NCERT Exemplar Class 11 Biology Solutions Chapter 19 Excretory Products and their Elimination

Multiple Choice Questions:

Question:1

The following substances are the excretory products in animals. Choose the least toxic from among them.

(a) Urea (b) Uric acid (c) Ammonia (d) Carbon dioxide

Answer:

The answer is the option (b) Uric acid

Explanation: The level of toxicity can be shown as below with ammonia being the
most toxic.
Ammonia;
Urea;
Uric acid

Excretory Products and their Elimination Exercise: 1.4

Question:2

Filtration of the blood takes place at

(a) PCT (b) DCT (c) Collecting ducts (d) Malpighian body

Answer:

The answer is the option (d) Malpighian body

Explanation: Glomerulus is also known as Malpighian body

Question:3

Which of the following statements is incorrect?

a. ADH—prevents conversion of Angiotensinogen in blood to angiotensin
b. Aldosterone—facilitates water reabsorption
c. ANF—enhances sodium reabsorption
d. Renin—causes vasodilation

Answer:

The answer is the option
(a) ADH—prevents conversion of Angiotensinogen in blood to angiotensin.

Question:4

A large quantity of one of the following is removed from our body by lungs

(a) CO 2 only (b) H 2 O only (c) CO 2 and H 2 O (d) Ammonia

Answer:

The answer is the option (a) CO_2
Explanation: - Water is excreted in major quantities from the skin as sweat, kidneys as urine and large intestine as faeces.

Question:5

The pH of human urine is approximately
(a) 6.5 (b) 7 (c) 6 (d) 7.5

Answer:

Ans. The answer is the option (c) 6

Question:6

Different types of excretory structures and animals are given below. Match them appropriately and mark the correct answer from among those given below:

Options:
(a) D—(i), (C)—(ii), B—(iii), A—(iv)
(b) B— (i), (C)—(ii), A—(iii), B—(iv)
(c) D—(i), (C)—(ii), A—(iii), B-(iv)
(d) B—(i), (C)—(ii), B—(iii), D—(iv)

Answer:

The answer is the option
(a) D – (i), C – (ii), B – (iii), A – (iv)

Question:7

Which one of the following statements is incorrect?
(a) Birds and land snails are uricotelic animals.
(b) Mammals and frogs are ureotelic animals.
(c) Aquatic amphibians and aquatic insects are ammonotelic animals.
(d) Birds and reptiles are ureotelic.

Answer:

The answer is the option (d) Birds and reptiles are ureotelic
Explanation: Birds and reptiles are uricotelic, i.e. they excrete the nitrogenous waste as uric acid.

Question:8

Which of the following pairs is wrong?
(a) Uricotelic — Birds (b) Ureotelic — Insects (c) Ammonotelic — Tadpole (d) Ureotelic — Elephant

Answer:

The answer is the option (b) Ureotelic - Insects
Explanation: Insects the ones who excrete nitrogenous waste as uric acid and hence are uricotelic.

Question:9

Which one of the following statements is incorrect?
(a) The medullary zone of kidney is divided into a few conical masses called medullary pyramids projecting into the calyces.
(b) Inside the kidney the cortical region extends in between the medullary pyramids as renal pelvis
(c) Glomerulus along with Bowman's capsule is called the renal corpuscle
(d) Renal corpuscle, proximal convoluted tubule (PCT) and distal convoluted tubule (DCT) of the nephron are situated in the cortical region of kidney

Answer:

The answer is the option (b) Inside the kidney, the cortical region extends in between the medullary pyramids as renal pelvis.

Question:10

The condition of accumulation of urea in the blood is termed as
(a) Renal Calculi
(b) Glomerulonephritis
(c) Uremia
(d) Ketonuria

Answer:

The answer is the option (c) Uremia.
Explanation: Renal calculi is also commonly known as kidney stones. In contrast, the accumulation of ketone is known as ketonuria.

Question:11

Which one of the following is also known as antidiuretic hormone?
(a) Oxytocin (b) Vasopressin (c) Adrenaline (d) Calcitonin

Answer:

The answer is the option b) Vasopressin
Explanation:
The water from the end parts of the tubule is made possible through vasopressin. This process prevents the diuresis and hence is called a antidiuretic hormone.

Question:12

Match the terms given in Column I with their physiological processes given in Column II and choose the correct answer

Options:
(a) A—(iii), B—(v), C—(iv), D—(ii), E—(i)
(b) A—(iii), B—(iv), C—(i), D—(v), E—(ii)
(c) A—(i), B—(iii), C—(ii), D—(v), E—(iv)
(d) A—(iii), B—(i), C—(iv), D—(v), E—(ii)

Answer:

The answer is the option (b) A – (iii), B – (iv), C – (i), D – (v), E – (ii)

Question:13

Match the abnormal conditions given in Column A with their explanations given in Column B and choose the correct option.

