osmoregulation and excretion Flashcards
1
Q
osmoregulation
A
regulation of water and ion balance in bodily fluids (e.g. lymph, blood, interstitial fluid, cytoplasm, haemolymph)
2
Q
excretion
A
elimination of toxic metabolic waste products e.g. CO2, H2O, nitrogenous compounds
3
Q
link between osmoregulation and excretion
A
osmoregulatory and excretory organs are often the same e.g. kidneys
4
Q
factors involved in osmoregulation
A
- solvent (water)
- solutes (ions)
- semi-permeable membranes
- diffusion
- osmosis
5
Q
isosmotic
A
- animal has the same osmotic concentration as the external environment (doesn’t truly exist as animals have different ions to the outside environment)
- equal exchange of water and ions between the organism and the external environment
6
Q
hyperosmotic
A
animal has a higher osmotic concentration than the environment (greater proportion of ions)
- organism needs to counteract the diffusion of water in and ions out using ion pumps (active transport)
7
Q
hyposmotic
A
- animal has a lower osmotic concentration than the environment (higher proportion of water)
- organism needs to counteract the diffusion of water out and ions in using ion pumps (active transport)
8
Q
excretory mechanism in many aquatic organisms
A
- eliminate ammonium via gills
- thin, highly permeable and vascularised
9
Q
ammonotelic organisms
A
organisms that can eliminate NH4+ straight away, quickest and most energy efficient. Most aquatic organisms
10
Q
excretory mechanisms in terrestrial organisms
A
- limited access to water, so NH4+ cannot be used as a waste product as it cannot be released immediately and is too toxic to be allowed to accumulate
- converted into a less toxic alternative so can accumulate to a degree
11
Q
ornithine cycle
A
process of deamination in vertebrates in liver, costly, requires water for elimination
12
Q
urea
A
- excreted by kidneys
- ureotelic animals include mammals, amphibians, some reptiles, cartilagenous fish
13
Q
uric acid
A
- solid and non toxic, eliminated need for bladder with water
- excreted by hind gut, space and weight saving
- uricotelic animals include terrestrial arthropods, snails, snakes, birds, many reptiles
14
Q
osmoconformers
A
- primarily marine invertebrates
- animal conforms to the osmotic concentration of the environment
- blood/haemolymph is in an isoosmotic state
Some osmoconformers regulate solutes but maintain osmotic concentration (ionic
regulators)
15
Q
osmoregulators
A
- animals in brackish and freshwater environments
- animal regulates its body fluids independent to external environment
- maintains blood/haemolymph at a certain osmolarity
16
Q
marine invertebrates
A
- osmoconformers
- sea water and ECF (blood) isotonic (same osmolarity)
- ICF (cytoplasm) has less Na+ (toxic to cells) and more K+ to replace Na+ (cytoplasmic safe ion)
- ICF has same osmotic pressure as ECF and sea but different ion concentrations
- ICF ion concentration regulated by ion pumps
17
Q
estuarine/intertidal/brackish invertebrates
A
- face changes in salinity, hostile environment, so primarily regulators
- all marine in origin
- some are osmoconformers e.g. mussels
18
Q
stenohaline
A
restricted to marine envrionments
19
Q
Mytilus edulis (Mussel)
A
- conform ECF
- regulate ICF
- have a ‘tidal clock’ so can use behavioural mechanisms to prepare for change in salinity such as closing shell first as it it less energetically expensive
- use amino acids to help prevent changes in ICF
- amino acids transported out of cell into blood and get broken down into ammonium (NH4+)
- release of NH4+ coupled with uptake of Na+
20
Q
factors affecting the movement of solutes and solvents across a semi-permeable membrane
A
- gradient
- membrane permeability (affects speed of diffusion)
- surface area
21
Q
ion pumps
A
- energetically expensive as constant movement of ions are needed to resist net movement of ions down a concentration gradient
- pumps often exchange more than one ion e.g. Na+/K+ ATPase
- symport pumps transport ions in the same direction
- antiport pumps transport ions in opposite direction
22
Q
water regulation
A
- water is small and polarised
- pumps cannot pump water molecules
- pumps transport ions and water moves passively via osmosis down a concentration gradient (low osmolarity to high osmolarity)
- ion pumps transport ions close to membrane, creating an area of localised high osmolarity, water diffuses in
22
Q
ammonium
A
- NH4+
- formed from deamination in the liver, breakdown of excess amino acids
- toxic, highly reactive and very alkaline
- highly soluble, so aquatic organisms can release it immediately into the environment down a concentration gradient through excretory organs
22
Q
nitrogen
A
- cannot be stored by body
- some in amino acid pool in blood
23
Q
freshwater invertebrates
A
- all osmoregulators as freshwater is too dilute
- hypertonic blood
- highest level of membrane impermeability to ions and water
