Homeostasis : The Steady State – 12th Class Biology Q Ans Lesson 18 – NIOS

Homeostasis : The Steady State – 12th Class Biology Q Ans Lesson 18 – NIOS

Homeostasis : The Steady State - 12th Class Biology Q Ans Lesson 18 - NIOS


  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 maintainedat partcular levels.
    Ans. (i) sugar, (ii) salt, (iii) water
  3. To obtain enough oxygen for respiration at high altitudes, what does the bodydo?
    Ans. The body adds more RBCs to the blood


  1. How do the following temperatures affect the enzymes?
    (i) 45°C and above – Denatured
    (ii) 0°C and below – Inactive
  2. (i) At what temperature range do enzymes act best? – 35-40°C
    (ii) What technical term do you use for this temperature? – Optimum temperature


  1. Classify the following animals as endotherm or ectotherm :
    Camel, Bat, Earthworm, Cockroach, Fish, Wall lizard, Polar bear, sparrow
    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:
    Ans. Poikilotherms : Animals whose body temperature changes along with
    that of the surroundings
    Warm blooded : 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:
    Ans. Crocodile : Basks in the sun on the land
    Honey bees : Crowd together for collective warmth
    Common frog : Hibernates
    Wall lizard : Hides at safe places


  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. – 37°C
    (ii) The function of feathers in bird and the hairs of rabbit. – trap air to prevent heat loss
    (iii) Effect of shivering. – warms up in cold weather


  1. Name the two kinds of feed back mechanisms.- Negative and positive
  2. Which kind of feed back mechanism normally operates in homeostasis? – Positive


  1. List the three conditions necessary for the body cells to function properly.
  2. When do we pass out more concentrated urine–during hot summers or coldwinters ?
  3. How does our body deal with any extra sugar absorbed into the blood aftermeals?
  4. What is our normal RBC count per cubic millimetre? Will it go up or go downif a plain dweller shifts to a mountain or hill?
  5. In which temperature range do the enzymes in our body act best?
  6. Name the two terms often used synonymously for ectotherms.
  7. Name any two animals, which tolerate the intense heat of the deserts bypromoting heat loss.
  8. Which kind of feedback mechanism–the positive or the negative, normally
    operates in bringing about water-salt balance in our body.
  9. How is the enzymatic activity affected upon cooling?
  10. How do honeybees fight cold during intense winter?
  11. Differentiate between the two terms homeotherms and poikilotherms.
  12. Give any two examples of preventing loss of body heat by postural behaviourin humans.
  13. List the components of homeostasis in their proper sequence.
  14. Differentiate between positive and negative feedback mechanism.
  15. Explain the role of the following in thermoregulation in humans:
    (i) Sweat glands
    (ii) Skeletal muscles
    (iii) Blood vessels in the skin
  16. What is meant by feed back mechanism? What are its two types? Which oneof these is applicable to thermoregulation and why?
  17. Why is thermoregulation required in our body?
  18. Differentiate between endotherms and ectotherms. Which ones of these do youthink can survive better if there is a suden change in environmental temperature?
  19. Differentiate between physiological and behavioral responses for thermoregulationin humans.
  20. Explain the role of hypothalamus during heat regulation in humans.
  21. Explain the relationship between sensor and integrating centre during any one kind of homeostasis.

NIOS 12th class biology Q Ans

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