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What is Adaptation ? Inherited traits that increase the chances of 1. Survival 2. Reproduction of an organism in a particular environment Different Habitats Savanna Forest North Pole Desert in southwest Africa Wetland Microsoft Encarta Encyclopedia Deluxe 2004

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what is adaptation
What is Adaptation ?

Inherited traits that increase the chances of

1. Survival

2. Reproduction

of an organism in a particular environment


Different Habitats



North Pole

Desert in southwest Africa


Microsoft Encarta Encyclopedia Deluxe 2004

how d oes evolution w ork
How Does Evolution Work
  • Natural selection leads to adaptation
  • Natural selection involves genetic variation and selection among variants present in a population
misunderstanding on adaptation
Misunderstanding on Adaptation
  • Myth: organism selects suitable environment for them to live in.
  • Fact: Environment selects suitable organisms to live in it.
use of phylogeny to understand adaptation
Use of Phylogeny toUnderstand Adaptation
  • Phylogeny is a method to classify organisms by natural evolutionary relationships
  • Organisms should be grouped together on the basis of shared specializations or shared-derived features
phylogenetic tree of bears
Phylogenetic Tree of Bears

# Base on their genetic similarity

Brown bear (Ursus arctos)

Polar bear (Ursus maritimus)

Asiatic black bear (Ursus thibetanus)

Black bear (Ursus americanus)

Sun bear (Ursus malayanus)

Sloth bear (Ursus ursinus)

Spectacled bear (Tremarctos ornatus)

Giant Panda (Ailuropoda melanoleuca)

ursidae family
Ursidae Family

Giant panda

Polar bear

Spectacled Bear

Asiatic Black Bear

Black Bear

Sun bear

Sloth bear

Brown bear

Microsoft Encarta Encyclopedia Deluxe 2004

what problems do polar bear face
What Problems Do Polar Bear Face ?
  • Cold
  • Unstable food source
  • Geographical change (melting ice)
  • Over heat
three major types of adaptation
Three Major Types of Adaptation
  • Morphological Adaptation
  • Physiological Adaptation
  • Behavioral Adaptation
morphological adaptation
Morphological Adaptation
  • High-mobility long neck
  • Low surface area to volume ratio (m2 vs m3)
  • Slip resistant footpad
  • Teeth pattern with flat skull characteristics.html

adaptation for carnivore
Adaptation for Carnivore

Diet and lifestyle willexert selective pressuresupon skull morphology !

Polar bear

Brown bear

Giant panda

Coronoid process 下顎齒骨冠突

physiological adaptation
Physiological Adaptation
  • Thick pelt
  • Fat storage
  • Blubber system
  • Haemoglobin
thick p elt
Thick Pelt
  • Inner short fur
  • Outer long transparent fur
  • Black skin
  • Two types (long / short)
  • Translucent (半透明的) hairs can:

(a) Reflect visible light back to the environment

(b) Absorb UV light to warm up its body

  • Water repellant

Sun light



Structure of outer fur

fat storage
Fat Storage
  • Mainly as Triacylglycerols in adipose cells
  • Constitute 84% of stored energy
  • Convert energy source from white adipose to brown adipose

White adipocyte

Brown adipocyte

blubber system
Blubber System
  • The insulation afforded

by blubber can be

bypassed when the

need for heat

dissipation increases.

  • Fur outside the skin

surface and its

insulation value cannot

be drastically changed

by a bypass

Animal Physiology 5/e (Cambridge university press) p263

oxygen binding affinity under different temperature
Oxygen Binding Affinity under Different Temperature
  • High temperature: Low affinity
  • Low temperature: High affinity
  • Contain special Cl-binding site
  • Lower ∆H of oxygenation
  • Lower the oxygen binding affinity
  • Easier to release oxygen to tissues
behavioral adaptation
Behavioral Adaptation
  • Posture
  • Swimming
  • Annual migration
  • Hibernation (Denning)





Use different postures to regulate heat lost

  • Polar bear as marine mammal
  • Ursus means bear maritimusmeans sea
  • Swim long time and distance (60miles)
  • To avoid over heating

Source: Polar bear pres


Types of Polar Bear Habitats

What causes ice-drift ?

Two types of habitats for polar bears

(1) Drift ice habitat (ice moved by wind or current)

Drift = pelagic

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

annual migration
Annual Migration
  • Pelagic polar bears move northwards (summer) when ice melting at the ice edge to counteract a continuous southwards ice drift.
  • While it moves southwards (autumn) during sea ice advance

True hibernation (does not occur in polar bears)

  • Body-core temperature close to freezing

Walking hibernation (denning for pregnant female)

  • When no food is available
  • In order to save energy

Using fat as the major energy source in order to

preserve essential protein and carbohydrate

molecular bases of hibernation


Molecular Bases of Hibernation
  • Triggered by pyruvate dehydrogenase kinase 4


  • A major effect on pyruvate metabolism
  • Allows modification of the pathways involving fatty acid production through acetyl co-A, and the tricarboxylic acid cycle to be markedly changed.
quick summary
Quick Summary
  • Environment selects the suitable guests to live in its room.
  • Only organisms with suitable characters can survive in a particular habitat.
  • Environment does change thus population changes as well.
why is this bear green
Why Is This Bear Green?

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

  • Prof. K.L. CHOW
  • Prof. WONG
  • Prof. SO
  • Dr. T.K. GOH
  • Dr. Maggie LI
  • Dr. Ice KO
  • Dr. Y.Y. REN
  • Mr. Wilfred LEUNG
  • Mr. Jack LI
  • Center for Enhanced Learning and Teaching

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

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