Options:
(a) A—(i), B—(iii), C—(ii), D—(iv)
(b) A—(iii), B—(ii), C—(iv), D—(i)
(c) A—(iv), B—(iii), C—(ii), D—(i)
(d) A—(iv), B—(ii), C—(iii), D—(i)

Answer:

The answer is the option (c) A – (iv), B – (iii), C – (ii), D – (i)

Question:14

We can produce concentrated/dilute urine. This is facilitated by a special mechanism. Identify the mechanism.
(a) Reabsorption from PCT
(b) Reabsorption from collecting duct
(c) Reabsorption/secretion in DCT
(d) Counter current mechanism in Henle's loop/Vasa recta

Answer:

The answer is the option (d) Counter current mechanism in Henle's loop/Vasa recta
Explanation:
The two limbs of Henle's loop, as well as vasa recta, witness counter currents when we move towards the descending limb the concentration increases whereas it is diluted as we move towards the ascending limb.

Question:15
Dialysing unit (artificial kidney) contains a fluid which is almost same as plasma except that it has
(a) High glucose
(b) High urea
(c) No urea
(d) High uric acid

Answer:

The answer is the option (c) No urea

Very Short Answer Type Questions:

Question:1

Where does the selective reabsorption of Glomerular filtrate take place?

Answer:
The proximal convoluted tubule is the place where selective reabsorption of Glomerular filtrate takes place.

Question:2

What is the excretory product from kidneys of reptiles?

Answer:

Uric acid is the excretory product from kidneys of reptiles.

Question:3

What is the composition of sweat produced by sweat glands?

Answer:
The composition of the sweat produced by sweat glands is sodium chloride, a small amount of urea and lactic acid.

Question:4

Identify the glands that perform the excretory function in prawns.

Answer:
Antennal glands or green glands perform the excretory function in prawns=

Question:5

What is the excretory structure in amoeba?

Answer:
Amoeba is unicellular organisms. Hence, they do not have a specific excretory system or structure. The waste is removed by osmosis in the case of amoeba and through the plasma membrane.

Question:6

The following abbreviations are used in the context of excretory functions, what do they stand for?
a. ANF
b. ADH
c. GFR
d. DCT

Answer:
The full forms are as follows:
(a) Atrial Natriuretic Factor
(b) Anti Diuretic Hormone
(c) Glomerular Filtration Rate
(d) Distal Convoluted Tubule

Question:7

Differentiate Glycosuria from Ketonuria.

Answer:
The difference between glycosuria and ketonuria is as follows:

Question:8

What is the role of sebaceous glands?

Answer:
The main function of the sebaceous glands is to secrete sebum. Sebum is responsible for making our hair and skin waterproof.

Question:9

Name two actively transported substances in Glomerular filtrate.

Answer:

Two actively transported substances in Glomerular filtrate are glucose and amino acids.

Question:10

Mention any two metabolic disorders, which can be diagnosed by analysis of urine.

Answer:

Two metabolic disorders, which can be diagnosed by analysis of urine, are jaundice and diabetes.

Question:11

What are the main processes of urine formation?

Answer:

There are three main processes for the formation of urine. They are glomerular filtration, reabsorption, and secretion.

Question:12

Sort the following into actively or passively transported substances during reabsorption of GFR:
Glucose, Aminoacids, Nitrogenous Wastes, Na + , Water

Answer:

Actively transported substances during reabsorption of GFR:
Glucose, amino acids and Na+

Passively transported substances during reabsorption of GFR:
nitrogenous wastes, Na+ and water

Question:13

Complete the following:
a. Urinary excretion = Tubular reabsorption + tubular secretion
b. Dialysis fluid = Plasma

Answer:

a) Urinary excretion = tubular reabsorption + tubular secretion —Glomerular filtration
b) Dialysis fluid = Plasma — nitrogenous wastes

Question:14

Mention the substances that exit from the tubules in order to maintain a concentration gradient in the medullary interstitium.

Answer:

Substances that exit from the tubules in order to maintain a concentration gradient in the medullary interstitium are Sodium chloride, water and urea.

Question:15

Fill in the blanks appropriately.
Organ Excretory wastes
1. Kidneys _____________________
2. Lungs _____________________
3. Liver _____________________
4. Skin _____________________

Answer:
(a) Urea
(b) Carbon dioxide
(c) bile, drugs
(d) sterols, hydrocarbons

Short Answer Type Questions:

Question:1

Show the structure of a renal corpuscle with the help of a diagram.

Answer:

Question:2

What is the role played by Renin-Angiotensin in the regulation of kidney function?

