class notes

Animal Diversity (Part 3) Lecture

Textbook Reference: Chapter 44 in Biology How Life Works (2nd ed.)
 Section 44.3 and 44.5; pp.963 to 972
 Required reading: pp. 963 (starting at Deuterstomes include..) to 966

Deuterostome Tree
• Based on:
 Shared features of larval development
 Strongly supported by molecular sequence
data


• Deuterostome tree includes three major phyla:
 Echinodermata (sea urchins)
 Hemichordata (acorn worms)
 Chordata (vertebrates and invertebrate
chordates)




Echinoderms Are Deuterostomes:
• Although they may seem to have little in common with phylum Chordata (which
includes the vertebrates) they share deuterostome characteristics:
 A cranium that protects a well-developed brain
 Pair of eyes
 Distinctive mouth for food capture and ingestion
 Internal skeleton commonly mineralized by calcium phosphate




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, Deuterostome diversity:
Phylum Description/Characteristics
Echinodermata - Sea urchins and sea stars




What about echinoderm symmetry? Why are they bilaterians when they look radially
symmetrical?




Hemichordata -sister group to echinoderms
Acorn worms - About 75 species of wormlike
animals that move through
seafloor sediments in search of
food particles



Pterobranchs - Consists of about a dozen
species of animals that attach to
the seafloor and use tentacles to
filter food from seawater




Phylum Chordata
• The other great branch of the deuterostome tree is the
chordates
• Within the phylum Chordata, there are three subphyla:
 Cephalochordates
 Tunicates
 Vertebrates

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