ZOL_320_Lecture_study_guide_4_2011_Evolu - ZOL 320 2011...

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ZOL 320 2011 Evolution of Development Chapter 3 pp. 1-13, 21-31, 47-56, 60-64, 73-84, 92-94 Define, describe or illustrate the following: Vendian Period Pikaia gracilens Triploblast have 3 germ layers deuterostome the mouth is the second opening to form about 180 degrees from the blastopore; the anal opening forms near or at the blastopore region pharyngula chordate phylotypic stage showing developmental innovations indirect development has larval stages heterochrony changes in development time neoteny acceleration of certain structures in relation to others plesiomorphy synapomorphy innovative and charactistic structure of a particular phylum positional value determine what growth, differentiation and morphogenetic decisions to make in that particular place of the emerging pattern. morphogen positional information there is a system for assigning individual cells their relative coordinates in that region. body plan paedomorphosis delay in the development of certain structures in relation to others direct development a smaller version of the adult forms and there is no need for complex reorganization amniote egg yolky egg surrounding embryo bilateral symmetry protostome mouth forms near blastospore area diploblast Ecto/endoderm Cambrian Period 1. What are the advantages of multicellularity over unicellularity? How did multicellularity arise? Being larger is advantageous in getting more nutrients, being a better predator and resisting predation, all allowing for better reproduction. Unicellular organisms can only reach a certain size and so selection pressure gave rise to cells that stuck together, perhaps simply by not fully detaching the daughter cells. Individual cells coming together is also possible but rarely used in extant animals. 2. What are the constraints to cell size increase?
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ZOL_320_Lecture_study_guide_4_2011_Evolu - ZOL 320 2011...

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