Answer:

The Role of Renin-Angiotensin can be described as follows:
The Angiotensinogen is converted into Angiotensin I and then next to Angiotensin II by Renin. Angiotensin II is an extremely effective vasoconstrictor, is responsible for increasing the blood flow to the glomerulus, which eventually increases the filtration rate of the glomerulus.

Question:3

Aquatic animals generally are ammonotelic in nature whereas terrestrial forms are not. Comment.

Answer:

The removal of the substance ammonia from the body requires plenty of water due to its highly toxic nature. This does not create problems with the aquatic animals as there is plenty of water available which has made them ammoniotelic, i.e. the animals which excrete ammonia. However, in the case of animals living in terrestrial habitat, the water availability is limited, and hence they are not ammoniotelic and show ureotelism.

Question:4

The composition of glomerular filtrate and urine is not same. Comment.

Answer:

Water and electrolytes are present in the glomerular filtrate in large quantities. The GFR is 180 L/day for a healthy human. The urine output on an average for a healthy human is 1.5 L/ day. So, we can deduce that there is the reabsorption of 90% or more glomerular filtrate. This reabsorption happens in order to retain the water and electrolytes in the body. This means the concentration of urine is higher than the glomerular filtrate, and that is what makes their compositions different from each other.

Question:5

What is the procedure advised for the correction of extreme renal failure? Give a brief account of it.

Answer:

A kidney transplant will be recommended to a patient who suffered from renal failure, and it is an extreme scenario. A kidney donor is found for the transplant to happen. Extreme care needs to be given in case of tissue matching, as tissue rejection after the transplant can cause a lot of problems. In many cases, the kidney of similar blood group person is chosen, or in some cases, the kidney of a brain-dead person can also be utilised for a transplant.

Question:6

How have the terrestrial organisms adapted themselves for the conservation of water?

Answer:

In the scenario of terrestrial habitat, water availability has some constraints, and that is the reason water is especially important for the terrestrial organisms for survival. When nitrogenous wastes are removed from the body, a lot of water is required to flush them out.

Since the water available in terrestrial habitats is limited, these organisms, practice to ureotelism and uricotelism modes of excretion which need less water as compared to ammoniotelic organisms. Also, the organisms that live in extremely dry places practice uricotelism so that more water is retained inside their bodies.

Question:7

Label the parts in the following diagram.

Answer:

Question:8

Explain, why a haemodialysing unit called an artificial kidney?

Answer:

The main function of filtration of nitrogenous wastes from the blood is performed by the haem dialysing unit, which is made of a cellophane membrane. This membrane is surrounded on all sides by a dialysing fluid. The dialysing unit receives the blood from an artery post which it is filtered, and the nitrogenous wastes are filtered. After this process, the filtered blood is sent back to the body.

The filtration of wastes happens through the process of osmosis, and in this way, the functions of a kidney are performed by the dialysing unit, which is often labelled as an artificial kidney.

Question:9

Comment upon the hormonal regulation of selective reabsorption.

Answer:

In the process of selection reabsorption and its regulation in kidneys, Antidiuretic Hormone (ADH) or vasopressin plays a crucial role. The osmoreceptors present in our body get activated when there is a change of the haemodynamic in the body. When there is an excess excretion/loss of fluids from our body, the activated osmoreceptors send signals to the hypothalamus in our brain to release ADH from the neurohypophysis.

The reason for releasing ADH is that it enables water to be reabsorbed from the parts of the tubule and tries to balance the loss of fluid. The osmoreceptors are deactivated when the fluid levels increase in our body, which leads to stopping the release of ADH, and that is how the cycle of feedback gets completed.

Long Answer Questions:

Question:1

Explain the mechanism of formation of concentrated urine in mammals.

Answer:

The Henle's loop and vasa recta have a significant tole to play when It comes to the ability of mammals to produce urine that is concentrated.

The Counter Current Mechanism
There is an opposite flow of the filtrate in the Henle's loop's both limbs, which results in a counter-current eventually. This same effect is also recognised in the flow of current through the vasa recta's both limbs. The maintenance of increasing osmolarity towards the inner medullary interstitium is achieved as a result of the nearness of vasa recta and Henle's loop and also the presence of counter-current in their limbs. The level of osmolarity increases from the cortex (300 mOsmol/L) to the inner medulla (1200 mOsmol/L).

The Role of Sodium hydrochloride (NaCl) and Urea in this process
The significance of NaCl and Urea is to cause osmotic gradient. The Henle's loop and its ascending limb are responsible for the transportation of NaCl which is then exchanged with the Vasa recta's descending limb. Post this exchange, through the ascending limb of vasa recta and collecting tubule, it is sent back to the interstitium.
The Effect of Osmotic Gradient
The easy exit of water from the collecting tubule is facilitated by the osmotic gradient, which is present in the interstitium, and this effect leads to the urine being concentrated. Hence, human urine is four times concentrated than the one out of the initial filtrate.

