In the damp soil of a Kerala garden, Anu finds a long animal with no legs.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
In the damp soil of a Kerala garden, Anu finds a long animal with no legs. Its skin is moist and slimy, it has a cloaca, and in spring its eggs hatch into larvae that breathe with gills. Her friend says it is a snake. Is he right? Name the class, and give the evidence.
Need a reminder? The key ideaShow
Cyclostomata: no jaws, 6 to 15 pairs of gill slits, no scales, no paired fins. Chondrichthyes: cartilage, ventral mouth, separate gill slits with no operculum, placoid scales, no air bladder. Osteichthyes: bone, terminal mouth, four pairs of gills under an operculum, air bladder. Amphibia: moist skin without scales, cloaca, a three-chambered heart, gills, lungs and skin for breathing.
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. Not a snake. A snake is a reptile. Its skin is dry and covered with scales, and its young hatch looking like small adults.
Step 2. The evidence. Moist, slimy skin, a cloaca and larvae that breathe with gills are features of amphibians. Development is indirect, through a larva.
Step 3. The animal. It is a limbless amphibian, such as Ichthyophis.
Answer: he is wrong. It is an amphibian (class Amphibia), like Ichthyophis: moist skin, a cloaca and gill-breathing larvae.
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