Excretion

Question 1

Name 3 waste products from the breakdown of food.

Answer 1

• CO2
• H2O
• Nitrogenous waste products (ammonia) from protein & amino acid metabolism

Question 2

What does deaminated mean?

Answer 2

Removal of NH2 group from amino acid

Question 3

What are the 3 most common types nitrogenous waste?

Answer 3

• Ammonia
• Urea
• Uric acid/urates

Question 4

What is an ammonotelic organism?

Answer 4

An organism that excretes ammonia

Question 5

What is a ureotelic organism?

Answer 5

An organism that excites urea

Question 6

What is a uricotelic organism?

Answer 6

An organism that excretes uric acid

Question 7

What is the chemical compound of ammonia?

Answer 7

NH3

Question 8

At typical body pH, what does ammonia react with and what does it form?

Answer 8

• Hydrogen
• Forms the ammonium ion (NH4+)

Question 9

Why does Ammonia need to be very dilute?

Answer 9

It is highly soluble so has to be dilute to avoid harmful effects

Question 10

Give 3 feature of urea (NH2)

Answer 10

• Soluble
• Diffuses rapidly across membranes
• Much less toxic than ammonia

Question 11

Where is urea synthesised?

Answer 11

In liver in ornithine cycle

Question 12

Give 3 features of uric acid

Answer 12

• Purine
• Very low toxicity
• Relatively insoluble in water so can be excreted as semi-solid paste or as dry pellets

Question 13

What is the main end product in some spiders, scorpions, ticks and other arthropods?

Answer 13

Guanine

Question 14

What is the main excretory product of most heterptera (bugs) + stick insect?

Answer 14

Allantoin

Question 15

What can be found in some mammals but only in very low concentrations?

Answer 15

Creatine & creatinine

Question 16

Why isn’t ammonotelism found in most terrestrial species?

Answer 16

Due to its toxicity & high solubility, which would put a severe strain on terrestrial animal’s scarce water resources

Question 17

What are some advantages of ureotelism & uricotelism to terrestrial animals?

Answer 17

• Both products contain > nitrogen than ammonia & as they are relatively non-toxic, they can be allowed to accumulate in the body to much higher levels than could ammonia
• This is useful when water is in short supply because terrestrial animals can reduce or cease urine production to conserve water and allow urea/uric acid to accumulate

Question 18

Are aquatic invertebrates ammonotelic, ureotelic or uricotelic?

Answer 18

Ammonotelic

Question 19

How do aquatic invertebrates lose their ammonia?

Answer 19

Across the gills & integument

Question 20

Give an example of an animal that can be both ammonotelic & ureotelic

Answer 20

• Lungfish
• Ammonotelic in water
• Ureotelic when aestivating
• Urine production decreases to conserve water & urea accumulates

Question 21

Are amphibians ammonotelic, ureotelic or uricotelic?

Answer 21

• Ammonotelic as tadpoles
• Ureotelic as adults

Question 22

Are reptiles & birds ammonotelic, ureotelic or uricotelic?

Answer 22

• Uricotelic

Question 23

Are mammals ammonotelic, ureotelic or uricotelic?

Answer 23

• All mammals are ureotelic regardless of habitat