Frog (Rana): Three Ways to Breathe, Three Chambers to Pump

In the paper

Unit 4 (Study of Selected Animals) carries 6 of the 40 zoology marks, and with three chapters sharing them, the frog averages about two (MEC publishes weights by unit, not by chapter). The MEC scope line is Morphology, Different body systems and physiology — no economic-importance point, so the questions stay inside the body. The paper (set 50:30:20) asks it in four ways:

• Recall — chambers of the heart, number of cranial nerves, the excretory product, the parts of the brain, the digits on each limb.
• Understanding — why a frog can stay under water for hours, why its ventricle is single yet the blood streams stay largely apart, why the tadpole and the adult excrete different wastes.
• Application — a frog kept in a dry jar, a tadpole reared in iodine-free water, a male caught in the monsoon with swollen thumbs, a heart that keeps beating after removal.
• Comparison — frog versus earthworm (or versus human) on one feature: heart, kidney, fertilisation, respiration.