EasyBiologyHigh School (11–12)Diversity of Living Organisms › Basis of Animal ClassificationConceptual
A liver fluke takes in food and gets rid of undigested waste through the same opening.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A liver fluke takes in food and gets rid of undigested waste through the same opening. A roundworm has a mouth at one end and an anus near the other.
- What kind of digestive system does each have?
- Why is the second kind called complete?
Need a reminder? The key ideaShow
Levels of organisation: cellular (Porifera), tissue (coelenterates), organ (Platyhelminthes), organ system (annelids, arthropods, molluscs, echinoderms, chordates). An incomplete gut has one opening; a complete gut has a mouth and an anus. Open circulation bathes the tissues in blood (arthropods, molluscs); closed circulation keeps it in vessels (annelids, chordates). Symmetry: asymmetrical, radial or bilateral.
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 fluke. One opening serves as both mouth and anus: an incomplete digestive system.
Step 2. The roundworm. A mouth and a separate anus: a complete digestive system.
Step 3. Why complete. Food passes one way, from the mouth to the anus, through the whole tube.
Answer: (a) the fluke, incomplete; the roundworm, complete; (b) it has both a mouth and an anus.
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