Identify a and b in the following pie chart.

The correct answer is Option (1) → a - Insects, b - Molluscs

The pie chart shows how the known species of invertebrates are shared among their main groups; the size of each slice shows the share of species. Among animals, insects are by far the most species-rich group. So the largest slice, a, is insects. The slice b, which lies between a (insects) and crustaceans, is molluscs, as in the book’s chart.

Option (1) a - Insects, b - Molluscs — Correct. a is the largest slice (insects) and b, the slice between insects and crustaceans, is molluscs. Both match the book’s chart.

Option (2) a - Molluscs, b - Insects — Incorrect. The two are swapped. Molluscs have far fewer species than insects, so they cannot fill the largest slice.

Option (3) a - Insects, b - Fishes — Incorrect. a is right, but fishes are vertebrates. They are shown in a separate chart of vertebrates, not among the slices next to crustaceans.

Option (4) a - Fishes, b - Molluscs — Incorrect. Fishes are vertebrates and have far fewer species than insects, so they cannot be the largest slice. Molluscs are also placed wrongly here.

NCERT Extract:
How Many Species Are There on Earth and How Many in India? – “… More than 70 per cent of all the species recorded are animals, while plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) comprise no more than 22 per cent of the total. Among animals, insects are the most species-rich taxonomic group, making up more than 70 per cent of the total. That means, out of every 10 animals on this planet, 7 are insects.”

Figure 13.1 Representing global biodiversity: proportionate number of species of major taxa of plants, invertebrates and vertebrates