Final answer:
The Mesozoic era ended around 65 million years ago due to the Cretaceous-Tertiary extinction event, highlighted by a meteor impact and massive volcanic eruptions that disrupted the climate and ecosystems, resulting in the extinction of dinosaurs and the rise of mammals and birds.
Step-by-step explanation:
End of the Mesozoic Era:
The Mesozoic era, also known as the "Age of Reptiles," came to a catastrophic end approximately 65 million years ago. This era was marked by the dominance of dinosaurs, which lasted until the end of the Cretaceous period, the last period of the Mesozoic. The Cretaceous-Tertiary extinction event led to significant changes on Earth, including the extinction of most large-bodied animals, with the exception of birds, which are descendants of a clade of theropod dinosaurs.
The era ended with significant environmental changes triggered by a large meteor impact near present-day Yucatan Peninsula, coupled with massive volcanic eruptions that altered global plant distribution and climate. These catastrophic events blocked sunlight due to the ejection of particles into the atmosphere, leading to a decline in plant life followed by a mass starvation of herbivores and carnivores alike. Over time, these extinctions allowed mammals and birds to radiate into the empty niches that were once occupied by dinosaurs, signifying a dramatic shift in Earth's biodiversity and paving the way for the Cenozoic Era.