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HOMEOSTATIC MECHANISMS• Most animals; majority of cells not in external environment but in internal body

fluids

• Insects &other animals w/ open circulatory have internal “pond” mad of hemolymph = bathes all body cells

• Vertebrates &other animals w/ closed circulatory have internal pond(interstitial fluid) that is serviced by blood

• Animals w/ closed circulatory system have three internal fluid compartments:

• Intracellular component-consists of the cytosol of cells

• Two extracellular compartment:• Blood plasma and interstitial fluid

• Homeostasis enables animals to survive changes (temp.) in environment by tempering changes in body fluids

• Physiological adjustments regulate hemolymph/interstitial fluid

REGULATION OF BODY TEMPERATURE

Four physical process account for heat gain or loss:

• Conduction-the direct transfer of thermal motion between molecules of objects in direct contact w/ each other

• Convection- transfer of heat by the movement of air or liquid past a surface

• Radiation- the emission of electromagnetic waves by all objects warmer than absolute zero, including the animal’s body, the environment, and the sun

• Evaporation- the removal of heat from the surface of a liquid that is losing some of its molecules as gas

ENDOTHERMS & ECTOTHERMS

Ectotherms-=cold-blooded; has low metabolic rate that amount of heat generates is too small to have effect on body temp

ex. Invertebrates, fishes, amphibians, and reptiles

Endotherms=warm-blooded; high metabolic rate generates heat to keep body warm than environment

ex. Mammals, birds, some fishes, a few reptiles, and numerous insectsSsss! I’m

an Ectotherm

RAWR! I’m an Endotherm

FOUR GENERAL CATEGORIES OF ADAPTATIONS HELP ANIMALS THERMOREGULATE:1. Adjusting the rate of heat exchange btwn the animal and its

surroundings. Vasodilation- increase in the diameter of superficial blood vessels

triggered by nerve signals that relax the muscles of the vessel walls. In Endotherms, vasodilation usually warms the skin, increasing the transfer of body heat to cool environment by radiation, conduction, and convection

Vasoconstriction- (reverse process) reduces blood flow and heat transfer by decreasing the diameter of superficial vessels

Countercurrent heat exchanger- helps trap heat in the body core and is important in reducing heat loss in many endotherms.

CONT.

2. Cooling by evaporative heat loss Terrestrial animals lose water by evaporation from the skin and

when they breathe Water absorbs heat when evaporates (Sweating or bathing also

enhances evaporative cooling)

3. Behavioral responses Changes in posture or movement Hibernation or migration to a more suitable climate

4. Changing the rate of metabolic heat production Only endotherms(mammals&birds) Increase metabolic heat production when exposed to cold

OSMOLARITY

• Total solute concentration (mosm/L)

• Osmoconformers=isotonic w/ aqueous surroundings do not regulate their osmolarity

• Osmoregulators=control water uptake and loss in a hypertonic or hypotonic environment; enables animals to live

• All freshwater &marine = maintain an internal osmolarity that differs from the surrounding water

• Humans &other terrestrail animals= compensate for water loss

• Stenohaline=animals that cannot tolerate substantial changes in external osmolarity

• Euryhaline=survive fluctuations of osmolarity in surroundings

WATER BALANCE IN DIFFERENT ENVIRONMENTS

Marine Animals:• Marine invertebrates=osmoconformers; isoosmotic with salt

water environment

• Marine vertebrates=osmoregulatorsSharks have an osmolarity slightly higher than seawater because

they retain urea

• Marine bony fishes lose water by osmosis to their hypertonic surroundings; compensate by drinking large amounts of sea water, pumping out excess salts, and excreting little urine.

** Organisms categorized as osmoconformers are most likely marine.

WATER BALANCE IN DIFFERENT ENVIRONMENTS CONT.

Freshwater Animals:• Constantly taking in water by osmosis

• Osmolarity of internal fluid higher than surroundings

ex. fishes-bail out water by excreting large amounts of very dilute urine&regaining lost salts in food or by active uptake from their surroundings

STILL CONTINUING… Life in Temporary Waters

• Anhydrobiosis = life without water

ex: some aquatic invertebrates living in temporary ponds and films of water

around soil particles can lose almost all body water and survive in a

dormant state when habitats dry up.

Terrestrial Animals

• Few capable of anhydrobiosis• Ex. Humans-die if lose 12% of body water

• Dessication = most important problem confronting terrestrial life (plant & animal)

• Combat dessication by:• Drinking & eating food w/ high water content• Nervous & hormonal control of thirst• Behavioral adaptations• Water-conserving excretory organs

OSMOREGULATION-depends on transport epithelia

• Transport Epithelium=a single sheet of cells facing the external environment or some channel that leads to the exterior through an opening on the body surface

-accomplished by transport of salt across Transport Epithelium followed by osmotic flow of water

ex. Marine Birds

VERTEBRATES EXCRETORY SYSTEM Tubular System:

-function in osmoregulation and excretion in many vertebrates

• Protonephridia• Flatworms• Simple tubular excretory system• Protonephridium - network of closed tubules lacking internal openings

Extracellular fluid is filtered into the protidia of flame-bulb systemBlind-ended tubules excrete a dilute fluid and function in

osmoregulation

• Metanephridia• Metanephridium=internal openings that collect body fluids• Metaphridia found in annelids (Earthworms)• Each segment of worm includes Meta.

• tubules immersed in coelomic fluid &enveloped by a lot of capillaries• Has excretory & osmoregulatory functions• Transport Epithelia pumps out salts for reabsorption, &dilute urine is

excreted through nephridiopores

TUBULAR SYSTEMS CONT.

• Malpighian Tubules in Insects• Remove nitrogenous wastes from the hemolymph; function in

osmoregulation• The insects excretory system very important because to them

conserving water is essential to live on land

KIDNEYS

MAYNE!

-Excretory tubules arranged into compact organs (Kidneys)

**IMPORTANT FOR THE EXCRETORY SYSTEM

Nephron- functional unit of the kidney

MAMMALIAN EXCRETORY SYSTEMEx. Humans

-Excretory tubules=consist of nephrons and collecting ducts

-Blood vessels and excretory pack the kidney

-Fluid from nephrons flow into collecting duct

-Collecting ducts passes urine to the renal pelvis-Ureter conveys urine from the renal pelvis to the urinary bladder

-Nephrons control composition of blood by filtration, secretion, and reabsorption

• Kidney has the ability to conserve water is a key terrestrial adaption for mammals

- Collecting duct (permeable to water but not to salt) carries filtrate through kidney’s osmolarity gradient and more water exits by osmosis.

- Urea diffuses out of tubule with salt and forms osmotic gradient that enables the kidney to make urine that is hyperosmotic to blood

- Osmolarity of urine regulated by nervous system and hormonal control of water and salt reabsorption

- Regulation involves ADH (anti-diuretic hormone), RAAS (renin-angiotensin-aldosterone system), & ANF (atrial natriuretic factor)

The End!

NOW GO PASS THE TEST… I DARE YOU!