What is a Bird?

Por

Luis A. Perez AyalaYael A. Barrientos Martinez

What is a Bird?

Por

Luis A. Perez AyalaYael 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 from extinct reptiles.

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

Highly efficient digestive systems. Respiratory, and circulatory systems. Aerodynamic feathers and wings Strong, lightweight bones Strong chest muscles.

Birds have a number of adaptations that enable them to fly. These adaptations include:

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

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.

Because birds are so numerous and diverse, they interact with Natural ecosystems and human society in many different ways.

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!

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!