Reptiles and Birds

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C-31-2 Birds
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BIRDS
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Birds

• Reptile-like animals that have maintained a
  constant internal body temperature
• Two legs covered with scales that are used for
  walking or perching
• Front limbs modified
  into wings

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Feathers
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Birds

• Outer covering of feathers made mostly of
  proteins and developed from pits in the birds
  skin
• Contour feathers
• Down feathers
• Powder down feathers

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Evolution of Birds

• A dinosaur with feathers
• Archaeopteryx first fossil found of an early
  bird-like animal
• Looked like a small, running dinosaur with
  well-developed feathers

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Evolution of Birds

• Unlike modern birds, it had teeth, a bony tail,
  and toes and claws on its wings
• It is a transitional species between dinosaurs
  and birds

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Form, Function, and Flight

• Adaptations for Flight
• Highly efficient digestive system, respiratory
  system, circulatory system
• Aerodynamic feathers and wings
• Strong chest muscles

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Body Temperature Control

• Endotherm animal that generates its own body
  heat and controls its body temperature from
  within
• Include birds, mammals and some other animals

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Body Temperature Control

• High rate of metabolism compared to ectotherms
• Metabolism produces heat
• A birds feathers insulate its body enough to
  conserve most of its metabolic energy

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Feeding

• Any body heat that a bird loses must be regained
  by eating food
• The more a bird eats, the more heat energy its
  metabolism can generate
• Small birds must eat more, relative to their body
  size

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Feeding

• Birds beaks, or bills, are adapted to the food
  that they eat
• Crop structure at the lower end of the esophagus
  in which food is stored and moistened
• Gizzard a muscular organ that helps in the
  mechanical breakdown of food

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Respiration

• Air sacs one of several sacs attached to a
  birds lungs into which air moves when a bird
  inhales allows for the one-way flow through the
  respiratory system
• Advantages
• The one-way flow of oxygen-rich air helps birds
  maintain their high metabolic rate
• Enables birds to fly at high altitudes where
  there is little oxygen in the atmosphere

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Respiration
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Circulation

• 4 chambered hearts and 2 separate circulatory
  loops
• 2 ventricles
• Complete separation of oxygen-
  rich and oxygen-poor
  blood
• This double-loop system ensures
  that oxygen collected
  by the lungs
  is distributed to the body tissue with
  maximum efficiency

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Circulation
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Excretion

• Similar to that of many reptiles
• Nitrogenous wastes are removed from the blood by
  the kidneys and converted into uric acid

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Excretion

• Uric acid is sent to the cloaca
• Water is reabsorbed into the body
• Uric acid crystals leaving the body are in a
  white, pasty form

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Response

• Well-developed sense organs to coordinate the
  movements required for flight
• Brain can quickly interpret and respond to many
  incoming signals
• Brain is large for its body
• Well developed eyes
• Can hear well
• Sense of taste and smell are not well-developed
  the olfactory bulbs in the brain are small

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Movement

• Some birds cannot fly
• Walk ostriches
• Swim penguins
• Flying birds many large bones are fused together
  to form a sturdy frame for flight

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Reproduction

• Both male and female reproductive tracts open
  into the cloaca
• The sex organs are internal and often shrink
  inside when birds are not breeding
• Amniotic eggs similar to reptilian eggs but have
  hard outer shells

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Groups of Birds

• There are nearly 30 orders of birds
• Some of the better known groups

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Groups of Birds

• Perching birds Passerines (includes songbirds
  such as larks, sparrows and finches)
• Pelicans and their relatives
• Birds of prey

• Parrots
• Cavity-nesting birds
• Herons and their relatives
• Ostriches and their relatives

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Ecology of Birds

• Birds interact with the natural ecosystems and
  human society in many ways
• Disperse seeds, pollinate plants
• Migrate long distances
• Serve as indicators of environmental health