BIOL10005 Lecture Notes - Lecture 15: Water Vascular System, Symmetry In Biology, Echinoderm
29 Jun 2018
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Lecture 15: echinoderms and chordates
PHYLUM: ECHINODERMS (sea star)
Symmetry:
oBilateral symmetry as larvae --> indicates bilaterally symmetrical ancestry
oPenta-radial symmetry as adults (re-evolved)
Triploblastic
Coelomate
Deuterostome
No segmentation
Spiny epidermis (protection)
Have water vascular system in the coelom
Echinoderm defence
Pedicellariae
oModified spines with claws and capable of movement
oUsed to remove encrusting organisms (things that land on them)
Ejection of intestines
oWhen startled, some species will expel sticky tubules to entangle predators
oMay also discharge deadly toxin
PHYLUM: CHORDATA
Marine, freshwater, terrestrial, aerial, subterranean
Bilateral
Triploblastic
Coelomate
Deuterostome
Partial segmentation
Defining feature:
oNotochord = stiff rod of mesoderm found next to nerve chord in all chordates
embryos
Function as an endoskeleton (i.e. backbone)
oDorsal Nerve chord
oGill slits
oPost-anal tail
Subphylum: vertebrata
Notochord: present in embryo but vertebrae grow around notochord + replace it
vertebrae surround and protect nerve cord (spinal chord)
oThings can hang off vertebrae (i.e. limbs, muscles)
Defining features:
oBackbond forms around notochord
oInternal + elaborate skeleton (cartilage or bone)
oDefined head + braincase (skull) and sensory organs
Evolution of jaws
Jaws derived from gill arches of chordates
Evolution of legs:
Most bony fish have fins made of long rays of bone
Some fishes developed more substantial bones in the fins
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Document Summary
Bilateral symmetry as larvae --> indicates bilaterally symmetrical ancestry. Have water vascular system in the coelom. Pedicellariae: modified spines with claws and capable of movement, used to remove encrusting organisms (things that land on them) Ejection of intestines: when startled, some species will expel sticky tubules to entangle predators, may also discharge deadly toxin. Defining feature: notochord = stiff rod of mesoderm found next to nerve chord in all chordates embryos. Function as an endoskeleton (i. e. backbone: dorsal nerve chord, gill slits o. Notochord: present in embryo but vertebrae grow around notochord + replace it. Vertebrae surround and protect nerve cord (spinal chord) Things can hang off vertebrae (i. e. limbs, muscles) o. Internal + elaborate skeleton (cartilage or bone: defined head + braincase (skull) and sensory organs. Jaws derived from gill arches of chordates. Most bony fish have fins made of long rays of bone. Some fishes developed more substantial bones in the fins o.
