Download Chapter 30 / Deuterostomes

Randa, Bio102
Chapter 30 / Deuterostomes
I. Introduction
A. Comprised of 2 major phyla: Echinodermata and Chordata
B. Development
1. blastopore: 1st opening anus
2. radial, indeterminate cleavage
3. bilateral symmetry
4. larval forms of 2 major phyla differ dramatically
II. Phylum Echinodermata
A. Characteristics
1. all marine
2. CaCO3 endoskeleton
3. pentamorous body plan
4. body symmetry changes
5. water vascular system
6. circulatory system
7. no brain
8. respiration: many have gills
9. digestion: carnivorous or herbivorous
B. Class Asteroidea
e.g., sea stars
1. central disc with arms/rays
2. surface features: skin gills, pedicellaria
a. aboral side: madreporite, anus
b. oral side: mouth, ambulacral groove
3. internal: stomach, digestive glands, gonads, H2O vascular system, skeleton
4. separate sexes
C. Class Echinoidea
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e.g., sea urchins
1. spines, long tube feet
2. test
3. special jaw-like mechanism
D. Class Crinoidea
e.g., sea lilies
filter feeders, feathery arms
E. Class Ophiuroidea
e.g., brittle stars
largest echinoderm group (diversity and numbers)
resemble sea stars; can move much more rapidly
F. Class Holothuroidea
e.g., sea cucumbers
1. flexible, soft, muscular body (endoskeleton reduced)
2. blood circulatory system
3. use tentacles to feed on algae
III. Phylum Hemichordata
possess proboscis, collar, and trunk
have a dorsal nerve cord, and pharyngeal gill slits
e.g., acorn worms
IV. Phylum Chordata
A. Characteristics
1. dorsal nerve cord
2. notochord
3. endoskeleton
4. pharyngeal gill slits; post-anal tail
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5. segmentation
6. closed circulatory systems
7. definite excretory systems
B. Subphylum Urochordata
1. free-swimming larva→sessile adults
2. filter feeders
incurrent siphon→pharynx→gill slits→
esophagus→stomach→intestine→(anus) excurrent siphon
3. reproduction: asexual
sexual
C. Subphylum Cephalochordata
1. free-swimming
2. dorsal nerve cord and notochord
3. filter feeders
4. notable segmentation
D. Clade Craniata (old: Subphylum Vertebrata)
Basic Craniate characteristics:
--pronounced cephalization
--vertebral column (most)
--closed circulatory system
--kidneys
--living endoskeleton
--respire with gills or internal lungs
--reproduction:
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oviparous
ovoviviparous
viviparous
--maintaining body temperature
poikilotherms, ectotherms
homeotherms, endotherms
The first vertebrates (extinct) were jawless, armored, filter-feeding fishes called
Ostracoderms (Cambrian through Devonian periods).
1. Extant jawless fishes:
a. Class Myxiniformes (Myxini) = hagfishes: scavengers,
b. Class Petromyzoniformes (Cephalaspidomorphi) = lampreys: external parasites
[Classes 1a and 1b above were formerly lumped together in the Class Agnatha. Both lack jaws,
scales, paired fins, and have cartilaginous skeletons and a notochord]
Evolution of jaws: gill arches
First evident in the Placoderms and Acanthodians in the late Silurian and Devonian periods.
2. Class Chondrichthyes
--cartilaginous skeletons (note: a derived character)
-- placoid scales
--lateral line system
--heterocercal tail
--liver oil
--cloaca
3. The bony fishes (formerly lumped in the Class Osteichthyes).
Basic characteristics:
bony skeleton
operculum
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swim bladder
2 major groups:
a. Class Actinopterygii: ray-finned fishes
b. Sarcopterygii:
Class Actnistia: lobe-finned fishes, e.g., coelocanths
Class Dipnoi: lungfishes
Tetrapods:
evolved from Sarcopterygians
some species have lost 4-legged condition
some species have lost terrestrial condition
adaptations for terrestrial life
4. Class Amphibia
--1st tetrapods
--moist skin, lungs
--rely on water for reproduction
--three-chambered heart
5. Class Reptilia
--1st to develop amniotic egg
--bodies covered with protective scales
--polyphyletic group
6. Class Aves
dinosaur ancestor
1st bird: Archaeopteryx
unique characteristics: feathers
lack teeth
adaptations for flight:
skeleton-respiration--
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circulation-digestion-secretion-reproduction-nervous-7. Class Mammalia
--reptilian ancestor
a. distinct features:
--hair
--mammary glands
--characteristic jaw joint
b. most are viviparous
c. three subclasses:
Subclass Prototheria (egg-laying mammals)
Subclass Metatheria (marsupial mammals)
Subclass Eutheria (“placental” mammals)
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