Water Balance in Terrestrial Organisms Flashcards
1
Q
Osmoregulation in terrestrial animals
A
- Tendency towards water loss unless humidity is more than 99%
- Higher temperature = more water loss
2
Q
Terrestrial strategies to avoid dessication
A
- Tolerance
- Escape/Avoidance
- Regulating water uptake
- Storing water
- Reducing water loss
3
Q
Tolerance in camels
A
- Camels lose water from fat first, not blood
- Thick capillaries for thicker blood
- More albumin in blood binds water, makes blood thicker
- Kidneys and intestine reabsorb water: feces is vert dry and urine concentrated
- Specially shaped blood cells orient so can move through thicker blood
- Blood cells smaller but can expand more
- Avoid cooling through evaporative mechanisms
4
Q
Escaping Dehydration
A
- Drought avoiders; ex: plant seeds that wait until it rains to sprout (triops eggs that wait for water to hatch)
- Resistant stages (tardigraves)
- Estivation; triggered by dryness (ex: reptiles, frogs, lungfish, gastropods, insects, some mammals; fat-tailed dwarf lemur)
- Daily torpor common among desert animals such as gerbils
- Migration; large mammals, birds and some insects, migrate due to dryness rather than photoperiod or temperature (ex: Wildebeests)
- Ex: Kangaroo rat - burrows during the day to stay cool
- Ex: California ground squirrel - active during day but retreats often to burrow
5
Q
Regulation: increasing uptake of water
A
- Drinking; birds, large mammals
- Food; dietary switch to succulents and most plants
- Condensation; on beetle and reptile backs
6
Q
Water storage
A
- Camel humps DON’T store water ; large fat reserves, lipid metabolism produces relatively more water than proteins or carbohydrates
- Urinary bladders; re-absorption in amphibians and some reptiles; reverses filtration process (pump Na/K into glomerular capillaries from urine, ,draw water by osmosis)
7
Q
Reducing loss - Loss depends on:
A
- Relative humidity
- Environmental temperature
- Wind speed
- Body temperature
- Body size
- Permeability
8
Q
Humidic organsims
A
- Earthworms, crustaceans, molluscs, most aphibians
- Very high permeability
- Lose >40%/day
- Live in humid environments
9
Q
“True” terrestrial organisms
A
- less permeable due mainly to increased lipid content of cell membranes
10
Q
Effective regulators
A
- Insects; some lose less than 1%/day
- Reptiles: some lost <5%/day
- A few frogs and toads
11
Q
Insect integument
A
- insects have thick integument, including exoskeleton and layer of insulating air, so they avoid water loss very effectively until about 29-30C
12
Q
Less effective regulators
A
- Birds and more mammals; lost more water because higher body temps and evaporative cooling
- However, kangaroo rats don’t use evaporative cooling and camels sweat but rarely pant and allow for overheating and have very concentrated urine*
13
Q
Fur
A
- Reduces heat gain, saving on water
14
Q
Reduce respiratory loss
A
- Loss depends on humidity, temp, body size and metabolic rate
- Designs of respiratory system important; • Water loss/O2 gain Ratios
• Amphibians; cutaneous; high water loss; highwater loss through skin
• Internal lungs, reduced net water loss because a lot of the water vapour and air can be absorbed or reabsorbed in the body
• Tracheal system in insects; minimize water loss because reabsorption of air, and can be closed or partially cosed
15
Q
Different type of structures - Evagination vs. Invaginations
A
- Evagination; External gill; water loss because SA/V ratio, this is good for freshwater animals but not terrestrial
- Invagination; Lung, tracheal system
- May have large SA/V ratio, but because internal it allows reabsorption of water from air
