HomeostasisHomeostasis

Maintenance of the internal conditions Maintenance of the internal conditions of an organism at some optimum level of an organism at some optimum level

for its functioning.for its functioning.

HomeostasisHomeostasis

Maintenance of Maintenance of individual individual internal internal

environmentenvironment

TemperatureTemperature EnergyEnergyMatterMatter

SurvivalSurvival GrowthGrowth ReproductionReproduction

ConstraintsConstraints

AdaptationsAdaptations

All Organisms Engage in All Organisms Engage in Maintaining Homeostasis in Some Maintaining Homeostasis in Some

Fashion.Fashion.

ExamplesExamples::

Shivering thermogenesis - caloric release due to Shivering thermogenesis - caloric release due to cleavage of high energy phosphate bonds. Utilizes cleavage of high energy phosphate bonds. Utilizes brown fatbrown fat. .

Tanning - melanin production Tanning - melanin production Sunning by lizards and other herpsSunning by lizards and other herps Muscles of butterfly warming up Muscles of butterfly warming up Biochemical buffering of pH of blood Biochemical buffering of pH of blood

HH++ + HCO + HCO33- - <-> H<-> H22COCO33

HH22COCO33 <-> CO <-> CO22+(aq) + H+(aq) + H22OO

COCO22(aq) <-> CO(aq) <-> CO22 (g) (g)

Reaction balance is driven by blood pH and COReaction balance is driven by blood pH and CO22

tension.tension.

Ultimate vs. Proximate Ultimate vs. Proximate Causes RevisitedCauses Revisited

What determines the best internal What determines the best internal condition?condition?

Ultimate vs. Proximate CausesUltimate vs. Proximate Causes

Proximate causeProximate cause is an event which is is an event which is closestclosest to, or immediately responsible for to, or immediately responsible for causing, some observed result.causing, some observed result.

Ultimate causeUltimate cause is a higher-level (or is a higher-level (or distal distal causecause) which is usually thought of as the ) which is usually thought of as the "real" reason something occurred "real" reason something occurred

Ultimate vs. Proximate CausesUltimate vs. Proximate Causes

Proximate Causation Is Proximate Causation Is EcologicalEcological Environmental stressEnvironmental stress Affects survival of an organismAffects survival of an organism

Ultimate Causation Is Ultimate Causation Is FitnessFitness Genotype/phenotype must maximize fitness Genotype/phenotype must maximize fitness

under specific environmental conditionsunder specific environmental conditions Fitness: ability to get genes into future Fitness: ability to get genes into future

generationsgenerations

Temperature RegulationTemperature Regulation

Path of causation between temperature Path of causation between temperature regulation and fitness is complex. regulation and fitness is complex.

We treat this as a problem in the We treat this as a problem in the economicseconomics of the characters in question of the characters in question

Cost vs. benefit analysisCost vs. benefit analysis or, an or, an optimization optimization function.function.

Cost vs. Benefit AnalysisCost vs. Benefit Analysis

Costs:Costs: measured in energy terms which measured in energy terms which may deplete fat reserves and make life may deplete fat reserves and make life difficult in face of a food shortage.difficult in face of a food shortage.

Benefits:Benefits: activity under conditions which activity under conditions which would otherwise be life threatening. This would otherwise be life threatening. This might be measured in terms of energy might be measured in terms of energy acquired by foraging.acquired by foraging.

Assessment of costAssessment of cost

Energetic cost, Energetic cost,

HeatHeat to maintain body temperature, or to maintain body temperature, or

ATPATP necessary for locomotion. necessary for locomotion.

Both of these are Both of these are maintenance costsmaintenance costs..

Energetic CostEnergetic Cost

How does this ruby-throated How does this ruby-throated hummingbird find enough hummingbird find enough energy to make its annual energy to make its annual migration across the Gulf of migration across the Gulf of Mexico.Mexico. South to Central AmericaSouth to Central America Northbound to U.S. Northbound to U.S.

Hummingbird MigrationHummingbird Migration Body Temperature:Body Temperature: Normally about 40.5 Normally about 40.5oo C C Energy Use: On a typical day, a RTHU needs about 10 calories of Energy Use: On a typical day, a RTHU needs about 10 calories of

food to survivefood to survive. This can come in the form of carbohydrates (sugar . This can come in the form of carbohydrates (sugar water or flower nectar) or fats and proteins (primarily from tiny insects water or flower nectar) or fats and proteins (primarily from tiny insects and spiders).and spiders).

Feeding Rate: Feeding Rate: Eats about its weight in nectar or sugar water each day; Eats about its weight in nectar or sugar water each day; Frequency:Frequency: Feeds about 5-10 times per hour for 30-60 seconds each Feeds about 5-10 times per hour for 30-60 seconds each

time during the daytime during the day Torpor:Torpor: On cold nights, a On cold nights, a RTHURTHU can lower its body temperature by can lower its body temperature by

about 20about 20ooC, thus conserving energy that we be used to maintain its C, thus conserving energy that we be used to maintain its normal temperature. The next morning, the RTHU speeds up its normal temperature. The next morning, the RTHU speeds up its metabolism and get its body temperature back up to normal within a metabolism and get its body temperature back up to normal within a few minutes.few minutes.

