Class Notes (806,815)
Canada (492,451)
Zoology (202)
ZOO 2090 (90)
Lecture 2

Lecture 2.docx

2 Pages
Unlock Document

University of Guelph
ZOO 2090
Fred Laberge

Lecture 2 ZOO*2090 September 11, 2013 Origin of chordates cont’d Chordate Origins: Competing Hypotheses - from an inverted annelid/anthropod ancestor o requires an inversion of the dorsoventral axis in order from the nerve cord to be above the gut o however, segmentation and nerve cords are not homologous and important differences in development separate the groups o the mouth and anus would also need to migrate back ventrally from their inverted position on the dorsal surface - from an echinoderm larva ancestor (Garstang) o requires advent of a new mode of locomotion with increasing size and loss of the adult stage o embryonic similarities and bilateral symmetry in both groups, but in agreement with molecular phylogeny - body axis inversion in deuterostome prechordate o support from development molecular evidence, asymmetrical position of the mouth in young amphioxus and molecular phylogeny o reason for the body axis inversion is unknown Overview of vertebrates Important Points for Today  5 characteristics of chordates  major groups of protochordates and their relationships  competing hypotheses on the origin of chordates Typical Exam Question: list 5 characters of chordates we have explored in class and describe their function in the cephalochordate amphioxus The origin of vertebrates - can be studied by: o fossil records – most direct, but never complete o phylogenetic approach: using shared derived characters to determine common ancestry - basil or primitive vs. advanced or derived? o (species/group vs. character) - lower, higher or advanced not ideal terms because characters can derive in one direction or the other Oldest Vertebrates (Early Cambrian, Chengjiang – very important fossil site) - rudimentary vertebrae surrounding a strengthened notochord, eyes might be present Major Vertebrate Innovations - Vertebral column o vertebrates display chordate characters plus a vertebral column (or backbone), where vertebrae replaces the notochord for support o bone or cartilag
More Less

Related notes for ZOO 2090

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.