. Mammary gland: It is a modified sweat gland. It is related to reproductive 
hormones and pregnancy.
Solution C.6.
Fever and sickness or any kind of vigorous activity can lead to perspiration even in cold 
outside.
Solution D.1.
Epidermis Dermis
1. Stratum corneum: It is 
the outermost layer having 
layers of flattened dead cells 
made up of horny protein 
called keratin.
It consists of elastic fibres, 
blood vessels, nerves, etc.
2. Granular layer: It is very 
thin middle layer having two 
or three sublayers of flattened 
cells.
 
3. Malpighian layer: It is the 
innermost region of the 
epidermis. The cells can 
actively divide to produce new 
cells.
 
Solution D.2.
Vasodilation: Dilation of blood vessels in the skin leading to an increase in the blood 
supply. 
Vasoconstriction: Narrowing of blood vessels leading to reduction in the blood supply to 
the skin. 
Temperature regulation in cold weather:
1. At low temperature, the blood vessels get narrowed or vasoconstricted. This 
reduces the blood supply to the skin.
2. There is less loss of heat by convection, conduction and radiation. There is less loss 
of heat through vapourization as reduced blood supply lowers the secretion of 
sweat by sweat glands.
Temperature regulation in hot weather:
1. At high temperature, the blood supply to the skin is increased by vasodilation or 
dilation of blood vessels in the skin.
2. This results in greater loss of heat by convection, conduction and radiation.There is 
more loss of heat through vapourization as more sweat is secreted due to rich 
supply of blood to the skin.
Solution D.3.
(a) Entry of germs: Skin prevents the entry of harmful substances or infectious agents 
inside the body. 
(b) Excessive loss of heat in severe cold: Skin prevents energy loss from the body. It 
conserves body heat in cold weather and facilitates loss of heat in hot weather. 
(c) Entry of harmful ultra-violet rays: Skin protects the body against harmful ultraviolet 
light.
Solution E.1.
Page 4


Chapter 13. Skin- “The Jack of All Trades”
Exercise 1
Solution A.
1. (d) the skin will turn dry and rough
2. (b) Albinism, Leucoderma
3. (c) Skin
4. (b) Dermis
5. (d) Palm
Solution B.1.
Hypothalamus, a portion of the forebrain is the principal body heat regulating centre in 
our brain.
Solution B.2.
Modified sweat gland: Mammary gland 
Modified sebaceous gland: Ceruminous gland
Solution B.3.
Sebaceous glands
Solution C.1.
Functions of the mammalian skin other than those concerned with heat regulation:
1. Storage of food: Skin acts as a storehouse of energy by storing reserve food in 
the form of fat in the hypodermis.
2. Synthesis of Vitamin D: Skin has the ability to synthesize small quantity of 
Vitamin D in the presence of sunlight.
Solution C.2.
A peculiar roughness of the skin produced by cold or fear, in which the hair follicles 
become erect and form bumps on the skin is called goose flesh.
Goose flesh occurs when the muscles at the base of hair known as erectors or arrectors, 
contract. The erector muscles are obliquely placed between the hair follicle and the outer 
part of dermis. They are smooth muscles that are necessary to move the hair. The 
contraction of erector muscle pulls the hair vertical and depresses the epidermis, 
resulting in goose flesh.
Solution C.3.
Man is a warm-blooded mammal. Our body must maintain an average temperature of 
98.6 degree Fahrenheit to function properly. When we feel too hot or too cold, our 
nervous system sends certain automatic and autonomic reflexes that help to keep us 
warm. In cold weather, the blood vessels get narrowed (vasoconstricted). Shivering 
occurs when our muscles expand and contract rapidly to produce extra body heat. The 
amount of heat produced is increased by increased metabolic rate and muscular activity, 
which occurs in the form of shivering. That is why, our body shivers and teeth chatter to 
protect from cold by generating more heat.
Solution C.4.
Leucoderma Albinism
Loss of skin pigmentation from 
smaller or larger patches at 
different regions of the body
Complete loss of pigmentation 
of the skin all over the body
Solution C.5.
Two glands found in the human skin are:
1. Ceruminous gland: It is a modified sebaceous gland found in the auditory canal. It 
secretes wax-like substance called ear wax.
2. Mammary gland: It is a modified sweat gland. It is related to reproductive 
hormones and pregnancy.
Solution C.6.
Fever and sickness or any kind of vigorous activity can lead to perspiration even in cold 
outside.
Solution D.1.
Epidermis Dermis
1. Stratum corneum: It is 
the outermost layer having 
layers of flattened dead cells 
made up of horny protein 
called keratin.
It consists of elastic fibres, 
blood vessels, nerves, etc.
2. Granular layer: It is very 
thin middle layer having two 
or three sublayers of flattened 
cells.
 
