NIOS Class 12 Biology Chapter 18 Solution – Homeostasis The Steady States
NIOS Class 12 Biology Solution Chapter 18 Homeostasis The Steady States . NIOS Class 12 Biology Chapter 18 Question Answers Download PDF. NIOS Class 12 Biology Notes.
Board |
NIOS |
Class |
12th (Higher Secondary) |
Subject |
Biology |
Topic |
Question Answer, Solution, Notes |
INTEXT 18.1
1.) Define homeostasis.
Ans: In order to maintain as constant internal conditions as possible, the body enters a state known as homeostasis (homeo: same/steady, stasis: state). Homeostasis is necessary because the body cells need to have suitable conditions around them for proper functioning. These conditions include, the presence of proper concentration of chemicals, proper temperature, and a suitable pH
2.) List any three chemicals whose concentration in our body has to be maintained at particular levels.
(i) Sugar
(ii) Salt
(iii) Water.
3.) To obtain enough oxygen for respiration at high altitudes, what does the body do?
Ans: Because of the reduced atmospheric pressure at high altitudes, there is inadequate oxygen carried by the usual number of RBCs. The body quickly increases the number of RBCs in the blood to carry the appropriate amount of oxygen within a day or two.
INTEXT 18.2
1.) How do the following temperatures affect the enzymes?
(i) 45°C and above . – It denatures the enzymes
(ii) 0°C and below – It inactivates the enzymes.
2.) (i) At what temperature range do enzymes act best?
. Ans: The enzymes act best at a narrow temperature range, usually between 35-40°C
(ii) What technical term do you use for this temperature?
Ans: The technical term is optimum temperature meaning the most suitable temperature
INTEXT 18.3
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:
(i) Poikilotherms .- Animals whose body temperature changes along with that of the surroundings. Other term is cold blooded
(ii) Homoiotherms.. : Animals whose body temperature remains steady and does not change with that of the surroundings ,Other term is warm blooded
3.) Mention one way each by which each of the following fight severe cold:
(i) Crocodile – Basks in the sun on the land
(ii) Honey bee – Crowd together for collective warmth
(iii) Common frog – Hibernates
(iv) Wall lizard- Hides at safe places
INTEXT 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.
Ans: The set point of human body temperature is taken as 37°C, which is also called the normal or core body temperature
(ii) The function of feathers in bird and the hairs of rabbit.
Ans: The function of feathers in birds and hairs of rabbit is to trap the air to prevent heat loss.
(iii) Effect of shivering.
Ans: : The metabolic rate is increased and more heat is produced in the body cells. The muscular activity is also increased which is sometimes this is the effect of shivering which keeps the body warm.
INTEXT 18.5
1.) Name the two kinds of feed back mechanisms.
Ans: The two kind of feedback mechanisms are Negative and positive
2.) Which kind of feed back mechanism normally operates in homeostasis?
Ans: Negative feed back mechanism normally operates in homeostasis.
TERMINAL EXERCISE
1.) List the three conditions necessary for the body cells to function properly.
Ans:
2). When do we pass out more concentrated urine–during hot summers or cold winters ?
Ans: In hot summers we pass out more concentrated urine
3.) How does our body deal with any extra sugar absorbed into the blood after meals?
Ans: Our body will deal with the extra sugar (greater than the typical blood sugar level) by storing it as glycogen in the liver.
4.) What is our normal RBC count per cubic millimetre? Will it go up or go down if a plain dweller shifts to a mountain or hill?
Ans: Normal RBC count is 5 million per cubic millimeter, and it will go down if a plain dweller shifts to a mountain or hill.
5.) In which temperature range do the enzymes in our body act best?
Ans: The ideal temperature range for the enzymes to function is typically between 35 and 40 °C.
6). Name the two terms often used synonymously for ectotherms.
Ans: Ectotherms are animals whose body temperatures fluctuate in response to changes in the ambient temperature. Poikilotherms and Cold-blooded are the words used synonymously for ectotherms.
7. ) Name any two animals, which tolerate the intense heat of the deserts by promoting heat loss.
Ans: Camels, desert rodents, and many other animals survive in the sweltering heat of tropical deserts mostly through encouraging heat loss.
8.) Which kind of feedback mechanism–the positive or the negative, normally operates in bringing about water-salt balance in our body.
