Download Phylum Chordata - Fish and Frogs

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PHYLUM
CHORDATA
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4 Main Characteristics
1.Notochord
- Firm but flexible tube that functions in support
- Present at least during embryonic development (but
often replaced by a backbone)
2.Gill slits
- Present at least during embryonic development
- Develop into gills or lungs in vertebrates
3. Dorsal nerve chord
- Becomes brain and spinal chord in vertebrates
4. Post anal tail
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Lancelet:
***note - most posses a backbone (Tunicates and Lancelets
are an exception to this rule)
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Other characteristics often shared by
vertebrates:
• Endoskeleton - made of cartilage or bone
and can support a larger body
• Bilateral symmetry
• High degree of cephalization - well
developed head and brain protected by
cranium
• Closed circulatory system - heart with 2, 3 or
4 chambers
• Only phylum to have bones
• Tube digestive system
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The Phylum Chordata Includes:
1. Subphylum Cephalochordata (=lancelets)
2. Subphylum Urochordata (= tunicates)
3. Subphylum vertebrata:
• Class Agnatha - jawless fish
• Class Amphibia
• Class Aves – birds
• Class Chondrichthyes - cartilaginous fish
• Class Osteichthyes - bony fish
• Class Reptilia
• Class Mammalia
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AMPHIBIANS
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Amphibians
• A.k.a. – “two lives”
• Most primitive of terrestrial
vertebrates
• Fossil records say they are similar
to fish
• May live on land or in water, but
MUST have moist or aquatic
environment to reproduce
• Includes frogs, toads, salamanders
and caecilians
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Appendages
• Adapted to where they spend their
time:
• Powerful hind limbs for leaping
• (frogs and toads)
• Sticky disks for grasping branches
• (frogs)
• Webs between toes for swimming
• (frogs)
• Paddle like tail for swimming
• (newts)
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Feeding
• Adults feed primarily on insects
• Larvae (tadpoles) feed primarily on plant matter
• Digestive system
• mouth, esophagus, stomach, small intestine, large intestine, cloaca
• Accessory glands
• pancreas (enzymes)
• liver (bile)
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Circulation
• Double looped with a 3 chambered heart
• 2 atria (receive blood)
• 1 ventricle (pumps blood out of heart)
• Larvae have a single loop and 2 chambered heart
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Respiration
• Lungs - internal air sacs lined with
membranes that stay moist even if
outside environment is dry
• Gills - external (unlike fish) so that gas
exchange occurs as water flows over
them
• Can also occur through the skin
and linings of the mouth
(this means their skin must
stay moist)
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Reproduction
• External fertilization
• Require moist or aquatic environment
• Young hatch into aquatic larvae or
tadpoles
• Only a few species care for their
young
• Metamorphosis
• A change in structure from larvae to
adult
• Often accompanied with a change in
habitat
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Other Characteristics
• Poison glands
• Found on some frogs and can be very
toxic
• On toads, “warts” are actually poison
glands under the skin
• Eyes can see in both water and air covered by nictitating membrane
• Tympanic membrane detects
sounds waves (hearing)
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1. Class Urodela
• Ex. salamanders
• Visible tail
• Body with two pairs of legs
• Smooth moist skin
• Larvae - have gills, live in streams,
lakes, rivers or ponds
• Adults - most have lungs and live on
land
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2. Class Anura
• Without a tail (as adults)
• Frogs
• Have smooth moist skin
• Longer legs, tapered bodies
• Live in or near water
• Toads
• Dry, bumpy skin more resistant to drying
• Only return to the water to reproduce
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3. Class Apoda
• No legs
• Ex. Caecillians
•
•
•
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Smooth skin, small eyes (but nearly blind) and worm like body
Body folds look like segments
Burrow through soil
Average about 30 cm
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FISH
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Class Agnatha
• No jaws
• Most primitive fish - paired fins are
absent so they are poor swimmers
• Bottom dwellers or parasitic
• Body is smooth, without scales and
cylindrical
• Skeleton made of cartilage
• 7 or more paired gill pouches
• Ex. hagfish and lamprey
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Class Chondrichthyes
• Cartilage fish (skeleton made
of cartilage)
• Ex. sharks and rays
• Hinged jaw
• Body scales = placoid
scales
• Teeth are modified
scales (can have 6-20
rows that continually
replenish)
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Class Chondrichthyes Continued…
• Paired fins - rigid, provide balance and lift while
swimming
• No swim bladder, instead they have an oily liver that
gives buoyancy and they sink if they don’t swim
• Must swim to move water across their gills or they
will suffocate
• Have good sense of smell
• Electroreceptors- allow them to sense weak electrical
charges made by muscle contractions in prey
• Lateral line system - fluid filled canal with sensory
receptors to detect pressure or vibration in the H2O
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Class Osteichthyes
• Bony fish
• Ex. salmon, goldfish, tuna
• Hinged jaw with real teeth
• Air bladder
• used to raise or lower fish in water
• in some species used as a very primitive lung
• Cycloid scales point posterior and are covered
by mucous… good for insulation, protection
and waterproofing
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Class Osteichthyes Continued…
• 4 pairs of gills, covered by operculum
• Kidney helps regulate salts
• Lateral line - detects vibrations
• Inner ear connected to swim bladder for hearing
• Heart consists
of 2 chambers
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Types of Bony Fish
• Lobe finned fish - only one
known living species,
believed to be the first
vertebrates to move out of
water
• Lungfish - have lungs as well
as gills and an eel like body,
some species can live out of
water for up to 4 years
• Ray-finned fish - fins made of
thin membranes supported
by bony rays for steering,
breaking, etc
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