deuterostome animals€¦ · phylum echinodermata sea stars, sea urchins, sea cucumbers, sand...
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Deuterostome Animals Echinoderms and Chordates
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Deuterostome Roots • We deuterostomes develop butt-first, and
we’re proud of it..
• But not many other clades of animals develop this way…
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Ancestral protist
No true tissues
Radial symmetry
Tissues
Bilateral symmetry
Sponges
Cnidarians
Molluscs
Flatworms
Annelids
Roundworms
Arthropods
Echinoderms
Chordates
Figure 17.5
Deuterostomes
Protostomes
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Two major kinds of Coelomates: • Protostome – mouth develops from blastopore. Rotifers, Flatworms, Annelids, Molluscs, Arthropods
• Deuterostome – anus forms from blastopore Echinoderms, Chordates
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Cleavage
Spiral- third division and subsequent are unequal…typical of protostomes
Radial- third division is equal…typical of deuterostomes
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, Based mainly on 18S RNA, Cameron et al. 2000 PNAS 97(9): 4469-4474
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Deuterostome Phyla
• Echinodermata (sea stars, urchins, crinoids)
• Hemichordata (acorn worms, pterobranchs, extinct graptolites)
• Urochordata (tunicates, salps)
• Chordata (cephalochordates, vertebrates)
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Phylum Echinodermata
Sea stars, sea urchins, sea cucumbers, sand dollars
Marine animals with:
• Spiny “skin”
• Water vascular system
• Tube feet
• Endoskeleton plates
• Radial symmetry as adults
• Bilateral symmetry as larvae
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Sea star
Sea urchin
Sea cucumber Sand dollar
Tube feet
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• Mainly carnivorous – evert stomach to carry out digestion.
• Locomotion mainly by tube feet- arms move only slowly
• Arms are short and thick, with coelomic extensions containing digestive glands and gonads
Class Asteroidea (Sea Stars)
Sea stars in time lapse https://www.youtube.com/watch?v=CYN0J3HCihI Star Fish Eating Clam https://www.youtube.com/watch?v=4dkieg7F37c sea-stars eating mussels https://www.youtube.com/watch?v=2DFXGafpGkQ
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Stomach
Digestive
gland
Anus Tube feet
Ampulla
Gonad Spine
Dermal gill
Pedicellariae
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Echinoderm water vascular system
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A seastar (Asterias) opening a bivalve
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Starfish facts: 11 facts about Sea Stars https://www.youtube.com/watch?v=I8as-z-EShc Sea Star Time-lapse: Eating Mussel https://vimeo.com/45154593 Zombie Starfish - Nature's Weirdest Events: Series 4 https://www.youtube.com/watch?v=KrfcglOmBYw
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Class Ophiuroidea - Brittle stars • central disc containing the organ systems
• arms longer, more slender than sea stars
• use arms for locomotion, capable of rapid movement by muscle action
• tube feet lack suckers
• No anus.
• Deposit, detritus, and suspension feeders
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Class Echinoidea (sea urchins, et al.)
• Globular or flattened, without arms
• Complex 5-part jaw apparatus (“Aristotle’s Lantern”)
• Mainly grazers on algae, a few feed on bryozoans or sponges.
• Some species harvested as food (the roe is eaten)
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• Elongated flexible bodies, propelled by 3 to 5 rows of tube feet
• Circle of modified tube feet surrounds mouth
• Gut has branches for respiration
Sea Cucumber https://www.youtube.com/watch?v=vsLBOkYLLeI Sea Cucumber Fights with Guts https://www.youtube.com/watch?v=wXf_YodWw40 Sea Cucumber expelling its intestines https://www.youtube.com/watch?v=aCxKFc3XtJs Seaview Science Video: Sea Cucumbers https://www.youtube.com/watch?v=MVNrbyU-Vck
Class Holothuroidea - Sea Cucumbers
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Class Holothuroidea - Sea Cucumbers
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Class Holothuroidea sea cucumbers
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• Tube feet around mouth form feeding tentacles, gather food and transfer to mouth.
• Gut has branches for respiration, and Cuvierian threads expelled for defense
Class Holothuroidea - Sea Cucumbers
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Class Crinoidea - Sea lilies, feather stars • Feather stars (unstalked) and sea lilies (stalked,
attached).
