Excretion Part 1 (10.1)

Question 1

What is osmoregulation?

Answer 1

• process where animals control solute concentration

- balance water gain and loss

Question 2

What happens in osmoregulation?

Answer 2

• maintenance of fluid environment of cells, tissues & organs
• keeping relative concs of H2O & solutes within fairly narrow limits
• ions maintained at concs. permitting normal activity of muscles, neurons & other cells
• based on controlled movement of solutes between internal fluids & external environment.

Question 3

Whats happens on a hyperosmotic side?

Answer 3

• higher solute conc.

- lower free H2O concentration

Question 4

Whats happens on a hypoosmotic side?

Answer 4

• lower solute concentration

- higher free H2O concentration

Question 5

What is osmolarity?

Answer 5

• unit of measurement of solute concentration (moles solute/L)

Question 6

What are the conditions of an osmoconformer?

Answer 6

• isoosmotic with its surroundings
• mostly marine animals
• stable environment

Question 7

What are the conditions of an osmoregulator?

Answer 7

• regulates internal osmolarity independent of external environment
• marine, fresh water & land animals
• changeable environment

Question 8

How does osmoregularatory work in a marine fish?

Answer 8

• they lose water by osmosis

- balance water loss by drinking large amounts of seawater

Question 9

How does osmoregularatory work in a freshwater fish?

Answer 9

• have problems gaining water by osmosis

- have problems losing salts by diffusion

Question 10

What are the energetics of osmoregulation?

Answer 10

• maintance requires alot of energy
• movement of water in/ out is caused by energy expended to maintain osmotic gradients
• energy cost: surroundings, movement of water on the surface, pumping mechanisms
• energy cost decreases by having body fluids adapted to salinity of animals habitat

Question 11

What happens in excretion?

Answer 11

• metabolic waste must be dissolved in water to be “excreted”
• the type & quantity of waste excreted may have a large impact on water balance
• the breakdown of nitrogenous compounds releases ammonia

Question 12

How is ammonia used in excretion?

Answer 12

• animals that excrete nitrogenous waste as ammonia need lots of water
• ammonia is released across the whole body surface
• less suitable for land animals, as less access to water

Question 13

How is urea used in excretion?

Answer 13

• produced in the liver, product of ornithine cycle
• low toxicity
• can be transported in the circulatory system
  energetically expensive
• used by mammals

Question 14

How is uric acid used in excretion?

Answer 14

• used by birds, insects, reptiles
• relatively non-toxic
• more energetically expensive to produce than urea