animal excretion Flashcards
1
Q
what is homeostasis and importance of water balance
A
- maintaining a ‘steady state’ or relatively constant internal environment despite fluctuations in the external environment
- favourable conditions
- maintain water balance, regulate what happens
- animals rely on a relatively constant water and solute composition of the body
- not the same water and solute composition, lack of fluctuation,
2
Q
how does loss of cellular function occur
A
- optimal enzyme function relies on precise pH / temperature
- membrane permeability can be affected by temperature
- waste must be removed (maintain gradient in kidney)
- water balance relies on regulation of ionic conc.
3
Q
how does a concentration gradient aid in transport
A
- varying composition of extra and intra cellular fluid
- allows gradient to be formed
- this is how diffusion occurs
- difference between high and low or one would be static
4
Q
how is water balance maintained
A
- water / solutes are exchanged continuously between organism and environment
- intake of food and fluids
- respiration
- elimination of wastes
- osmosis / diffusion (aquatic) or evaporation from surface (terrestrial)
- environment changes rate at which you can maintain water balance
5
Q
what is osmo-conforming
A
- do not actively regulate osmolarity and conform to environment in which you live
- tissue = isotonic to environment, only seen in marine invertebrates (aqueous environment = stable, little changes in osmotic pressure)
- smaller animals, sponge (simple, osmoconform)
6
Q
what is osmo-regulating
A
- actively regulate osmolarity to achieve homeostasis
- tissue: can be hypo or hyper tonic to environment so one doesn’t experience osmotic stress
- marine fish, freshwater animals, terrestrial animals
7
Q
describe osmotic regulation in freshwater fish
A
- hypotonic environment: gain water, lose salt, cells burst = not effective at gas exchange
- movement: across body is minimal, majority occurs across gills (diffusion and osmosis)
- gills: epithelial cells, direct contact with water (respiration), efficient, gain water / lose salt
- homeostasis: large glomerulus (filter a lot of blood, very dilute water), gills (active salt pumps, reabsorption of NaCl), intestinal walls (reabsorb salt across gut)
8
Q
describe osmotic regulation in marine fish
A
- drink water: gain salt (seawater) via attaining water through lack of filtering
- urine: little urine secreted
- gills: active salt pumps, secrete salt across gills
- faeces: reabsorb salt and transfer it via faeces
9
Q
describe water balance in terrestrial animals
A
- evaporation is an issue for terrestrial animals like osmosis is an issue for marine animals
- atmosphere has very low water potential (-30 mP), transpirational pull like plants)
- major source of water loss
- mouse: nocturnal, burrow (humid, affects evaporative pull, similar to plants)
10
Q
what are nitrogenous waste products
A
- impact on water balance
- produced from proteins / nucleic acid
- excreted as ammonia, urea and uric acid (dependent on habitat and water balance)
- properties: differing solubility in water, water loss, toxicity, energy cost (ATP required to make molecule)
11
Q
what is ammonia (NH3)
A
- solubility in water: highly soluble (1 N atom)
- water loss: very high
- toxicity: very toxic, strong base, irritant, raises pH, affects mitochondria, detoxification
- energy cost: none
- excreted by: aquatic animals in urine across gills, cannot be stored in body
12
Q
what is urea
A
- solubility in water: moderate solubility (2 N atoms)
- water loss: moderate loss
- toxicity: less toxic than NH3
- energy cost: moderate
- excreted by: mammals, amphibians, sharks, rays, land turtles in urine
13
Q
what is uric acid
A
- solubility in water: insoluble in water (4 N atoms)
- water loss: very low
- toxicity: non-toxic (storage)
- energy cost: high (24 ATP for 1)
- excreted by: birds, reptiles, insects via faeces (paste)
14
Q
what are different methods of excretion for sharks / rays / slater bugs
A
- aquatic = NH3
- terrestrial = urea / uric acid
- changes: tadpoles (NH3 = aquatic) and frogs (urea = terrestrial)
- sharks / rays: secrete / store urea, ability to osmoregulate, less toxic (won’t poison or be an irritant), doesn’t require as much water, maintains osmotic tissue
- slater bug: secrete NH3 (terrestrial), live in soil (moist environment), able to secrete ammonia as a gas and are not effected by toxicity
15
Q
describe the structure of the kidney
A
- nephron: functional unit of kidney, long tubule / glomerulus (network of capillaries)
- bowman’s capsule: cup like sac / structure, contains glomerulus, receives filtrate
- proximal tubule: reabsorption / secretions of substances
- loop of henle: creates osmotic gradient
- distal tubule: regulated by hormones, reabsorption of Na and Cl at expense of K
- collecting duct: regulated by hormones, reabsorption of H2O
