Component 3.4 - Excretion & Osmoregulation In Different Environments

Question 1

What do aquatic organisms excrete?

Answer 1

They excrete ammonia
Highly toxic but extremely soluble in water
Fish gills allow ammonia to diffuse out rapidly (large SA)

Question 2

What do birds, reptiles and insects excrete?

Answer 2

• Convert amino acids into Uric acid
• Uric acid is almost insoluble in water and it is non-toxic
• Requires little water for excretion which allows them to conserve water and be light enough for flight

Question 3

What do mammals excrete?

Answer 3

• Mammals excrete urea

- Toxic (less than ammonia) so tissues and body fluids dilute below toxic concentration

Question 4

What is a behavioural adaptation to conserve water?

Answer 4

• Animals may remain underground where it is cooler and humid
• This reduces water loss by evaporation

Question 5

What happens to surplus amino acids?

Answer 5

Delaminates in liver, amino group forms ammonia which is converted to less toxic urea and then transported into blood plasma

Question 6

Why do beavers have a short loop of Henlé?

Answer 6

They have a large availability of water due to living in an aquatic environment, therefore they only need a short loop of Henlé to absorb enough water for bodily functions.