Final answer:
The three geologic periods of the Mesozoic are the Triassic, Jurassic, and Cretaceous, representing an era marked by dinosaurs' dominance and significant geological and biological evolution.
Step-by-step explanation:
Explanation in 200 words: The Mesozoic Era, often called the Age of Reptiles, consists of three main geologic periods. The Triassic period is the earliest, lasting from about 252 to 201 million years ago, which followed the Permian and preceded the Jurassic. It was during this time that the first dinosaurs appeared. The Jurassic period, known for the diversification of dinosaurs and the rise of birds, spanned from around 201 million years ago to 145 million years ago. The Cretaceous period, lasting from about 145 to 66 million years ago, saw the peak and eventual extinction of the dinosaurs, and is also notable for the development of flowering plants. These three periods collectively represent an important chapter in Earth's geological history, characterized by significant tectonic activities, evolution of flora and fauna, and climatic changes.