Biology Questions and Answers – Excretory System in Animals

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This set of Biology Multiple Choice Questions & Answers (MCQs) focuses on “Excretory System in Animals”.

1. Which of the following is not accumulated by the body of living organisms?
a) Ammonia
b) Carbon dioxide
c) Urea
d) Oxygen
View Answer

Answer: d
Explanation: Oxygen is not accumulated by the body of living organisms as this is required by the cells to perform respiration. Also, it is not a waste product of the cells. Animals accumulate ammonia, urea, uric acid, carbon dioxide, water, and ions like Na+, K+, Cl, phosphate, sulphate, etc., by certain metabolic activities.
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2. Which of the following is not the major form of nitrogenous wastes?
a) Ammonia
b) Urea
c) Carbon dioxide
d) Uric acid
View Answer

Answer: c
Explanation: Ammonia, urea, and uric acid are the major forms of nitrogenous wastes excreted by the animals. These substances have to be removed totally or partially from the body.

3. Which of the following is the most toxic form of nitrogenous waste?
a) Guanine
b) Ammonia
c) Urea
d) Uric acid
View Answer

Answer: b
Explanation: Ammonia is the most toxic form of nitrogenous waste as it is corrosive. Also, it requires large amounts of energy for its elimination. Ammonia also needs a huge amount of water for its removal from the body.
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4. Ammonia is generally excreted through which of the following?
a) Kidneys
b) Gills
c) Lungs
d) Skin
View Answer

Answer: b
Explanation: Ammonia is generally excreted through the gills. It is generally excreted by the diffusion across the body surfaces or through the gill surfaces as it is readily soluble. Kidneys do not play a significant role in the elimination of ammonia.

5. The process of excreting ammonia is called as ureotelism.
a) True
b) False
View Answer

Answer: b
Explanation: The process of excreting ammonia is called as ammonotelism while the process of excreting urea is known as ureotelism. Many bony fishes, aquatic amphibians and aquatic insects are known to be ammonotelic. Ureotelic organisms include cockroaches, humans, etc.
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6. Which of the following organisms is not ureotelic?
a) Bony fishes
b) Mammals
c) Terrestrial amphibians
d) Marine fishes
View Answer

Answer: a
Explanation: Mammals, many terrestrial amphibians, and marine fishes mainly excrete urea and are called as ureotelic animals. Terrestrial adaptations necessitated the production of lesser toxic nitrogenous waste like urea.

7. In ureotelic organisms, ammonia is converted into which of the following?
a) Uric acid
b) Carbon dioxide
c) Remains as such
d) Urea
View Answer

Answer: d
Explanation: In ureotelic organisms, ammonia produced by metabolism is converted into urea in the liver of these animals and released into the blood which is filtered and excreted out by the kidneys.
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8. Which of the following is not a uricotelic organism?
a) Mammals
b) Reptiles
c) Birds
d) Land snails
View Answer

Answer: a
Explanation: Those organisms which secrete uric acid as a nitrogenous waste are known as uricotelic organisms. Some uricotelic organisms are reptiles, birds, land snails, and insects. They excrete uric acid in the form of a pellet or paste to conserve water and to reduce the weight of the body because removal of uric acid requires a minimum amount of water.

9. Which of the following is not a guanotelic organism?
a) Spiders
b) Scorpions
c) Starfish
d) Marine birds
View Answer

Answer: c
Explanation: Guanotelic organisms are those organisms whose main excretory product is guanine in the urine. These include spiders, scorpions, and some marine birds like an arctic tern, etc.
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10. Excretion of which of the following is for the adaptation of water conservation?
a) Ammonia
b) Urea
c) Uric acid
d) Carbon dioxide
View Answer

Answer: c
Explanation: Excretion of uric acid is an adaptation for water conservation as uric acid is least soluble in water and is formed by nucleic acid metabolism.

11. In most of the invertebrates, kidneys are present for excretion.
a) True
b) False
View Answer

Answer: b
Explanation: In most of the invertebrates, kidneys are not present for excretion. Their excretory structures are simple tubular forms like nephridia, flame cells, etc. It is the vertebrates who have complex tubular organs called kidneys.

12. Which of the following organism has flame cells for excretion?
a) Flatworms
b) Roundworms
c) Hookworms
d) Pinworms
View Answer

Answer: a
Explanation: Flame cells are also known as protonephridia. These are the excretory structures of flatworms like planaria, rotifers, some annelids and some cephalochordates like the Amphioxus. Flame cells are the primitive forms of nephridia.

13. Which of the following phyla have nephridia as an excretory structure?
a) Arthropods
b) Annelids
c) Platyhelminthes
d) Ctenophora
View Answer

Answer: b
Explanation: Nephridia are the tubular excretory structures of earthworms and other annelids. Nephridia help to remove nitrogenous wastes and maintain a fluid and ionic balance.

14. Malpighian tubules are the excretory structures of which of the following?
a) Insects
b) Flatworms
c) Roundworms
d) Crustaceans
View Answer

Answer: a
Explanation: Malpighian tubules are the excretory structures of most of the insects including cockroaches. Malpighian tubules help in the removal of nitrogenous wastes and osmoregulation.

15. Which of the following are the excretory structures of crustaceans?
a) Nephridia
b) Protonephridia
c) Malpighian tubules
d) Antennal glands
View Answer

Answer: d
Explanation: Antennal glands or green glands perform the excretory function in crustaceans like prawns. Protonephridia are the excretory structures which are primarily concerned with ionic and fluid volume regulation.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter