Transcript Chapter 20: Vertebrates

Vertebrates
Vertebrate Survey
Anatomy and Physiology of
Vertebrates
Vertebrate Evolution
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Phylum Chordata is the group of
animals with a notochord – a flexible,
supporting structure along the back
Contains the invertebrate chordates,
and Subphylum Vertebrata, which
have evolved vertebral columns
Serves as site for muscle attachment,
protects nerve cord
Trends in Vertebrate Evolution
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Development of true bony jaws
Development of paired pectoral and
pelvic limb girdles
Development of bones
Most vertebrates have two sets of
appendages (arms and legs), a closed
circulatory system with a ventral heart,
and either gills or lungs for breathing
Class Agnatha
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Jawless fish
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Ex. Lampreys and hagfishes
Only living vertebrates without jaws
Parasites – survive by attaching themselves
to other fish or aquatic animals, feeding on
their blood and body fluids
Scavengers – eat decaying carcasses
Class Chondrichthyes
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Cartilaginous fish
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Ex. Sharks, skates, rays
Skeletons made of cartilage
Some are fearsome predators, other eat
small fish, mollusks, or plankton
Class Osteichthyes
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Bony fish
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Contain half of all vertebrate species, all
aquatic habitats
Ray-finned fish – sub-class containing
almost all fish species – well-developed
bone systems, specialized jaws with teeth
Lobe-finned fish – sub-class with lungs
and gills, relatives of amphibians
Class Amphibia (amphibians)
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Lay eggs in water and spend part of
their life cycle there (gills)
As adults, live on land and breathe
through lungs
Most have moist skin, as part of their
respiration occurs through skin
Class Amphibia
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Examples include:
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Newts and salamanders (lay eggs in water,
hatch into young that resemble adults –
larvae have gills that disappear and are
replaced by lungs as they grow)
Frogs and toads (eggs hatch in water as
tadpoles, which look completely different
from adults)
Class Reptilia (reptiles)
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Fully terrestrial
Reproduce by internal fertilization –
egg/sperm fuse within body of the
female
Produce leathery eggs to prevent water
loss
Dry scaly skin to retain moisture
Developed lungs
Class Reptilia
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Order Chelonia – turtles and tortoises,
protective shell of bony plates (long
fossil record)
Order Crocodilia – crocodiles,
alligators, caimans (long fossil record)
Order Squamata – lizards and snakes,
most abundant group
Class Aves (Birds)
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Only vertebrates with feathers
Used for flight and conservation of body
heat
Lay eggs
Class Mammalia (mammals)
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Named for presence of mammary
glands, enable females to nourish
young with milk
Have hair to retain body heat
Class Mammalia
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Three groups:
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Monotremes – egg-laying mammals like duckbilled platypus – have body hair/fur, lay leathery
eggs
Marsupials – live young born very early in their
development and continue to develop within
marsupium – kangaroos, koalas, opossums
Placental mammals – largest group, names for
placenta (organ that connects mother with
developing embryo, allows for nutrient, gas, and
waste exchange)
Support and Movement
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All have an endoskeleton surrounded by
muscles and skin
Vertebral column (backbone) is the main
part of the skeleton
Adapting to life on land led to changes in
limb positions
Amphibians had limbs that are horizontal
while reptile limbs are vertical to support
increased body mass
Feeding and Digestion
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All food sources presented problems as
vertebrates evolved
Meat is easy to digest, but must first be
caught then cut up for swallowing
Plant matter is easy to find, but must
be pulverized and shredded before
swallowing, and cellulose is hard to
digest
Feeding and Digestion
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Adaptations are present in teeth
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Meat requires teeth that hold, shred
Plants require teeth that grind/pulverize
Feeding and Digestion
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Adaptations seen in digestive tracts
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Meat digests easily, so carnivores have
short digestive tracts that secrete enzymes
to break down proteins
Plants need to be broken down slowly, so
herbivores spend more time
chewing/rechewing, and long digestive
tracts full on bacteria help digest cellulose
Respiration (gas exchange)
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Method/system depends on
environment
Fish rely on gills for respiration
Amphibians have gills as tadpoles and
poorly developed lungs as adults
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No muscles to inflate/deflate lungs
