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Vertebrates
Biology 11
Relate the complexity of the form and
function of vertebrates to the
evolutionary continuum of animals.
• Their unifying characteristics
• Compare members of two or more classes
• Compare the vertebrates and invertebrates in
terms of increasing complexity with reference to:
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Endoskeleton vs exoskeleton
Presence or absence of vertebral column
Closed vs open circulatory system
Describe the diverse ecological role of vertebrates
Phylum Chordata
• 3 subphyla:
– Urochordata (Tunicates)
– Cephalochordata (Lancelets)
– Vertebrata
3 Main characteristics
• Notochord- develops into vertebrate backbone
– Found in embryo of most vertebrates
– Supports and protects the nerve cord
• Dorsal Hollow Nerve Cord- develops into
vertebrate brain and spinal cord
• Pharyngeal slits/pouches
– Most chordates only have during embryonic stages
– Become gill slits in aquatic vertebrates and
becomes jaw, inner ear, and tonsils in terrestrial
vertebrates
• Postanal Tail
– Lost during
embryonic
development in
many vertebrates
Characteristics of Chordates
• Bilateral symmetry
• Coelomates
• Segmentation
• Vertebrae- segmented and flexible to protect
nerve cord
• Endoskeleton- cartilage and/or bone which grows
with animal, protects internal organs, allows
muscle attachment for movement
• Cephalization- brain with specialized sense organs
enclosed in skull for protection
• Closed circulatory system- heart with 2chambers, blood contained in arteries, capillaries,
and veins
• Respiratory System- blood contains
hemoglobin to pick up oxygen and carbon
dioxide
• Reproductive system- separate sexes, mainly
sexual reproduction with internal or external
fertilization
• Excretory System- kidneys remove metabolic
wastes and reabsorb H20
Body Temperature
Birds and mammals are endothermic (warmblooded)
Can regulate body temperature regardless of
external environment.
Rest of the vertebrates are ectothermic (coldblooded).
Their body temperature varies with changes in
external environment.
Subphylum Vertebrata: Classification
 Class Agnatha – lampreys
 Class Chondrichthyes – sharks
 Class Osteichthyes – fishes
 Class Amphibia – amphibians (frogs and newts)
 Class Reptilia – reptiles (snakes and lizards)
(embryo surrounded by membrane & shell)
 Class Aves – birds
 Class Mammalia – mammals
Class Agnatha
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Most primitive fish
Do not have a jaw (jawless fishes)
No fins or scales on body
Have no bones, only cartilage
Ex) Lamprey, hagfish
Class Chondichthyes
• Means cartilaginous fish
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Have no bones, only cartilage
Have fins and scales
Hinged jaw
No swim bladder
Ex: sharks, rays
Class Osteichthyes
• Bony fishes
 Skeleton made of bone
 Hinged jaw
 Covered gill slits
 Swim bladder  to adjust buoyancy
Ex: goldfish, tuna, halibut, etc.
Characteristics of Fish
(Cartilage and Bony)
• Breathe using gills
• Have three chambered hearts
– 2 atria and 1 ventricle
• Reproduce sexually
– Mostly external fertilization
• Have fins- balance, steering, swimming
• Have scales- thin bony plates
How fish breathe
Water is drawn in through the mouth of the fish.
 The fish then closes the mouth and contracts the
muscles in the mouth
Forces water past the gills and out past the gill
covers.
Evolutionary Importance of Fish
 Development of Jaws
 Enables animals to grasp and crush prey
 Development of Bone
 Hard, mineralized living tissue that makes up the
vertebrate endoskeleton
 Development of Vertebrae
 Major support structure for vertebrate skeleton, but
still provided flexibility for movement.
 Development of Teeth
 Enables animal to rip, tear and grind up prey.
From Water to the Land
What challenges would this present?
