From Reptiles to Aves

First Vertebrates

Evolutions of Fish to AmphibiansEvolution of Amphibians to

Reptiles

Evolution of Reptiles to Dinosaurs to Birds

Common Ancestor of Birds and Reptiles: Thecodonts

Bipedal Thecodonts to Birds Caudipteryx “tail feather”

◻ Existed in Cretaceous Period ~124.6 million years ago

◻ Peacock-sized dinosaur ◻ Velociraptor-like◻ Feathers on tail and arms◻ Arms were too short to be

wings.

⬜ Then what is the function of feathers?

Archaeopteryx - An evolutionary link between reptiles and birds

http://channel.nationalgeographic.com/videos/the-feathered-dinosaur/

Archaeopteryx “ancient wing”First known bird fossil ~ 150 million years old

◻ Dinosaur-like... ⬜ Skull has teeth⬜ Few fused bones⬜ Solid bones⬜ Long reptilian tail⬜ No enlarged breast

bone⬜ Dinosaur forelimbs

Archaeopteryx:First known bird fossil

◻ Bird like...⬜ Contour flight feathers

on wings and tail⬜ Wishbone (furcula)

Fossil RecordWhy are many fossil records incomplete?

Bird Classification

◻ Domain: ?

◻ Kingdom: ?

◻ Phylum: ?

◻ Class: ?

What adaptations make birds so successful?

What adaptations make birds so successful?◻ Feathers and ability to fly for most◻ Hollowed bones◻ 4 chambered heart◻ Amniotic eggs◻ Advanced system of lungs and air sacs

What key characteristics do all birds have in common?

Similarities between birds and reptiles?

1. Vertebrates2. ________ Eggs3. Oviparous (except

some reptiles are viviparous)

4. Scaly lower legs and feet with claws made of _______.

Differences between birds and reptiles?

1. Birds have ________2. Birds can ___ (most)3. Birds are __________,

and reptiles are ectotherms

4. Birds have 4 limbs (2 hind limbs for walking and 2 front limbs for flying) and reptile limbs vary between 0-4

5. Birds do not have teeth they have a hard bill, and reptiles have teeth.

6. Birds have a ____ chambered heart, and most reptiles have a _____ chambered heart with a partial ______.

How are the bones of birds different from the bones of other vertebrates?

Bird Skeleton

◻ Lightweight and _____

◻ Pneumatized _____

◻ Respiratory air pockets in bones

◻ Furcula “little fork” often called the ________. (formed by the fusion of two clavicles)⬜ Shock absorber for wings⬜ Stabilize thoracic skeleton

Bird Muscles◻ Control wings and legs

◻ Largest muscle is the __________ muscle, it makes up 15-25% of bird’s mass⬜ Connects sternum to

humerus⬜ Paired with the

Supracoracoideus muscle they make up __-__% of the bird’s mass

◻ Why would birds need so much muscle in their thoracic region?

What are feathers used for? What are feathers used for?

◻ Flight◻ Warmth◻ Mating◻ Camouflage◻ Intimidation

Feathers

◻ Reptile scales adapted into feathers

◻ Feathers are replaceable

◻ 2 types of feathers⬜ Contour

■ Flight feathers

⬜ Down■ Warmth

Feathers

◻ Down Feathers⬜ Soft⬜ Fluffy⬜ Used for _____⬜ Smaller and closer to body

◻ Contour Feathers⬜ Flight feathers⬜ Provide _____ and _____⬜ Strong and stiff

Bird Circulatory System

◻ 4 Chamber heart, 2 loops• Complete septum prevents mixing of

oxygen-rich and oxygen-poor blood

Bird Respiratory System

◻ Air sacs allow unidirectional flow of air

◻ 2 lungs and 7-9 air sacs

◻ Air sacs form air pockets in the skeleton

◻ More efficient than mammals⬜ Transfer more oxygen with each

breath

Bird Digestive System

◻ Pathway of food:

• Mouth

• Esophagus

• Crop - stores food

• Gizzard - grinds food

• Intestines

• Cloaca

Bird Beaks

◻ Many types of beaks⬜ Specialized for food types

◻ Other uses⬜ Grooming⬜ Moving objects⬜ Preying on food⬜ Feeding young

Bird Reproduction

◻ Internal fertilization

◻ Lay eggs

◻ One or both parents incubate eggs⬜ Stimulates growth

⬜ 12-80 days before hatching

◻ Care for young until they can fly

Why do birds migrate? Why do birds migrate?

• For food • Nesting locations

Navigation◻ Sun

◻ Stars

◻ Magnetic Field⬜ Brain contains magnetite, an iron

oxide crystal that aligns with magnetic north similar to a compass needle

⬜ Homing pigeons with magnets on their heads get very confused and disorientated

Physics of Flight

◻ Birds use wings, feathers, and physics to fly

Bernoulli’s Principle◻ Bernoulli's principle states that as air moves

around an object, it creates different pressures on that object. Faster air means less pressure. Slower air means more pressure.

◻ The key to flight is creating pressure upwards on the bird's wing to keep the bird in the air.

◻ This pressure produces an upward force called lift.

Lift◻ Lift is caused by the pressure under the wing

being greater than the pressure above the wing.

◻ The shape and angle of the wings create the air speed/pressure difference.

Thrust◻ Thrust is a forward force caused by the

flapping of the bird’s wings.

◻ Overcomes the drag force caused by air resistance.

What forces are acting on the bird?

What forces are acting on the bird?

Thrust

Lift

Drag

weight

What forces are acting on the bird?

FAT

FA

L

FF =

drag

FG

= weight

Lift

Thrust

Resulting Force