What is Adaptation ?

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(No Transcript)
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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

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Different Habitats
Savanna
Forest
North Pole
Desert in southwest Africa
Wetland
Microsoft Encarta Encyclopedia Deluxe 2004
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How Does Evolution Work

• Natural selection leads to adaptation
• Natural selection involves genetic variation and
  selection among variants present in a population

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Misunderstanding on Adaptation

• Myth organism selects suitable environment for
  them to live in.
• Fact Environment selects suitable organisms to
  live in it.

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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

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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)
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Ursidae Family
Giant panda
Polar bear
Spectacled Bear
Asiatic Black Bear
Black Bear
Sun bear
Sloth bear
Brown bear
Microsoft Encarta Encyclopedia Deluxe 2004
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What Problems Do Polar Bear Face ?

• Cold
• Unstable food source
• Geographical change (melting ice)
• Over heat

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Three Major Types of Adaptation

• Morphological Adaptation
• Physiological Adaptation
• Behavioral Adaptation

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Morphological Adaptation

• High-mobility long neck
• Low surface area to volume ratio (m2 vs m3)
• Slip resistant footpad
• Teeth pattern with flat skull

www.ngo.grida.no/.../ characteristics.html
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Adaptation for Carnivore
Diet and lifestyle will exert selective pressures
upon skull morphology !
Polar bear
Brown bear
Giant panda
Coronoid process ??????
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Physiological Adaptation

• Thick pelt
• Fat storage
• Blubber system
• Haemoglobin

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Thick Pelt

• Inner short fur
• Outer long transparent fur
• Black skin

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Fur

• Two types (long / short)
• Translucent (????) hairs can
• (a) Reflect visible light back to the environment
  
• (b) Absorb UV light to warm up its body
• Water repellant

Sun light
Reflection
Hollow
Structure of outer fur
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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
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Special Character of Brown Adipose
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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
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Oxygen Binding Affinity under Different
Temperature

• High temperature Low affinity
• Low temperature High affinity

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Haemoglobin

• Contain special Cl- binding site
• Lower ?H of oxygenation
• Lower the oxygen binding affinity
• Easier to release oxygen to tissues

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Behavioral Adaptation

• Posture
• Swimming
• Annual migration
• Hibernation (Denning)

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Posturing
Use different postures to regulate heat lost
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Swimming

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

Source Polar bear pres
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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)
http//seis.natsci.csulb.edu/rmorris/seaice/drift.
htm
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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

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Hibernation

• 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

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Aerobic Respiration
Energy
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Molecular Bases of Hibernation

• Triggered by pyruvate dehydrogenase kinase 4
• (PDK-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.

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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.

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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

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How Do Polar Bears Relate to Us ?
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Enjoy the Nature
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Acknowledgements

• 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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HKUST

• http//www.ust.hk
• Way bo_lkwag_at_stu.ust.hk
• John bo_ssl_at_stu.ust.hk