Vertebrates

When did vertebrates evolve?
After the Cambrian explosion
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In terms of cleavage, what is the difference between protostomes and deuterostomes?
Protostomes- Spiral cleavage, Deuterostomes- Radial cleavage
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Spiral Cleavage
Formation- Oblique to original body axis (slanting, diagonal)
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Radial cleavage
Formation- Parallel with and perpendicular to the original body axis (- Development of coelom from the mesodermal pockets that bud off from the cavity of the gastrula, formation of mouth at opposite end to blastopore)
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What is a notochord?
Flexible rod-shaped structure which forms the main support of body, found in embryonic stage of all the chordates and also in adult stage of chordate species
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What is a hemichordate?
(Half chordates), lack a true notochord but have a stomochord
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When and how does the stomochord arise?
In embryonic development, as an out pocketing from the roof of the embryonic gut anterior to the pharynx
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What are the hemichordates larvae like?
They are ciliated and bilaterally symmetrical
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What are the adult forms of hemichordates?
They are worm-like
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What are the 2 main groups of hemichordates?
Acorn worms and pterobranchia
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Acorn worms
Pharynx behind mouth, opens through pharyngeal slits, blood flow allows pharyngeal slits to act as gills, water pumped out mouth through them, proboscis (nose) coated with sticky mucus that traps prey, mucus conveyed by cilia into mouth
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What morphological features are all chordates characterised by?
At some point during development they will have- Dorsal hollow nerve chord, muscular tail extending beyond anus, dorsal supporting rod (notochord), pharyngeal slits (gills)
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What are most adult cephalochordates and urochordates like?
Sessile filtering bags, large space (atrium) enclosed by a tunic-like covering, beside slits, a ciliated groove (the endostyle) which transports food towards the oesophagus
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Cephalochordate
30 species, small animals, marine, notochord & pointed ends enable them to 'lance' into sand or mud, notochord extends to near the front of head, 50-70 v-shaped muscle blocks enable swimming, separate sexes (release gametes into water)
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Urochordates larvae
Pharyngeal slits, dorsal hollow nerve cord, notochord in tail, swim in plankton then metamorphoses into sessile adult, filter feeder,
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Urochordate adults
Sessile, lost notochord, bag-like body enclosed in tough tunic include a type of cellulose, filter feeder
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What is larvaceans?
Small planktonic animals that retain notochords and nerve cords throughout their lives, they make slimy houses to ensnare sinking organisms
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Other cards in this set

Card 2

Front

In terms of cleavage, what is the difference between protostomes and deuterostomes?

Back

Protostomes- Spiral cleavage, Deuterostomes- Radial cleavage

Card 3

Front

Spiral Cleavage

Back

Preview of the front of card 3

Card 4

Front

Radial cleavage

Back

Preview of the front of card 4

Card 5

Front

What is a notochord?

Back

Preview of the front of card 5
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