NCERT Solutions for Class 11 Biology Chapter 19
Excretory Products and their Elimination Class 11
Chapter 19 Excretory Products and their Elimination Exercise Solutions
Exercise : Solutions of Questions on Page Number : 300
Q1 :
Define Glomerular Filtration Rate (GFR)
Answer :
Q2 :
Explain the autoregulatory mechanism of GFR.
Answer :
The mechanism by which the kidney regulates the glomerular filtration rate is autoregulative. It is carried out by the juxtaglomerular apparatus. Juxtaglomerular apparatus is a microscopic structure located between the vascular pole of the renal corpuscle and the returning distal convoluted tubule of the same nephron.
Q3 :
Indicate whether the following statements are true or false:
(a) Micturition is carried out by a reflex.
(b) ADH helps in water elimination, making the urine hypotonic.
(c) Protein-free fluid is filtered from blood plasma into the Bowman's capsule.
(d) Henle's loop plays an important role in concentrating the urine.
(e) Glucose is actively reabsorbed in the proximal convoluted tubule.
Answer :
(a) True
(b) False
(c) True
(d) True
(e)
Q4 :
Give a brief account of the counter current mechanism.
Answer :
The counter current mechanism operating inside the kidney is the main adaptation for the conservation of water. There are two counter current mechanisms inside the kidneys. They are Henle's loop and vasa rectae.
The osmolarity increases from 300 mOsmolL -1 in the cortex to 1200 mOsmolL -1 in the inner medulla by counter current mechanism. It helps in maintaining the concentration gradient, which in turn helps in easy movement of water from collecting tubules. The gradient is a result of the movement of NaCl and urea.
Q5 :
Describe the role of liver, lungs and skin in excretion.
Answer :
Liver, lungs, and skin also play an important role in the process of excretion. Role of the liver:
Liver is the largest gland in vertebrates. It helps in the excretion of cholesterol, steroid hormones, vitamins, drugs, and other waste materials through bile. Urea is formed in the liver by the ornithine cycle. Ammonia - a toxic substance
- is quickly changed into urea in the liver and thence eliminated from the body. Liver also changes the decomposed haemoglobin pigment into bile pigments called bilirubin and biliverdin.
Role of the lungs:
Lungs help in the removing waste materials such as carbon dioxide from the body. Role of the skin:
Skin has many glands which help in excreting waste products through pores. It has two types of glands - sweat and sebaceous glands.
Sweat glands are highly vascular and tubular glands that separate the waste products from the blood and excrete them in the form of sweat. Sweat excretes excess salt and water from the body.
Q6 :
Explain micturition.
Answer :
Micturition is the process by which the urine from the urinary bladder is excreted. As the urine accumulates, the muscular walls of the bladder expand. The walls stimulate the sensory nerves in the bladder, setting up a reflex action. This reflex stimulates the urge to pass out urine. To discharge urine, the urethral sphincter relaxes and the smooth muscles of the bladder contract. This forces the urine out from the bladder. An adult human excretes about 1
Q7 :
Match the items of column Iwith those of column II:
Column I |
Column II |
||
(a) |
Ammonotelism |
(i) |
Birds |
(b) |
Bowman's capsule |
(ii) |
Water reabsorption |
(c) |
Micturition |
(iii) |
Bony fish |
(d) |
Uricotelism |
(iv) |
Urinary bladder |
(d) |
ADH |
(v) |
Renal tubule |
Answer :
Column I |
Column II |
|||
(a) |
Ammonotelism |
(iii) |
Bony fish |
|
(b) |
Bowman's capsule |
(v) |
Renal tubule |
|
(c) |
Micturition |
(iv) |
Urinary bladder |
|
(d) |
Uricotelism |
(i) |
Birds |
|
(d) |
ADH |
(ii) |
Water reabsorption |
|
|
|
|||
Q8 :
What is meant by the term osmoregulation?
Answer :
Q9 :
Terrestrial animals are generally either ureotelic or uricotelic, not ammonotelic, why?
Answer :
Terrestrial animals are either ureotelic or uricotelic, and not ammonotelic. This is because of the following two main reasons:
(a) Ammonia is highly toxic in nature. Therefore, it needs to be converted into a less toxic form such as urea or uric acid.
(b)
Q10 :
What is the significance of juxtaglomerular apparatus (JGA) in kidney function?
Answer :
Juxtaglomerular apparatus (JGA) is a complex structure made up of a few cells of glomerulus, distal tubule, and afferent and efferent arterioles. It is located in a specialised region of a nephron, wherein the afferent arteriole and the distal convoluted tubule (DLT) come in direct contact with each other.
The juxtaglomerular apparatus contains specialised cells of the afferent arteriole known as juxtaglomerular cells. These cells contain the enzyme renin that can sense blood pressure. When glomerular blood flow (or glomerular blood pressure or glomerular filtration rate) decreases, it activates juxtaglomerular cells to release renin.
Q11 :
Name the following:
(a) A chordate animal having flame cells as excretory structures
(b) Cortical portions projecting between the medullary pyramids in the human kidney
(c) A loop of capillary running parallel to the Henle's loop.
Answer :
(a) Amphioxus is an example of a chordate that has flame cells as excretory structures. Flame cell is a type of excretory and osmoregulatory system.
(b) The cortical portions projecting between the medullary pyramids in the human kidney are the columns of Bertini. They represent the cortical tissues present within the medulla.
(c)
Q12 :
Fill in the gaps:
(a) Ascending limb of Henle's loop is _to water whereas the descending limb is _to it.
(b) Reabsorption of water from distal parts of the tubules is facilitated by hormone _.
(c) Dialysis fluid contains all the constituents as in plasma except .
(d) A healthy adult human excretes (on an average) gm of urea/day.
Answer :
(a) Ascending limb of Henle's loop is to water, whereas the descending limb is to it.
(b) Reabsorption of water from distal parts of the tubules is facilitated by the hormone .
(c) Dialysis fluid contains all the constituents as in plasma, except .
(d) A healthy adult human excretes (on an average) gm of urea/day.