Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

What evidence do scientists most likely use to support the conclusion that land vertebrates evolved from ancient fish?

1. Comparing the genetics of modern fish

2. Studying the fossils of ancient fish and land vertebrates

3. Analyzing the diets of modern land vertebrates

4. Observing the behavior of modern fish species

The correct answer is: Studying the fossils of ancient fish and land vertebrates

Scientists most likely use fossil evidence to support the conclusion that land vertebrates evolved from ancient fish because fossils provide a direct record of biological transitions over time. By studying the fossilized remains of both ancient fish and early land vertebrates, researchers can observe morphological changes, such as the development of limb structures that enabled movement onto land. Transitional fossils, like Tiktaalik, showcase characteristics of both groups, bridging the gap between aquatic and terrestrial life. The comparison of these fossils allows scientists to construct a timeline of evolution, illustrating how certain features adapted over generations for new environments. This evidence substantiates the hypothesis of common ancestry and helps to understand evolutionary processes, such as natural selection and adaptation.