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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
North Pole
Forest
Desert in southwest Africa
Savanna
Wetland
Microsoft Encarta Encyclopedia Deluxe 2004
How Does Evolution Work
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Natural selection leads to adaptation
Natural selection involves genetic variation
and selection among variants present in a
population
Misunderstanding on Adaptation
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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
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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
# 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
Giant panda
Sun bear
Polar bear
Sloth bear
Spectacled Bear
Brown bear
Asiatic Black Bear
Black Bear
Microsoft Encarta Encyclopedia Deluxe 2004
What Problems Do Polar Bear Face ?
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Cold
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Unstable food source
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Geographical change (melting ice)
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Over heat
Three Major Types of Adaptation
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Morphological Adaptation
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Physiological Adaptation
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Behavioral Adaptation
Morphological Adaptation
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High-mobility long neck
Low surface area to volume ratio
(m2 vs m3)
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Slip resistant footpad
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Teeth pattern with flat skull
www.ngo.grida.no/.../ characteristics.html
Adaptation for Carnivore
Diet and lifestyle will exert selective pressures upon skull
morphology !
Polar bear
Brown bear
Coronoid process 下顎齒骨冠突
Giant panda
Physiological Adaptation
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Thick pelt
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Fat storage
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Blubber system
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Haemoglobin
Thick Pelt
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Inner short fur
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Outer long transparent fur
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Black skin
Fur
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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
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Water repellant
Sun light
Reflection
Hollow
Structure of outer fur
Fat Storage
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Mainly as Triacylglycerols in adipose cells
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Constitute 84% of stored energy
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Convert energy source from white adipose to brown
adipose
White adipocyte
Brown adipocyte
Special Character of Brown Adipose
Blubber System
The insulation afforded
by blubber can be
bypassed when the
need for heat
dissipation increases.
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Fur outside the skin
surface and its
insulation value cannot
be drastically changed
by a bypass
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Animal Physiology 5/e (Cambridge university press) p263
Oxygen Binding Affinity under
Different Temperature
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High temperature: Low affinity
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Low temperature: High affinity
Haemoglobin
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Contain special Clbinding site
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Lower ∆H of
oxygenation
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Lower the oxygen
binding affinity
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Easier to release
oxygen to tissues
Behavioral Adaptation
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Posture
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Swimming
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Annual migration
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Hibernation (Denning)
Posturing
a
b
c
Use different
postures to
regulate heat lost
Swimming
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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
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
Annual Migration
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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
Hibernation
True hibernation (does not occur in polar bears)
 Body-core temperature close to freezing
Walking hibernation (denning for pregnant female)
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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
Aerobic Respiration
Energy
Molecular Bases of Hibernation
Triggered by pyruvate
dehydrogenase kinase 4
(PDK-4)
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A major effect on pyruvate
metabolism
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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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energy
Quick Summary
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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?
Symbiosis: Algal growth inside the hollow hairs
of polar bears in warm climates causes the pelt
to have a green appearance
How Do Polar Bears Relate to Us ?
Enjoy the Nature
Acknowledgements
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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
HKUST
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http://www.ust.hk
Way: [email protected]
John: [email protected]