Vertebrate Origins 1 Flashcards
Bilateral is defined by the split between
Protostomata and Deuterostomata
Ambulacraria is defined by the split between
Echinodermata and hemichordates
Deuterostomata is defined by the split between
Ambulacraria and Chordata
Chordata is defied by the split between
Cephalochordata and olfactores (urochordates)
What are the characteristics of Echinodermata?
7330 extant species, marine, radial symmetry, no head, endoskeleton of calcareous plate, water vasculature system, nerve ring around mouth, nerve cord (arms), no brain, through gut tube, indirect development (larvae)
What are the characteristics of Hemichordata?
118 extant species, marine, enteropneusts are diverse and well studied, similar larvae to echinoderms, filter feeding, pharyngeal slits, enterocoelic coelom, stomochord (made of collagen & short), double nerve chord (dorsal and ventral)
What are the characteristics of Cephalochordata
Have a notochordm neural plate, myomeres, specifies neural plate, somite derived, sclerotome, post-anal fin with tail, dorsal hollow nerve cord, paired nerves, hindbrain, midbrain, diencephalon, no eyes
What is a notochord
It is made of collagen and provides structural integrity and is important in signaling
What are myomeres
Segmented muscle blocks
What are somites
Building blocks of the vertebrate body plan
What is sclerotome
The ventral and medial portion of somite that proliferates mesenchyme, which migrates about the notochord to form the axial skeleton and ribs
What are characteristics of Urochordata
3020 extant, indirect development (larvae), sessile, filter feeding, expels water in “sea squirts”, hermaphrodite.
Has a notochord, but degenerates @ adult, reabsorb tail and hind gut as adults, 2 pharyngeal slits. So, notochord, coelom, and post-anal tail were lost, nerve cord reduced, deals with currents, and feces/gametes exit through atriopore
What are the general statements on Bilaterian Evo-Devi
Relatively linear genotype-phenotype relationship & C-value enigma
What is meant by “linear genotype-phenotype” relationship?
There is a direct connection between genetic instructions and physical features
What is the C-value enigma?
Genome size doesn’t positively correlate with structural complexity
What are some Genetic Variations that may occur?
Mutation, genome rearrangements, and recombination
What is the Regulatory Genome?
The ability to use the same genes over and over again for different reasons for different physiological tasks
How can the Regulatory Genome be affected by Variation?
impacting..
- genes whose products regulate the expression of structural genes
- cis-regulatory mechanisms (transcription)
- RNA regulation (translation)
- post-translational regulation (protein activity)
New regulation can cause pattern changes. What are the 3 different kind of pattern changes?
Heterchrony - timing of expression
Heterotopy - position of expression
Heterometry - intensity/amount of expression
How is WNT important for A-P positioning?
WNT curve. More WNT = more posteriorizing (tails and whatnot) signal across all germ layers
What are the three germ layers
Ectoderm, mesodermal, and endoderm
What are some characteristics/information about the Dorsal-Ventral (DV) Axis Specification?
Bilaterian stem lineage, bilateral ymmetry. Think of BMP gradient; a WNT antagonist!
Along stem-chordata, inversion occurred
When did the DHNC show up in the Deuterostomata crown?
Along the Chordata stem, where the paraxial tail, hindbrain, midbrain, notochord, and somites/myomeres showed up
