What is Adaptation ?What is Adaptation ?

Inherited traits that increase the Inherited traits that increase the chances ofchances of

1. Survival1. Survival 2. Reproduction2. Reproduction

of an organism in a particular of an organism in a particular environmentenvironment

Desert in southwest AfricaDesert in southwest Africa WetlandWetland

Microsoft Encarta Encyclopedia Deluxe 2004

North PoleNorth Pole ForestForest SavannaSavanna

Different HabitatsDifferent Habitats

How How DDoes Evolution oes Evolution WWorkork

Natural selection leads to adaptationNatural selection leads to adaptation

Natural selection involves genetic Natural selection involves genetic variation and selection among variation and selection among variants present in a populationvariants present in a population

Misunderstanding on Misunderstanding on AdaptationAdaptation

Myth: organism selects suitable Myth: organism selects suitable environment for them to live in.environment for them to live in.

Fact: Environment selects suitable Fact: Environment selects suitable organisms to live in it. organisms to live in it.

Use of Phylogeny toUse of Phylogeny toUnderstand AdaptationUnderstand Adaptation

Phylogeny is a method to classify Phylogeny is a method to classify organisms by natural evolutionary organisms by natural evolutionary relationshipsrelationships

Organisms should be grouped Organisms should be grouped together on the basis of shared together on the basis of shared specializations or shared-derived specializations or shared-derived featuresfeatures

Phylogenetic Tree of BearsPhylogenetic Tree of Bears

Asiatic black bear (Asiatic black bear (Ursus thibetanusUrsus thibetanus))

Polar bear (Polar bear (Ursus maritimusUrsus maritimus))

Brown bear (Brown bear (Ursus arctosUrsus arctos))

Black bear (Black bear (Ursus americanusUrsus americanus))

Sun bear (Sun bear (Ursus malayanusUrsus malayanus))

Sloth bear (Sloth bear (Ursus ursinusUrsus ursinus))

Spectacled bear (Spectacled bear (Tremarctos ornTremarctos ornatusatus))

Giant Panda (Giant Panda (Ailuropoda melanoleAiluropoda melanoleucauca))

# Base on their # Base on their genetic genetic similaritysimilarity

UrsidaeUrsidae Family Family

Giant pandaGiant panda

Sun bearSun bear Sloth bearSloth bear Brown bearBrown bear

Polar bearPolar bear Spectacled BearSpectacled Bear Asiatic Black BearAsiatic Black Bear

Black BearBlack Bear

Microsoft Encarta Encyclopedia Deluxe 2004

What Problems Do Polar Bear What Problems Do Polar Bear Face ?Face ?

ColdCold

Unstable food sourceUnstable food source

Geographical change (melting ice)Geographical change (melting ice)

Over heat Over heat

Three Major Types of Three Major Types of AdaptationAdaptation

Morphological AdaptationMorphological Adaptation

Physiological AdaptationPhysiological Adaptation

Behavioral AdaptationBehavioral Adaptation

Morphological AdaptationMorphological Adaptation

High-mobility long neckHigh-mobility long neck

Low surface area to volume ratLow surface area to volume ratio (mio (m22 vs m vs m33))

Slip resistant footpadSlip resistant footpad

Teeth pattern with flat skull Teeth pattern with flat skull

www.ngo.grida.no/.../ characteristics.html

Adaptation for CarnivoreAdaptation for Carnivore

Diet and lifestyle willDiet and lifestyle will exert selective pressuresexert selective pressures upon skull morphologyupon skull morphology ! !

Polar bear

Brown bear

Giant panda

Coronoid process Coronoid process 下顎齒骨冠突下顎齒骨冠突

Physiological AdaptationPhysiological Adaptation

Thick peltThick pelt

Fat storageFat storage

Blubber system Blubber system

HaemoglobinHaemoglobin

Thick Thick PPeltelt

Inner short furInner short fur

Outer long transparent furOuter long transparent fur

Black skinBlack skin

FurFur Two types (long / short)Two types (long / short)

Translucent (Translucent ( 半透明的半透明的 ) hai) hairs can:rs can:

(a) Reflect visible light back (a) Reflect visible light back to the environment to the environment

(b) Absorb UV light to warm (b) Absorb UV light to warm up its bodyup its body

Water repellantWater repellant

Sun light

Hollow

Reflection

Structure of outer fur

Fat StorageFat Storage Mainly as Triacylglycerols in adipose cellsMainly as Triacylglycerols in adipose cells

Constitute 84% of stored energyConstitute 84% of stored energy

Convert energy source from white adipose to broConvert energy source from white adipose to brown adiposewn adipose

White adipocyte Brown adipocyte

Special Character of Brown AdiposeSpecial Character of Brown Adipose

Blubber SystemBlubber System The insulation affordThe insulation afford

ededby blubber can beby blubber can bebypassed when the bypassed when the need for heat need for heat dissipation increases. dissipation increases.

