Maintaining Water Balance - Animals Chapter 22

Adaptation & Water Balance Adaptations allow living things to be well suited to their environment Adaptations allow living things to be well suited to their environment Can be structural, physiological or behavioural Can be structural, physiological or behavioural Water balance: Water balance: - some animals’ cells are isotonic to their environment e.g. jellyfish - some animals’ cells are isotonic to their environment e.g. jellyfish - they have no need to regulate their water balance - they have no need to regulate their water balance - most aquatic animals have cells that are hyper or hypotonic to their environment - most aquatic animals have cells that are hyper or hypotonic to their environment - they often have adaptations that allow them to regulate their water (and ion) concentrations - they often have adaptations that allow them to regulate their water (and ion) concentrations

Osmoregulation - freshwater fish - Mouth & gill membranes are selectively permeable - Mouth & gill membranes are selectively permeable - constant inflow of water by osmosis - constant inflow of water by osmosis - excess must be removed - excess must be removed Adpatations include: Adpatations include: - many large glomeruli – allows high filtration rate - many large glomeruli – allows high filtration rate - kidney tubules very efficient at reabsorbtion - kidney tubules very efficient at reabsorbtion - large volume of dilute urine produced - large volume of dilute urine produced - gills have chloride secretory cells – salt absorbed from water (needs active transport) - gills have chloride secretory cells – salt absorbed from water (needs active transport)

Osmoregulation – saltwater fish Water continually lost through gills Water continually lost through gills Several adaptations help Several adaptations help - Sea water is drunk to replace loss - Sea water is drunk to replace loss - Kidney has a few small glomeruli – low filtration rate - Kidney has a few small glomeruli – low filtration rate - Small volume of urine produced - Small volume of urine produced - Waste converted to non-toxic form - Waste converted to non-toxic form - Chloride secretory cells work in reverse (salt excreted) - Chloride secretory cells work in reverse (salt excreted)

Adaptations in migratory fish Fish that spend time in fresh and salt water e.g. Atlantic salmon Fish that spend time in fresh and salt water e.g. Atlantic salmon Salmon eggs laid in river bed Salmon eggs laid in river bed Salmon hatches & develops into a smolt – migrates downstream Salmon hatches & develops into a smolt – migrates downstream Linger in estuaries to acclimatise to salt water Linger in estuaries to acclimatise to salt water Leave river and enter seas Leave river and enter seas Feed off Greenland coast for 1-6 years Feed off Greenland coast for 1-6 years Then migrate back, developing reproductive ability Then migrate back, developing reproductive ability Re-acclimatises to fresh water in estuaries Re-acclimatises to fresh water in estuaries Hormones likely adapt osmoregulation systems Hormones likely adapt osmoregulation systems

Water conservation in desert mammals Have to practice water conservation Have to practice water conservation Obtain water from food e.g. seeds for kangaroo rats Obtain water from food e.g. seeds for kangaroo rats Physiological Adaptations Physiological Adaptations Rat’s mouth & nose is dry – water not lost during breathing Rat’s mouth & nose is dry – water not lost during breathing Blood has high level of ADH Blood has high level of ADH Kidney tubules have very long loops of Henle Kidney tubules have very long loops of Henle Large intestine very effective at reabsorbing water Large intestine very effective at reabsorbing water Animal never sweats Animal never sweats Behavioural Adaptations Behavioural Adaptations Animal very inactive & burrowed underground during the day Animal very inactive & burrowed underground during the day Active at night – forages for food Active at night – forages for food