why can birds fly pp

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Why can birds fly?

By Erin Thomas

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Flight for Survival

Flight is the reason that birds still exist.Without it, predators would have caused the

Aves to go extinct millions of years ago. This

special adaptation is unique to birds, excluding

bats and flying insects. The ability to fly enables

birds to find food easier and to escape from

predators.

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Physical Adaptations

Over time, birds have adapted to their 

surroundings. All systems of their bodies

have changed in order to better equip

them for, well, survival. Throughout theyears, new species have been formed

because of change in environment. The

class of the Aves is not about to go

extinct because of their incredibleadaptability.

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Skeletal Adaptations

No teeth

Fused pelvic bone

Reduction of bones

Hollow and light bones

 All of these adaptations

make birds lighter, more

aerodynamic, and morebalanced, which makes

flying possible.

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Muscular Adaptations

A bird¶s pectoral muscles

count for 15-40% of its

body weight (1-2% in

humans) No heavy back muscles

or facial muscles.

(stability and balance)

Supercoracoidius (muscle

that pulls wings back) is

connected to the sternum

rather than the back bone

for even more balance.

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Nervous System Adaptations

The cerebellum in the brain is enlarged in

proportion to size, which is the part of the

brain used for balance and coordination.

Bird BrainHuman Brain

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Optics

Proportionally, birds eye¶s are 10-15% larger than

human eyes.

Birds¶ eyes account for 15% of the weight of their head,

while in humans they are only 1% of our head weight. A bird¶s retina is 1-1.5% thicker than mammals¶.

The cones (located in the fovea) are also more

concentrated than humans.

 ± Bird- 1 million cones/ sq. mm ± Human- 200,000 cones/ sq. mm

Birds can see in color because of special oil droplets in

the retina. These oil droplets also improve contrast and

reduce haze.

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More Optics

A Hawk¶s vision is 8x better than humans

Most birds of prey have two fovea; one central for side vision,

and one temporal for front vision.

S

clerotic ring is a ring of bones around edge of eye. The ringfixes it so eye can't move. Birds make up for the lack of 

movement by having really flexible neck.

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Smell and Taste

Birds do not have a very keen sense of smell of 

taste.

The kiwi has the best sense of smell.

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Hearing

Birds have some of the best hearing of all

animals.

However, their hearing lacks focus.

Two types of birds use echolocation; Oilbird and

Cave Swiftlet.

Oilbird Cave Swiftlet

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Excretory and Digestive System

Birds have no urinary bladder 

The cloaca is the common canal for both

reproductive and excretory systems, which reduces

extra weight. Birds have very efficient digestive enzymes

They eat high energy foods to use for flight.

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Respiratory System

Birds use air sacs which are pockets used

along with the lungs to assist breathing

 ± They also make birds more buoyant

 ± They cool birds¶ high metabolism

 ± They cushion deep dives for waterfowl

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The Evolution of Flight

Since the  Archaeopteryx (the earliest fossil

found of a bird), flight has changed a lot.

Wing length and shape have changed inorder to best suit the type of food that a

bird needs.

Flight will continue to change

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So why can birds fly?

Birds have adapted over time in order to findfood easier and to flee from predators.

Their bodies have changed in order to make

flight possible. ± Better vision and hearing

 ± Light weight

 ± Hollow bones

 ± Better balance and coordination Birds will continue to evolve and adapt, making

them unstoppable.

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