Excretory systems

Question 1

What is waste management?

Answer 1

• All living things take materials from their environment
• Chemical reactions inside cells modify these materials and waste is produced.
• Chemical reaction in organisms- metabolism
• Removal of metabolic wastes produced by organisms is called excretion

Question 2

How does the excretory systems excrete CO2?

Answer 2

• CO2- metabolic waste product of cells. Produced by chemical reactions of respiration.
• Excreted by lungs in humans, gills in fish, tracheal system in insects.

Question 3

What are examples of nitrogenous waste?

Answer 3

• All contain nitrogen
• Ammonia
• Urea
• Uric acid

Question 4

How does excretory system excrete proteins?

Answer 4

• Nutrient protein is eaten-> broken down from digestion into amino acids -> amino acids transported to cells where cells produce new protein
• Excess amino acids can’t be stored by cells in the body
• Transported into bloodstream into liver
• Liver removes amine groups from amino acids by deamination
• Waste products of this process is ammonia-> poisonous cells must be removed

Question 5

Excretion in fish

Answer 5

• Ammonia transported in the bloodstream to the gills into the surrounding water.

Question 6

Excretion in mammals

Answer 6

• Ammonia produces in deamination is converted by liver into urea
• Urea is less toxic than ammonia-> cells can tolerate higher concentration of urea than ammonia
• Organism lose less water when excreting urea instead of ammonia

Question 7

Excretion in birds

Answer 7

• The black blob is the bird’s stool (the leftover products of digestion).
• The white powder is uric acid.
• Birds have only one body opening through which both uric acid and body waste pass.
• Birds (and most adult insects) convert their nitrogen
  waste from ammonia to urea and then to uric acid.