Waste

Question 1

How is nitrogenous waste generated?

Answer 1

Breakdown of proteins and nucleic acids. Amino group (NH2) is removed. Occurs in:
the digestive system
For energy or conversion to fats/carbohydrates –

Question 2

Why does nitrogenous waste need o be removed from the body?

Answer 2

Because it forms a toxic ammonia, which raises the pH of body fluids and inhibits key enzymes

Question 3

In what form is the nitrogenous waste excreted by most aquatic animals?

Answer 3

As ammonia

Question 4

In what form is the nitrogenous waste excreted by mammals, amphibians and sharks?

Answer 4

As urea

Question 5

In what form is the nitrogenous waste excreted by reptiles and birds?

Answer 5

As uric acid

Question 6

What are the benefits of excreting ammonia?

Answer 6

Doesn’t require energy, is a small molecule, so very rapid diffusion.

Question 7

What is necessary for excteritian via ammonia?

Answer 7

Lots of water, as is very toxic and can only be tolerated at very low concentration

Question 8

Where is urea produced?

Answer 8

In the liver, from ammonia and carbon dioxide

Question 9

Why can’t terrestrial animals excrete ammonia?

Answer 9

Because has to be stored in the body at low concentrations in large volumes of water, which most terrestrial animals don’t have access to

Question 10

What are the benefits of urea?

Answer 10

1000x less toxic than ammonia, can be transported in the circulatory system and stored safely at high concentration, Much less water is lost.

Question 11

What are the costs of extortion by urea?

Answer 11

Requires energy

Question 12

What is the benefits of exerting uric acid?

Answer 12

Relatively non toxic and insoluble in water, therefore can be excreted as a semisolid, paste with little water loss. Useful if developement takes place inside an egg

Question 13

What are the costs of uric acid?

Answer 13

Even more energetically expensive than urea

Question 14

How does habitat influence ammonia excretion in frogs?

Answer 14

Tadpoles excrete ammonia, but adults excrete urea

Question 15

How do protozoa excrete waste?

Answer 15

Via a contractile vesicle

Question 16

How so annelids, molluscs and Platyhelminthes etc excrete waste?

Answer 16

Via nephridia, a tubule open to the exterior, collecting tubules throughout the body lead to this

Question 17

How do Insects excrete waste?

Answer 17

Malpighian tubules, spread throughout the body in the haemolymph and open into the insects hindgut for excretion

Question 18

How do vertebrates excrete waste?

Answer 18

Via the kidneys. Consists of highly organised tubules that are closely associated with a network of capillaries

Question 19

Why do insects excrete uric acid?

Answer 19

Have relatively high SA:V ratio, which means high rate of water loss, so uric acid excretion conserves water

Question 20

What are the mechanisms of excretion in the Malpighian tubules?

Answer 20

Salts and nitrogenous waste actively transported into gut lumen, water follows by osmosis. Reabsorption occurs the rectum, H20, ions and valuable organic molecules pumped back into heamolymph. Water follows by osmosis
Uric acid is excreted as nearly dry matter in faeces

Question 21

What happens during filtration in the kidneys?

Answer 21

Fluids in the blood are collected

Question 22

What happens during reabsorption?

Answer 22

Selective transport of needed substances back to

tissue fluid/blood

Question 23

What happens in the renal cortex?

Answer 23

Ultrafiltartion

Question 24

What role of the renal medulla?

Answer 24

Regulate salt and water concentration in the blood

Question 25

What is a nephron?

Answer 25

Consists of a single long table and a ball of capillaries called the glomerulus, Which is where the bowman capsule is effective

Question 26

When does filtration occur?

Answer 26

As blood pressure forces fluid from the blood in the glomerulus into the lumen of the bowman’s capsule. This is non selective filtration - all small molecules will pass through

Question 27

Where does fluid travel after being filtered in the bowman’s capsule?

Answer 27

To the proximal table, where water and salts are reabsorbed

Question 28

What happens in the loop of hence?

Answer 28

Has a descending and ascending limb. In the descending limb, water leaves the filtrate which increases its osmolarity. In the ascending limb, salt leaves the filtrate, which decreases the osmolarity.

Question 29

What does this reabsorption process mean for excretion?

Answer 29

Can produce hyper osmotic urine, where there is a much higher solute concentration than the body fluids

Question 30

What is the counter current multiplier system?

Answer 30

Tubule fluid in descending limb flows in opposite direction from ascending limb, which means there is a steep osmotic gradient. Loops increase solute potential of surrounding tissue fluid setting up a concentration gradient

Question 31

Where does fluid from the kidneys go?

Answer 31

Flows from all of the collecting ducts of the kidney into the renal pelvis, which is drained by the uterus

Question 32

What is the homeostatic negative feedback loop that takes place in water regulation?

Answer 32

Increased osmolarity of extracellular fluids is detected by osmoreceptors, which sends signal to hypothalamus. This increases water permeability of the distal tubule and collecting duct, so osmolarity decreases.