Question

Arrange the periods of Palaeozoic era in ascending order in a geological time scale:

• A. Cambrian $\to$ Ordovician $\to$ Silurian $\to$ Devonian $\to$ Carboniferous $\to$ Permian
• B. Cambrian $\to$ Devonian $\to$ Ordovician $\to$ Silurian $\to$ Carboniferous $\to$ Permian
• C. Cambrian $\to$ Ordovician $\to$ Devonian $\to$ Silurian $\to$ Carboniferous $\to$ Permian
• D. Silurian $\to$ Devonian $\to$ Cambrian $\to$ Ordovician $\to$ Permian $\to$ Carboniferous

Answer 1

Answer: (A)

Palaeozoic era: (i) Cambrian: Origin of most invertebrate phyla; diverse algae. (ii) Ordovician: First vertebrates (jawless fishes), marine algae abundant. (iii) Silurian: Diversity of jawless vertebrates; colonization of land by plants and arthropods; origin of vascular plants. (iv) Devonian: Diversification of bony fishes; first amphibians and insects. (v) Carboniferous: Extensive forests of vascular plants; first seed plants; origin of reptiles; amphibians dominant. (vi) Permian: Radiation of reptiles, origins of mammal-like reptiles and most modem orders of insects; extinction of many marine invertebrates.