Hummingbird MigrationHummingbird Migration

DISTANCE:DISTANCE: At most about 845km (525mi) non- At most about 845km (525mi) non-stop across the Gulf of Mexico, and then up to stop across the Gulf of Mexico, and then up to another 1,600km (1,000mi) into Central America; another 1,600km (1,000mi) into Central America; RTHURTHU that nest in Canada must also fly from there to that nest in Canada must also fly from there to

the Gulf Coast, a distance of another 1,600km the Gulf Coast, a distance of another 1,600km (1,000mi) or so.(1,000mi) or so.

ELAPSED TIME:ELAPSED TIME: Estimated 18-20 hours to fly Estimated 18-20 hours to fly across the Gulf of Mexico. (Some across the Gulf of Mexico. (Some RTHUsRTHUs may may go overland through Mexico or short-cut the Gulf go overland through Mexico or short-cut the Gulf flight by flying from the Texas coast into Mexico)flight by flying from the Texas coast into Mexico)

Hummingbird MigrationHummingbird Migration

Ruby-throats begin moving north as early as Ruby-throats begin moving north as early as January, and by the end of February they are at the January, and by the end of February they are at the northern coast of Yucatan, gorging on insects and northern coast of Yucatan, gorging on insects and spiders to add a thick layer of fat in preparation for spiders to add a thick layer of fat in preparation for flying to the U.S. flying to the U.S.

Some will skirt the Gulf of Mexico and follow the Some will skirt the Gulf of Mexico and follow the Texas coast north, while most apparently cross the Texas coast north, while most apparently cross the Gulf, typically leaving at dusk for a nonstop flight of Gulf, typically leaving at dusk for a nonstop flight of up to 500 miles, which takes 18-22 hours depending up to 500 miles, which takes 18-22 hours depending on the weather. on the weather.

Birds have just enough energy to cross GulfBirds have just enough energy to cross Gulf

Hummingbird MigrationHummingbird Migration Source of energy for migrationSource of energy for migration

Hummingbirds are carnivores Hummingbirds are carnivores Nectar is fuel to power insect catching activityNectar is fuel to power insect catching activity Depend on insects that are not abundant in Depend on insects that are not abundant in

subfreezing weather, so most of them must retreat to subfreezing weather, so most of them must retreat to Central America in the winter or risk starvationCentral America in the winter or risk starvation

Before departing, each bird will nearly double its weight Before departing, each bird will nearly double its weight by feeding on nectar, insects and spidersby feeding on nectar, insects and spiders From about 3.25 g to over 6 g at departure timeFrom about 3.25 g to over 6 g at departure time Back down to nearly 2.5 g after crossing GulfBack down to nearly 2.5 g after crossing Gulf Birds have just enough energy to cross the GulfBirds have just enough energy to cross the Gulf

Hummingbird MigrationHummingbird Migration

Costs:Costs:

Benefits:Benefits:

Assessment of CostAssessment of Cost

Constraints on organism function Constraints on organism function (opportunity cost) (opportunity cost)

ex. in plants, growth in high light ex. in plants, growth in high light environments is constrained by adaptation for environments is constrained by adaptation for optimal photosynthesis in shade optimal photosynthesis in shade

ex. in lizards, foraging is constrained by the ex. in lizards, foraging is constrained by the need to bask (intrinsic constraint – need need to bask (intrinsic constraint – need warmth for digestion) and warmth for digestion) and predationpredation pressure pressure (extrinsic constraint). (extrinsic constraint).

Photosynthesis vs light intensity

Foraging vs BaskingForaging vs Basking

Coping with Environmental ChangeCoping with Environmental Change

Change vs stability Change vs stability most environments experience changemost environments experience change caves, hot springs, deep ocean, insides of warm-caves, hot springs, deep ocean, insides of warm-

blooded animals approach stabilityblooded animals approach stability

Type of changesType of changes day vs night: temp; lightday vs night: temp; light summer vs winter: temp; light; moisturesummer vs winter: temp; light; moisture drought vs wet perioddrought vs wet period

Coping strategies for maintaining Coping strategies for maintaining homeostasishomeostasis physiologicalphysiological behavioralbehavioral structuralstructural

Smallmouth Bass DevelopmentSmallmouth Bass Development

Development of embryo depends on temperatureDevelopment of embryo depends on temperature Bass eggs hatch in only 2 days at 72°F, but take 5 days Bass eggs hatch in only 2 days at 72°F, but take 5 days

at 67°F. at 67°F. Cold weather following spawning will delay hatching. Cold weather following spawning will delay hatching.

