Download Phylum Echinodermata and Phylum Chordata

Phylum Echinodermata and Phylum Chordata
Objectives:
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Differentiate between protostome and deuterostome characteristics.
Identify traits of echinoderms.
Differentiate between the different Chordate subphyla.
Perform a Sea Star dissection.
All Animals Are:
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heterotrophs
multicellular
eukaryotes
are mobile at some stage of life
store carbohydrates as glycogen, not starch, as in plants
have an early developmental stage called a blastula
have RNA (extracellular matrix)
Protostomate and Deuterostomate Lineages:
Figure 1 Protostome and Deuterostome
The names protostome and deuterostome derive from the differing fate of the initial opening of the
primitive digestive tract (the archenteron) in an embryo. As illustrated in the following picture, in
protostomes, this initial opening develops into the mouth, and an opening that develops later
becomes the anus. In deuterostomes, it develops into the anus, and an opening that develops later
becomes the mouth.
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Figure 2 (Images from the University of Tennessee at Martin Biology pages)
Determinate cleavage is characteristic of protostomes. After the initial cell division the fate of the
resulting daughter cells is determined -- these cells can only develop into specific tissues, not the
whole organisms. Indeterminate cleavage is characteristics of deuterostomes. After the initial cell
division the fate of the resulting daughter cells is not determined -- each has the potential to develop
into an entire organism. Sometimes this occurs; resulting individuals are genetically identical (in
humans, they are called identical twins).
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Figure 3 Protostome and deuterostome cleavage differs in other ways
too.
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Figure 4 (Images from the University of Tennessee at Martin Biology pages)
Coelom Development:
A coelom is a body cavity completely surrounded by mesoderm. The coelom can be used as a
hydrostatic skeleton, i.e., for support. It provides an avenue for release of, for example, gametes and
excretory waste. It also provides a place for internal organ placement.
The coelom can develop via two pathways: In protostomes: blocks of mesoderm hollow out to form
the coelom. Deuterostomes; pockets of mesoderm pinch off to form the coelom.
Phylum Echinodermata: Starfish, Sea Urchins
Tissues:
Three distinct tissue layers in embryo, leading to multiple tissue types in
adult.
Symmetry:
Bilateral in the larva, but adults are more or less radially symmetrical
(pentaradial, since they have five arms).
Body cavity:
Coelom
Proto/deutero:
Deuterostome
Digestive tract:
Complete digestive tract (mouth at one end andanus at the other).
Other features:
Body not clearly segmented. Calcareous endoskeleton. Hydrostatic
skeleton (water vascular system). Water vascular system. Planktonic
larvae.
You might not guess it from looking, but the echinoderms are probably our closest relatives
outside our own phylum.
Key echinoderm features include:
Endoskeleton:
Much like our own skeleton, the echinoderm skeleton consists of
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numerous calcified structures joined by more flexible tissues.
Water-vascular system:
A system of water-filled tubes running throughout the animal’s
body, the water-vascular system functions as an elaborate and
flexible hydrostatic skeleton. (Echinoderms therefore have two
skeletons: the hard plates of the endoskeleton and the flexible
hydrostatic skeleton.) The water-vascular system includes tube
feet, which are used by sea stars and other echinoderms to walk
and to grab prey items.
Coelom:
The coelom in echinoderms is large, filling much of the body.
The coelom is just a big, fluid-filled space. It’s not the water
vascular system, which contains water in a closed system of
vessels, and it’s not the gut, which is smaller and also enclosed.
The coelom is the space where the other organs (water vascular
system, gut, gonads, etc.) form.
Examples: sea urchins, starfish, sea cucumbers:
Figure 5: Sea Cucumber
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Figure 6: Starfish
Figure 7 Sea Urchin
Water vascular system - system unique to this phylum. Functions in movement, support,
respiration, digestion.
Decentralized nervous system.
Rapid regeneration.
Secondary radial symmetry Larvae are bilaterally symmetrical. Adults are radially symmetrical.
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A tube foot, an extension of the water
vascular system of a starfish. The tube feet
act like little suction cups which enable to
starfish to grasp onto the sediment
for movement or to break into bivalves
for food. Note that since this is not a
muscular system, they will not tire.
Figure 8: Tube Foot
Major Classes of Echinoderms
Sea urchins; class Echinoidea:
Sea stars (starfish); class Asteroidea:
No arms; spiny body. Detritivores.
Five or more arms. Predators.
Sea cucumbers; class Holothuroidea: No arms; body often soft. Detritivores
Brittle stars; class Ophiuroidea:
Five arms with central disk;
delicate and thin. Detritivores.
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Phylum Chordata:
This is your phylum. The phylum Chordata includes humans and other vertebrates
Examples: Sea squirts, lancelets, vertebrates
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Notochord
Pharyngeal Gill Slits
Dorsal Hollow Nerve Cord
Post Anal Tail
Figure 9: Chordate Body Plan
Chordate Characteristics
Tissues:
Three well-defined tissue layers in embryo.
Symmetry:
Bilateral, with cephalization.
Body Cavity:
Coelom
Proto/deuterostome:
Deuterostome: the blastopore formed during gastrulation eventually
becomes the anus; the mouth forms later.
Digestive Tract:
Complete digestive tract.
