Download Biol 1309

Biol 1309
Echinoderms & Chordates
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But first a few words about
Development
• Blastula- zygote first develops into a hollow ball of
cells
• Deuterostome - “mouth second”
• Protostome - “mouth first”
• Cleavage - describes early cell divisions in relationship
with an axis
• Coelom - cavity contains digestive etc
• Enterocoely - process (in deuterostomes) that forms
coeom - mesoderm forms as evaginations of the
developed gut that pinch off
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So what is a Protostome?
“Mouth First”
Three major groups:
• Ecdysozoa (arthropods, nematodes)
• Platyzoa (platyhelminthes, rotifers)
• Lophotrochozoa (molluscs, annelids)
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So then – what is a deuterostome?
• Distinguished by embryonic development:
– the first opening (the blastopore) becomes the
anus (in protostomes it becomes the mouth)
– Also known as enterocoelomates because
their coelom develops through enterocoely.
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The 4 Existing Deuterostome
Phyla:
• Phylum Chordata (vertebrates)
• Phylum Echinodermata (sea urchins, sea
cucumbers, sea stars...)
• Phylum Hemichordata (acorn worms)
• Phylum Xenoturbellida (only 2 species of
worm-like animals)
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Echinoderms!
• Means “tough skin”:
Spiny skin that covers endoskeleton made of
calcium plates.
• water vascular system –
hydraulic fluid-filled tube system (and tube feet!)
used for movement.
• five-part symmetry –
(pentaradial) around a central disc with a central
mouth.
• Includes:
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crinoids (feather stars, sea lilies)
sea stars
brittle stars
sea cucumbers.
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Echinoderms- so many kinds of spiney skins!
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Onward - to the Chordates!
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What is a Chordate?
Share four common characteristics…
At some point in their lives, chordates
have:
1. Stiff, rod-like notochord running down the
back (serves as a skeleton)
2. Hollow dorsal nerve cord
3. Pharyngeal slits (in throat region)
4. Muscular postanal tail
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Additional Chordate Traits
• Bilateral symmetry
• Have coeloms
• Most develop an extensive endoskeleton
(cartilage or bone)
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CEPHALOCHORDATA:
• Common Name:
Lancelets.
• Small fish-like
chordates retain all
four chordate
characteristics
throughout their lives.
(Consider these guys to
be invertebrate
chordates.)
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UROCHORDATA:
Common name: sea
squirts
Their tadpole-like larvae
have the four
chordate
characteristics.
As adults, most of these
characteristics are
lost when adults settle
down to filter feed.
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CRANIATES:
Hagfishes +
Vertebrates.
These animals have a
skull.
Includes: hagfishes,
lampreys,
cartilaginous fishes,
bony fishes,
amphibians, reptiles
(including birds), and
mammals.
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VERTEBRATES:
Lampreys + gnathostomes.
These animals have a vertebral column (spine)
made of repeating vertebrae. The notochord is
replaced or surrounded by the vertebral column.
They also have more extensive skulls plus other
characteristics, such as kidneys.
The vertebrates include lampreys, cartilaginous
fishes, bony fishes, amphibians, reptiles
(including birds), and mammals.
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GNATHOSTOMES:
These animals have jaws and paired
appendages (fins or limbs).
Include: cartilaginous fishes, bony fishes,
amphibians, reptiles (including birds), and
mammals.
An important advancement for this group
was jaws, allowing biting teeth to evolve.
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TETRAPODS:
• Four limbs
• Modified for life on land.
• Limbs have common pattern: humerus,
radius, ulna, wrist/ankle bones, bones of
feet and finger bones.
• Include amphibians, reptiles (including
birds), and mammals.
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Limbs
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Amniotes:
• Amniotic egg
• Include the reptiles
(including birds) and
mammals.
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Egg Power!
• The amniotic egg usually has a shell that
protects the developing embryo inside.
The amniotic egg creates a little "pond" for
the embryo to develop within.
• Allowed amniotes to reproduce on land,
away from water.
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The Amniote Egg
Four extraembryonic membranes:
(1) Amnion – (produces amniotic fluid to
cushion the developing embryo)
(2) Chorion – (allows gas exchange)
(3) Allantois- (stores embryo metabolic wastes)
4) Yolk sac – (supplies embryo with nutrients
(yolk)
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HAGFISHES
Craniates without vertebral
column.
Look somewhat like eels,
with elongated bodies.
Scavengers that feed on
dead or dying
invertebrates and fishes.
Produce slime when
threatened.
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LAMPREYS
Parasitic jawless fishes.
Lamprey can grab onto
live prey with suckerlike mouth and use
tongue to rasp away
flesh.
Although most are
aguatic, there are
some marine species
that must spawn in
fresh water.
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Hagfishes
Slime!
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Lampreys
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Cartilagenous Fishes
• Internal skeletons mainly of cartilage.
• Presence of pointed or cone-shaped scales
(called placoid scales).
• A major evolutionary advance- development of
jaws ( allow biting or crushing prey)
• The scales of cartilaginous fishes (called
denticles)  similar to the structure of their
teeth, complete with enamel and dentin.
One evolutionary possibility is that denticles lead to the
development of teeth within the jaw.
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Cartilagenous Fishes (cont.)
Developed two sets of paired fins: pectoral fins (front) and
pelvic fins (back) – provides stability, support and
maneuverability
Includes: sharks, rays and skates.
Their bodies (like most fishes) are more dense than water,
so they tend to sink.
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Bony Fishes
• More different species than any other group of
chordates.
• Developed internal skeleton made of bone
(much stronger than cartilage)
Because the ancestor of bony fishes apparently lived in
stagnant, fresh-water pond environments, adaptation
that evolved in ancestral bony fish was the lung.
• Modern bony fish have swim bladders, derived
from the ancestral lung.
This gas-filled internal structure allows a fish to maintain
its position in the water without expending a great
deal of energy.
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Bony Fishes (cont.)
Majority have fins that are supported by slender
rods or rays (often called the ray-finned fishes).
Some of the bony-fishes have fleshy, lobed fins
that are supported by skeletal elements of bone.
Ancestral lobe-finned fishes gave rise to
amphibians.
Modern-day lobed-finned fishes include the
coelacanth and lungfishes in Australia, Africa,
and South America.
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