- primarily lose ions and gain water through gills (thin membrane, highly vascularised)
- use excretory systems to regulate ECF, produce lots of very dilute urine (Daphnia >200% body mass per day)
24
Q
hyper-hyposmotic organisms
A
- can live in freshwater and marine environments
- very rare
- ECF hyperosmotic in freshwater and hyposmotic in sea water
- include crustaceans such as Chinese mitten crab, Palaemonetes (salt marsh shrimp) and Artemia (brine shrimp)
25
Q
Artemia, hyper-hyposmotic organism
A
- can tolerate x3 strength of sea water
- salt glands on gills very good at osmoregulation
- shrimp drinks salt water and eliminates Na+ using salt glands, Cl- follows passively
26
Q
terrestrial invertebrates
A
- limited access to water, need to be able to uptake it and minimise water loss
- many have behavioural responses to maintain moist environment
27
Q
hygrophiles
A
live within moist environments
28
Q
terrestrial inverts, water uptake
A
- can be fluid feeders, taking up water from eating or drinking (water can be obtained from metabolic catabolism of sugar)
- can take up water directly from moist air e.g. spiders, mites
29
Q
water uptake in woodlice
A
- biramous appendages, legs are made up of two structures
- the top structure can absorb water from moist surfaces using capillary action
30
Q
osmoregulatory organs in invertebrates
A
4 main types:
- contractile vacuoles (protozoans, sponges and also protists)
- nephridial glands (platyhelminthes)
- antennal/green glands
- malpigian tubules
31
Q
contractile vacuoles
A
- protozoans and sponges
- one vacuole or multiple
- very small so difficult to monitor and study, the action of these vacuoles are only a hypothesis
- freshwater paramecium (protist) have them to maintain hyperosmotic ECF
- membrane bound, impermeable to water
- lined with radial canals
- surrounded my mitochondria (active)
- contains actin and myosin for contraction
32
Q
action of contractile vacuoles
A
- water flows into channels through osmosis
- ions flow into channels
- ions actively removed, water left behind
- water flows into vacuole and collects
- vacuole meets external membrane and contracts, expelling water from the cell
33
Q
protonephridia
A
- earliest evolutionary type of nephridia, seen in platyhelminthes (flatworms)
- internal network of blind ending tubules which connect to
the environment via nephridophores - tubules are nephridoducts
- cap cell on end of tubules with a large flagellum/a projecting into the tube
- the cap cell has interdigitations with the tube cell, creating filtration sites
- tubules lined with cilia
34
Q
action of protonephridia
A
- flagella beats creating a negative pressure gradient at the end of the tube, drawing fluid within animal through digitations into tubule, filtering it
- cilia beat forcing fluid rapidly down length of the tubule, maintaining the pressure gradient and ensuring water doesn’t diffuse back into the animal
- tubule is lined with ion pumps transporting ions back into the animal
- primary filtrate exits animal through nephridophore
35
Q
metanephridia
A
- evolutionarily linked with protonephridia, more complex
- common to annelids, molluscs etc
- open tubules from coelomic cavity which exit at the exterior at a nephridiopore
- coelomic fluid passes into collecting tubule via nephrostome (ciliated funnel)
- selective reapsorbtion turns primary urine into secondary urine
- bladder stores urine
36
Q
cap cells
A
2 types:
- flame cells with several flagella
- solenocytes with a single flagellum
37
Q
arthropods
A
- require different mechanism due to their
open circulatory system. - Increase in complexity and reduction in the number required
- Aquatic crustaceans excrete NH4+ across their gills, they have antennal or green glands
- Terrestrial arthropods excrete mainly uric acid, urea etc
38
Q
antennal/green glands
A
- eliminate divalent ions in aquatic crustaceans (NH4+ eliminated through gills)
- terminates at nephropore at base of 2nd (larger) antennae
- blind-ending at an end-sac (due to open circulatory system)
- lined with podocytes (same as mammalian kidney)
- opens into labyrinth (spongy and large surface area, reabsorbs ions)
- through canal into bladder
- only 2 needed as very selective, efficient and complex
39
Q
action of antennal glands
A
- pressure generated in haemolymph causes water and ions in haelocoel to pass between podocytes (filtration) into end sac
- labyrinth reabsorbs ions
- through canal (some reabsorption) into bladder as secondary urine
- stored and released via nephropore
40
Q
Carcinus, estuarine crab
A
- can tolerate a degree of freshwater
- is able to alter composition of urine to combat uptake of water (produces lots of very dilute urine when in freshwater)
41
Q
malpigian tubules
A
- insects
- blind ending tubules which extend from mid-gut between mid and hind gut