Circulatory System:
Closed in vertebrates; open in a few others.
Other Important Features:
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Segmented body; vertebrae, for example.
Endoskeleton
Notochord: a connective-tissue body stiffener.
Dorsal tubular nerve cord – forms the brain and spinal cord.
Pharyngeal pouches and slits – gill related structures that may appear early in development. In
addition to forming gills, these structures also develop into jaw bones and other structures in
vertebrates.
Post anal tail: In many worms, the anus is at the very end of the animal’s body; chordates
typically have a tail beyond the anus.
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Non- Vertebrate Chordates
Subphylum Urochordata - the sea squirts
• Larval stage possesses all of the chordate characteristics.
• Most of these characteristics are lost when the
larvae undergo metamorphosis and emerge as adults.
Adult stage are primarily sessile filter-feeders.
Figure 10: Urochordate
Subphylum Cephalochordata - the lancelets
• Possesses all of the chordate characteristics throughout life cycle.
• Burrow into sand and use mucous-secreting organs to filter-feed.
• Feeble swimmers
Figure 11: Lancelet
Vertebrates
The vertebrates (phylum Chordata, subphylum Vertebrata) include fish, amphibians, reptiles
(including birds) and mammals. All these animals have the basic characteristics of chordates, with
some added twists:
• The anterior region of the dorsal hollow nerve cord expands to become a brain and is encased
within a skeletal cranium.
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Mesodermal blocks develop not only myotomes, but a segmented vertebral column that
protects the posterior region of the dorsal nerve cord (spinal cord) and replaces the notochord.
The cranium and vertebral column comprise the axial skeleton of vertebrates allowing an
elaborate central nervous system and powerful muscle action with a flexible body.
• The development of a brain has further spurred the development of more sophisticated
cephalic sensory organs, especially eyes, nostrils and ears.
• To support their enhanced homeostasis, vertebrates also have a closed circulatory system with
distinctive types of heart and kidneys, and a greater suite of endocrine organs.
The notochord, one of the unique defining characteristics of chordates, is a semi-stiff rod of
connecting tissue that forms in the embryo and serves to guide the development of the vertebral
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column (backbone) of vertebrates, along with other structures. In your own body, the notochord has
mostly disappeared; the only remnants are the cartilaginous disks between your vertebrae.
Subphylum Vertebrata
Bone - reduction of notochord (vertebral disks)
Class Agnatha - the jawless fish (not
monophyletic)
Examples: lamprey, hagfish
• No jaws
• Most are parasitic fish
• Very diverse group in past. Now, only a few
species are still hanging on.
Figure 12: Lamprey
Class Chondrichthyes - the cartilaginous fish
Examples: sharks, rays, skates
• Endoskeleton is composed entirely of cartilage.
• Heterocercal caudal fin
• Two-chambered heart
• Numerous rows of teeth
• Internal fertilization and separate sexes
Figure 14: Stingray
Figure 13: Sand Tiger Shark
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Class Osteichthyes - bony fish (not monophyletic)
Figure 15: Scaley Head
Figure 16:
Seahorse
Figure 17: Stickleback
Examples: marlin, bass, catfish, angelfish, eels
• Most diverse group of vertebrates.
• Paired fins with fin rays of cartilage or bone.
• Respiration by gills supported by bony gill arches and
covered by a common operculum.
Figure 18: Coelocanth
• Swim bladder often present.
• Two-chambered heart.
• Sexes separate and fertilization is usually external.
Ray-finned fish - most fish possess this fin structure
Lobe-finned fish - lung fish, Coelacanth, etc.
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The lobe-finned fish gave rise to tetrapods
Class Amphibia - amphibians (not
monophyletic)
Examples: frogs, salamanders
• Living skin - must be moist to breathe
• Lay eggs in water
• Outcompeted in water (fish) and land
(reptiles)
Figure 19: Amphibian
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Class Reptilia - reptiles (not monophyletic)
Examples: lizards, snakes, gators
• First truly terrestrial animals
• Amniotic egg
• Scales (lungs now sole respiratory organ)
• Modifications of pectoral and pelvic girdles to
facilitate movement on land
Figure 20: Reptile
Class Aves - birds (monophyletic)
Examples: robin, jays, emu
• Feathers
• Warm-blooded (high metabolic rate)
• Hollow bones
Figure 21: Ave
Class Mammalia - mammals (monophyletic)
Examples: elephant, bats, Al Gore
• Hair
• Mammary glands
• Occlusional teeth
• Warm-blooded (high metabolic rate)
Figure 23: Deer Mouse
Figure 22: Vampire Bat
Figure 24: Elephant
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Lab Exercise:
Observe the preserved specimens for this lab.
View the following prepared slides:
Amphioxus-or lancelet, a fish-like marine chordate in the invertebrate subphylum
Cephalochordata.
Starfish arm-Note the coelom, tube feet and radial canal (parts of the water vascular system), pyloric
ceca (digestive glands), and pedicellaria (pincers on the outer surface of the body).
Starfish development
Starfish, ray
Dissection of a Preserved starfish dissection (separate document)
Sources: http://www.uic.edu/classes/bios/bios100/labs/animaldiversity.htm
http://facultyfiles.deanza.edu/gems/heyerbruce/6AManual15S.pdf
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