Ans: Negative feedback mechanism normally operates in bringing about water-salt balance in our body.
9.) How is the enzymatic activity affected upon cooling?
Ans: Upon cooling the efficiency of the enzymes declines steadily below the optimal temperature. When temperatures drop below zero, enzymes may become completely inactive.
10.) How do honeybees fight cold during intense winter?
Ans: During the cold winter nights, honey bees gather within the hive to share body heat.
11.) Differentiate between the two terms homeotherms and poikilotherms
Ans: Homoiotherms are organisms that maintain a steady, warm body temperature, while Poikilotherms are organism that determine body temperature based on the surrounding temperature.
. 12.) Give any two examples of preventing loss of body heat by postural behaviour in humans.
Ans: When sitting or standing, we securely cross our arms over our chest. In a curved position, we frequently hold our arms and legs close to the body when we sleep in bed. Such positions reduce the amount of exposed body surface that can radiate heat.
13.) List the components of homeostasis in their proper sequence.
Ans: components of homeostasis are as follow:
i) Set point or the norm
ii) Sensor
iii) Integrating centre
iv) Effectors
14.) Differentiate between positive and negative feedback mechanism
Ans:
Positive feedback mechanism | negative feedback mechanism |
positive feedback mechanism is to continue in the direction of the change. | Negative feedback mechanism is to reverse a condition |
All the feedback mechanisms in blood
coagulation are of the positive type. |
In thermoregulation the kind of feedback mechanism operating is of the negative
type |
15.) Explain the role of the following in thermoregulation in humans:
(i) Sweat glands : Pour out the perspiration so that it can evaporate and make you cool.
(ii) Skeletal muscles : rapidly contract (shiver) to generate heat
(iii) Blood vessels in the skin : enlarge (vasodilate) to carry more blood to the surface of the body so that heat can be released
16.) What is meant by feed back mechanism? What are its two types? Which one of these is applicable to thermoregulation and why?
Ans: It is the mechanism that regulates the internal environment of the body. There are two types of mechanism positive and negative mechanism. The type of feedback mechanism involved in thermoregulation is a negative one. To return to the set point’s condition, any divergence from it must be reversed.
17.) Why is thermoregulation required in our body?
Ans: The usual temperature range in which living things can exist is between 0 and 45 degrees Celsius. However, organisms frequently change their behaviour. The organisms may suffer in a variety of ways above 45°C: the enzymes are damaged, the proteins get denatured, the plasma membrane disintegrates, and the cells lose oxygen. under 0 degrees Celsius. When it is below freezing, ice crystals the size of needles may grow inside and between the cells, causing the cells to burst and the organisms death.
18.) Differentiate between endotherms and ectotherms. Which ones of these do you think can survive better if there is a suden change in environmental temperature?
Ans: Endotherms are organisms that maintain a constant body temperature regardless of the ambient temperature while, Animals whose body temperatures shift in response to changes in the surrounding temperature are referred to as Ectotherms. Endotherms can survive better if there is a suden change in environmental temperature
19). Differentiate between physiological and behavioral responses for thermoregulation in humans
Ans: Vasodilation or vasoconstriction, sweating or not, an increase or decrease in cell metabolism, shivering, etc. are examples of changes in blood circulation. These changes are all outside of our control of will, this is called physiological response, while behavioral response includes the conscious and subconscious acts for example When it is chilly, we relocate to warmer locations (such as open sunlight or in front of heat radiators), close the windows to block the entry of cold gusts, and wrap up in blankets.
20.) Explain the role of hypothalamus during heat regulation in humans.
Ans: The hypothalamus, a region of the forebrain, holds the main heat-regulating centre. This component functions as a thermostat.
The body “switches on” or speeds up the heat-producing processes and at once “shuts off” the heat-losing ones when it must deal with cooling below the normal temperature.
The body speeds up the cooling process and “switches off” the heat-producing cells when it overheats in the summer or after vigorous activity.
21.) Explain the relationship between sensor and integrating centre during any one kind of homeostasis.
Ans: sensor and integrating centre both are the components of homeostasis, Sensors have a sensory component that detects changes to the set point while, the component that receives information about a change in the set point of a given state, interprets it, and then provides the command for correction is known as the integrating centre.
Also See: Next Chapter 19 Question Answer