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Evolution of Birds Evolution of Birds

Evolution of Birds - PowerPoint Presentation

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Evolution of Birds - PPT Presentation

Evolution of birds Kingdom Animalia Phylum Chordata Class Aves Where did they come from From the Mesozoic Era a debate of how they originated Two Hypotheses exist Thecodont ID: 376003

birds flight ground mya flight birds mya ground model theropods evolved pterosaurs theropod thecodonts animals gliding carnosaurs coelurosaurs powered

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Slide1

Evolution of BirdsSlide2

Evolution of birds

Kingdom

Animalia

, Phylum Chordata, Class AvesWhere did they come from?From the Mesozoic Era, a debate of how they originated. Two Hypotheses exist: Thecodont vs.TheropodSlide3

Evidence to link birds and dinosaurs

Hundreds of similar skeletal features

Hollow bones

Feathers in some dinosaursLungsHeartReproductive and Sleeping PostureSlide4

More Evidence

Similarities:

Gizzard Stones, Brooding and Care of young, Pulmonary Tract

Less DNA repetitions, proposed to aid in flight.T. Rex bones found with same amino acid sequence (made from DNA) as in chickens. This sequence is for collagen tissue created in common birds.Slide5

Archaeopteryx

First universally accepted bird. Estimated to be 150 million years old.

Had teeth, flight feathers, long bony tail, wishbone (fused collar bone), and many more theropod features.

At least 10 found by now.Slide6

190

MYA

135

MYA

65

MYA

225

MYA

Turtles

Lizards & Snakes

Crocodiles

Mammals

ANAPSIDS

DIAPSIDS

SYNAPSIDS

THERAPSIDS

THECODONTS

SAUROPODS

THEROPODS

CARNOSAURS

COELUROSAURS

ORNITHISCHIA

PTEROSAURS

DINOSAURIA

SAURISCHIA

So, Reptiles, But Where Birds?

Tertiary

Cretaceous

Jurassic

Triassic

PermianSlide7

190

MYA

135

MYA

65

MYA

225

MYA

Turtles

Lizards & Snakes

Crocodiles

Mammals

ANAPSIDS

DIAPSIDS

SYNAPSIDS

THERAPSIDS

THECODONTS

SAUROPODS

THEROPODS

CARNOSAURS

COELUROSAURS

ORNITHISCHIA

PTEROSAURS

DINOSAURIA

SAURISCHIA

Tertiary

Cretaceous

Jurassic

Triassic

PermianSlide8
Slide9

Slide10

DINOSAURIA

SAUROPODS

THEROPODS

CARNOSAURS

COELUROSAURS

ORNITHISCHIA

SAURISCHIA

Theropods

(ground runners)

give

rise to

Carnosaurs

&

Coelurosaurs

THECODONTS

Carnosaurs

Coelurosaurs

Velociraptor

is associated with this group.Slide11

Theropod Hypothesis

Theropod

has a 3-toed foot similar to modern bird.

Carpal wrist bone in Theropod and Archeaopteryx similar.Shoulder sockets similar to modern birds and allow “wings” or arms to tuck in close to body.

Lays eggs in nest that were incubated/protected

.

This Hypothesis aligns with “Ground Up” model for flight.Slide12

Thecodonts

give rise to crocodilians, dinosauria, & pterosaurs

Theropods

’ ancestors: Known for being smaller, long tails, short forelimbs.

Some scientists hypothesize that this group includes the small, lizard-like, flying reptiles.

These were around before

Theropods

.Slide13

ThecodontsOne example:

Microraptor

As seen in DVD “The Four-Winged Dinosaur”Slide14

Thecodont Hypothesis

Gliding seems more reasonable than

ground-runners” to giving flight.Birds bodies are flattened top-bottom, Theropods were flattened side-to-side.Feathers more likely evolved as flight stabilizers instead of a runners warmth.This hypothesis aligns with “Top Down” model for flight.Slide15

Evolution of Flight!Slide16

Two Main, Opposing Hypotheses

Arboreal Model

Trees Down” Model(Thecodont)Cursorial Model“Ground Up”

Model

(

Theropod

)Slide17

“Trees Down

Model

Ancestors of birds were tree-dwellers (arboreal)Powered flight evolved from gliding/parachuting:Tree-dwelling animals jumped from branch to branchThose with a gliding/parachuting surface could travel further, so selection favored development of increased wingsEventually, forms modified the gliding surface to give them additional thrust: powered flightSeems like a reasonable scenario for the origins of the other powered flying vertebrates (pterosaurs, bats)Makes sense energetically, since the early gliding phases can use gravity to help them fly long before the need for the development of strong arm muscles

Gliders/parachuters are VERY common, and tetrapod gliders/parachuters have consistenly evolved convergently from arboreal animalsSlide18

“Ground Up

Model

Ancestors of birds were ground running animals (cursorial)Powered flight evolved from activity useful to runners, outside of the context of a tree-dwelling phaseEvolution of the wing stroke evolved in some non-flight context (possibly food capture; possibly as a speed-aid or an aid for leaping and jumping)Feathers originally evolved in a non-locomotion context, but were exapted for whatever the possible pre-flight use of the forelimbs wasThrough enlargement of the proto-wing in the non-flight context, the forelimbs became large enough and developed enough to begin to carry the animal through the airBirds only got into the trees after having developed the early phases of flightSlide19

“Ground Up

Model

Birds, unlike bats and pterosaurs, do not make use of a membrane to fly; and there is no fossil evidence that they ever didUnlike bats and pterosaurs, the hind limb is not part of the flight surface; in fact, most modern and fossil birds have perfectly good running legs (just as their out groups had)Until recently, all the known member of avialian outgroups (

Deinonychosauria

,

Oviraptorosauria

,

Therizinosauria

,

Ornithomimosauria

) were fairly large bodied animals that were unlikely to have spent much time in trees

But there was a lack of good modern analogues for whatever the ground use scenario would have been

Also, some questioned whether it would have been energetically feasible for animals

to

have achieved

powered flight directly from a running/leaping behaviorSlide20

Youtube: 1of5--Evolve-Flight by History Channel 1 of 5 (see all 5)