Practical 6: The life cycle of the frog
The frog belongs to the class of amphibians. When spring comes and the water warms, male frogs call to the females, and the females lay clumps of eggs in shallow water. The top of each egg is dark and absorbs the sun’s warmth well; inside the egg cells divide, an embryo forms and it uses the food store in the egg. A tadpole hatches: it looks like a fish, breathes with gills, has a fin and feeds on tiny algae and one-celled organisms. The tadpole grows, first forming hind legs, then front legs, its tail is absorbed and lungs develop in place of gills, and it becomes a young frog. The adult frog breathes with lungs and skin and hunts small insects and other invertebrates, catching prey with its fast, sticky tongue. A frog needs about 3 years to become adult. Frogs help people by eating harmful insects; they are sensitive to pollution, so water bodies need to be kept clean. In many places in the world frog numbers are falling.
Draw the frog’s life cycle as a six-stage circle diagram (adult frog → eggs → developing larva → tadpole → tadpole with hind legs → young frog). Add a one-sentence caption to each stage. Safety: do not bring frog eggs, tadpoles or frogs home from a pond; stay at the pond edge only with adults; if you touch a frog, wash your hands with soap (its skin can carry harmful germs).