A sea squirt larva is 2.5 mm long, and its tail, which holds the notochord, makes up 60 % of that…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A sea squirt larva is mm long, and its tail, which holds the notochord, makes up of that length. A lancelet is mm long. How long is the notochord in the larva, in the adult sea squirt and in the adult lancelet?
Need a reminder? The key ideaShow
A chordate has a notochord, a dorsal hollow nerve cord, paired pharyngeal gill slits and a post-anal tail at some stage. Urochordata keep the notochord only in the larval tail, Cephalochordata keep it from head to tail for life, and Vertebrata replace it with a vertebral column. Non-chordates have a ventral, solid, double nerve cord and no notochord.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The larva. The notochord fills the tail: mm.
Step 2. The adult sea squirt. The tail and the notochord are lost when the larva settles: mm.
Step 3. The lancelet. Its notochord runs from head to tail and stays for life: mm.
Answer: larva mm, adult sea squirt mm, lancelet mm.
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