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Origin of chordates - Coggle Diagram
Origin of chordates
5 features of Chordates:
1. notochord
2. dorsal nerve chord
3. pharyngeal gill slits
4. post-anal tail
5. endostyle
Notochord:
1. skeletal rod for body support
2. extends length of body
3. axis for muscle attachment
4. stiff longitudinally
5. flexible from side to side
6. located on dorsal side of gut
Dorsal nerve cord:
1. tubular (hollow)
2. located on dorsal side of notochord
3. anterior end becomes enlarged to form the brain
Pharyngeal gill slits:
1. perforations leading to pharynx to outside
2. paired on either side
3. originated as adaptations for filter feeding
4. later developed as primary respiratory organ (i.e. gills in fish) or as other body structures
Endostyle:
1. groove in the pharynx floor
2. ciliated
3. secretes mucous
4. moves food to stomach
5. in humans, becomes the thyroid
6. lampreys have both endostyle and thyroid
Post-anal tail:
1. tail structure after end of digestive tract
2. part of skeletal support, muscles and nervous system
3. aids locomotion/agility
4. balance
Other features:
1. bilaterally symmetrical
2. segmented muscles
3. closed circulatory system with ventral heart
4. pronounced cephalisation
5. complete digestive system
-
Hemichordata:
1. worm-like benthic dwellers
2. marine
3. body plans
- solitary species (acorn worms Enteropneusta)
- filter feeding colonial species (Pterobranchia)
What makes them not a chordate?:
1. have a dorsal nerve cord
2. gill slits
Only have 2 out of 5 chordate features
Craniata / Vertebrata (fish, amphibians, reptiles, birds and mammals):
1. large & highly successful sybphyla (~570000 species)
2. notochord, dorsal nerve cord, pharyngeal gill slits & post-anal tail present at some stage
3. notochord usually replaced by spinal column of vertebrae in adults
4. vertebrae surround dorsal nerve cord
5. living endoskeleton of bone / cartilage
6. complex muscle system
Features:
1. distinct head with highly advanced sense organs (eyes, nose, ears)
2. usually two pairs of joimted appendages
3. elaborate nervouse system for sensory, motos & organ function
4. efficient respiratory system consisting of gills, moist skin or lungs
5. efficient closed circulatory system with heart (2-4 chambers) and blood containing haemoglobin
Deuterostome:
1. anus develops from blastophore
2. radial cleavage
3. indeterminate cells
4. anus formed first then mouth second
Phylum Chordata:
1. highly diverse and successful phylum
2. includes lampreys, fish, amphibians, reptiles, birds & mammals
- most complicated mechanisms of self maintenance than any other group in the animal kingdom
- structural body plans retains many features of more advanced invertebrates
Terminology:
1. Chordate: notochord at some stage in life
2. Protochordata / acraniata: no cranium
3. Craniata: has a cranium
4. Vertebrata: has (or had) vertebrae
5. Agnatha: craniata without jaws
6. Gnathostomata: craniata with jaws
7. Pisces: jawed vertebrate with appendages in the form of fins
8. Tetrapoda: jawed vertebrate with 4 limbs
9. Amniota: vertebrates whose embryos develop in fluid-filled sac
Are hagfish vertebrates?:
1. lack all traces of vertebrate
2. lack the pineal eye and eye muscles
3. no Mauthner neurons. in brain stem
4. heart pumpong is intrinsic with no coordination
5. blood system has a few immune reactions done by vertebrates
6. no spleen
7. different arrangement of cranial nerves
8. no renal collecting ducts in kidney
9. no osmoregulation
They are VERTEBRATES due to genetics. Lampreys and hagfish are more closely related to each other than either is to the jaws fishes.