UNIT 16 (CH. 22)GAS EXCHANGE & EXCRETION

How do organisms:

Obtain oxygen and eliminate carbon dioxide?(or vice versa…in plants?)

Maintain osmotic balance?

Excrete nitrogenous waste products? 300

Part 2

EXCRETION OF METABOLIC WASTE

&MAINTENANCE OF OSMOTIC BALANCE

CH. 22.2

EXCRETION OF METABOLIC WASTE…

IS DIFFERENT FROM THE ELIMINATION OF DIGESTIVE

WASTES!

EXCRETION♦What is excretion?

♦removal of wastes produced from metabolism of nutrients (& other non-useful materials)♦CO2♦excess water♦nitrogenous waste

♦All metabolic wastes removed through excretory organs (nephridia, Malpighian tubules, kidneys)♦exception = CO2, excreted with water vapor through lungs

EXCRETION♦Why must cellular wastes be removed?♦can be toxic

♦Which life characteristic does excretion relate to?♦homeostasis

♦mostly from protein metabolism♦& some from nucleic acids

♦amino groups quickly pick up H♦to become ammonia

♦highly toxic♦may be excreted directly or converted to less toxic forms♦urea♦uric acid

NITROGENOUS WASTE

♦ammonia♦excreted by

aquatic organisms♦urea

♦excreted in small amount of water♦ urine

♦uric acid♦insoluble♦excreted as

crystals♦in arid environments

NITROGENOUS WASTES

How is the production of urea/uric acid an adaptation to life on land/dry environments?

H2O conservation

OSMOTIC BALANCE♦concentration of dissolved particles in

liquid inside & outside cell is the same (isotonic)♦What if the concentrations are different?

♦hypotonic♦ cytolysis

♦hypertonic♦ plasmolysis

♦Adaptations for waste removal may also be responsible for maintaining osmotic balance

Importance of H2O: reactions, part of blood, disperse heat

SALT WATER ORGANISMS♦excretion

♦ammonia is soluble♦diffuses from (cells) into water

♦osmotic balance♦naturally in

balance♦no special adaptations needed

FRESH WATER ORGANISMS♦excretion

♦waste diffuses from (cells) into water

♦osmotic balance♦not naturally in

balance (hypotonic environment)♦Adaptations to help maintain?♦contractile vacuole

♦ex. ParameciumVideo of Paramecium--Contractile Vacuole

♦Planaria♦excretion of wastes & osmotic balance♦system of excretory canals & flame cells♦canals branch into excretory ducts♦open as pores on the surface

FRESH WATER ORGANISMS

LAND ANIMALS♦cannot diffuse ammonia

♦must convert to urea or uric acid♦can safely build up in body fluids until excreted

♦wastes transported by blood or tissue fluid

♦system excretes N-wastes & is a factor in osmotic balance♦H2O conservation

emphasizedUric acidUric acid

♦ammonia♦diffuses

through skin♦into soil moisture

♦urea♦eliminated

through nephridia♦filtering organs

LAND ANIMALS: EARTHWORM

♦Malpighian tubules♦filter blood♦reabsorb water ♦uric acid enters

intestine♦excreted thru anus

♦Why is ammonia converted uric acid (crystals)?♦H2O

conservation

LAND ANIMALS: GRASSHOPPER

♦Habitat?♦desert

♦Can survive without drinking H2O.♦How is this

possible?♦gets water from food♦extremely efficient kidneys♦reabsorbs almost all water that passes through them♦excretes very

concentrated urine

LAND ANIMALS: Kangaroo Rat

HUMAN EXCRETION♦Which parts of the human body carryout excretion?♦lungs

♦CO2 & H2O (vapor)♦skin

♦H2O & salts♦= sweat

♦urinary system♦urea, H2O, salts

♦= urine

HUMAN EXCRETION♦What are the parts of the urinary system?♦ kidneys (& associated

blood vessels)♦ main excretory organ

♦ ureters♦ (urinary) bladder♦ urethra

HUMAN EXCRETION: THE KIDNEY

♦main excretory organ

♦3 parts♦outer part

♦cortex♦inner layer

♦medulla♦inner collecting

area♦pelvis

5 STEPS TO HOW KIDNEYS WORK1. blood w/ waste brought

to kidneys from renal artery

2. blood is filtered by nephrons (by diffusion)

3. wastes pass thru ureters to bladder as urine

4. clean blood sent back to body thru renal vein

5. bladder stores urine (until passes out of body thru urethra)

1 million nephrons per kidney!!!

How Kidneys Work Video

♦What is a nephron?♦functional unit

of the kidney♦responsible for filtration of waste from blood

♦~1 million nephrons per kidney!!!

NEPHRON

NEPHRON: STRUCTURE♦nephron consists of:♦Bowman’s capsule

♦cup-shaped♦surrounds glomerulus♦narrows into coiled tubule

NEPHRON: STRUCTURE♦glomerulus

♦mass of capillaries in center of Bowman’s capsule that forms from branch of renal artery♦carries unfiltered “waste-filled” blood to nephron

♦another arteriole loops away from glomerulus & divides into capillaries that surround tubule

NEPHRON: STRUCTURE♦capillaries surround tubule♦merge to form venules & veins♦which merge to form renal vein which returns filtered blood back to body

PROCESSES IN THE NEPHRON♦filtration of blood/

urine production ♦requires three

distinct processes: 1. glomerular

filtration2. tubular

reabsorption3. tubular secretion

♦excretion of urine

♦1. filtration♦“waste-filled” blood

brought to kidney by renal artery♦blood pressure forces plasma from blood in glomerulus into Bowman’s capsule of nephron♦this liquid = filtrate (water, urea, salts, glucose, amino acids & other dissolved materials)

♦large proteins & blood cells do not enter

PROCESSES IN THE NEPHRON

♦2. tubular reabsorption♦filtrate travels

through nephron in tubule♦needed materials are reabsorbed into surrounding capillaries♦ex. most of water, salts, glucose, vitamins, etc.♦by active or passive

transport♦excess materials remain in the collecting duct♦water , urea, salts

♦concentrated fluid = urine

tubule.

PROCESSES IN THE NEPHRON

♦3. tubular secretion♦molecules present in blood

in great excess (or natural poisons) may be removed from capillaries & transferred to tubules for excretion♦often by active transport

♦ex. drugs such as antibiotics♦“clean” blood sent back to body through renal vein

PROCESSES IN THE NEPHRON

♦excretion♦urine (urea,

excess salt, small amount of water) leaves nephron & passes from collecting duct to renal pelvis♦leaves kidney via ureters♦to bladder where stored until once filled & urine is excreted through urethra (urination)

How Kidneys Work VideoPROCESSES IN THE NEPHRON

PROCESSES IN THE NEPHRON

PROCESSES IN THE NEPHRON

PROCESSES IN THE NEPHRON