Transcript What is a Bird?

What is a Bird?
Por
Luis A. Perez Ayala
Yael A. Barrientos Martinez
What is a Bird?
Por
Luis A. Perez Ayala
Yael A. Barrientos Martinez
What is a Bird?
 Birds are reptilelike animal that maintain a constant
internal body temperature.
 They have an outer covering of feathers; tow legs that
are covered with scales and are used for working o
perching.
 Front limbs modified into wings.
 The single most important
characteristic is that they has
feathers.
What is a Bird?
 Feathers are made mostly of protein and develop from
pits in the birds skin.
 Feathers help birds fly and also keep them warm.
 There are two main type of feathers; contour feathers
and down feathers.
 Herons and some other birds that live on or in water
also have powder down, which release a fine powder
that repels water.
Evolution of Birds
 Paleontologist agree that birds evolved
extinct reptiles.
from
Evolution of Birds
 Birds excrete nitrogenous waste
in the form of uric acid.
 The bones that support the front
and hind limbs, and several other
parts of the skeleton, are similar in
both groups.
 Most think that birds evolved
directly from dinosaurs.
Evolution of Birds
Evidences consists of Archaeopteryx,
first birdlike fossil discovered.
This fossil dates from the Jurassic Period,
about 150 million years ago.
Archaeopterys looked so much like a
small, running dinosaur that it would be
classified as a dinosaur except for one
important feature: It had well-developed
feathers covering most of its body.
Those feathers led to the classification of
Archaeopteryx as an early bird.
Form, Function, and Flight
Birds have a number of adaptations that enable
them to fly. These adaptations include:
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Highly efficient digestive systems.
Respiratory, and circulatory systems.
Aerodynamic feathers and wings
Strong, lightweight bones
Strong chest muscles.
Body Temperature Control
 Unlike reptiles, which must draw body
warmth from their environment, birds can
generate their own body heat.
 Animal that can generate their own body
heat are called endotherms.
 Endotherms have a high rate of metabolism
compared to ectotherms such as reptiles.
 Metabolism produces heat.
Feeding
 Any body heat that bird loses must be regained by
eating food.
 The more food a bird eats, the more heat energy its
metabolism can generate.
 Because small birds lose heat
relative faster than large ones,
small birds eat more, relative to
their body size.
 Bird’s beaks, or bills, are adopted
to the type of food they eat.
Feeding
 Insect-eating birds have shorts, fine bills that
can pick ants and other insects off leaves and
branches, or can catch flying insects.
 Seed-eaters have short, thick bills.
 Long, thin bills can be used
for gathering nectar form
flower or probing soft mud
for worms and shellfish.
Feeding
 Large, long bills help birds to pick fruit from branches,
while long, flat bills are used to grasp fish.
 Carnivorous birds, such a eagles,
shred their prey with strong
hooked bills.
The digestive System of a Bird
 Birds lack teeth, and therefore they cannot
break down food by chewing.
 However, many birds have specialized structures
to help digest food.
 One structure is the crop,
which is located at the lower
end or the esophagus.
The digestive System of a Bird
 Food is stored and moistened in the crop
before it moves further in the digestive tract,
 In some birds, such as pigeons, the crop has a
second function.
 During nesting season, the breakdown of cells
in the crop produces a substance that is rich in
protein an fat.
 Parents birds regurgitate this substance and
feet their newly hatched young with it.
The digestive System of a Bird
 From the crop, moistened food moves into the
stomach.
 The form that a birds stomach takes depends
on the bird’s feeding habits.
 Birds that eat meat or fish have an expandable
area in which large amounts of soft food can be
stored.
 Birds that eat insects or seeds, however, have a
muscular organ called the gizzard that help in
the mechanical breakdown of food by grinding
it.
The digestive System of a Bird
 The gizzard forms part of the stomach.
 In many species of birds, the gizzard contains
small pieces of stone and gravel that the bird
has swallowed.
 The thick, muscular walls
of the gizzard grind the
gravel and food together,
crushing food particles
and making them easier to digest.
Respiration
 Birds have a unique and
highly efficient way of
taking
in oxygen and
eliminating carbon dioxide.
 When a birds inhales, most air first enters large
posterior air sacs in the body cavity and bones.
