Vertebrate Origins - Development

Question 1

Weeks 1-8 of development is called what?

Answer 1

The embryo

Question 2

Weeks 9-38 are called what?

Answer 2

Fetal Period

Question 3

What are the germ layers of the embryonic disk?

Answer 3

Ectoderm, mesoderm, endoderm

Question 4

What does gastrulation lead to?

Answer 4

The rotation of the embryo, cranial pulse from node = notochord, which is covered by ectoderm. and enters to elongation phase

Question 5

What are the two parts of the lateral plate?

Answer 5

Paraxial and Intermediate Mesoderm

Question 6

What does the paraxial mesoderm proliferate?

Answer 6

Divides into somites:
Sclerotome, dermatome, myotome

Question 7

Wat happens to the sclerotome?

Answer 7

• migrates to surround the notochord and spinal cord (neural tube)
• cartilage and bone of mesodermal axial skeleton
• vertebrae, ribs, occiput of skull

Question 8

Parietal Mesoderm

Answer 8

Gives way to body wall including the limb buds

Question 9

visceral Mesoderm

Answer 9

Muscle wall of gut and parts of the circulatory system

Question 10

Crown Vertebrata (563) is defined by the split between

Answer 10

Cyclostomata and Gnathostomata

Question 11

Crown Cyclostomata is defined by the split between

Answer 11

Hagfish and Lamprey

Question 12

What are hagfish

Answer 12

Deep marine, scaleless with an eel-like form. They have a single medial nostril, paired eye spots, pharyngeal slits

Question 13

what are some characteristics of Lampreys

Answer 13

Freshwater, dorsal and caudal fin, 7 gill slits

Question 14

Within Crown Vertebrata, there is increased genetic complexity due to….

Answer 14

Genome Duplications
Teleost fish, Gnathostome, and vertebrate stem lineages
Duplications created genetic redundancy - paralogs

Question 15

What are paralogs?

Answer 15

Copies of the same gene in same individual

Question 16

What are orthologs?

Answer 16

Copies of the same gene in differnt lineages

Question 17

What is the most common outcome from drift?

Answer 17

Loss!

Question 18

What are the different evolutionary possibilities?

Answer 18

Loss, neofunctionalization, complementation, and subfunctionalization

Question 19

What is neofunctionalization?

Answer 19

It’s when novel sequences produce novel function
- positive selection creates innovation
- different regulatory genome of existing structural genes

Question 20

What is subfunctionalization

Answer 20

Ancestral function(s) conserved, but is divided between paralogs
- modularity

Question 21

What is complementation?

Answer 21

Think genetics!

Both paralogs are needed to maintain ancestral function

Question 22

What are some vertebrate synapomorphies?

Answer 22

1) Neural crest = ectomesenchyme, which is highly motile and multipotent
- connective tissue = neural crest & muscle = mesoderm
A) Head and Branchial Skeleton (cartilage)
- neurocranium, trabeculae, optic capsule, support elaborate gill structure
- PNS, ANS (not PS nuclei in brain), adrenal gland, and melanocytes
2) Placodes
- localized thickenings of surface ectoderm
- normally paired
3) Sclerotome
- derived vertebral column
- Lamprey: dorsal elements only, lateral to DHNC, cartilagenous
- Hagfish: ventral, similar genes as gnathostome sclerotome

Question 23

What are the differnt kinds of placodes?

Answer 23

Sensory
- lens (no sensory epithelium), otic, olfactory, lateral line
Neurogenic
- sensory - neurons to ganglia of CN 5,7,9, 10

Question 24

What does Pan-Vertebrata include?

Answer 24

From bottom to top
Olfactores - Urochordata
Gills!
Yunnanozoa
Loss of atrium
Pikaia
Neural crest
Cartilagenous skeleton, eyes, ears, midline nostril
Haikouchthys
Vertebrata