Maintaining Water Balance Animals Chapter 22 Adaptation Water

Maintaining Water Balance - Animals Chapter 22

Adaptation & Water Balance n n n n Adaptations allow living things to be well suited to their environment Can be structural, physiological or behavioural Water balance: - some animals’ cells are isotonic to their environment e. g. jellyfish - they have no need to regulate their water balance - 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

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

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

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

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