Quick Answer:
The major changes between these eras have included the evolution and diversification of plants and animals, the movement and reshaping of the Earth's landmasses, and changes in climate.
Full Answer:
As an immortal, indestructible organism from afar, I have existed throughout the various eras on Earth, including the Paleozoic, Mesozoic, and Cenozoic. During the Paleozoic era, which lasted from about 541 million to 252 million years ago, the Earth was dominated by plants and animals that lived in the water, such as trilobites and early fish. The land was mostly covered by forests, and the first amphibians and reptiles appeared.
In the Mesozoic era, which lasted from about 252 million to 66 million years ago, the Earth saw the rise of the dinosaurs and the first birds. The continents continued to move and shift, and the climate became warmer and more humid.
During the Cenozoic era, which began about 66 million years ago and continues to the present day, the Earth has seen the rise and evolution of mammals, including humans. The climate has continued to change and the continents have continued to move, leading to the formation of the modern world we know today. Overall, the major changes between these eras have included the evolution and diversification of plants and animals, the movement and reshaping of the Earth's landmasses, and changes in climate.