excretory system

Question 1

nitrogenous wastes

Answer 1

• DNA and amino acids get broken down into NH3
• NH3 is toxic but very water soluble
• large quantities of water must be readily available to organisms that secrete ammonia
• for most terrestrial animals, water availability is limited so NH3 is converted into a less toxic form either urea or uric acid

Question 2

birds, insects, and reptiles

Answer 2

change urea to uric acid which precipitates and forms a solid (saves water) great for developing an egg too. solid and liquid waste both exit through cloaca

Question 3

evolution of excretory system

Answer 3

dynamic homeostasis, osmoregulation, removal of excess N

Question 4

flame cells

Answer 4

• platyhelmenthis and planarians
• filters body fluid and removes wastes and excess salt
• ex: tape worm

Question 5

nephridia

Answer 5

• 1 pair per segment in annelids
• selectively filtered and concentrated waste (excreted through excretory pore)
• earth worm

Question 6

malpighian tubules

Answer 6

• arthropods and terrestrial insects
• tube connects to midgut and filters waste. tube then connects to hindgut where liquid and solid waste are excreted all the time

Question 7

kidney

Answer 7

produce urine, one on either side of the spine (rib 12)

Question 8

nephron

Answer 8

filtering unit of kidney - about 1 million per kidney

Question 9

glomerulus

Answer 9

cluster of capillaries, where filtration of blood occurs

Question 10

filtration

Answer 10

normal BP causes solutes and excess fluid called filtrate to leave blood. RBCs are too big to pass through

Question 11

stuff in filtrate

Answer 11

glucose, salts, vitamins, nitrogenous wastes, excess water

no blood/no bacteria

Question 12

peritubular capillaries

Answer 12

used for reabsorbing solutes and water that we may need later

Question 13

movement of filtrate

Answer 13

Bowman’s capsule -> proximal convoluted tubule -> loop of Henle -> distal convoluted tubule

Question 14

movement of filtrate after nephron

Answer 14

collecting duct -> renal pelvis -> ureter -> bladder -> urethra

Question 15

proximal convoluted tubule

Answer 15

• has microvilli
• passive diffusion of water into renal cortex
• active transport of 3/4 of all the salt into cortex

Question 16

descending loop of Henle

Answer 16

• passive loop of water to cortex and medulla

- no microvilli or mitochondria for pumps here

Question 17

ascending loop of Henle

Answer 17

• passive diffusion of salt in medulla (most of water is gone by now which makes the filtrate hypertonic to its surrounding)
• active transport of salt into cortex (3/4 of all salt is here so the filtrate is pumped against the concentration gradient)
• water impermeable

Question 18

distal convoluted tubule

Answer 18

active transport of salt into cortex

Question 19

collecting duct

Answer 19

• water to cortex (passive)
• salt to cortex (active)
• water to medulla (passive)
• urea moves in and out of the medulla passively depending on environment

Question 20

urea

Answer 20

• mammals
• NH3 is toxic to us and must be converted to urea on liver
• requires little water to excrete

Question 21

glomerular filtration rate

Answer 21

125 ml/min
180 L or 50 gal / day
99% reabsorbed