Download Today:

Today:
„
The Animal Kingdom
and Its Traditional
Classification Scheme
„
Major Trends in
Animal Evolution
„
The Invertebrates and
Beyond?
“Making
the
Grade”:
Winter College Transfer Fair! Thursday, February 10, 2005
9:00am - 12:30pm
The Major Grades: 4 Dichotomies
The ParazoaParazoa-Eumetazoa Dichotomy
Animals lacking
true tissues are
called parazoans
All other groups
have true tissues
(eumetazoans)
eumetazoans)
The Major Grades: 4 Dichotomies
The RadiataRadiata-Bilateria Dichotomy
Radiata tend to be sessile or planktonic
(What’s the advantage??)
The Major Grades: 4 Dichotomies
The RadiataRadiata-Bilateria Dichotomy
The EUMETAZOANS
can be separated into two
groups based on symmetry
Radial symmetry =
Radiata
Bilateral Symmetry =
Bilateria
The Major Grades: 4 Dichotomies
The RadiataRadiata-Bilateria Dichotomy
In contrast the Bilariata have a dorsal (top) and
ventral (bottom side), as well as a anterior and
posterior end
They demonstrate a tendency
towards CEPHALIZATION,
or the concentration of sensory
equipment on the anterior end
(important for mobile animals!)
1
The Major Grades: 4 Dichotomies
The RadiataRadiata-Bilateria Dichotomy
In addition, the Radiata are
DIPLOBLASTIC
(two GERM Layers)
The ECTODERM (outer layers,
nervous system in some)
The ENDODERM (innermost layer,
gives rise to the digestive tract related
organs)
The Major Grades: 4 Dichotomies
The Acoelomate,
Acoelomate, Pseudocoelomate and
Coelomate Grades
The simplest Bilateria have solid bodies (no
cavity between the digestive tract and outer
body wall) and are acoelomates (“without
hollow”)
The Major Grades: 4 Dichotomies
The RadiataRadiata-Bilateria Dichotomy
The Bilateria are
TRIPLOBLASTIC and
have an additional
middle layer, the
MESODERM
(gives rise to muscles and
many internal organs)
The Major Grades: 4 Dichotomies
The Acoelomate,
Acoelomate,
Pseudocoelomate and
Coelomate Grades
In animals with a body cavity,
the cavity may be completely
lined by MESDERM, (a
TRUE COELOMATE) or
only partially lined (a
PSEUDOCOELOM)
The Major Grades: 4 Dichotomies
The Major Grades: 4 Dichotomies
The ProtostomeProtostome-Deuterostome Dichotomy
The ProtostomeProtostome-Deuterostome
DichotomyDichotomy- Cleavage
PROTOSTOMES (mollusks, annelids, and arthropods)
are distinguished from DEUTEROSTOMES
(echinoderms and chordates) based on differences
during development:
A. Cleavage
B. Coelom Formation
C. Blastopore Fate
2
The Major Grades: 4 Dichotomies
The Major Grades: 4 Dichotomies
The ProtostomeProtostome-Deuterostome
DichotomyDichotomy- Coelom Formation
The ProtostomeProtostome-Deuterostome
DichotomyDichotomy- Blastopore Fate
PROTOSTOMES
DEUTEROSTOMES
Using Grades
to Construct
a
Phylogenetic
Tree of the
Animal
Kingdom
PROTOSTOMES
“first mouth”
DUETEROSTOMES
“second mouth
Are Grades
Clades??
Complicated by RAPID
EVOLUTION of
the animal phyla!
An Arthropod fossil from the
Burgess Shale; ©Natural
History Museum London
The Cambrian Explosion
„
„
Possible Reasons for the Cambrian
Explosion
1. EcologicalEcologicalpredatorpredator-prey
relationships evolve
Nearly all major animal
body plans appear in
Cambrian rocks dating
543543-525 mya.
mya.
Rapid emergence makes
analyzing fossil record
for evolution of groups
difficult!
2. GeologicalGeologicalhigher concentration
of O2
The Burgess Shale, British Columbia
3. GeneticGenetic- Variation in
expression of Hox
genes (“evo
(“evo--devo”)
devo”)
3
So Is a Grade a Clade?
Molecular Evidence
„
Sequencing SSUSSU-rRNA (and Hox genes) has
provided additional evidence with which to
construct Phylogenetic Trees
Adding
SSUSSU-rRNA
to the
Picture
How does it
look??
Resolving the
Protostomes
(Rearrangement #1)
What
happened to
the Coelom?
