Ravi dissects a cockroach and a fish in the school laboratory.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Ravi dissects a cockroach and a fish in the school laboratory. Using the nerve cord, the heart, the pharynx and the tail, write four differences he should expect to see between them.
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 nerve cord. The fish has a single, hollow nerve cord on its back. The cockroach has a double, solid nerve cord along its belly.
Step 2. The heart. The fish's heart lies on the lower, ventral side. The cockroach's heart lies on the upper, dorsal side.
Step 3. The pharynx. The fish's pharynx has gill slits. The cockroach has none.
Step 4. The tail. The fish has a tail behind the anus. The cockroach has no post-anal tail.
Answer: dorsal hollow single nerve cord against ventral solid double; ventral heart against dorsal heart; gill slits against none; a post-anal tail against none.
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