Problems:
Solutions:
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No support on land
Gills stick together
Desiccation
Sound, light, and
smell is perceived
differently on land
Cartilagebone
Lungs
Skin and scales
Adapt ability to
perceive sound,
smell, and light
differently
From Fish  Amphibian
Class Amphibia
• Includes salamanders, newts, caecilians, frogs,
and toads
Class Amphibia
• Not fully adapted for life on land
• Rely on water for:
– Reproduction (external fertilization in water)
– Prevents desiccation
• Ectotherms (cold blooded)- heat comes from
external sources
• Have 3 chambered heart (2 atria and 1
ventricle)
– 1 ventricle means partial mixing of oxygenated
and deoxygenated blood
• Offspring develop my metamorphosis
• Tadpoles (aquatic larva) resemble fish
 Respire through poorly developed lungs and
moist skin (more important)
Class Reptilia
• Examples: Snakes, lizards, turtles, crocodiles
Characteristics
• Complete life cycle on land
– All have lungs
– No longer need water for reproduction
• Ectotherms (cold blooded)
• Internal fertilization
• Reptiles have scales on their skin
– Prevent water loss and for protection
• Most have 3
chambered heart
with partially divided
ventricle
• Crocodiles have a 4
chambered heart
• Develop from an amniotic egg
– Yolk provides nourishment for developing embryo
– Amnion is a membrane filled with fluid that
cushions and prevents it from desiccation
– Leathery shell for protection
• Temperature determines the sex of hatchling
green turtles (Chelonia mydas)
Class Aves
• Archeopteryx believed to be evolutionary link
between reptiles and birds
• Have both reptilian and aves characteristics
• Feathers (flight and insulation)
– Evolved from scales
• Scales on their legs
• All have wings and most can fly some used
for swimming
Takes in oxygen through lungs and air sacs
 efficient for supplying high levels of oxygen to
muscles during flight
Endotherm (warm blooded)
Hollow bones – lightweight for flight.
Lay amniotic eggs
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Some parental care of eggs and young.
• 4 chambered heart
– Separates oxygenated and
deoxygenated blood
Class Mammalia
Class Mammalia
• Internal fertilization
• Most do not lay eggs but give birth to live
young
• Young are nourished with milk (rich in fat,
sugar, proteins, minerals, and vitamins) that is
secreted from mammary glands
– Parental care
• Have hair
Endothermic (warm blooded)
Have sweat glands to cool off.
Have lungs operated by a diaphragm.
Thin muscle that can increase the size of the lung
cavity to allow breathing.
Highly developed brains
Capable of learning!
 Includes humans, cats, dogs, etc… and also
dolphins and whales
 3 Types of Mammals:
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Monotremes, Marsupials, Placentals.
Monotremes- egg laying
• Mammals that lay eggs instead of giving birth
to live young
• Eg. Platypus and the echidna
Marsupials- pouched mammals
• Live birth
– Premature young
• Feed on milk in the pouch
– Only females have pouches
Marsupials give birth to partially-developed
young who then migrate to a special pouch in
the mother's body
 Ex: Kangaroo, Koala, Possum
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Placental- nourishing plantea
Live birth
Fetus is nourished during development in the
uterus by a placenta
Umbilical cord passes nutrients and oxygen to
the developing embryo).
 The offspring are carried in the mother's
uterus until fully developed.
 Humans - 9 months
 Cats - 8 to 12 weeks
 Dolphins 12 months
 Elephant - 18 months
 Phylum: Chordata
Class: Mammalia
Other Orders of Mammals
 INSECTIVORA - hedgehogs, shrews and moles
 DERMOPTERA - flying lemurs
 CHIROPTERA - Bats
 EDENTATA & PHOLIDOTA - toothless mammals, are
exclusively American and contain the anteaters, tree-sloths
and armadillos
 LAGOMORPHA - the rabbits and hares
 RODENTIA - mice
 CETACEA –whales and porpoises
 CARNIVORA – bears, dog, raccoons, weasels, cats
 UNGULATES - hoofed mammals
 PRIMATES – monkeys, humans