Question

How do data from the fossil record support the concept that organisms are related through common descent? Explain.

Answer 1

1. Sequential Change Over Time: Fossils show that the types of organisms change gradually over geological time. Earlier strata contain simpler organisms, and more recent strata show more complex ones, indicating a gradual evolution from simple to complex life forms. 
2. Transitional Forms (Missing Links): Fossils provide evidence of intermediate forms linking two different groups of organisms. For example, the fossil bird Archaeopteryx lithographica has features of both reptiles (teeth in jaws, long tail, solid bones) and birds (feathers, wings, bird-like limb bones). This suggests birds evolved from reptilian ancestors, indicating descent with modification.
3. Evolution of Specific Groups: Fossil records of animals like the horse reveal a gradual change in body size, limb structure, and teeth over millions of years, showing a progression from small, multi-toed ancestors to large, single-toed modern horses adapted for running on grasslands.
4. Common Ancestry: The overall fossil evidence fits a pattern where species have descended from common ancestors and diversified over time. Fossils demonstrate lines of descent where modifications accumulate gradually, producing new species.
5. Mass Extinctions and Adaptive Radiations: Fossil evidence also shows episodes of mass extinction followed by the emergence of new species, supporting the dynamic nature of evolutionary history.