3. Malpighian layer: It is the 
innermost region of the 
epidermis. The cells can 
actively divide to produce new 
cells.
 
Solution D.2.
Vasodilation: Dilation of blood vessels in the skin leading to an increase in the blood 
supply. 
Vasoconstriction: Narrowing of blood vessels leading to reduction in the blood supply to 
the skin. 
Temperature regulation in cold weather:
1. At low temperature, the blood vessels get narrowed or vasoconstricted. This 
reduces the blood supply to the skin.
2. There is less loss of heat by convection, conduction and radiation. There is less loss 
of heat through vapourization as reduced blood supply lowers the secretion of 
sweat by sweat glands.
Temperature regulation in hot weather:
1. At high temperature, the blood supply to the skin is increased by vasodilation or 
dilation of blood vessels in the skin.
2. This results in greater loss of heat by convection, conduction and radiation.There is 
more loss of heat through vapourization as more sweat is secreted due to rich 
supply of blood to the skin.
Solution D.3.
(a) Entry of germs: Skin prevents the entry of harmful substances or infectious agents 
inside the body. 
(b) Excessive loss of heat in severe cold: Skin prevents energy loss from the body. It 
conserves body heat in cold weather and facilitates loss of heat in hot weather. 
(c) Entry of harmful ultra-violet rays: Skin protects the body against harmful ultraviolet 
light.
Solution E.1.
Solution E.2.
(a)
1. Sweat pore
2. Sebaceous gland
3. Sweat gland
4. Fat
5. Dermis
6. Stratum malpighian
7. Stratum corneum
8. Epidermis
9. Hair
(b)
Function of part 2 (Sebaceous gland): It produces oil called sebum, which plays 
a role in keeping our skin moist.
Function of part 4 (Fat): The skin reserves food in the form of a layer of fat.
Function of part 3 (Sweat gland): It secretes a transparent liquid (sweat) 
containing water and salts from the body in order to regulate body temperature.
Function of part 9 (Hair): Hair provide a sensation of touch and are also helpful 
in forensic investigations.
Page 5


