Download Introduction to Phylum Chordata

Introduction to Phylum Chordata
General Characteristics
• Best known of all animal phyla. Consists of
only about 45,000 species.
• Includes the vertebrates and two groups of
invertebrates known as lancelets and
tunicates.
• All have bilateral symmetry.
General Characteristics (continued)
• 4 characteristics appear in all of them at some
stage of their development:
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A single, dorsal nerve cord.
A dorsal rod of cartilage called a notochord
Pharyngeal (gill) slits, and
A tail.
General Characteristics (Continued)
• The notochord serves as a structure to which
muscles can attach. It enables increased
strength and flexible movement. It was an
important evolutionary advancement.
• Phylum chordata is broken into 3 subphyla:
– Subphylum Cephalochordata (lancelets),
– Subphylum Urochordata (tunicates),
– Subphylum Vertebrata (vertebrates).
General Characteristics
• Subphylum Vertebrate is composed of 7 classes:
1. Class Agnatha (jawless fish, including lampreys and
hagfish),
2. Class Chondrichthyes (cartilaginous fish, including sharks,
rays, and skates),
3. Class Osteichthyes (bony fish, including perch, salmon,
eels, and sea horses),
4. Class Amphibia (amphibians, including frogs, toads, and
salamanders),
5. Class Reptilia (reptiles, including lizards, alligators,
crocodiles, turtles, and snakes),
6. Class Aves (birds, including penguins and ostriches), and
7. Class Mammalia (mammals, including bats and humans).
Subphylum Vertebrata
• Found on land and in fresh and marine waters.
• Notochord replaced by cartilage or bone,
forming segmented vertebral column (the
backbone). Important evolutionary
advancement: allowed for great size, powerful
movement.
• Have distinct head and brain inside a skull,
another important evolutionary advancement.
Subphylum Vertebrata
• Gill slits may remain or be modified into other
structures during development.
• Hollow dorsal nerve cord remains, protected
by backbone.
• Vertebrata refers to the vertebrate (segments
of backbone) surrounding dorsal nerve cord.
• About 43,700 species.
Evolution of Vertebrates Summarized
• Jawless fishes were the first vertebrates.
Lampreys and hagfishes are the only surviving
jawless fishes. Sharks were among the first
vertebrates to have jaws, which allow them to
bite. Sharks have a lightweight skeleton of
cartilage. They also have streamlined bodies
and paired fins, which allow for fast swimming
with better control. Bony fishes have a
heavier skeleton of bone and a swim bladder,
which provides buoyancy.
Evolution of Vertebrates Summarized
• Amphibians (frogs, toads and salamanders)
were the first vertebrates to live on land.
However, they lack watertight eggs and so
cannot reproduce in environments in which
their eggs would dry out.
Evolution of Vertebrates Summarized
• Each of the adaptations that allowed
amphibians to lead a terrestrial
existence was refined in reptiles.
Reptiles (snakes, lizards, turtles,
crocodiles, and alligators) replaced
amphibians as a large terrestrial
vertebrates. Once reason that reptiles
were successful on land is that their
dry skin prevents water loss. Another
reason is that reptile eggs are
watertight, preventing the embryo
against drying.
Evolution of Vertebrates Summarized
• Mammals evolved at the same time the
dinosaurs first appeared. Birds evolved from
dinosaurs. Feathers on birds and fur on
mammals are adaptations that enabled these
groups of animals to survive the dramatic
global cooling that took place 65 million years
ago, when the dinosaurs disappeared.
Evolution of Vertebrates Summarized
• There are three groups of
mammals. Monotremes are
mammals that lay eggs. The
duckbill platypus is a
monotreme. Marsupials suckle
their young, which are born
after a short period of
development, in an external
pouch. Koalas and opossums
are marsupials. Placental
mammals nourish their
developing embryos by means
of a placenta, a structure that
transfers nutrients from the
mother’s blood directly to the
growing embryo.
Subphylum Cephalochordata
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Blade-shaped, marine animals known as lancelets.
Live in warm, shallow waters.
Have no internal skeleton.
Keep their notochord, dorsal nerve cord, gill slits, and tail throughout their life.
