Transcript Chapter 36: Comparing Vertebrates

Chapter 36: Comparing Vertebrates
Section 1: Evolution of the
Vertebrates
Evolution of the Vertebrates
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Ever since the first vertebrates appeared
more than 500 million years ago, they have
been evolving
 Have developed many new and unusual
features
 Sharper claws
 Longer hair
 Amniotic egg
 Paired front and rear limbs
The Vertebrate Family Tree
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Most scientists agree that:
 Amphibians evolved from lobe-finned fish
ancestors
 Reptiles evolved from amphibian ancestors
 Birds and mammals evolved from reptile
ancestors
Trends in Vertebrate Evolution
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Two general trends appear repeatedly during
the course of vertebrate evolution
 If closely related evolutionary lines are
subjected to different forces of natural
selection, they tend to become more
dissimilar as they evolve
 If evolutionary lines encounter
extremely similar forces of natural
selection, they tend to become more
similar to one another as they evolve
Trends in Vertebrate Evolution
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As different vertebrate groups evolved, they
utilized the same basic sets of body parts for
many uses
The pattern of evolution known as adaptive
radiation is also known as divergent
evolution
 One species gives rise to many species
that appear different externally but are
similar internally
Trends in Vertebrate Evolution
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Convergent evolution is just the opposite
 Adaptive radiations among different
organisms produce species that are similar
in appearance and behavior
Body Temperature Control
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Many chemical reactions work better at certain
temperatures
When the body temperature is too low, animals slow down
and become immobile
When the body temperature is too high, body systems are
stressed and fail to function properly
Many techniques of temperature control have appeared in
vertebrates
 Incorporate three important features
 A source of heat for the body
 A way to conserve that heat
 A method of eliminating excess heat when necessary
Chapter 36: Comparing Vertebrates
Section 2: Form and Function in
Vertebrates
Form and Function in Vertebrates
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Vertebrates perform the essential functions of
life with a variety of body structures
Evolutionary processes have modified certain
basic structures over time
As you move through the vertebrate
classes from fishes to mammals, organ
systems tend to become increasingly
complex
Movement
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All vertebrates except jawless fishes have a vertebral
column (backbone) made of numerous individual
bones called vertebrae
 Connected to one another by tough ligaments that
allow the vertebral column to bend to a certain
extent
 Two pairs of limbs are attached to this basic
supporting structure by sets of bones called limb
girdles
 Most of the bones in the body can be made to move
through the contraction of muscles that are attached
to the bones
Movement
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Fish and snakes
 Main body muscles are arranged into blocks that are
positioned on either side of the vertebral column
 Contract in waves, one after another
 Make the body bend rapidly back and forth
Amphibians, reptiles, birds, and mammals
 The position of the limbs relative to the body shifts
toward the center
 The movement of the vertebral column when the animal
runs changes from a side-to-side motion to an up-anddown motion
Feeding
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The heads of vertebrates show many adaptations
for feeding
The organs of the digestive systems of vertebrates
are equally well adapted for different feeding habits
 Carnivores
 Short digestive tracts with special enzymes that
break down meat
 Herbivores
 Long intestines and stomachs with bacteria that
break down cellulose
Respiration
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Aquatic vertebrates
 Use gills for respiration
 As water passes over the gill filaments, oxygen
diffuses into the blood in the capillaries and carbon
dioxide diffuses from the blood into the water
Terrestrial vertebrates
 Use lungs to breathe
 When the animals inhale, oxygen-rich air enters the
lungs
 When the animals exhale, carbon dioxide-rich air is
expelled
Internal Transport
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Fishes and larval amphibians
 Single-loop circulatory system
 Blood travels from the heart to the gills to
the body and back to the heart
 Two chambered heart
Vertebrates with lungs
 Double-loop circulatory system
 Heart and lungs
 Heart and body
Excretion
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Excretory systems eliminate nitrogenous wastes and regulate
the amount of water in the body
Most vertebrates rely on kidneys for excretion
Nitrogenous wastes are first produced in the form of ammonia
 Aquatic amphibians and fish
 Ammonia diffuses from the gills into the surrounding
water
 Mammals, terrestrial amphibians, and cartilaginous fishes
 Ammonia is changed into urea
 Reptiles and birds
 Ammonia is changed into uric acid
Response
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All vertebrates display a high degree of
cephalization
The size and complexity of the cerebrum and
cerebellum increase as you move through the
vertebrate classes from fish to mammals
Reproduction
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Almost all vertebrates reproduce sexually
In some vertebrates fertilization is external
In other fertilization occurs inside the body of
the female
Reproduction
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Vertebrates show three different modes of
development
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Oviparous
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Ovoviviparous
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Eggs develop outside the mother’s body
Eggs develop inside the mother’s body but the embryos
receive the nutrients they need from the yolk that
surrounds them, not from the mother directly
Viviparous
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Developing embryos obtain nutrients directly from the
mother’s body