Question

Explain how scientists use evidence such as fossils, anatomy, and embryos to determine evolutionary relationships. Include at least two types of evidence and what each shows.(4 points)

Answer 1

Scientists combine multiple lines of evidence to infer how species are related and when they diverged.

- Fossils: preserve the bodies of extinct organisms and show transitional forms and changes through time. Fossil sequences (plus radiometric dating) tell when lineages split — e.g., Tiktaalik as a fish-to-tetrapod intermediate; Archaeopteryx linking dinosaurs and birds.

- Comparative anatomy: similar structures in different species (homologous structures) indicate common ancestry, while vestigial organs show descent from ancestors that used them. Example: the similar bone arrangement in human, whale, and bat forelimbs is evidence they share a common ancestor.

- Embryology (development): embryos of related species show similar early-stage features and developmental patterns, implying shared ancestry and conserved developmental genes. Example: vertebrate embryos have pharyngeal pouches and a tail at early stages.

(Optionally) Molecular evidence: DNA and protein sequence similarities quantify relatedness and can be used to build evolutionary trees; more similar sequences usually mean more recent common ancestry.

Using several types together makes evolutionary relationships more reliable because different kinds of evidence independently support the same branching patterns.