Download Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class

Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class Aves
A Separate Taxon?
Molecular and fossil evidence has
convinced most biologists that birds are
actually reptiles.
The evidence indicates that crocodilians
and birds are more closely related to
each other than either one of them is to
snakes and lizards.
Characteristics of Birds
Endothermic
Bony beak, no teeth
Large muscular stomach
Bipedal
Large, yolked, hard-shelled, amniotic
eggs
The parent bird provides extensive care
of the young until it is grown
Strong, lightweight skeleton
Specialized adaptations for flight:
– Keratinous feathers (modified scales) that
function in both flight and insulation
– Specialized wing shape that produces lift
Internal Anatomy
Wings
Most birds have airfoil-shaped wings.
Wing shape is closely related to wing
function.
High Metabolic Rate
Birds have a system of branching air sacs
that function with their lungs in respiration.
The system of air sacs supplies the high levels of
oxygen needed to support a high rate of
metabolism for the hard-working flight muscles.
This high metabolic activity also provides heat
for endothermy.
Weight-Reduction
The air-sac system reduces the
overall density of the bird
Bones have a honeycombed
structure that makes them
lightweight but strong
Birds are missing some of the
internal organs found in other
vertebrates:
– Females have one ovary instead of two
– No teeth (a hard beak and a gizzard
with stones for grinding food)
Circulatory System
Bird circulatory systems efficiently
deliver oxygen to cells.
Like amphibians and reptiles, birds
have two pathways of blood flow:
one from the heart to the lungs and
back, and the other from the heart
to the rest of the body and back.
Unlike amphibians and most
reptiles, birds have a fourchambered heart with two separate
ventricles that keep oxygen-rich
blood from the lungs separate from
the oxygen-depleted blood that
passes through the heart.
The Origin of Birds
Most paleontologists agree that the
common ancestor of all existing birds was
a type of small, feathered dinosaur.
Recent fossil discoveries of feathered
dinosaurs in China support this
hypothesis.
Caudipteryx zoui
Microraptor gui
Sinornithosaurus millenii
Archaeopteryx
Represents an animal that
lived about 150 million years
ago.
Unlike modern birds,
Archaeopteryx had clawed
forelimbs, teeth, and a long tail
with vertebrae—all reptilian
characteristics.
In fact, if the feathers had not
been preserved in the fossil,
Archaeopteryx probably would
have been identified as a small
dinosaur.
Bird Biodiversity
There are about 9,000
species of birds living
today, far outnumbering
mammal species.
Tremendous diversity of
flying styles, beak and
foot adaptations, and
behavioral characteristics.
Flying Styles
Different styles of flying:
– Cardinals and finches rapidly change
altitude as they fly, a behavior that helps
them avoid predators.
– Falcons and albatrosses are hunting birds that
soar, using their wings to gain altitude and then
gliding on air currents without flapping.
– Hummingbirds flap their wings as many as 80
times per second, enabling them to hover.
– Penguins are flightless diving birds that use the
same basic flight stroke to swim.
– Chickens belong to a group of birds that can fly
short distances, but are incapable of long flights.
– Ostriches, emus, and kiwis are cannot fly at all.
Beak Adaptations
Also called “bills”
Made of keratin
Nostrils function in
breathing
Variety of beak
shapes reflects a wide
range of functions
Beaks are not used
for chewing, though
some are used to
break food into
smaller pieces
Foot Adaptations
Various birds use their feet for
walking, perching on branches, wading,
paddling through water, grasping food,
in defense, and in some courtship
rituals
Most bird feet are covered in scales
Most birds have four toes on each foot,
though the arrangement varies from
species to species
Behavioral Adaptations
Bird brains are relatively highly
developed, with a brain to body size
ratio second only to mammals.
Birds are capable of complex behavior,
especially in elaborate courtship rituals,
caring for their young, and communication.
A crow making a tool from an oak branch
A crow bending a wire to make a tool
A crow using traffic to crack a nut