Updated Jan 2003
UNIT 2
Deuterostome Phyla
Phylum Echinodermata
Major features
symmetry: bilateral in larvae, pentamerous radial in adults
water vascular system Fig. 33.38 (33.37); all marine; endoskeleton
Taxonomic groups Fig. 33.37 (33.36)
Class Asteroidea - starfish or sea stars
Class Ophiuroidea - brittle stars and basket stars
Class Echinoidea - sea urchins, heart urchins, sand dollars
Class Holothuroidea - sea cucumbers
Class Crinoidea - sea lilies and feather stars
Phylum Chordata - Text Chapter 34
Four major features Fig. 34.2 (34.1)
Taxonomic groups Figs. 34.1, 7 (34.6)
Subphylum Urochordata - tunicates Fig. 34.3 (34.2)
Subphylum Cephalochordata - lancelets Fig. 34.4 (34.3)
Subphylum Vertebrata - vertebrates (new outline follows)
Subphylum Vertebrata - animals with a brain and skull
Class Agnatha - jawless fishes, two very different groups
Subclass Ostracodermi (ostracoderms) - Late Cambrian through Devonian
Subclass Cyclostomata - lampreys and hagfishes Figs. 34.8, 9 (34.7)
Class Placodermi (placoderms; see Fig. 34.6)) - extinct; first with jaws
and paired fins; evolution of jaws from gill arches Fig. 34.10
(34.8); all living jawed fishes make up the following two classes:
Class Chondrichthyes - (cartilaginous fish) sharks, skates, rays:
cartilage skeleton; no swim bladder, no lung, 5-7 pair of gill
openings; placoid scales and vertebrate teeth; spiral valve in
intestine; lateral line Fig. 34.11 (34.9)
Class Osteichthyes (bony fish) - skeleton mostly bone; one gill cover;
most have swim bladder; no placoid scales; subclassification varies
Figs. 34.12-14 (34.11):
Subclass Actinopterygii (ray-finned fishes)
Primitive superorders - e.g. sturgeons, paddlefishes, bowfin, gars
Superorder Teleostei - teleost fishes (the vast majority of bony
fishes, about 35 taxonomic orders)
Subclass Dipneusti (lungfishes) - 6 living species (Fig. 34.13)
Subclass Crossopterygii (lobed-finned fishes) Fig. 34.14 (34.12)
Coelocanth (Latimeria) and Rhipidistians (extinct)
Class Amphibia - amphibians Figs. 34.17, 18 (34.15)
Two main orders: Anura & Urodeles (=Caudata)
Characteristics, reproduction, warning coloration, reduced numbers
Amniotes (reptiles, birds, mammals) Figs. 34.19-21
Class Reptilia - reptiles Figs. 34.22-24 (34.17-21)
Characteristics
Orders: Testudines (=Chelonia), Squamata, Crocodilia, Sphenodonta
Class Aves - birds Figs. 34.25-29 (34.22-25)
Class Mammalia - mammals Figs. 34.30-40; Table 34.1 (34.26-32)
Characteristics
Classification
Subclass Prototheria (monotremes, 3 species)
Subclass Theria
Infraclass Metatheria (marsupials)
Infraclass Eutheria (placentals) - representative orders
The Fossil Record - pp. 484-492 (464-473)
Fossils - definition
Kinds of fossils:
original material, petrifications, molds, casts, imprints
Requirements for fossilization
Limitations of the fossil record
Dating of rocks: a. using radioisotopes b. sedimentary rocks
Earth History Overview - 4.5 BYA to present
Precambrian - 4.5 BYA to 570 MYA; milestones, Edicarian fossils
Phanerozoic - 570 MYA to present - animal fossils abundant
Paleozoic Era - 570 to 245 MYA
Mesozoic Era - 245 to 65 MYA
Cenozoic Era - 65 to present
Earth History in Detail
Paleozoic Era
Cambrian Period, focus on Burgess Shale
Ordovician and Silurian Periods
Devonian Period - age of fishes, first land vertebrates
Carboniferous Period - swamp forests, insects, first reptiles
Permian Period - ends with great extinctions
Mesozoic Era - Triassic, Jurassic, Cretaceous Periods
Geological events
Rise of flowering plants and coevolution of insects
Diversity in reptiles; first mammals and birds
Cretaceous extinctions
Cenozoic Era
Geological and climatic changes
Adaptive radiation of mammals
Human Evolution - pp. 707-715 (656-665)
Figs. 34.34-41 (34.30-35)
Primate adaptations to arboreal life
Primate groups
Suborder Prosimii
Suborder Anthropoidea
Superfamilies: New World Monkeys, Old World Monkeys, Hominoidea
Hominoid characteristics and phylogeny
Problems associated with the study of the human fossil record
Some important fossil hominid species
Australopithecus afarensis - Lucy, footprints
A. africanus; A. robustus and A. boisei
Homo habilis
H. erectus
H. sapiens - including neanderthalensis and Cro-Magnon
Theory of Evolution
Development of the concept of evolution (Chapter 22)
Pre-Darwin
Linnaeus 1758 - Systema Naturae
Erasmus Darwin - grandfather of Charles
Lamarck - hypothesis published 1809
Charles Darwin & A.R. Wallace - natural selection
Early 20th Century
Development of Population Genetics
Factual and theoretical aspects of theory of evolution
Evidence for evolution as a fact of nature
The fossil record
Comparative studies of living species via anatomy,
embryology,biochemistry, etc.
Artificial selection
Theory as to causes of evolution; mainly driven by natural
selection
The Evolution of Populations (Chapter 23)
Natural Selection
Detailed overview of the concept
Stabilizing selection
Directional selection: e.g. insecticide resistance
Disruptive (=Diversifying) selection
Biston betularia
Mimicry in Limenitis arthemis butterflies
Genetic drift and evolution in small populations
Genes in populations - Hardy-Weinberg Law
Speciation - formation of new species (Chapter 24)
The biological species concept (Mayr) - groups of
individuals reproductively isolated from other such groups -
extremely little or no gene exchange between them
Sympatric vs allopatric populations
Why speciation is hard to study
Mechanisms of speciation (a barrier to gene flow is
essential)
Anagenesis - time is the barrier; no multiplication of
species
Cladogenesis - splitting evolution; multiplication of
species
(1) Allopatric - geographic barrier
a. Two models:
- Gradualism - large subpopulations
- Punctuated equilibrium - founders and other
small populations (e.g., Williamson snail study)
b. Results of isolation breakdown
- hybridization and loss of differences, still
one species
- reproductive isolation, separate species
Prezygotic mechanisms - behavioral, etc
Postzygotic mechanisms - sterility, etc
(2) Sympatric - nongeographic barrier
a. Polyploidy - chromosome number differences
create sterility barrier
b. Other mechanisms -Rhagoletis pomonella (Apple
maggot) as a possible example
Adaptive Radiation - oceanic islands provide many examples
Evolution at higher levels - genus, family, order, etc.