Hint: Developmental history of different organisms from simplest to the most complex ones shows successive changes that occurred through several generations in the biological population. The history of developments of living organisms is represented in three important eras (long and distinct periods of history) which are the Palaeozoic era, Mesozoic era, and Coenozoic era.
All living organisms arise from the simplest types of cells. Within a due course of time, several changes occurred in the environment. Because of these changes, various types of changes also occurred in living organisms. Important changes brought about the development of different species of animals and plants as well other species were removed and became extinct and different species accumulated changes and gave rise to present-day species of organisms.
Mesozoic era is the second of Earth’s three major geological eras; the period name is derived from the Greek term meaning middle life. The Paleozoic era was started earlier which was followed by the Mesozoic era. This Mesozoic era is also considered as the time interval between two fifty-two million years and extending to sixty-six million years. The Mesozoic era is also known as the age of the reptiles or age of the conifers.
This era is considered as the middle and connecting era between the old or ancient era and the modern or new era. It is divided into three major periods that are Triassic, Jurassic, and the Cretaceous period. This era showed the rise of the dinosaurs (a group of reptiles) as they first appeared during the mid-Triassic era and were the dominant vertebrates that lived on the land. The animal life was dominated by different species of dinosaurs such as mosasaurs, pterosaurs, and other aquatic reptiles. Therefore, the Mesozoic era is considered as the age of reptiles.
Note: This Mesozoic era is also known as the golden age of the reptiles because during this era reptiles were dominant and ruling land vertebrates. Different species of the dinosaurs existed during this era and also flourished during the era.