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The word amphibian means 'double life'. Most amphibians start in the water and live on land as adults. There are about 6,770 kinds, in three groups: frogs and toads (the biggest group), salamanders, and caecilians, which have no legs.

Amphibian skin is moist and lets water and gases through. Amphibians take in most of their water through their skin, and they breathe with their skin and mouth as well as lungs; most salamanders have no lungs at all.

A tadpole has gills and a tail but no legs. During metamorphosis it loses its gills and tail, grows four legs and develops lungs. Frog eggs are protected by jelly but would dry out quickly, so they are laid in water or damp places.

Experiment: Basking test

1. Fill both bottles with the same amount of water from the same jug. They are your 'lizards'.
2. Measure and write down the starting temperature of each.
3. Put one bottle in the sun and the other in the shade, at the same time.
4. Measure the temperature of each bottle every 5 minutes for 30 minutes.
5. Fair test: what did you change, what did you measure, and what did you keep the same?
6. Draw a line graph with both bottles on it.

Time (min)	Sun bottle (°C)	Shade bottle (°C)
0	Which bottle will warm up faster?
5	Which bottle will warm up faster?
10	Which bottle will warm up faster?
15	Which bottle will warm up faster?
20	Which bottle will warm up faster?
25	Which bottle will warm up faster?
30	Which bottle will warm up faster?

Questions

1. Describe the life cycle of a frog in three or four steps.

2. Give two differences between the skin of a reptile and the skin of an amphibian.

3. In your basking test, what did you change, what did you measure and what did you keep the same?

4. Use your results to explain why a lizard sits in the sun in the morning.

Sources for every fact on this sheet: echoesof.science/school/reptiles-amphibians/sources/

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