Final answer:
It is true that ideas about dinosaurs have changed dramatically since the 1820s, due to advancements in paleontology and the continuous discovery of new evidence influencing theories of species evolution and behaviors. The correct answer is option A.
Step-by-step explanation:
The statement 'Ideas about dinosaurs have changed dramatically since the 1820s' is true. Over the past two centuries, our understanding of dinosaurs and their evolution has undergone significant changes. In the 18th century, naturalists like James Hutton and later Charles Lyell, provided us with new ideas about the Earth's geological changes and the greater age of Earth, affecting theories on species evolution.
Further discoveries, such as the fossil of Archaeopteryx, have reinforced the idea of gradual evolutionary change and common ancestry among species. Paleontology has made great strides, from early beliefs about the age of Earth, to new discoveries of dinosaur species and behaviors, and the understanding of mass extinctions and their impact on life's evolution. As our methods improve and new evidence is unearthed, our perspectives on these ancient creatures continue to evolve.