Fur outside the skin Fur outside the skin surface and its surface and its insulation value cannot insulation value cannot be drastically changed be drastically changed by a bypassby a bypass

Animal Physiology 5/e (Cambridge university press) p263

Oxygen Binding Affinity under Oxygen Binding Affinity under Different TemperatureDifferent Temperature

High temperature: Low affinityHigh temperature: Low affinity

Low temperature: High affinity Low temperature: High affinity

HaemoglobinHaemoglobin Contain special Contain special

ClCl-- binding sitebinding site

Lower ∆H of Lower ∆H of oxygenationoxygenation

Lower the oxygen Lower the oxygen binding affinitybinding affinity

Easier to release Easier to release oxygen to tissuesoxygen to tissues

Behavioral AdaptationBehavioral Adaptation

PosturePosture

SwimmingSwimming

Annual migrationAnnual migration

Hibernation (Denning)Hibernation (Denning)

a

b

c

Use different Use different postures to postures to

regulate heat regulate heat lostlost

PosturingPosturing

SwimmingSwimming

Polar bear as Polar bear as marine marine mammalmammal

UrsusUrsus means bear means bear mamaritimusritimus means seameans sea

Swim long time and Swim long time and distance (60miles)distance (60miles)

To avoid over heatinTo avoid over heatingg

Source: Polar bear pres

Two types of habitats Two types of habitats for for polar bearspolar bears

(1) Drift ice habitat ((1) Drift ice habitat (ice ice moved by wind moved by wind oror current)current) Drift = pelagicDrift = pelagic

(2) Land-fast ice habitat (2) Land-fast ice habitat (ice surrounding islands)(ice surrounding islands)

http://seis.natsci.csulb.edu/rmorris/seaice/drift.htm

What causes ice-drift ?What causes ice-drift ?

Types of Polar Bear HabitatsTypes of Polar Bear Habitats

Annual MigrationAnnual Migration

Pelagic polar bears move northwards Pelagic polar bears move northwards (summer) when ice melting at the ice (summer) when ice melting at the ice edge to counteract a continuous edge to counteract a continuous southwards ice drift.southwards ice drift.

While it moves southwards (autumn) While it moves southwards (autumn) during sea ice advanceduring sea ice advance

HibernationHibernation

True hibernationTrue hibernation (does not occur in polar bears) (does not occur in polar bears) Body-core temperature close to freezingBody-core temperature close to freezing

Walking hibernationWalking hibernation (denning for pregnant fem (denning for pregnant female)ale)

When no food is availableWhen no food is available In order to save energyIn order to save energy

Using fat as the major energy source in order to Using fat as the major energy source in order to preserve essential protein and carbohydratepreserve essential protein and carbohydrate

Aerobic RespirationAerobic Respiration

Energy

Molecular Bases of Molecular Bases of HibernationHibernation

Triggered by pyruvate dehydrTriggered by pyruvate dehydrogenase kinase 4 ogenase kinase 4 (PDK-4)(PDK-4)

A major effect on pyruvate meA major effect on pyruvate metabolismtabolism

Allows modification of the patAllows modification of the pathways involving fatty acid produhways involving fatty acid production through acetyl co-A, and tction through acetyl co-A, and the tricarboxylic acid cycle to be he tricarboxylic acid cycle to be markedly changed.markedly changed. energy

Quick SummaryQuick Summary Environment selects the suitable Environment selects the suitable

guests to live in its room.guests to live in its room.

Only organisms with suitable Only organisms with suitable characters can survive in a particular characters can survive in a particular habitat. habitat.

Environment does change thus Environment does change thus population changes as well.population changes as well.

Why Is This Bear Green?Why Is This Bear Green?

Symbiosis: Symbiosis: AlgalAlgal growth inside the hollow growth inside the hollow hairs of polar bears in warm climates hairs of polar bears in warm climates causes the pelt to have a causes the pelt to have a greengreen appearance appearance

How Do Polar Bears Relate to How Do Polar Bears Relate to Us ?Us ?

Enjoy the NatureEnjoy the Nature

AcknowledgementsAcknowledgements

Prof. K.L. CHOWProf. K.L. CHOW Prof. WONGProf. WONG Prof. SOProf. SO Dr. T.K. GOHDr. T.K. GOH Dr. Maggie LIDr. Maggie LI Dr. Ice KODr. Ice KO Dr. Y.Y. RENDr. Y.Y. REN Mr. Wilfred LEUNGMr. Wilfred LEUNG Mr. Jack LIMr. Jack LI Center for Enhanced Learning and TeachingCenter for Enhanced Learning and Teaching

This project is supported by the funding from This project is supported by the funding from Center for Enhanced Learning and TeachingCenter for Enhanced Learning and Teaching

HKUSTHKUST

http://www.ust.hkhttp://www.ust.hk

Way: bo_lkwag@stu.ust.hkWay: bo_lkwag@stu.ust.hk John: bo_ssl@stu.ust.hkJohn: bo_ssl@stu.ust.hk