Lab 1: Amphioxus, Ammocetes, Chordate Evolution

Question 1

Amphioxus

Answer 1

Invertebrate Chordate

Genus: Branchiostoma (branch=gill, stoma=mouth)

Lancelets: named for lance-like body shape

Question 2

Ammocoetes

Answer 2

Larval stage of lamprey

Jawless vertebrate

Question 3

Amphioxus is an _______ animal that swims by __________

Answer 3

Elongate, lateral undulation

Question 4

Lateral undulation

Answer 4

Bending of body in fish-like manner

Question 5

Notochord

Answer 5

Stiff but flexible rod of tissue in a mid-dorsal position extending on length of the body

Chordate synapomorhpy

Precursor to the spine

Question 6

Rostrum

Answer 6

Front of the animal

Question 7

Cephalochordata

Answer 7

Cephal=head, chord=cord/string; subphylum of Amphioxus

Question 8

Myomeres

Answer 8

Muscle masses in amphioxus that are paired segmentally and shaped like this&raquo_space;>

Question 9

Myoseptum

Answer 9

Connective tissue layer between each myomere

Question 10

Fins in Amphioxus

Answer 10

Median, unpaired fins

Dorsal