Reptiles and Birds

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Reptiles and Birds

• Biology I Chapter 31-1

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REPTILES
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Reptile Characteristics

• Subphylum Vertebrata
• Dry, scaly skin, and lungs
• Dry, scaly terrestrial eggs with several
  membranes

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Reptile Characteristics

• Backbone
• Tail
• Two limb girdles
• Four limbs
• Example iguana

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Exceptions

• Snakes are limbless!

• Turtles have hard
• shells fused to their
• vertebrae!

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Reptiles

• Dry body prevents water loss in a dry environment
• Disadvantage the skin must be shed as it grows
• Can live across the globe, except in extremely
  cold environments

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Evolution of Reptiles

• Reptiles were the first animals to adapt their
  eggs to dry habitats
• First reptiles are from 350 mya
• Did not become common until about 40-50 million
  years later when the conditions of Earth were
  drier

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Mammal-Like Reptiles

• At the end of the Permian Period 245 mya, a
  great variety of reptiles roamed the Earth

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Mammal-Like Reptiles

• Displayed a mixture of mammalian and reptilian
  characteristics
• Dominated many land habitats
• Became extinct in just a few million years
• Replaced by another group of reptiles

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Enter the Dinosaurs

• Late Triassic and Jurassic periods
• Two groups of large aquatic reptiles swam in the
  seas
• Ancestors of modern turtles, crocodiles, lizards,
  and snakes populated many land habitats

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Enter the Dinosaurs

• Dinosaurs were everywhere!
• Saurischia lizard-hipped dinosaurs
• Ornithischia bird-hipped dinosaurs
• Dinosaurs are the ancestors of modern birds

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Exit the Dinosaurs

• Mass Extinction 65 mya the end of the Cretaceous
  Period
• Caused by a dramatic series of natural disasters
• Volcanic eruptions, dropping in sea level, huge
  asteroid or comet smashing into the now Yucatan
  Peninsula in Mexico, etc.
• Opened up niches on land and in the sea,
  providing opportunities for other kinds of
  organisms to evolve

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Form and Function in Reptiles

• Adaptations that have contributed to the success
  of reptiles on land
• Well developed lungs
• Double-loop circulatory system
• Water-conserving excretory system

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Form and Function in Reptiles

• Adaptations that have contributed to the success
  of reptiles on land (continued)
• Strong limbs
• Internal fertilization
• Shelled, terrestrial eggs
• Control of body temperature by changing
  environments

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Body Temperature Control

• The ability to control body temperature is an
  enormous asset for active animals
• Ectotherm animal that relies on interactions
  with the environment to help it control body
  temperature
• Turtles, snakes and other modern reptiles

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Body Temperature Control

• To keep warm bask in the sun during the day or
  stay under water at night
• To cool down move into the shade, go for a swim,
  or take shelter in underground burrows

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Body Temperature Control
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Feeding

• Eat a wide variety of foods
• Iguanas are herbivores and have long digestive
  systems to break down plant material
• Snakes, crocodiles and alligators are carnivores
• Chameleons have sticky tongues as long as their
  bodies to catch insects

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Respiration

• Lungs are spongy, providing more gas-exchange
  area than those of amphibians
• Many have muscles around their
  ribs that expand the chest
  cavity to
  inhale and collapse the cavity to
  force air out
• To exchange gases with the environment, reptiles
  have two efficient lungs, or like some snakes,
  one lung

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Circulation

• Efficient double-loop circulatory system
• Blood to/from lungs
• Blood to/from body
• 2 atria and 1 or 2 ventricles
• Most have 1 ventricle with a partial septum, or
  wall, separating the oxygen-rich and oxygen-poor
  blood

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Circulation

• Crocodiles and alligators have the most developed
  hearts of living reptiles
• 2 atria and 2 ventricles
• Arrangement also found in birds and mammals

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Circulation
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Excretion

• Urine is produced in the kidneys
• Urine contains either
  ammonia or uric acid
• Ammonia those reptiles
  that drink a lot
  of water
  i.e. crocodiles and alligators
• Uric acid those reptiles that need to conserve
  water, that live entirely on land eliminated
  into a pasty white solid

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Response

• Pattern of brain is similar to that of an
  amphibian
• The cerebrum and cerebellum are large compared to
  rest of the brain
• Active during the day

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Response

• Tend to have complex eyes and can see color well
• Pair of nostrils snakes have a good sense of
  smell
• Pair of sensory organs in the roof of the mouth
  detect chemicals
• Simple ears with an external eardrum

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Movement

• Reptiles with legs
• Run, walk, burrow,
  swim or climb
• Reptiles without legs
• Squirm and twist
• Backbones of reptiles help accomplish much of
  their movement

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Reproduction

• All reproduce by internal fertilization
• Most males have a penis that allows them to
  deliver sperm into the females cloaca
• The fertilized egg is covered with a leathery
  shell

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Reproduction

• Most are oviparous and lay the eggs in nests
• Amniotic egg egg composed of shell and membranes
  that create a protected environment in which the
  embryo can develop out of the water
• An important adaptation to land

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Groups of Reptiles

• The four surviving groups of reptiles
• Lizards and snakes
• Crocodilians
• Turtles and tortoises
• Tuatara

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Lizards and Snakes

• Order Squamata scaly reptiles
• Most lizards
• Legs
• Clawed toes
• External ears
• Movable eyelids

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Lizards and Snakes

• Order Squamata scaly reptiles
• Most snakes
• Lost both pairs of legs during their evolution
• Highly efficient predators
• Some can produce venom

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Crocodilians

• Order Crocodilia
• Alligators, crocodiles, caimans, and gavials
• Long, broad snout and squat appearance
• Fierce carnivores

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Crocodilians

• Maternal care of young
• Live only in the tropics and subtropics
• Alligators live only in fresh water, exclusively
  in North and South America
• Crocodiles live in either fresh or salt water
  and are native to Africa, India and Southeast
  Asia

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Turtles and Tortoises

• Order Testudines
• Shell built into the skeleton
• Carapace the dorsal part of the shell
• Plastron ventral part of the shell
• Lacking teeth, these reptiles have horny ridges
  that cover the upper and lower jaws

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Turtles and Tortoises

• Turtle live in the water
• Tortoises live on land
• Terrapin turtle that is found in water that is
  somewhat salty

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Tuataras

• Order Sphenodonta
• Only member of its order
• Found in a few small islands off the coast of New
  Zealand
• Resemble lizards
• Lack external ears and retain primitive scales
• Third eye part of a complex organ located on
  top of the brainfunction still unknown

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Ecology of Reptiles

• Many are in danger because of loss of habitat
• Humans also hunt them for food, to sell as pets,
  for their skins, etc.
• Some are now protected