Lecture 8 - Bilaterian Animals Flashcards
Chart: Before Bilateria
Porifera, Ctenophora, Cnidaria
Chart: Protostomes group 1
Rotifera, Platyhelminthes, Annelida & Mollusca
Chart: Protostomes group 2
Nematoda, Tardigrada, Onychophora & Arthropoda
Chart: Deutoerstomes
Echinodermata & Chordata
What is a Bilaterian? (6 traits)
Bilateral symmetry, triploblastic, true coelom, nervous system, muscles, through-gut
What are the two main lineages of Bilateria
Protostomes, Deuterostomes
What is spiral cleavage?
Cells divide at oblique angles
What is radial cleavage?
Cells are arranged directly on top of each other
What is determinate cleavage?
Fate of cell is set in early development, isolated blastomeres cannot develop into an entire animal, cytoplasmic determinants
What is indeterminate cleavage?
Fate of cells not set in early development, isolated blastomeres can develop into an entire animal, induction
Traditional model for protostomes cleavage
Sprial and determinate
Traditional model for deuterostomes cleavage
Radial and indeterminate
Traditional model: formation of protostomes
Schizocoelous: solid masses of mesoderm split to form coelom, mouth develops from blastopore
Traditional model: formation of deuterostomes
Enterocoelous: fields of archenteron form coelom, anus develops from blastopore
Where is priapulids located?
Directly before protostomes group 2