Question:2

Draw a labelled diagram showing reabsorption and secretion of major substances at different parts of the nephron.

Answer:

There are three important steps involved in the formation of the urine.
These are: glomerular filtration, tubular reabsorption, and urinary secretion

Here is a diagram showing reabsorption and secretion of major substances at different parts of the nephron.

The important points which can be inferred from the diagram above are:
- The transportation of NaCl takes place to the descending limb of vasa recta from the ascending limb of Henle's loop.
- After reaching the descending limb of vasa recta, NaCl is transported back to the ascending limb of vasa recta.
- In a similar manner, urea in small amounts enter the ascending limb of the Henle's loop and by the collecting duct is sent back to the interstitium.
- The passage of water through the membrane of the collecting tubule is made easier by the presence of interstitial gradient.
- The osmolarity level rises from 300 mosmol/L in the cortex to 1200 mosmol/L in the medulla.

Question:3

Explain briefly, micturition and disorders of the excretory system.

Answer:

Micturition
The phenomenon when the urine passes out of the urinary bladder is termed as micturition. This phenomenon is under the control of our brain and is somewhat a voluntary action. This process involves the following steps:

- Stretching of the urinary bladder by getting filled with urine
- Transmission of signals to the central nervous system by the stretch receptors in the walls of the bladder.
- The smooth messages of the urinary bladder get motor messages from the central nervous system
- Contraction of the muscles in the urinary bladder which leads to rushing out of urine from the bladder. Post this the sphincter of urethra gets relaxed, and it results in the outflow of urine.
Disorders of Excretory System

1) Renal Impairment
This disorder affects the filtration in the excretory system. It reduces the efficiency of filtration. This results in nitrogen waste accumulation in our body. It also affects osmoregulation and causes complex problems. The disorder is generally cured through dialysis, and the only option for a permanent cure is a kidney transplant.
2) Renal calculi
Popularly known as a kidney stone, it is the presence of an insoluble crystal-like substance in the kidney. In many cases, by increased fluid intake, it can be cured, but in some serious cases, surgery is required to take out the stones.
3) Glomerulonephritis
it is a condition in which the glomerulus gets swollen. It happens as a result of an infection in the body.

Question:4

How does tubular secretion help in maintaining ionic and acid-base balance in body fluids?

Answer:

For maintaining the acid-base balance in the fluids of our body on an ionic level, Tubular secretion is responsible. The process can be elaborated as below:

Proximal Convoluted Tubule
A selective secretion takes place. It involves ammonia, hydrogen ions and potassium in the Proximal Convoluted Tubule, which maintains the acid-base balance or the pH balance in the fluids of our body.

Distal Convoluted Tubule
A Selective secretion takes place in Distal Convoluted Tubule which contains hydrogen ions, ammonia, and potassium along with the absorption of the ions of bicarbonate. Just like PCT, this process also helps in maintaining the pH balance in the fluids of our body.

Collecting Duct
Hydrogen and potassium ions are selectively secreted in the collecting duct, which helps to maintain a balance of ions as well as in terms of pH values.

Question:5

The glomerular filtrate in the loop of Henle gets concentrated in the descending and then gets diluted in the ascending limbs. Explain.

Answer:

The Henle's loop has two limbs. An ascending limb and a descending limb. The descending limb allows water to pass through but does not allow any electrolytes.

So, the presence of electrolytes leads to an increase in the concentration as we move down the descending loop. The other limb of Henle's loop, which is the ascending limb, allows electrolytes to pass through but does not allow the passage of water.

So, as we move towards the ascending limb of Henle's loop, the concentration decreases, and the filtrate gets diluted.

Question:6

Describe the structure of a human kidney with the help of a labelled diagram.

Answer:

Structure of Kidney
Length: 10-12 cm
Width: 5-7 cm
Thickness: 2-3 cm
Location: both sides of the vertebral column

The hilum is a notch which is present on the inner surface towards the centre of the kidney. This notch allows the entrance of blood vessels, nerves and ureter in the kidney.
Renal Pelvis
Funnel-shaped structure towards the inner hilum. It has two zones. The inner zone is known as the medulla, and the outer zone is known as the cortex.
Medulla
It is divided into small medullary pyramids which are conical in shape. These are projected through the calyces.
Cortex
It is a structure which is present between the renal columns and the medullary pyramids. Columns of Bertini is another name of the renal columns.
Nephrons
These are particularly important and functional units of a kidney. They are complex tubular structures present in the count of millions. There are two parts of a nephron which include glomerulus and tubule. The glomerulus is responsible for the filtration of blood and toxic substances like nitrogenous wastes and ammonia.