Chordates and Hemichordates Flashcards
What are the 3 clades belonging to Chordates?
Lancelets (Cephalochordates), Tunicates (Urochordates) and Vertebrates.
When are evolutionary relationships most evident in chordates?
In the early developmental stages.
What are the differences between lancelets and tunicates?
Lancelets retain chordate body plan throughout life whereas tunicates only retain chordata body plan in larvae.
What features are common of invertebrate chordates?
Bilaterally symmetrical, segmented body, triploblastic, well developed coelom, radial, indeterminate cleavage, indirect development (larval stages).
What features are common of all chordates at some point?
Dorsal, hollow nerve cord, A tail that extends beyond the anus, A notochord, Pharyngeal slits , endostyle
What is the function of the Endostyle?
Secretes mucus to trap food.
What is the Postanal tail?
Posteriror elongation of body containing skeleton elements and muscles for locomotion.
What are the three groups of tunicates?
Sea squirts (Ascidians), Thaliaceans and Larvaceans
How is the Pharynx modified in sea squirts?
It is enlarged into a pharyngeal basket that filters prey from the water
What are general characteristics of Cephalochordata?
Oral hood with tentacles around mouth for filter-feeding, large pharynx with slits lined with mucus, gonads (dioecious), external fertilisation, free swimming larvae.
What do Hemichordates lack?
Notochord and post-anal tail.
What are the two main groups of Hemichordates?
Enteropneusts (Acorn worms) and Pterobranchs.
What re the three body regions of hemichordates?
Proboscis, collar and trunk
What features are common of Acorn worms?
Gut breathing, digestive tract is a mouth, pharynx and intestine, vascularised tissue around the slits is a gas exchange surface, prey is captured via large proboscis.
What features are common of Pterobranchs?
Tubes secreted by proboscis, collar has 1-9 pairs of arms with tentacles for prey capture and gas exchange, only one pair of pharyngeal slits.
