Transcript Bird Evolution and Classification

Bird Evolution and
Classification
Dr. Girish Jathar
Scientist-in-charge
ENVIS Centre
BNHS
What are birds?
• Bipedal
• Feathers (diagnostic)
– Insulation
– Lift and thrust
• Toothless bills covered with
horny sheath
• Wings
• Ability to fly
• Egg laying and Parental
Care
• Warm Blooded
Characteristics (cont.)
• Adaptations
associated with flight:
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Skeleton
Musculature
Physiology
Reproductive system
Central Nervous
System
Other features?
• Nucleated RBCs
• Scales on legs
• Ankle in tarsal bones (not between long
bones and tarsals)
• Bipedal (theropods)
• Yolked, polar, cleidoic egg
• Females are heterogametic - Female WZ
Chromosomes and Male ZZ chromosomes
Evolution of Birds
Link Between Birds and Reptiles
• Lots of morphological, behavioral and
physiological similarity between Reptiles
and Birds. Archaeopteryx lithographica
Founding of Archaeopteryx
• Lithograph Quarrymen – Jurassic limestone
• Single feather impression – 1861, Bavarian
Quarry
• Complete skeletal impression – Few months
later
• 2nd complete skeleton – 1877, quarry near
Eichstatt, Germany
• Herman von Meyer
– Archaeopteryx lithographica
Archaeopteryx
• Debates
– Support of Darwinian evolution
• Darwin predicted transitional fossils in 1859
• ‘one of the best links between two taxa’ (Feduccia, Ostrom, etc.)
– Creation / Evolution debate
– Evolution of feathers (flight or insulation first?)
– Evolution of homeothermy in birds
– Evolution of flight
• Ground-up vs. Trees down
Could it fly?
The ‘historical’ evolution of flight
debate
• Two main hypotheses:
– Ground-up (cursorial hypothesis)
– Trees-down (arboreal hypothesis)
Ground-up
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Assume biped, cursorial ancestor
Has to be bipedal to use wings at all
Large legs for running muscle attachment
Bones of legs are long
Once running:
– Use feathers for other things
• Catch insects
• Pick up minimum speed for lift: Flight
Trees-down
• Assume semi-bipedal leaping and gliding
ancestor
• Use of claws to scale trees, then glide to ground
• Claws retained in winged appendages
• Short hand wing (power), relatively long arm
wing (lift)
• Claw geometry (Feduccia’s study)
• Large attachment sites for downstroke on
humerus but no keeled sternum
• Flying squirrels?
Winner?
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Trees-down…maybe
Largely historical debate
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More productive???
– Why evolve flight?
(1) To help escape from predators
(2) To help catch flying or speedy prey
(3) To help move from place to place (leaping or gliding)
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Vigilence
Migration, etc…
Nomadism
(4) To free the hindlegs for use as weapons
Adaptive Radiations
(within adaptive radiations)
• Evolution of ecological diversity within a
rapidly multiplying lineage (Schluter, 2000)
• 150-160 MYA
• >10,000 species extant
– Fraction of what has existed
Ancestor Bird
Bird Classification
Old Classification
• Old Fashion
- based on colour
- based on type – flying
birds/non flying birds
- based on food type –
insectivorous/piscivor
ous/grainivorous/frugi
vorous
Systematics
• Imprint of Linneaus 1758
– Binomial nomenclature
• Upupa epops
Genus
Kingdom
Phylum
Class
Order
From
Genus
species
species
– Standard English Names (“Common Name”)
- In India there is no common naming system
for the classification
Current Classification
• 29 orders
• 187 Families
• 2000+ Genera
• 10000+ species
• Rapidly changing
Current Classification
Molecular Phylogeny
• Started in 1990 by Sibley
and Ahlquist
• DNA-DNA Hybridization
• In 2003 Dr. Paul Herbert
used mt DNA to Barcode
the bird species.
• He identified 4 new
species of North
American birds
• This is revolution in the
Avian Taxonomy
Many Things to come in Future
• In India there are only
once study on mtDNA
i.e. Large-billed Reed
Warbler Acrocephalus
orinus
Thank You