Question

Which animal dominated in the Paleozoic era?
A. Reptiles
B. Fishes
C. Birds
D. Mammals

Answer 1

Hint: The geological time scale gives us an idea about the evolutionary history of different organisms on earth. The time scale was developed by the study of physical rock layers and also fossils. The defined period of division is called eons. Eons are divided into eras which are further divided into periods, epochs and ages.

Complete answer: The geological time scale is broadly classified into four groups- the late Proterozoic, Paleozoic, Mesozoic and Cenozoic. The Paleozoic era is one of the longest that lasted from 541 to 251.902 million years. It is further subdivided into six periods- Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian. The Cambrian period was the one where the most rapid and wide diversification of life took place. The Paleozoic era started with the breaking up of the supercontinent Pannotia. Following this the Pannotia was further broken down into a number of continents. Towards the end of the era the supercontinent Pangea was formed. The climate of this era was mostly warm and it was during this time that atmospheric oxygen started to evolve and the level of carbon dioxide started going down. During this era all major invertebrates appeared along with fishes and amphibians. But the animal that dominated the Paleozoic era was mostly fishes.

So the correct option is B) Fishes.

Note: The geological timescale is very important as it helps us gain an insight into not only the evolution of organisms on earth but also plants and the change of temperature and other climatic conditions.