Sunday 27 July 2014

CBSE Class 10 - Science - Ch6 - Gist on Excretory System (Life Processes)

Gist on Excretory System
(Short Q & A)
A Pair Of Kidneys
(image credits: openclipart)

Q1: Define Excretion.

Answer: Excretion is a biological process by which an organism gets rid of metabolic toxic wastes from its body.

Q2: List the toxic wastes of metabolism.

Answer: These wastes are nitrogenous materials i.e. ammonia, urea and uric acid, carbon dioxide, inorganic salts, excess of water.

Q3: What is Osmoregulation? 

Answer: It is a process that maintains the amount of water and ionic balance in the body.

Q4: Where Urea is formed in mammals?

Answer: Urea is made in the liver via the ornithine cycle by combining the ammonia
made by deamination with carbon dioxide made from respiration

Q5: What are the major excretory products of plants?

Answer: Oxygen, Water, Carbon DiOxide, Latex, gums, resins, excessive salts, calcium oxalate and other toxic substances are excretory organs of plants.

Q6: How does excretion occur in amoeba?

Answer: Contractile vacuoles in amoeba performs excretion.

Q7: What is gout?

Answer: In humans the high concentrations of uric acid in the blood cause uric acid crystals to precipitate in the kidneys and joint membranes. This can cause excruciating pain and swelling in the joints, particularly in the big toes.

Q8: Name the excretory organs of earthworm.

Answer: Nephridia

Q9: List the excretory system organs in human beings.

Answer: The excretory system in humans consists of:
   - a pair of kidneys
   - a pair of ureter
   - a urinary bladder
   - a urethra

Q10: Name the functional and structural unit of kidney.

Answer: Nephron is the structural and functional unit of kidney. Each kidney of the pair contains millions of nephrons.

Q11: How does a pair of kidneys in human beings related to homeostasis?

Answer: Kidney is also concerned with homeostasis since it carries out osmoregulation of body fluids and controls the pH of the blood.

Q12: How does excretion takes place in segmented worms, like earthworms?

Answer: Segmented worms, such as earthworms, produce urea that is excreted through long tubules called nephridia.

Q13: What are the excretory organs of insects like grasshoppers?

Answer: Malpighian tubules

Q14: What is Hemodialysis?

Answer: It is a process of separating wastes from the blood by passing through a semipermeable membrane.

OR (2 Marks)

If somehow due to infection, injury or restricted blood flow, the kidneys get damaged which is
called kidney failure (renal failure). Then the process of excretion is performed by artificial
kidney. This process is called dialysis. Dialysis machine cleans the blood of person by removing
the nitrogenous wastes products from it.

Q15: Why does uric acid is the best nitrogenous waste product for insects, reptiles and birds?

Answer: Uric acid has low solubility and does conserve water in insects, reptiles and birds.

Q16: Name the two methods in use during chronic renal (kidney) failure.

Answer: Hemodialysis and kidney transplant

Q17: What is the main excretory product in Amoeba and jellyfish?

Answer: Ammonia (NH3)

Q18: What are the two main functions of kidneys?


  1. remove toxic metabolic waste products (for example, urea, uric acid, ammonia, salts etc.) from the blood, for excretion
  2. regulate the blood pH, blood water and salt content, blood osmotic pressure, blood pressure (homeostasis)

Q19: What is the purpose of making urine?

Answer: Its purpose is to filter out waste products (urea or uric acid) from the blood.

Q20: How does excretion take place in plants?

Answer: The methods used by plants to get rid of excretory products are:

The oxygen produced during photosynthesis gets removed through stomata.
Carbon dioxide produced during respiration also gets removed through stomata.
The excess of water gets removed through transpiration.
Some waste gets removed by secreting them in the form of gums and resins.
Some waste gets removed along with dead cells by shedding of leaves.
Some waste products are removed through petals, fruits and seeds.
Some waste substances are excreted through roots into the soil around them.
Some waste products are stored in cellular vacuoles.

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