MediumBiologyHigh School (11–12)Diversity of Living Organisms › Basis of Animal ClassificationConceptual
Amit cuts open a cockroach and an earthworm in the laboratory.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Amit cuts open a cockroach and an earthworm in the laboratory.
- In the cockroach, the blood is not held in fine vessels; it fills spaces around the organs. What kind of circulation is this?
- In the earthworm, the blood runs in vessels all round the body. What kind is this?
- Name one more group with each kind.
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. (a) The blood bathes the tissues directly: open circulation.
Step 2. (b) The blood stays inside vessels: closed circulation.
Step 3. (c) Molluscs also have open circulation. Chordates also have closed circulation.
Answer: (a) open; (b) closed; (c) molluscs, open; chordates, closed.
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