18 Homeostasis: The Steady State

NIOS Biology Intext Solutions Chapter 18

INTEXT QUESTIONS 18.1

1. Define homeostasis.

Ans: Homeostasis is the regulation of a steady internal condition.

2. List any three chemicals whose concentration in our body has to be maintained at partcular levels.

Ans: (i) sugar, (ii) salt, (iii) water

3. To obtain enough oxygen for respiration at high altitudes, what does the body do?

Ans: The body adds more RBCs to the blood

INTEXT QUESTIONS 18.2

1. How do the following temperatures affect the enzymes?

(i) 45°C and above 

(ii) 0°C and below

Ans: 

• (i) Denatured 
• (ii) inactive

2. (i) At what temperature range do enzymes act best?

(ii) What technical term do you use for this temperature?

Ans: 

• (i) 35-40°C
• (ii) Optimum temperature

INTEXT QUESTIONS 18.3

1. Classify the following animals as endotherms or ectotherms:

Camel, Bat, Earthworm, Cockroach, Fish, Wall lizard, Polar bear, sparrow

Ans: 

• Endotherms: Camel, Bat, Polar bear, sparrow. 
• Ectotherms: Earthworm, Cockroach, Fish, Wall lizard

2. Explain the following terms and give one or more synonymous terms for each:

(i) Poikilotherms .

(ii) Homoiotherms

Ans: 

• (i) Poikilotherms: Animals whose body temperature changes along with that of the surroundings
• (ii) Homoiotherms: Animals whose body temperature remains steady and does not change with that of the surroundings

3. Mention one way each by which each of the following fight severe cold:

(i) Crocodile.

(ii) Honey bee 

(iii) Common frog.

(iv) Wall lizard 

Ans: 

• (i) Homoiotherms Crocodile: Basks in the sun on land
• (ii) Honey bees: Crowd together for collective warmth
• (iii) Common frog: Hibernates
• (iv) Wall lizard: Hides in safe places

INTEXT QUESTIONS 18.4

1. Rearrange the following in their correct sequence in homeostasis:

Effector, Set point, Integrating centre, Sensor.

Ans: Set point, Sensor, Integrating centre, Effectors

2. State in one word or sentence :

(i) The normal body core temperature of humans.

(ii) The function of feathers in birds and the hairs of rabbits.

(iii) Effect of shivering.

Ans: 

• (i) 37°C
• (ii) trap air to prevent heat loss
• (iii) warms up in cold weather

INTEXT QUESTIONS 18.5

1. Name the two kinds of feedback mechanisms.

Ans: Negative and positive

2. Which kind of feedback mechanism normally operates in homeostasis?

Ans: Negative.

Additional Study Materials

• Chapter 06 Root system
• Chapter 07 Shoot system
• Chapter 08 Absorption, Transport, and Water Loss in Plants
• Chapter 09 Nutrition in plants – Mineral Nutrition
• Chapter 10 Nitrogen Metabolism
• Chapter 11 Photosynthesis
• Chapter 12 Respiration in Plants
• Chapter 13 Nutrition and Digestion
• Chapter 14 Respiration and Elimination of Nitrogenous Wastes
• Chapter 15 Circulation of Body Fluids
• Chapter 16 Locomotion and Movement
• Chapter 17 Coordination and Control – The Nervous and Endocrine Systems