Transcript Chordates Notes

An Introduction to
Vertebrate Animals
Introduction
 Chordates (vertebrates) are the group of
animals most familiar to us
 Ex: mammals, birds, amphibians, reptiles, fish
 Name comes from: Notochord “Back” “Cord”
 Def: a skeletal rod made of body of cells enclosed
by a fibrous covering, which extends, in most cases
the length of the body
 Primary purpose/function: to support and stiffen
the body, provide muscle support
 In most vertebrates the notochord is displaced by
vertebrae
Introduction
 Five distinct/unique characteristics** to
chordates:
1) Dorsal, tubular nerve cord (anterior end becomes
enlarged to form brain)
2) Notochord
3) Pharyngeal slits /pouches (will become middle ear
cavity, tonsils, parathyroid glands, etc.)
4) Endostyle (becomes thyroid gland) for filter feeders
5) Post-anal tail for propulsion (vestigial structure in
humans; coccyx)
** Some of these characteristics appear ONLY in the
embryonic (pre-birth) stages of vertebrates!!!
Introduction
 Chordates have many characteristics
that are similar to some invertebrate
animals:
1. Bilateral symmetry (like mollusks, arthropods)

Anterior to posterior axis , right/left halves
2. Coelom well developed (Tube-within-a-tube
arrangement )
3. Metamerism (segmentation) restricted to
outer body wall, head and tail and not into
coelom
4. Cephalization (concentrated head region)
Introduction
 Chordates have many characteristics
that are similar to some invertebrate
animals:
5. Endoskeleton (some mollusks, arthropods)
6. Paired appendages (arthropods)
7. Sensory organs are highly developed
(mollusks, some arthropods)
8. Three germs layers (ectoderm, mesoderm,
endoderm)
9. Complete digestive system
Diversity
 Belong to Phylum Chordata
 Enormous variation
 Live in all ecosystems on earth
 Most adaptable phylum on earth
 LARGE fossil record
 According to fossil record, chordates are ~500 million years
old
 Approximately 60,000 different species
Characteristics
 Endoskeleton:
 Grows as animal grows
 Series of vertebrae surrounding a spinal cord
 Skull is attached to anterior end of backbone
(head-region)
 Functions:
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Protection, muscle attachment, organ attachment
Characteristics
 Circulation:
 Closed system
 Contain arteries, vessels, veins, ventral heart
 Allows for rapid circulation of blood
 Most have separation of oxygenated and
deoxygenated blood
 Can regulate body temperature (one of two ways)
 1) Endotherms – control with internal body
processes (mammals, birds)
 2) Exotherms – control by outside environment (fish,
amphibians, reptiles)
Characteristics
 Endocrine system:
 All chordates have a thyroid gland
 Function: to produce hormones
 Nervous system:
 Cephalization is present
 Concentrated in anterior region
 VERY highly developed
 Allows for much, higher-order processes
 Sensory receptors highly developed (eye, nerve endings,
brain processes, etc)
Classification: 3 Subphyla
Three subphyla:
 1) Urochordata
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Example: sea squirt
 2) Cephalochordata
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Examples: lanceletes
 3) Vertebrata
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Examples: birds, mammals, reptiles, amphibians
Classification
 Three subphyla:
 1)
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Urochordata
Known as tunicates
Examples: sea squirts
2000 species
Found in all seas (shoreline to great depths)
Most are sessile (permanent) adults, some are free living
Name tunicate comes from “tunic”
 This is a tough surrounding that protects animal
May be solitary or live in colonies
Hermaphrodites (contain both sexes)
Classification
 Three subphyla:
 2)
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Cephalochordata
Examples: lanceletes
Only 25 species
Found in marine environments
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Sandy bottoms of coastal regions
VERY small (5-7 cm in length)
Free living, swimmers
Separate sexes
Considered the evolutionary beginning to all other
chordates
Classification
 Three subphyla:
 3) Vertebrata
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Examples: mammals, birds, fish, amphibians, reptiles
Largest and most diverse chordate subphylum
~57,000 species
Found in all ecosystems, environments
WIDE range of sizes
Grouped together because of the skull region (bony or
cartilaginous braincase)
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Tripartite brain (fore, mid and hindbrain)
Can possess both endoskeleton AND
exoskeleton