BIOEE 1780 Lecture Notes - Lecture 21: Triploblasty, Motility, Synapomorphy
7 May 2018
School
Department
Course
Professor
Deuterostomes are upside down and backwards (compared to protostomes).
• Blastopore becomes anus
• Second opening in gastrulation becomes the mouth.
• Dorsal central nervous system
o Sog gene - protostomes
o Chordin gene - deuterostomes
Deuterostomes Synapomorphies: blastopore becomes the anus, Pharyngeal gill slits
Two pieces of evidence indicate that the deuterostomes share a common ancestor that's not shared
with the protostomes:
1. Deuterostomes share a pattern of early development (blastopore develops into the anus)
2. DNA sequences
All deuterostomes are triploblastic and coelomate. Skeletal support features, when present, are internal
rather than external. Some species have segmented bodies, but the segments are less obvious than
those of annelids and arthropods.
Major Clades of Deuterostomes
1. Echinoderms
a. Synapomorphies:
i. Water vascular system with tube feet
a. Water Vascular System: a network of water-filled canals leading to extensions
called tube feet
a. Functions in gas exchange, locomotion, and feeding
ii. Internal Skeleton
a. Calcified internal plates covered by skin and muscle, which fuses inside the entire body,
forming an internal skeleton
iii. Pentaradial symmetry as adults
1. Have bilateral symmetry as larva, but this changes to pentaradial symmetry in adults
(body parts are arranged along 5 radial axes; symmetry in fives or multiples of five)
b. Feeding Modes
i. Filter feeding
ii. Scavenging
iii. Grazing
iv. Predators (mostly starfish)
c. Secondarily lost gill slits
d. Have ciliated larva that are bilaterally symmetric
e. Don't have a head
f. Have an oral side (containing the mouth) and an aboral side (containing the anus)
g. With the exception of crinoids, most echinoderms are motile.
h. Marine and benthic (live on the ocean floor)
i. Examples
i. Crinoids: a clade of echinoderms
0. Some have more than 5 arms
1. Sessile and attach to a substrate via a stalk as juveniles, but free-swimming as adults
2. Include the sea lilies
3. Filter feeders
Document Summary
Deuterostomes are upside down and backwards (compared to protostomes): blastopore becomes anus, dorsal central nervous system. Second opening in gastrulation becomes the mouth: sog gene - protostomes, chordin gene - deuterostomes. Deuterostomes synapomorphies: blastopore becomes the anus, pharyngeal gill slits. Two pieces of evidence indicate that the deuterostomes share a common ancestor that"s not shared with the protostomes: deuterostomes share a pattern of early development (blastopore develops into the anus, dna sequences. Skeletal support features, when present, are internal rather than external. Some species have segmented bodies, but the segments are less obvious than those of annelids and arthropods. Major clades of deuterostomes: echinoderms, synapomorphies, water vascular system with tube feet, water vascular system: a network of water-filled canals leading to extensions called tube feet, functions in gas exchange, locomotion, and feeding. Internal skeleton: calcified internal plates covered by skin and muscle, which fuses inside the entire body, forming an internal skeleton.
