{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}


Feb7_Handout_Morph - IB 200B Principals ofPhylogentic...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
IB 200B Principals ofPhylogentic Systematics Spring 2008 MorphologicalData II - Ontogeny & Structure of Animals All members of monophytetic taxa share a common ancestor whose developmental pathway has been modified toproduce descendant morphologies. But at what level or stage does morphology reveal patterns of relatedness? 1. Gametes - gastropod sperm - polyplacophoran eggs 2. Early cell division patterns - Spiral & Radial cleavagepatterns,polar lobes, unequalvs.equalcleavage. 3. Larval forms - Planula, trochophore, Veligers,Instars, direct development Hennig recognized the both the problems and advantages of ontogeny and coined term semaphoront - an organism at a particular stage in ontogeny. Also augmentation criteria. Studyof links between development and evolutionwas relativelyneglected until Ontogeny andPhylogeny was published by Gould in 1977.Gouldpresentedhis own ideas on heterochrony(evolutionarychanges in the timing of development),presenting a unified view of neoteny,recapitulation,paedogenesis,retardation,progenesis, etc. Basic idea is that all heterochronyis a result of accelerationor retardationof different developmental processes (growth,sexual maturation,morphological changes, etc.), and that it is these processes that are important rather than their results. Ontogenyenters into our considerationof phylogenyat three levels: (1) Polarization of character state transformations (augmentation or primary). (2) Assessment of homology. (3) The recognition and exploration ofheterochronic (and heterotopic) patterns in the mgroup. In addition to heterochrony, hetertopic or changes in spatial patterning of ontogenetic processesis also important. While heterochrony is of interest in part because it can produce novelties constrainedalong ancestral ontogenies,and hence result in parallelism between ontogeny and phylogeny, heterotopy can producenew morphologiesalong trajectories differentfrom those that generated the forms of ancestors (Haeckel, 1866).
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Modificationof ontogenies involves both deletions and insertions.Nonterminal characters -- charactersthat occur in the ontogeneticsequencebefore a terminal character.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.
  • Spring '08
  • RO, Recapitulation theory, polar body, Evolutionary developmental biology, cell lineage, ro eneno ro

{[ snackBarMessage ]}

Page1 / 9

Feb7_Handout_Morph - IB 200B Principals ofPhylogentic...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon bookmark
Ask a homework question - tutors are online