BI 173 - Chapter 7 - Homeostasis
Maintain optimal conditions for body chemistry.
Balance between necessary external connections
Oxygen in, wastes out, etc.
Body surfaces & circulation systems.
And responses to external changes.
"Open" and "closed," while getting all jobs done.
Marine Animals.
Osmotic Conformers. Usually restricted to stable areas.
Water Levels are in balance.
Nonstable marine environments.
Preadaptations for other areas...
Fresh Water.
Osmosis in & Diffusion Out.
Answers:
Pump water out, hold other materials in.
Block water & material movement: Waterproofing.
Land Animals.
Losses & sources.
Excretory Products:
Ammonia. Toxic but Highly Soluble.
Requires quick access to lots of water.
Urea. Less toxic, somewhat less soluble.
Circulatable.
Moderate water loss, more processing.
Uric Acid. Nontoxic, virtually nonsoluble.
Loss as powder or colloid.
Little water loss, more processing.
Use in Eggs.
Salt Glands.
Excretion Intimately Associated w/ Water Regulation.
Single-Celled & Small Animals:
Diffusion. Proximity to surface exchange.
Nephridia: Osmotic / Excretory Tube Systems.
Protonephridia: Distributed Flame Cells w/ tubes, excretory pores.
Closed system - everything enters through membranes.
Flagellar Tuft generates negative pressure.
Some Materials pulled through then reabsorbed.
Metanephridia. Annelids, Molluscs, a few others.
Open system: fluid swept up (cilia) from hemolymph.
Associated blood vessels reabsorb needed materials & add wastes.
Antennal Glands: Crustaceans.
Blood filters in, then reabsorption & secretion follows.
Malpighian Tubules. Insects & Spiders.
Osmotic Pull of materials from hemolymph into tubules.
Uric Acid formed & dumped into hindgut.
Water, materials reabsorbed there.
Vertebrate Kidneys:
Functionally similar (derived?) from nephridium.
Most primitive form is segmented system - only in rare embryos.
Advanced vertebrate embryos go through 3 "family tree" stages...
Ontogeny recapitulates phylogeny...
Nephron.
Blood physically filtered through glomerulus.
Small molecules, much of water.
Tubules. Surrounded by blood vessels.
Water, needed materials reabsorbed.
Nonfiltered wastes added.
Ectotherms / Poikilothermic vs Endotherms / Homeothermic.
Advantages, Disadvantages.
Enzyme repertoire & Chemistry vs High Energy Use.
Regulation in Ectotherms:
Behavioral Adjustments:
Placement, orientiation, timing.
Metabolic Adjustments.
Heat Generation.
Normal Multiranges.
Regulation in Endotherms:
Some behavioral adjustments.
Core vs extremity temperatures.
Use of Evaporative Cooling.
Cold environment adaptations:
Insulation.
Body: Fur, feathers, fat...
Environmental: Burrows, Nests, Snow...
Heat Exchangers.
Basic Idea.
Similar Systems: Gills, etc.
Varied "Set" Temperature:
Daily Torpor.
Hibernation.
vs simple inactivity.
Michael McDarby,
Based Upon Hickman-Roberts-Larson
Biology of Animals,
1998,
WCB McGraw-Hill.
Internet Version Uploaded
2001.