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VERTEBRATES > Origin on birds > Flashcards

Origin on birds Flashcards

1
Q

How do birds process their food?

A
  • With a gizzard
  • Gizzard contains stones that help break up food
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2
Q

Was flightlessness (ratites) the origin of birds?

A
  • Ratites are distributed over the southern land masses
  • First suggested they were a monophyletic group
  • More recently it has been suggested that they are a polyphyletic group that have evolved convergently
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3
Q

When did birds arise and then when did they diversify
?

A

Arose in the Jurassic
Diversified in the Cretaceous

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4
Q

What are the suggestion of what birds evolved from?

A
  • Early archosaurs
  • Crocodilians
  • Theropods (main accepted hypothesis)
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5
Q

What were theropods?

A
  • Small carnivorous dinosaurs
  • Diverse group
  • Most diverse group of saurischians
  • Huge size variation
  • Not just the t-rex
  • Spinosaurus ← giant theropod (18m long)
  • Obligate bipeds
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6
Q

What were the diets of theropods?

A
  • Wide branch of diets in later diversifications
  • Insectivores, carnivores, herbivores
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7
Q

What did the birds share a common ancestor with?

A

Dromeosaurs
Sister group to the clade aves

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8
Q

What did thomas huxley suggest?

A

Said there was an evolutionary link between birds and theropods

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9
Q

What were the shared derived characteristics of dromeosaurs?

A
  • Modification of fore limb, allows seizing action (flexible)
  • Suggested feathers were for insulation or sexual selection (maybe)
  • Not flight
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10
Q

How did small birds evolve from giant dinosaurs?

A

50 million years of miniaturisation

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11
Q

What other features changes alongside Miniaturisation?

A
  • Skull is large relative to the rest of the body
  • Reduction in number of digits
  • Paedomorphic dinosaur skull in birds - skull shape remains similar between juvenile and adults
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12
Q

What are the dinosaur features found in birds?

A
  • Egg laying
  • Scales (feathers are derived scales)
  • S shapes neck
  • Tridactyl foot
  • Bipedal
  • Toes bearing weight of body
  • Wishbone (evolved in the theropods)
  • Fused sternum (also found in theropods)
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13
Q

What is Archaeopteryx?

A
  • First fossil with well-developed feathers from jurassic deposits
  • 150 mya
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14
Q

What is special about Archaeopteryx?

A

Shows a transitional form between birds and reptiles

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15
Q

What are Archaeopteryx reptilian features?

A
  • Stong thick bones
  • Teeth
  • No fusion of vertebrae
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16
Q

What are the bird features of Archaeopteryx?

A
  • Well developed feathers
  • Three fingers
  • S shaped neck
17
Q

What do Arcchaeopteryx feathers show?

A
  • Asymmetrical feathers - typical of flight feathers
  • Had a similar moulting strategy to modern birds - helps to maintain feathers for flight
  • Primitive shoulder that would have limited ability to flap wings
  • Glide - lived in areas without trees - would glide not flap wings
  • Closed structure that suggested they weren’t climbing
  • Similar flight to a pheasant
18
Q

Archaeopteryx hind-foot

A

Similar to hind-foot of modern birds

19
Q

Archaeopteryx Furcula

A
  • Wish bone
  • Fused clavicle
  • Found in theropods and birds
20
Q

Archaeopteryx had a hyper extendable second toe, what group also showed this?

A
  • Seen in dromaeosaurs
  • Not seen in modern birds
  • The terrible claw
  • Believed to be used for hunting
21
Q

Differences between Archaeopteryx and modern birds?

A
  • Archaeopteryx had a smaller brain case than modern birds
  • Individual vertebrae (not fused like in modern birds)
  • Longer tail compared to modern birds
  • Modern birds has large sternum
  • Modern birds have 2 digits - Archaeopteryx 3
22
Q

Was Archaeopteryx the first bird?

A
  • Recently new species of small feathered dinosaurs have been found
  • Unsure if its convergent evolution / closely related cousins etc?
  • Rahonavis, auromis, scansoriopteryx - other small feathered dinosaurs
  • Unsure where Archaeopteryx belongs in the phylogeny

VERTEBRATES (16 decks)

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