- pumps that line tubules actively pull nitrogenous waste (soluble potassium urate) and other ions from haemolymph and water flows passively
- pumps in hind gut actively pumps K+ out, water follows passively
- K+ recycled, precipitation of potassium urate into uric acid (solid)
- constant recycling of water, no bladder needed, very effective at retaining water
42
Q
vertebrate osmoregulatory organs, integument permeability
A
integument = tissue surrounding an organism’s body
- permeability varies
- amphibians (mostly freshwater) permeable
- fish impermeable (scales)
- reptiles, birds, a few desert amphibians, terrestrial mammals impermeable
- secondary aquatic mammals impermeable
43
Q
marine vertebrates
A
3 main groups:
- osmoconformers, blood very similar in composition as seawater, hagfish
- ionoregulators but osmoconformers, blood isosmotically but ionically different, elasmobranchs (sharks), Rana, coelocanths etc
- osmoregulators, blood approximately 1/3 of sea water, ionically and osmotically different, teleosts
43
Q
hagfish
A
- in deep sea, scarce food availability (yearly)
- can uptake nutrients across skin
- conserve energy by doing nothing, so does not waste energy by osmoregulating
- basal simple vertebrate group, only vertebrate with same osmotic strategy as invertebrates
44
Q
hagfish, osmotic strategy
A
- ECF has slightly higher osmolarity than sea water
- slightly more Na+ and Cl-
- allows hagfish to slowly take up water passively to be able to eliminate heavy divalent ions (so has lower levels of divalent ions in ECF than blood)
- slightly regulate ECF but classed as osmoconformers
- regulates ICF
- kidney removes divalent ions in urine
45
Q
elasmobranchs (sharks, skates and rays), coelocanths and Rana, osmotic strategy
A
- isosmotic but lower Na+ and Cl- levels in blood, osmoregulators
- top up with urea ( and other organic osmolytes, TMAO that offsets toxicity of urea by stabilising blood proteins) to bridge osmotic gap
- kidneys reabsorb urea
- no net movement of water as isosmotic
- passive uptake of Na+ and Cl-, eliminated by rectal gland, kidneys and maybe gills
46
Q
marine teleosts (bony fish), osmotic strategy
A
- osmoregulators and ionoregulators
- hyposmotic, constantly lose water and gain salts through gills
- drink sea water as it is the only way to replace water loss
- 2 main osmoregulatory organs
- gills, eliminate Na+ and Cl- from blood (active transport, chloride cells)
- kidneys, remove divalent ions
47
Q
marine teleosts, structure of gills
A
- contain alternating chloride and accessory cells
- highly effective and conserved
- apical membrane of chloride cell is highly permeable to Cl-
- basal membrane of chloride cell is highly convoluted, increasing surface area to increase number of ion pumps
- basal membrane has two different ion pumps, transport Na+ and Cl- into chloride cell and Na+ATPases transport Na+ back out of chloride cell into blood
- accessory cells can regulate the opening and closing of chloride cells depending on ion levels in ECF
48
Q
marine teleosts, action of gills
A
- active transport of Na+ and Cl- across the basal membrane into chloride cell
- Na+ATPases actively transport Na+ back into the blood
- very high levels of Cl- accumulate in chloride cell
- Cl- diffuses out of highly permeable apical membrane into sea
- generates local negative charge in surrounding sea water
- Na+ is pulled through passively down gradient between accessory and chloride cells into the sea
49
Q
freshwater vertebrates, osmotic strategies
A
- always hyperosmotic, constantly gain water and lose solutes
- do not drink water
- produce lots of very dilute urine
- kidneys reabsorb ions through active transport, high filtration rate
50
Q
freshwater teleosts (bony fish), osmotic strategy
A
- Na+ and Cl- actively taken up from environment by gills (linked to CO2 elimination), similar mechanism to marine teleosts, but opposite action
- kidneys produce lots of very dilute urine, active reabsorption of ions
51
Q
freshwater amphibians, osmotic strategy
A
- gain water and lose ions through skin (relatively permeable)
- integument, Na+ and Cl- actively taken up from environment (linked to elimination of CO2)
- kidneys produce lots of very dilute urine, active reabsorption of ions
52
Q
terrestrial vertebrates, water loss
A
Main challenge is water loss/conservation
dehydration through:
- thermoregulation, evaporative cooling
- eliminating nitrogenous waste, urea
- ventilation, gases dissolves in fluid in respiratory organs
53
Q
terrestrial amphibians, strategies to prevent water loss
A
- behavioural including seeking shade, nocturnal, living underground
- very short developmental time, tadpole stage synchronised to water availability
- eliminate nitrogenous waste using uric acid (solid)
- highly impermeable integument (not completely, still used for respiration)
- reduced metabolic rate
54
Q
terrestrial amphibians water loss prevention strategies, Ranoidea spp.