Chapter 13. Skin- “The Jack of All Trades”
Exercise 1
Solution A.
1. (d) the skin will turn dry and rough
2. (b) Albinism, Leucoderma
3. (c) Skin
4. (b) Dermis
5. (d) Palm
Solution B.1.
Hypothalamus, a portion of the forebrain is the principal body heat regulating centre in 
our brain.
Solution B.2.
Modified sweat gland: Mammary gland 
Modified sebaceous gland: Ceruminous gland
Solution B.3.
Sebaceous glands
Solution C.1.
Functions of the mammalian skin other than those concerned with heat regulation:
1. Storage of food: Skin acts as a storehouse of energy by storing reserve food in 
the form of fat in the hypodermis.
2. Synthesis of Vitamin D: Skin has the ability to synthesize small quantity of 
Vitamin D in the presence of sunlight.
Solution C.2.
A peculiar roughness of the skin produced by cold or fear, in which the hair follicles 
become erect and form bumps on the skin is called goose flesh.
Goose flesh occurs when the muscles at the base of hair known as erectors or arrectors, 
contract. The erector muscles are obliquely placed between the hair follicle and the outer 
part of dermis. They are smooth muscles that are necessary to move the hair. The 
contraction of erector muscle pulls the hair vertical and depresses the epidermis, 
resulting in goose flesh.
Solution C.3.
Man is a warm-blooded mammal. Our body must maintain an average temperature of 
98.6 degree Fahrenheit to function properly. When we feel too hot or too cold, our 
nervous system sends certain automatic and autonomic reflexes that help to keep us 
warm. In cold weather, the blood vessels get narrowed (vasoconstricted). Shivering 
occurs when our muscles expand and contract rapidly to produce extra body heat. The 
amount of heat produced is increased by increased metabolic rate and muscular activity, 
which occurs in the form of shivering. That is why, our body shivers and teeth chatter to 
protect from cold by generating more heat.
Solution C.4.
Leucoderma Albinism
Loss of skin pigmentation from 
smaller or larger patches at 
different regions of the body
Complete loss of pigmentation 
of the skin all over the body
Solution C.5.
Two glands found in the human skin are:
1. Ceruminous gland: It is a modified sebaceous gland found in the auditory canal. It 
secretes wax-like substance called ear wax.
2. Mammary gland: It is a modified sweat gland. It is related to reproductive 
hormones and pregnancy.
Solution C.6.
Fever and sickness or any kind of vigorous activity can lead to perspiration even in cold 
outside.
Solution D.1.
Epidermis Dermis
1. Stratum corneum: It is 
the outermost layer having 
layers of flattened dead cells 
made up of horny protein 
called keratin.
It consists of elastic fibres, 
blood vessels, nerves, etc.
2. Granular layer: It is very 
thin middle layer having two 
or three sublayers of flattened 
cells.
 
3. Malpighian layer: It is the 
innermost region of the 
epidermis. The cells can 
actively divide to produce new 
cells.
 
Solution D.2.
Vasodilation: Dilation of blood vessels in the skin leading to an increase in the blood 
supply. 
Vasoconstriction: Narrowing of blood vessels leading to reduction in the blood supply to 
the skin. 
Temperature regulation in cold weather:
1. At low temperature, the blood vessels get narrowed or vasoconstricted. This 
reduces the blood supply to the skin.
2. There is less loss of heat by convection, conduction and radiation. There is less loss 
of heat through vapourization as reduced blood supply lowers the secretion of 
sweat by sweat glands.
Temperature regulation in hot weather:
1. At high temperature, the blood supply to the skin is increased by vasodilation or 
dilation of blood vessels in the skin.
2. This results in greater loss of heat by convection, conduction and radiation.There is 
more loss of heat through vapourization as more sweat is secreted due to rich 
supply of blood to the skin.
Solution D.3.
(a) Entry of germs: Skin prevents the entry of harmful substances or infectious agents 
inside the body. 
(b) Excessive loss of heat in severe cold: Skin prevents energy loss from the body. It 
conserves body heat in cold weather and facilitates loss of heat in hot weather. 
(c) Entry of harmful ultra-violet rays: Skin protects the body against harmful ultraviolet 
light.
Solution E.1.
Solution E.2.
(a)
1. Sweat pore
2. Sebaceous gland
3. Sweat gland
4. Fat
5. Dermis
6. Stratum malpighian
7. Stratum corneum
8. Epidermis
9. Hair
(b)
Function of part 2 (Sebaceous gland): It produces oil called sebum, which plays 
a role in keeping our skin moist.
Function of part 4 (Fat): The skin reserves food in the form of a layer of fat.
Function of part 3 (Sweat gland): It secretes a transparent liquid (sweat) 
containing water and salts from the body in order to regulate body temperature.
Function of part 9 (Hair): Hair provide a sensation of touch and are also helpful 
in forensic investigations.
Part which has at least three functions: 
Sebaceous gland:
1. Skin protection
2. Secretes an oily substance known as sebum that lubricates hair and skin of 
mammals
3. Presence of sebum enables to experience a wet skin even when we have not taken 
bath for days
(c) The one function which may be common to both men and women is that the fat 
serves as a food reserve and heat insulating layer as well as a shock absorber.