• globular body (calyx) partially encased in skeletal plates
• exaggerated, branched arms used for suspension feeding
• oral surface turned upward
• greatest diversity in Paleozoic
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Ancestral protist
No true tissues
Radial symmetry
Tissues
Bilateral symmetry
Sponges
Cnidarians
Molluscs
Flatworms
Annelids
Roundworms
Arthropods
Echinoderms
Chordates
Figure 17.5
Deuterostomes
Protostomes
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Phylum Chordata
• ~45,000 species, 97% of them are vertebrates
• Subphylum Urochordata
• Subphylum Cephalochordata
• Subphylum Vertebrata
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Cameron et al. 2000 PNAS 97(9): 4469-4474,
Based mainly on 18S RNA
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The invertebrate chordates The chordates include all of the vertebrates (fish, amphibians, reptiles, mammals and birds), but also two non-vertebrate subphyla: the Urochordata and the Cephalochordata
never develop a vertebral column
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Characteristics of the Chordata
• bilaterally symmetrical
• triploblastic
• have a well developed coelom
• have a complete digestive system
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• Notochord
• Dorsal, tubular nerve cord
• Pharyngeal pouches or gill slits
• Post anal tail (extends beyond anus)
Not all of these characteristics are apparent in adult organisms and may appear only in the embryonic or larval stages.
Characteristics of the Chordata
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Chordate Body Plan
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Notochord
• Notochord: the notochord is a flexible, rodlike structure. It extends the length of the body and is an anchor point for muscles.
• The notochord bends without shortening so it permits the animal to undulate.
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Figure 23.01
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Notochord
• In nonvertebrates and the jawless vertebrates the notochord is present throughout life.
• However, in the jawed vertebrates it is replaced by the vertebral column; the remnants of the notochord being found in the intervertebral disks.
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Chordates
–Chordates consists of three groups of invertebrates:
• Tunicates, or sea squirts, also lack a cranium
• Lancelets are bladelike animals without a cranium.
• Hagfishes are eel-like forms that have a cranium.
–All other chordates are vertebrates.
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Mouth
Tail
Lancelet Tunicates
Lancelets
Tunicates
https://www.youtube.com/watch?v=2VravyjZta0 https://www.youtube.com/watch?v=2wJP_iB1hyc
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Ancestral chordate
Tunicates
Lancelets
Hagfishes
Lampreys
Cartilaginous fishes
Bony fishes
Amphibians
Reptiles
Mammals
Ch
ord
ates
Ve
rteb
rates
Tetrapo
ds A
mn
iote
s
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Tunicates Subphylum Urochordata
• Marine animals with tough tunics
• Suspension-feeders
• Adult is sessile and feeds via pharyngeal slits
• Larvae are free swimming - dorsal tubular nervous system
- notochord and
- gill slits
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Ciona intestinalis
(a solitary sea squirt)
Sea squirts (Class Ascidiacea, Tunicates) • Adults are marine, sessile, filter feeding organisms
that live either solitarily or in colonies.
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Tunicate larvae (tadpole)
Free-swimming, • dorsal tubular
nervous system • notochord and • gill slits
Searches for a place to settle and then attaches and metamorphoses into an adult
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• Barrel-shaped, planktonic tunicates, drift through the open ocean
• Moves by contracting, thus pumping water through its gelatinous body
Salps
Giant Pyrosome and Salps - pelagic sea squirts https://www.youtube.com/watch?v=5EQGA_4BZ5s Sea Salps https://www.youtube.com/watch?v=-Jooz4gz264
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• In the 1920’s it was proposed that the vertebrates were derived from an ancestral ascidian that retained its characteristics into adulthood (the process by which juvenile characteristics are retained into adulthood is referred to as paedomorphosis).
Garstang’s hypothesis of chordate larval evolution
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Figure 23.12
Garstang’s hypothesis of chordate larval evolution
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Garstang’s hypothesis of chordate larval evolution
• Garstang’s hypothesis is supported by embryological evidence, but more recently molecular analyses have suggested that sessile ascidians are a derived form and that the free-living Cephalochordates are more likely to be the closest relatives of the chordates.
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Subphylum Cephalochordata - Lancelets
• Invertebrates most similar to vertebrates
• Small segmented fishlike animals that inhabit sandy sediments of coastal waters.
• Lack a distinct head and have no cranium
• Burrowing filter-feeders
• 29 species
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Subphylum
Cephalochordata:
the lancelet
Amphioxus
(Branchiostoma)
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Subphylum
Cephalochordata:
the lancelet
Amphioxus
(Branchiostoma)
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Amphioxus
• Amphioxus is a filter feeder.
• Water enters the mouth and then is moved by beating cilia through the pharyngeal slits, where food is trapped in mucus. Cilia then move the food to the gut.
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Amphioxus • Amphioxus is considered to be the closest living relative of the
vertebrates
• Shares several characteristics with vertebrates that Urochordates do not possess.
– Segmented blocks of striated muscle
– Dorsal and ventral aortas
– Branchial (gill) arches (blood vessels running over the gills
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Pikaia
• Paleozoic fossil, 505 MYA • Rod running along its back
resembled a backbone-like structure.
• Markings on the sides typical shape of chordate muscle bundles
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Devonian - Age of Fish
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, Based mainly on 18S RNA, Cameron et al. 2000 PNAS 97(9): 4469-4474
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