Deuterostomia Flashcards
What are the three main phyla within Deuterostomia
Echinoderms, Hemichordates, and Chordates
What is the embryonic feature that define Deuterostomes
The second embryonic opening becomes the mouth
What type of cleavage is associated with Deuterostomes
Radial cleavage
How was the Deuterostome clade confirmed
Through molecular phylogenetic evidence which supported earlier morphological suspicions
What are the five classes of Echinoderms
Asteroidea (starfish), Ophiuroidea (brittle stars), Echinoidea (sea urchins), Holothuroidea (sea cucumbers), Crinoidea (sea lilies and feather stars)
What kind of symmetry do mature echinoderms have
pentaradial symmetry
Is the radial symmetry in echinoderms primary or secondary
secondary - they evolved bilaterally symmetrical ancestors
How do we know echinoderms evolved from bilateral ancestors
Their larvae are bilaterally symmetrical, and this is supported by molecular data and fossil evidence
What is the madreporite
A structure that controls water intake into the water vascular system
How do starfish feed
They evert their stomach through the mouth, secrete digestive enzymes onto prey, and absorb nutrients
Describe the echinoderm water vascular system
A network of water-filled canals (ring and radial) with tube feet for movement, gas exchange, and feeding
What is the Echinoderm skeleton made of
Calcium carbonate ossicles, covered in living tissue
What habitat are all echinoderms restricted to, and why
Marine environments; they cannot osmoregulate
What distinguishes brittle stars (Ophiuroidea)
Highly flexible, thin arms with moveable ossicles, detritivores, no anus
What adaptations do sea urchins (Echinoidea) have
Spines (muscular control), pedicellariae, and Aristotle’s lantern for grazing
How is bilateral symmetry seen in sea urchins
Some species show secondary bilateral symmetry for burrowing locomotion
What defence mechanisms do sea cucumbers (Holothuroidea) have
Ejection of sticky Cuvierian tubules or intestines to deter predators
How are sea cucumbers related to sea urchins
Morphologically similar, seen as elongated, reduced-ossicle urchins turned on their side
What is unique about crinoids (Crinoidea)?
They are sessile (or free-floating) with an upward-facing mouth and feathery arms
What are the two main classes of Hemichordates
Enteropneusts (acorn worms) and Pterobranchs
Describe the body plan of an acorn worm
Three parts: Proboscis, Collar, Trunk
How do enteropneusts feed
Filter feeding via ciliated pharyngeal slits that set up water currents
What are Pterobranchs
Tiny, colonial or solitary, sessile animals that live in tubes and resemble acorn worms internally
What are the six key features of generalised chordates
- Pharyngeal slits
- Dorsal hollow nerve cord
- Notochord
- Endostyle
- Post-anal tail
- Lateral muscles
