4 - Fishes 3

Question 1

Importance of excretion and osmoregulation

Answer 1

• major function of kidneys and gills

- marine and freshwater environments associated with different osmoregulatory challenges for fish

Question 2

Freshwater toleosts excretion/osmoregulation

Answer 2

• fish has higher osmotic concentration than water
• water diffuses passively into fish and ions passively diffuse into environment
• Large volume of dilute urine
• active uptake of salt via gills (and kidneys)

Question 3

Saltwater toleosts excretion/osmoregulation

Answer 3

• environment has higher osmotic concentration than fish
• water passively diffuses out of fish and ions passively diffuse into the fish
• Fish drinks seawater and produces small volume of urine
• active transport of ions out of fish

Question 4

`Diadromous fish

Answer 4

migrate between fresh and seawater

Question 5

How do diadromous fish do it

Answer 5

hormonal control of ion transport mechanisms in response to environmental or developmental cues is the best explanation

Question 6

Elasmobranchs (sharks) excretion/osmoregulation

Answer 6

Unique

• retain urea in body fluids to make the same osmotic concentration as seawater
• ion concentrations are controlled by active transport via the rectal gland

Question 7

Nitrogenous wastes

Answer 7

most ammonia, some urea

Question 8

Reproductive strategies in bony fish

Answer 8

oviparous

eggs fertilized externally and develop outside the female from stored yolk

Question 9

Reproductive strategies in elasmobranchs

Answer 9

Ovoviviparous
embryos develop in a modified oviduct
Nutrients supplied from yolk within eggs\
Some have egg cases

Question 10

Some elasmobranchs and bony fish reproductive strategies

Answer 10

Viviparous

Internal development with some or all nutrients from the female

Question 11

Parental care?

Answer 11

Most oviparous species abandon their eggs after fert.
Some parental care
Mouth brooding
Defend eggs and early life stages
Fewer eggs=higher investment of parental care/resources to increase odds of survival