Ordovician - Primitive plants and fungi colonize land, first jawless vertebrates,  Mass extinction at end of period

TLS Online TPP Program

#Id: 1597

#Unit 5. Developmental Biology

Mediolateral intercalation in the formation of the primitive streak (Cellular Dance Mechanism) cells came down the sides of the epiblast to undergo a medially directed intercalation of cells in the posterior margin

TLS Online TPP Program

#Id: 1598

#Unit 5. Developmental Biology

Cell migration mediated by the activation of the Wnt planar cell polarity pathway in the epiblast next to Koller’s sickle, at the posterior edge of the embryo.

TLS Online TPP Program

#Id: 1599

#Unit 5. Developmental Biology

The Wnt PCP pathway activated by fibroblast growth factors (FGFs) produced by the hypoblast.

TLS Online TPP Program

#Id: 1600

#Unit 5. Developmental Biology

Convergent extension is responsible for the progression of the streak.

TLS Online TPP Program

#Id: 1601

#Unit 5. Developmental Biology

If Wnt PCP pathway is blocked, the mesoderm and endoderm form peripherally instead of centrally.

 

TLS Online TPP Program

#Id: 1602

#Unit 5. Developmental Biology

As cells enter the primitive streak, they undergo an epithelial-to-mesenchymal transformation.