If the shallows drop to 50°F, the fry will not emerge for 13 If the shallows drop to 50°F, the fry will not emerge for 13 days. days.

At lower temperatures, the eggs fail to develop. At lower temperatures, the eggs fail to develop. A severe cold front sometimes causes males to abandon the A severe cold front sometimes causes males to abandon the

nest, resulting in a complete loss of eggs or fry. nest, resulting in a complete loss of eggs or fry.

Smallmouth Bass

What happens when variations What happens when variations exceed the tolerance range?exceed the tolerance range?

Organism fails to cope and diesOrganism fails to cope and dies

Adults die but some other life history stage Adults die but some other life history stage survivessurvives

eggseggs

pupaepupae

seed bankseed bank

Insects can diapause as eggs, larvae, or pupae

Sarracenia purpurea seeds in Sphagnum moss

Plants can suvive bad times as seeds in soil seed bank

What happens when variations What happens when variations exceed the tolerance range?exceed the tolerance range?

Enter resting stateEnter resting state

hibernationhibernation - winter: low temp; low metab - winter: low temp; low metab

aestivationaestivation - hot/dry: low temp; low metab - hot/dry: low temp; low metab

torportorpor - daily response to hot or cold; low - daily response to hot or cold; low body temp and low activity (hummingbirds body temp and low activity (hummingbirds and chickadees at night)and chickadees at night)

True Hibernation

Diapause allows insects to hibernate over the winter, and usually occurs due to a reduction in photoperiod. Diapause ceases when conditions change, such as a certain number of cooling hours have been accumulated

Aestivation also occurs and is in response to an unpleasant stimulus (heat, dryness). Aestivation ceases when the stimulus is removed. Desert spadefoot toad.

Native

Coccinella septempunctata

Harmonia axyridis

Asian Lady Beetle

Note the M on the thorax

During October and November, adult Asian Lady Beetles seek out protective sites and congregate at these locations to overwinter (hibernate) in clusters.

In their native home (Japan, Korea and other parts of Asia), these beetles are attracted to vertical surfaces and usually overwinter on cliffs.

DormancyDormancy

Carnivorous hibernators such as skunks, Carnivorous hibernators such as skunks, raccoons, badgers, and bears do not truly raccoons, badgers, and bears do not truly hibernate. hibernate. A variety of physiological characteristics set them A variety of physiological characteristics set them

apart from true hibernators. apart from true hibernators. Because carnivorous animals such as bears Because carnivorous animals such as bears

cannot be described as hibernators, most cannot be described as hibernators, most scientists have titled their lethargic winter activity scientists have titled their lethargic winter activity as dormancy, meaning "lying asleep or as if as dormancy, meaning "lying asleep or as if asleep." asleep."

BearsBears

Large body mass inhibits them from experiencing a Large body mass inhibits them from experiencing a marked reduction in body temperature, metabolic marked reduction in body temperature, metabolic rate or heart raterate or heart rate

Bears have full sensibility and use of their facilities Bears have full sensibility and use of their facilities and are capable of coordinated movement and are capable of coordinated movement

Female bears are able to give birth during dormancy Female bears are able to give birth during dormancy Bears are easily aroused even in their most Bears are easily aroused even in their most

lethargic state and may awaken several times lethargic state and may awaken several times during the period of dormancy during the period of dormancy

TorporTorpor

Coma-like state that involves a severe reduction in Coma-like state that involves a severe reduction in both body temperature and metabolismboth body temperature and metabolism

May be more appropriate for many small animals May be more appropriate for many small animals instead of hibernationinstead of hibernation Deep torpor interrupted by activityDeep torpor interrupted by activity More like a short-term hibernationMore like a short-term hibernation If animals like chipmunks remained near brain dead for If animals like chipmunks remained near brain dead for

long time, they would likely dielong time, they would likely die Activity allows some true "sleep" as well as feeding from Activity allows some true "sleep" as well as feeding from

cached foodcached food

Eastern Chipmunk

Ruby Throated Hummingbird

Black capped Chickadee

What happens when variations What happens when variations exceed the tolerance range?exceed the tolerance range?

MigrateMigrate Many species of birdsMany species of birds Mammals e.g. Caribou herds of arctic grey whalesMammals e.g. Caribou herds of arctic grey whales Insects e.g. Monarch butterfliesInsects e.g. Monarch butterflies Soil invertebrates go below frost lineSoil invertebrates go below frost line

Acclimate - physiological adjustments that Acclimate - physiological adjustments that produce shift in tolerance rangeproduce shift in tolerance range e.g. Winter cold tolerances for fishe.g. Winter cold tolerances for fish e.g. Oxygen levels for mountain goats (also humans)e.g. Oxygen levels for mountain goats (also humans)

Sandhill Cranes

Monarch Butterflies

MigrationMigration