BIOL 1020U Lecture Notes - Lecture 10: Agnatha, Axial Skeleton, Deuterostome

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21 Jun 2018
School
Department
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 sequences data
Deuterostome tree includes three major phyla:
Echinodermata (sea urchins and sea stars)
Hermichordata (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:
Named for jointed skeleton running along main
axis of body, forming vertebrae
Shared features with other chordates, vertebrates
animals distinguished by:
oCranium that protects well-developed
brain, pair of eyes, distinctive mouth for
food capture/ingestion, internal skeleton
commonly mineralized by calcium phosphate
Vertebrate Phylogeny
Vertebrates are named for their jointed
skeleton running along the main axis of
the body, forming vertebrate
In addition to features shared with other
chordates vertebrates
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Vertebrate diversity:
Phylum Group Description/Characteristics
Vertebrata
Jawless fish
(general)
Molecular data favor the view shown here, that hagfish and
lampreys together form the sister group to all other
vertebrates
-defining characteristics of both – no jaws, no paired fins-
Hagfish -jawless, cartilaginous skull
-lack vertebrates
-use segmented muscles for movement
-notochord retained in adult
-small brain, eyes, ears
-tooth-like formations in mouth (made of keratin)
Lampreys -inhabit various marine and freshwater habitats
-no jaws
-skeleton made of cartilage – contains stiff protein matrix
instead of collagen as in other vertebrates
-Notochord persists as axial skeleton – cartilaginous pipe
surrounding notochord
-presence of vertebral column in lampreys convince many
biologists that lampreys are sister group to other
vertebrates and hagfish the sister group to all vertebrates,
including lampreys.
Phylum Group Description/Characteristics
Vertebrata Chondrichthyes -includes sharks, rays, and chimaeras
-all have jaws and cartilaginous skeletons
-deposit calcium phosphate minerals only in their teeth and
in small tooth-like structures call denticles embedded in
skin
Osteichthyes
bony fish – have cranium, jaws, and bones embedded in
skin
-mineralized by calcium phosphate
-20,000-25,000 fresh and seawater
-far more diverse group of vertebrates w/ unique features –
facilitate occupation of diverse niches
-system of moveable elements in their jaws allowing them
to specialize and diversify feeding on many diff. types of
food
-swim bladder, a gas filled sac – permits control over their
position in water column through changes in buoyancy
-kidneys, which allow them to regulate water balance and
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