A
- live in Australia
- burrows and secretes impermeable mucous cocoon during summer
- stores water up to 30% of body weight in bladder that can be reabsorbed
55
Q
terrestrial reptiles, water conservation strategies
A
- dry scaly skin is very effective at reducing evaporative water loss
- eliminate nitrogenous waste as uric acid (solid)
56
Q
terrestrial mammals water conservation strategies, Kangaroo rat
A
- adapted to very dry environment in southern USA and Mexico
- if air humidity >10% it does not need to drink water as so effective at reducing water loss
- behavioural strategies, nocturnal, lives underground in a burrow
- does not sweat or pant, relies almost entirely on behavioural thermoregulation strategies
- very dry faeces
- very concentrated urine (long loops of Henle)
- nasal countercurrent exchange system traps water leaving nose through exhalation
- eat seeds and grains, majority of water obtained is through metabolism
57
Q
vertebrate kidney
A
- main osmoregulation organ of terrestrial mammals
- the are many nephrons in a kidney
- ability of the kidney to concentrate urine is linked to the animals environment
58
Q
vertebrate kidney, the nephron
A
- glomerulus
- proximal convoluted tubule
- loop of Henle
- distal convoluted tubule
- collecting duct
59
Q
nephron, the glomerulus
A
- blood pressure forces compounds from the glomerulus (ball of capillaries) into the Bowman’s capsule (blind ending tubule)
- filtrate is formed in the Bowman’s capsule, including water, ions, urea, glucose, amino acids, H+
- large molecules are retained
60
Q
nephron, proximal convoluted tubule
A
- active reabsorption to recapture ions, water and valuable nutrients (active transport, facilitated diffusion, cotransport)
- some active secretion into the PCT e.g. drugs and toxins
61
Q
nephron, loop of Henle
A
- countercurrent concentrating system
- ascending limb is impermeable to water, Na+ and Cl- is pumped out, increasing the osmolarity of the medulla and decreasing the osmolarity of the ascending limb
- descending limb is permeable to water and has low permeability to ions, water moves out to the high osmolarity in the medulla
62
Q
nephron, distal convoluted tubule
A
- reabsorption of salts, Ca2+ and regulation of blood pH
63
Q
nephron, collecting duct
A
- ADH/vasopressin released by posterior pituitary (regulated by osmoreceptors in hypothalamus)
- controls permeability of collecting duct
- absence = permeability decreased, water cannot pass out of filtrate, dilute urine formed
- presence = more permeable, water reabsorbed, concentrated urine formed
64
Q
different types of nephrons
A
- concentrating ability depends on how long the loop of Henle is, how much it extends into the medulla
- juxtamedullary nephrons have long loops of Henle
- cortical nephrons have short loops of Henle
- desert rodents etc need concentrated urine so have lots of juxtamedullary nephrons
- beavers and pigs need dilute urine so have lots of cortical nephrons
- humans have a mixture of both
65
Q
polar teleosts
A
- hyposmotic blood means it has a higher freezing point than the sea water around it
- have antifreeze glycopeptides in blood
- kidneys do not operate via ultrafiltration or antifreeze proteins would be filtered out, so glomeruli are absent
- eliminate ions through active secretion
66
Q
marine mammals
A
- hypotonic blood
- no free freshwater so water limited
- baleen/mysticeti whales eat marine invertebrates (high salt load)
- odontoceti/ toothed whales eat marine vertebrates (less high salt load)
- both produce very concentrated urine, hyposmotic to blood and sea water
- very long loops of Henle
67
Q
marine reptiles
A
- hypotonic blood
- no loops of Henle, kidney doesn’t eliminate salt, can’t produce very dilute urine
- eat marine invertebrates, corals and seaweed (high salt load)
- have salt glands very similar to marine teleosts (highly conserved)
- turtles have salt glands in eyes, crocodiles have salt glands on tongue, iguanas (and birds) have salt glands in nasal passage
