Marine origins of vertebrates

Question 1

What are the arguments for FW origin?

Answer 1

• glomerular kidney

Question 2

What are the 3 main arguments against FW origin?

Answer 2

• high pressure filtration kidney needed for processing N-wastes
• filtration kidney not restricted to vertebrates
• hagfish are osmoconformers (filtration kidney)

Question 3

What are the major adaptations to re-invasion of salt water in vertebrates? (4)

Answer 3

• lower osmolarity and salinity of body fluids
• gills for osmoregulation and ion balance
• Kidneys form concentrated urine
• salt secreting glands

Question 4

How do kidneys form concentrated urine?

Answer 4

• long loops of henle in wales

Question 5

What are the salt secreting glands in elasmobranchs

Answer 5

• rectal gland