 The inhaled air then flows through the lungs.
 Air travels thought the lungs in a series of small tubes.
Respiration
 These tubes are lined with specialized tissue,
where gas exchange takes places.
 The complex system of air sacs and out
through the lungs in a single direction.
 The one-way flow constantly expose the lungs
to oxygen-rich air.
Circulation
 Birds have four-chambered hearts and two separate
circulatory loops.
 The bird’s hearts has two separate ventricles, the right
ventricle and the left ventricle.
 There is complete separation
of oxygen-rich and oxygen-poor
blood.
 One half of the hearts receives
oxygen-poor blood from the body and pumps this
blood to the lungs.
Circulation
 Oxygen-rich blood returns to the other side
of the heart to be pumped to the rest of the
body.
 This double-loop system ensures that oxygen
collected by the lungs is distributed to the
body tissue with maximum efficiency.
Excretion
 Nitrogenous waste are removed from the blood by the
kidneys, converted to uric acid, and deposited in the
cloaca.
 Most of the water is reabsorbed,
leaving uric acid crystals in a white,
pasty form that you may recognize
as bird droppings.
Response
 Birds have well-developed sense
organs, which are adaptations
that enable them to coordinate
the movements required for flight.
 Birds also have a brain that can quickly interpret and
respond to a lot of incoming signals.
 A bird’s brain is relatively large for its body size.
 The cerebrum, which controls such behaviors as flying,
nest building, care of young, courtship, and mating, is
quite large.
Response
 The cerebellum is also well developed, as you might
expect in an animal that uses precise, coordinated
movements.
 The medulla oblongata coordinates basic body
processes, such as the heartbeat.
 Birds have extraordinarily well developed eyes and
sizable optic lobes in the brain.
 Birds see color very well, in
many cases, better than humans.
Response
 Most bird species can also hear quite well.
 The senses of taste and smell, however, are not
well developed in most birds, and the olfactory
bulbs in bird’s brain are small.
Movement
 Some birds cannot fly.
 Instead, they get around
mainly by walking or running,
like the penguins.
 The vast majority of birds can fly.
 The skeletal and muscular systems of flying
birds exhibit adaptations that enable flight.
Movement
 The bones in a bird’s wings are homologous to
the bones in the front limbs of other vertebrates,
they have very different shapes and structures.
 In flying birds, many
large bones, such as
the collarbone, are fused
together, making a bird’s
skeleton more rigid than a
reptiles.
Reproduction
 Male and female reproductive tracts open into the
cloaca.
 The sex organs often shrink in size when the birds are
not breeding.
 As birds prepare to mate, the ovaries and testes grow
larges until they reach functioning size.
 Mating birds press their cloacas
together to transfer sperm from
the male to the female.
Reproduction
 Some birds have a penis
that transfers sperm to
the female’s cloaca.
 Bird eggs are amniotic
eggs.
 They are similar to the eggs of reptiles but
have hard outer shells.
 Most birds incubate their eggs until the eggs
hatch.
Reproduction
 Went a chick is ready to hatch, it uses a small
tooth on its bill to make a hole in the shell.
 After much pushing, poking, and prodding by
the chick, the eggshell breaks open.
 Once the exhausted bird has hatched, it
collapses for a while and allows its feathers to
dry.
 Both parents may be kept busy providing food
for their hungry offspring.
Ecology of Birds
Because birds are so numerous and diverse, they
interact with Natural ecosystems and human
society in many different ways.
 Hummingbirds pollinate flowers in
both tropical and temperate zone.
 Fruit-eating birds swallow seeds but
may not digest them, so their droppings disperse seed
over great distances.
Ecology of Birds
 Insect-eating birds, such as swallows and chimney swifts,
catch great numbers of mosquitoes and other insects,
and therefore help control insect populations.
 Many birds migrate long distances, often over hundreds
of kilometers of open sea.
 Such migration are usually seasonal.
 Because birds are highly visible and are an important
part of the biosphere, they can serve as indicators of
environmental health.
Check Points!
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What is Archaeopteryx?
What is an endotherm?
How is their respiratory system advantageous to bird?
Do birds have external or internal fertilization?
Thank for your attention!