MediumBiologyHigh School (11–12)Diversity of Living Organisms › Basis of Animal ClassificationConceptualNEETBoard Exam
Three cross-sections of worm-like animals are shown under a microscope…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Three cross-sections of worm-like animals are shown under a microscope.
- Section P: mesoderm lines the body wall and also covers the gut, with a fluid-filled space between.
- Section Q: there is a space around the gut, but mesoderm appears only in a few pouches under the body wall.
- Section R: mesoderm cells fill all the space between the body wall and the gut.
Name the kind of body cavity in each, and a phylum that fits.
Need a reminder? The key ideaShow
Diploblastic animals have ectoderm and endoderm with mesoglea between (coelenterates). Triploblastic animals add mesoderm. A coelom is a cavity lined by mesoderm (annelids to chordates). In a pseudocoelom the mesoderm is in scattered pouches (Aschelminthes). Acoelomates have no body cavity (Platyhelminthes).
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. P. A cavity lined by mesoderm on both sides: a coelom. Annelida fits, such as the earthworm.
Step 2. Q. A cavity not lined all round, with mesoderm in pouches: a pseudocoelom. Aschelminthes fits.
Step 3. R. No cavity: acoelomate. Platyhelminthes fits.
Answer: P coelomate (Annelida); Q pseudocoelomate (Aschelminthes); R acoelomate (Platyhelminthes).
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