Midterm Lectures (1 - 5) Flashcards
Megalodon
- Emerged 20 mya, largest shark 18m.
- Consumed broad range of prey, may have contributed to large size.
- Extinction: End of Pliocene
Hybodus
- 2m, 2 dorsal fins.
- Teeth: upper, lower jaws.
- Numerous rows of replacement teeth, abundance, regularly arranged teeth.
- 1st appeared late Devonian
- Extinction: Cretaceous palaeogene boundary
Greenland shark
- Vision And Eyes: Small functioning eyes, almost all blind, parasitic crustaceans on corneas, destroying limited vision in process.
- Flesh: Placoid scales, toxic high levels of trimethylamine.
Hammerhead Sharks
- Lateral expansion of head
- Head wing: Cephalofoil, increase maneuverability, energetic cost, increased visuals.
- Holding breath: close gill slits at certain depths, conserves heat.
Where Are The Chordate Features?
1) Pharyngeal slits = gills / jaw
2) Endostyle = thyroid gland
3) Notochord = Vertebral column
4) Postanal tail = caudal tail
5) Nerve Cord = brain and spine
Early Tetrapods: Temnospondyls
- Flat skulls
- More robust limbs and girdles
- some fully aquatic adults
Early Tetrapod: Icthyostega
- Notochord extended into braincase
- Dorsalventral flexion of vertebral column (function unknown)
- Internal gills
- Polydactyl feet (7 digits)
Early Tetrapds: Acanthostega
- 4 footed, earliest group, late Devonian period
- Branchial arches support internal gills
- Notochord connects to skull
- Dermal skull bones, Polydactyl feet (8) digits Pentadactyl chiridium (5 toe, each)
Endostyle (Phylum Chordata)
- Glandular groove in floor of pharynx
- Assist in filter feeding and iodine metabolism
- Thyroid gland
Postanal Tail (Phylum Chordata)
- Extension beyond anus
- Elongates chordate locomotor apparatus
- Allows for swimming movements
Cranium
- Bone / Cartilage supporting sensory organs in head
- Skull
Pharyngeal Slits (Phylum Chordata)
- Series of pouches / arches
- Part of digestive tract
- Water flow one way: suspension feeding
Notochord (Phylum Chordata)
- slender rod
- tough sheath of fibrous tissue filled with cells and fluid.
- For locomotion (side to side flexion)
Nerve Cord (Phylum Chordata)
- Dorsal hollow nerve tube / cord
- “Dorsal” to gut
- “hollow”
- surrounds neurocoele (fluid filled central canal)
Cephalochordata
- Name comes from: head, notochord.
- Notochord goes to the rostral tip of body.
- Striated (striped) muscle cells arranged transversely (across) the body.
Tunicates (Urochordata)
- Show all 5 chordate features at some point in life history.
- Rudimentary heart and circulating blood cells, bag like.
Vertebrae
-series of bones / cartilage blocks joined as a backbone.
- with intervertebral disk / bodies
- compression pads
Centrum
- encloses notochord / spinal cord.
Jawless Fish (Agnathans)
- Muscularized pharynx: stream of water and food into mouth.
- Before (Amphioxus)
- Cilia to move mucous.
- Now pairs of muscular tissue in buccal cavity, not cilia.
Ostracoderms
- Head shield
- 2 close set eyes
- median nostril
- likely inactive lifestyle: stirred up / drawn water into pharynx.
Myxinoidea: Hagfish
- Jawless, but teeth.
- Keratinized teeth bore into fish, don’t eat skin or bones.
- Living Agnathan, Prominent notochord (gone in adults), no bone (no vertebrae)
- Poor developed skull, median nostril, slime attack.
Petromyzontiformes Lampreys
- Skull and vertebrae
- Jawless w/ teeth
- No bones or surface scales
- Vertebral elements that are small and cartilaginous
Lampreys Part 2
- Median Nostril
- Notochord
- Suspension feeding and ciliary tracts
- True endostyle as young larvae
- Gill openings, some have dorsal fins
Early Chordate
- Notochord goes to rostral tip of body.
- Striated (striped) muscle cells annoyed transversely (across) body.
- No heart, lacks pulsations.
- Heptic vein, ventral aorta, bulbils help pump colourless blood.
Forward Extension Of Gut (Cephalochordata)
- Forerunner of liver and pancreas.
Endostyle Collects Iodine (Cephalochordata)
- thyroid gland
- (pharyngeal endocrine gland) in later vertebrates collects iodine.
Early Vertebrate Evolution
- Suspension feeding
- Muscular pump to produce water current 4 food.
- Fins
- Primitive vertebrae
- Some jawless (agnathans)
- Primitive cranium / skull
- Not fully functioning teeth