BIOL 112 Lecture Notes - Lecture 1: Archaeopteryx, Phylogenetic Tree, Theropoda
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Answers: scientists make comparisons between living species and fossils of extinct species by studying morphology (structure/anatomy) and dna sequences. They are looking for similarities and differences in characters, especially homologies that are due to inheritance from a common ancestor. An animal might be prey for another animal, their remains are not available to be fossilized. Organisms that die are left to the elements, wind and rain can destroy evidence of their existence. A soft-bodied organism is not likely to fossilize. Once an organism is buried, and does fossilize, that fossil must be exposed and human paleontologists must find it. If a fossil is exposed, elements can (like wind and erosion) can destroy it before it is found. 3a) living birds are considered dinosaurs because their most recent ancestor is a theropod dinosaur (archaeopteryx). Birds share homologous traits with theropod dinosaurs that were passed down from their ancestor(s) in the theropod lineage.