Rely on diffusion through thin, moist skin
Respiration (gas exchange)
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Reptiles are fully adapted to life on land
and have more developed lungs that
are divided into chambers to increase
surface area
Reptiles also have muscles to
inflate/deflate lungs
Respiration (gas exchange)
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Mammals require higher rate of gas
exchange because of higher metabolic
rate
Most developed lungs
Bronchi (air tubes) enter lungs then
branch to create more surface area,
ending in alveoli
Respiration (gas exchange)
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Alveoli are bubblelike structures
surrounded in capillaries
Efficient at gas exchange, but inefficient
because air must move in and out
through the same passageway
Respiration (gas exchange)
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Birds have highest requirements for
lung efficiency because they fly
Have branched bronchi and alveoli like
mammals, but also have air sacs within
some bones
Air is pumped in one direction
Internal Transport
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Closed circulatory systems
Two types: single-loop and double loop
Internal Transport
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Single-loop circulatory systems are
found in fish – blood is pumped from
the heart to the gills where respiration
takes place, then flows from the gills to
the rest of the body, returning to the
heart
Heart has two chambers – one atrium
(receives) and one ventricle (pumps)
Internal Transport
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Vertebrates with lungs have a doubleloop circulatory system
First loop carries blood between the
heart and lungs (pulmonary)
Second loop carries blood between the
heart and the rest of the body
(systemic)
Internal Transport
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Amphibians and reptiles have a threechambered heart – two atria and one
ventricle
Birds and mammals have a fourchambered heart – two atria and two
ventricles
Temperature Control
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Vertebrates need to control their body
temperature because chemical reactions
operate differently at various
temperatures
Need a way to heat the body, conserve
that heat, and eliminate excess heat
Temperature Control
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Fish, amphibians, and reptiles are
ectothermic because they rely on
interactions with their environment to
control body temperature
Lay in sun to warm themselves, stay in
shade or burrow to cool down
Temperature Control
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Mammals and birds are endothermic
because they generate heat in body
tissues through chemical reactions in
the body
Also have layers of fat and fur/feathers
to conserve heat
Shivering generates more heat, panting
or sweating dissipates heat
Excretion
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Elimination of nitrogen-containing
wastes linked to maintaining water
balance
Aquatic vertebrates get rid of ammonia
by diffusion (fish through gills,
amphibians through skin)
They also have the beginnings of a
kidney (primitive, gets more complex)
Excretion
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Mammalian kidney most complex
Use the conversion to urea and uric acid
and concentration to conserve water
Urea eliminated in urine, uric acid in
solid waste
Response
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All vertebrates are cephalized
Bundle of nerves and neural
connections in head called the brain,
and the long, thick collection of nerves
running down the back is the spinal
cord
Spinal cord protected by vertebral
column
Response
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Pairs of nerves run out between individual
vertebrae to connect muscles, organs, and
sensory receptors around the body
More complex behavior means more complex
brain
All vertebrates have a cerebrum (thinking)
and cerebellum (balance, coordination,
movement)
Reproduction
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All vertebrates reproduce sexually
Fish and amphibians have external
fertilization
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Female lays thousands of eggs in water,
male deposits sperm
Young develop and hatch in water
Reproduction
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Reptiles, birds, and mammals have
internal fertilization (inside female)
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Fewer eggs are produced
Developing embryo is nourished inside the
egg by a yolk (food) and wrapped in
membranes (called the amniotic egg)
Membranes bathe embryo in liquid and
receive and store wastes
Reproduction
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Amniotic egg also has a shell for
protection and allows for gas exchange
Important step in evolution – no water
necessary
Reproduction
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How eggs are handled is different
amongst vertebrates
Oviparous animals lay their eggs, and
the embryo completes its development
and hatches outside of the female’s
body
Reproduction
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Ovoviviparous animals keep their
eggs inside the body until the embryo
fully develops and hatches
Viviparous animals have eggs with
very little yolk (if at all) because the
female nourishes the embryo internally
for a long period of time, and the young
are born alive (do not hatch)