ectotherms 8

Question 1

Why is excretion important?

Answer 1

To maintain solute homeostasis in body tissues
Remove toxins
To preserve osmotic pressure within the body

Question 2

What are the different methods through which fish regulate their body osmolarity with reference to the environment?

Answer 2

Osmoconformers which conform to the osmolarity of the environment
Hyperosmotic fresh water fish
Osmoregulators which regulate their own osmolarity through discharging excess water

Question 3

What are the different types of kidneys?

Answer 3

Freshwater fish have kidneys packed full of nephrons to produce a large amount of urine
Salt water fish have kidneys focused on water conservation frequently having small or missing glomeruli with the main function to get rid of divalent ions such as Ca2+, Mg 2+
Frogs have kidneys like freshwater fish when in larval form when on land they are focused on water conservation using the bladder as an extra absorption surface
Lizards have kidneys highly focused on water retention with water being reabsorbed both at the kidney and cloaca

Question 4

What are the nitrogenous waste products?

Answer 4

Ammonia, Urea and Uric acid

Question 5

What are the features of ammonia as a waste product?

Answer 5

It is produced by fully aquatic organisms this is due to the compound having a high toxicity so it can’t be allowed to build up within tissues
It has a small molecular mass and is highly soluble allowing it to be easily excreted

Question 6

What are the features of urea as a waste product?

Answer 6

Often used by terrestrial organisms and is produced by the ornithine cycle
Sharks use this compound as an osmotic filler to prevent water loss to the marine environment
Lungfish use this product when in air (switch to ammonia in water)
This metabolite is non toxic

Question 7

What are the features of uric acid as a waste product?

Answer 7

This is used by animals with limited access to water

It is highly insoluble non toxic and the waste product used in the amniotic egg

Question 8

What is unique with how amphibians gain water?

Answer 8

They don’t drink and instead absorb it directly through the skin by pressing their ventral surface on damp soil or moss this can allow them to absorb 6-10g of water per hour