Chordates 1 Flashcards
4 Characters of Chordates
- Notochord
- Dorsal Hollow Nerve Chord
- Pharyngeal Slits
- Muscular Post-anal tail
4 Characters of Chordates:
Notochord
longitudinal flexible rod of fluid filled cells; located between digestive tract and nerve cord. Provides skeletal support in higher vertebrates.
- started as a series of fluid filled cells that provided rigidity -> into spine
4 Characters of Chordates:
Dorsal Hollow nerve chord
Develops into CNS. Ventrally located in other
animals (e.g. arthropods).
- evolves into the central nervous system
- invertebrates = ventral
- vertebrate = dorsal
4 Characters of Chordates:
Pharyngeal slits
Allow water to pass through mouth without entering digestive tract. involved in filter feeding and respiration (as gills)
- filter feeding devidces(NOT gills)
- eventually become gills
4 Characters of Chordates:
Muscular post-anal tail
propulsion
- humans exhibit all of the above traits in their ontogeny(development)
All chordates exhibit all 4 characters at some point during development, but ______.
may not be present in the adult stage.
Important evolutionary adaptations in the chordates (see figure 34.2)
- Evolution of 4 chordates characters (notochord, nerve chord, slits, tail)
- Head
- Vertebral column
- Jaws, mineralized skeleton, paired fins
- Lungs / lung derivatives
- Lobed fins
- Legs
- Amniotic egg
- milk
Major Phylogenic Lineages(1-8)
- Lancelets
- Tunicates
- Hagfish
- Lampreys
- Condrichthyes
- Ray-fin Fish(Osteichthyans)
- Lobe-fin Fish(Osteichthyans)
- Tetrapoda
Major Phylogenic Lineages:
- Lancelets
1.exhibit all four characters as an adult
2. Fish-like (but not a fish)
3. Pharyngeal slits used in filter feeding; cirri aid in this
a. Produce mucus to trap suspended particles
4. No respiratory system; gas exchange though skin
- very small
5. Closed circulatory system: no heart / hemoglobin; rarely
blood cells
- Rudimentary
Major Phylogenic Lineages:
- Tunicates(sea squirt)
- Mobile larvae morphologically similar to lancelet
- During adult metamorphosis, tunicates lose 3 of 4 chordate characters and become sessile
- Adult stage is sessile filter feeder (using mucus to trap food)
- Circulatory system with heart; pharyngeal slits perform some gas exchange
Major Phylogenic Lineages:
- Hagfish
Sub-group – Craniates (chordates with heads) <- cephalization
- Cartilaginous skull
- bone has not evolved yet
- lack jaws and vertebrae
- produce slime as an anti-predator defense
- enemy doesn’t get slime out of mouth/gills it will suffocate and die
- very powerful defense
- Pharyngeal slits become gills
Major Phylogenic Lineages:
- Lampreys
cartilaginous vertebral column (not calcified)
- lack jaws
- Feeding
- Juveniles – filter feed using mucus (like lancelets)
- adults – most don’t feed; some parasitic, suck blood
Major Phylogenic Lineages:
- Condrichthyes
Sub-group – Gnathostomes (jawed vertebrates); Evolution of jaws (from skeletal rods supporting gill slits; paired fins).Also evolve paired fins
and acquired immunity (i.e. immunological memory)
- Cartilate becomes mineralized
o Turns it to bone
- Immunological memory
o Adaptive immune system
= create antibodies
Sharks and rays –
- cartilaginous skeleton w/ some bones.
- Dorso-ventrally flattened
- just the jaw is mineralized- the rest is still cartilage
Major Phylogenic Lineages:
- Ray-fin Fish(Osteichthyans)
bony fish.
Evolution of bony Endoskeleton(first time of full bone skeleton). Two Groups.
- Ray-fin fish
a. rudimentary lungs
b. swim bladder.
c. Laterally flattened
d. Most diverse of fish
Major Phylogenic Lineages:
- Lobe-fin fish(Osteichthyans)
Evolution of fins with rod-shaped bones supporting muscle
a. Coelacanth - thought extinct for 75 my
b. Lung fish - have gills; survival terrestrial desiccation via estivating in mud in mucus cocoon
- Literally have lungs and can breath
- Moved into shallow water then further into land
o Locks them into ephemeral waters and adapt to survive droughts