Use their muscular tail to wriggle backward into the sand.
Use cilia to draw water into their pharynx through their mouth.
Food particles in the water are trapped as the water passes through the numerous slits in the
pharynx.
The food enters the intestine to be digested, while the water leaves the body through an opening
called the atriopore.
About 2 dozen species.
Subphylum Urochordata
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Barrel-shaped, marine animals known as tunicates or sea squirts.
Live on the sea bottom – sessile.
Have no internal skeleton.
Bodies are covered by a tough covering, or tunic.
Adults have no notochord, dorsal nerve cord, or tail.
Most are sessile.
Propelled by the beating of cilia, water enters the body through an incurrent siphon, passes
through slits in the pharynx, and exists through an excurrent siphon.
Food that is filtered by the pharynx moves into the stomach
Undigested materials leaves via the anus, which empties into the excurrent siphon.
Tunicates are hermaphrodites.
About 1,250 species.
Subphylum Vertebrata
• Notochord is replaced with a backbone or
vertebrae – bone or cartilage that surround
and protect the nerve cord.
• Includes sharks, bony fishes, amphibians,
birds, and mammals
Stop for Animal Activity
Subphylum Vertebrata Notes
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Class Agnatha: Jawless
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Lack true jaws
Snakelike bodies
Skeleton of cartilage
Smooth skin with scales
Ectothermic and oviparous
Includes Lampreys and Hagfish
Class Agnatha: Lamprey
Class Agnatha: Lamprey
Class Agnatha: Hagfish
Class Agnatha: Hagfish
Class Chondrichthyes: Cartilaginous
Fishes
• Skeleton made of cartilage
• Hinged jaw, paired fins, toothlike scales cover
body
• Ectothermic
• Some are oviparous, most are ovoviviparous
• Includes sharks, rays, and skates
Class Chondrichthyes: Sawfish
Class Chondrichthyes: Blue-spotted
Ray
Class Chondrichthyes: Brown shark
Class Chondrichthyes: Whale shark
Class Osteichthyes: Bony Fishes
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Skeleton of bone
Hinged jaws, paired fins
Overlapping scales
Air bladder
Ectothermic
Oviparous
Including salmon, trout, perch, carp and eels
Class Osteichthyes: Hippo tang
Osteichthyes: Lungfish
Osteichthyes: Common Dolphifish
Osteichthyes: Yellow perch
Class Amphibia: Soft eggs
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Moist thin skin, No scales
Four limbs
If present, feet lack claws are often webbed
Most undergo metamorphosis
Most use gills, lungs and skin for respiration
3-chambered heart
Oviparous: eggs most remain moist
Ectothermic
Class Amphibia: Tadpole
Class Amphibia: Eastern Tiger
salamander
Class Amphibia: Northern Cricket Frog
Class Amphibia: Green Climbing Toad
Class Reptilia: Amniotic egg
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Dry skin and a scale covered body
Four limbs (except snakes)
Live and reproduce on land
Amniotic eggs (eggs that contain layers of
specialized membranes)
• Lungs and a 3-chambered heart with a partially
divided ventricle
• Ectothermic
• Most are oviparous but some are ovoviviparous
(python snakes and garter snakes)
Class Reptilia: Black Mamba
Class Reptilia: Komodo Dragon
Class Reptilia: Albino Chinese Softshelled turtle
Class Reptilia: American Crocodile
Class Reptilia: American Alligator
Class Aves: Wings/Feathers
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Birds that have wings and feathers
Feathers are essential for flight and insulation
Forelimbs are modified into pair of wings
Lightweight rigid skeleton
Endothermic; rapid metabolism allows for flight
Lungs associated with air sacs
All oviparous
4-chambered heart needed for flight
Class Aves: Ostrich
Class Mammalia: Produce milk
• Placental development and mammary glands
that produce milk
• Hair or fur
• Endothermic
• 4 chambered heart
• Most are viviparous
Class Mammalia: Platypus
Class Mammalia: Vampire bat
Class Mammalia: Sperm whale
Class Mammalia: White-tailed Deer
(fawn)