(Rearrangment #2)
Acoelomates
(flatworms)
now with the
Protostomes
Rearrangement
#3:
Rearrangement
#3:
Emergence of the
Ecdysozoa
Emergence of the
Lopho-trochozoa
4
Revised Version of the Cambrian
Explosion?
In Lab: A Survey of Animal Phyla
3 Major Groups of Bilateria
Emerge:
Lophotrochozoans
Ecdysozoans
Deuterostomes
Sequence difference
between these groups is
large.
Sequence difference within
much more subtle!
Can you make the grade??
1. Radially Symmetrical,
True Tissues
2. A Deuterostome
?
?
How did
you do??
3. No True Tissues
4. A Protostome
Ancestral Colonial
Choanoflagellate
One More Chance: Who’s
who??
One More Chance: Who’s
who??
5
Looking More Closely at
the Animal Kingdom
One More Chance: Who’s
who??
The Porifera (Parazoa)
We’ll
Start
Here…
The Porifera: Typical Anatomy
Ancestral lineagelineage- no
true tissues
„ Lined with choanocyteschoanocytescreate currents, trap
food
„ Skeleton composed of
spicules
„
The Porifera: Sponge Sex
Most sponges are hermaphrodites;
eggs are retained in the mesophyl
while sperm are released into the
water. Fertilized zygotes develop
into swimming larvae.
Reproduction can also
be asexual
(fragmentation)
6
The Cnidarians
„
„
Next
Up:
„
„
„
Radially symmetrical
Diploblastic embryos (ectoderm and
endoderm)
Central digestive compartment
(gastrovascular cavity) with single
opening
Can be either a polyp or medusa
Stinging cells called cnidocytes
contain capsules, the nematocyst, for
snagging and poisoning prey
The Cnidarians: Anatomy
The Cnidarians: Anatomy
The Cnidarians: Reproduction
The Cnidarians: Anatomy
(one example!)
Cool Advances:
• Simple nerve net to
coordinate movement
• Muscle-like contractile
fibers (bundles of
microfilaments)
• Can sense light, gravity,
and more
7
Cnidarian ‘Cousins’: The
Ctenophora
The Cnidarians: Diversity
1. Hydrozoa- mostly marine,
polyp and medusa in most,
polyp often colonial
(a separate, radial phylum)
• Morphologically similar,
evolutionary relationship
uncertain
2. Scyphozoa- marine,
reduced polyp, large
medusas
• Two long retractable tentacles
used in capturing prey
3. Anthozoa- marine, no
medusa stage, sessile,
mostly colonial
• Use cilia for locomotion
Worms and Beyond
„
And Now
For
Something
Completely
Bilateral…
The Platyhelminthes
„
„
„
„
„
Acoelomates
Earliest extensive
organorgan-system
development
Nervous system
with small “brain”
Cephalization
evident (eyespots!)
Digestive track has
single opening
All remaining phyla are triploblastic,
triploblastic, and are
bilaterally symmetrical at some point in their
life history
The Diversity of Platyhelminthes
The Flukes:
Tapeworms:
Why am I so
flat???
Planaria:
8
The Nematodes (Roundworms)
„
„
The Diversity of
Platyhelminthes
Digestive tract complete
Pseudocoelom
Ascaris:
Trichinella:
Vinegar Eels:
The Annelids (Segmented worms)
„
„
„
„
„
True Coelomates (+ all animals beyond)
Annilids are schizocoelous
Closed circulatory system
Nervous system, oneone-way gut Earthworm
Primarily freefree-living
(Lumbricus):
Leeches:
The Development of the Coelom
Planaria
Ascarics
Lumbricus
Acoelomate
Pseudocoelomate
Eucoelomate
The Molluscs
„
„
General body plan includes the foot, the visceral
mass, and mantle
Open circulatory system with chambered heart
The Arthropods
„
„
„
„
„
Segmented body, covered by exoskeleton
Typically divided into 3 tagmata:
tagmata: the head,
thorax, and abdomen
Open circulatory system w/heart
Reduced coelom
WellWell-developed nervous system
9
The Echinodermata
„
Leaving the
Protostomes
„
„
„
„
The Chordates
Phylum includes sea squirts
(tunicates), lampreys and
hagfishes, fishes, amphibians,
reptiles, birds and mammals
Deuterostomes!
Deuterostomes!
5-part body plan
Water vascular system w/tube feet
Bilateral larvae w/ “radial” adults
Spiny skin, internal skeleton
The Chordates
4 Common Features:
1. Flexible supporting skeletal rod called a
notochord
2. Dorsal hollow nerve cord above the
notochord
3. Pharyngeal pouches in the pharynx
4. Post anal tail
The Chordates
10