WATERWATEREVERYWHERETHEOBJECTIVES:Gain a general understanding of water balance budgetsExplain mechanisms used in direct and indirect water conservation and lossEvaluate water balance adaptations and explain how they complement animal life history and environmentTHEMAJORCONCEPTS:The Water Budget ConceptDirect control vs. indirect control of waterResistance to evaporative water lossWater absorption from sub-saturated air THEDETAILS:1.Major water balance problems in different habitat typesa.The water budget concepti.Potential avenues of water lossii.Potential avenues of water gain2.Two major strategies of maintaining a water budgeta.Direct control of water balanceb.Indirect control of water balance by controlling osmotic flux (osmoregulation) 3.The Biophysics of Water Balance a.In terrestrial animals EWL = -D xWV / di.D = diffusion coeficienyii.xWV= difference in water vapor densityiii.d = diffusion path length b.Not usually measured in this way but rather as resistance i.Resistance r is substituted for D & xWV ii.EWL xWV / rSome Adaptations for Direct control of water
4.Contractile vacuolesa.spongiomelayer.b.Arginine vasopressin5.Adaptations for retarding water loss across body surfaces a.Mollusks b.Arthropods – epicuticlec.Fishd.Amphibians –i.“Waterproof” frogs –wipingbehavior cutaneous lipid glandsii.Casque-headed frogs (Trachycephalus) - co-ossifiedskull iii.Estivating amphibianse.Aminote vertebrates - Keratinized epidermal cells, stratum corneumf.Reptiles g.Mammalsi.Three possible adaptations for preventing water loss from mammalian respiratorysurfaces in the absence of heat stress.ii.Do not fully saturate expired air.iii.Higher oxygen extraction. (Greater than 5%)iv.Exhale air at lower than body temperature.v.Temporal counter-current heat exchangerh.Female mammals have an additional water burden during lactation. 6.Direct water vapor absorption from sub-saturated air via hygroscopic organs.a.agranular cellsb.eversible bladderc.rectal sacs containing hygroscopic fluid7.Storage of watera.Chiroleptes, OSMOREGULATIONANDEXCRETIONSecretory Organs of ExcretionTHEOBJECTIVES:Describe the relationship between osmoregulation and excretionExplain the two basic types of excretory organsList and describe the basic function of various cells/organs present in various animal groups
THEMAJORCONCEPTS:Ultrafiltration, reabsorption and secretionChloride cellsSalt glandsMalpigian tubulesTHEDETAILS:1.Basic Processes of Excretiona.Ultrafiltration b.Active transporti.Active secretionii.Active reabsorption2.The following are secretion (not filtration) organs and thus are specific to certain compounds.3.The teleost gill - Chloride cellsa.Gill filament - Secondary lamellae (1)Lamella epithelium (2)Chloride cells b.Keys and Willmer (1)(trans-cellular transport)(2)(para-cellular transport)4.Salt glandsa.Controli.Hypothalamus and osmoreceptorsii.Hormonesiii.Major advantageb.Location (1)Birds and reptiles.