6-2/3 Notes – Biological Evidence & Plate Tectonics Chapter 6 Lessons 2 & 3

Comparative Anatomy Comparative anatomy is the study of similarities and differences in the physical structures of organisms.

Comparative Anatomy At some point in our pasts, humans, frogs, bats, birds, and cats all shared a common ancestor.

Homologous Structures Homologous structures are parts of organisms that are similar in BOTH ancestral origin and structure. - are the result of evolution - can indicate how closely two or more species share common ancestors

Homologous Structures - The humerus bones in the upper limbs of these animals are homologous structures.

Analogous Structures Analogous structures appear similar, but have different ancestral origins. - the wings of birds and insects - result from similar environmental conditions that produced similar natural selection outcomes

Vestigial Structures Another source of evidence for evolution is vestigial structures: structures that have no function in their present-day form.

Vestigial Structures Scientists hypothesize that the structures once functioned in an ancestor.

Vestigial Structures in Humans Appendix Nictitating Membrane Wisdom Teeth Tailbone from our large-jawed ancestors with bad dental hygiene from our herbivore ancestors from our tailed primate ancestors present when we are embryos

Vestigial Structures in Humans The recurrent laryngeal nerve goes from the brain to your voice box. It helps us speak and swallow. It takes a very long course, looping from the brainstem down around the aorta and then back up to the larynx. WHY?

Vestigial Structures in Humans We evolved from very different ancestors. That’s why our bodies are full of glitches, and this nerve is one of them. The nerve used to line up with a blood vessel, and both serviced the gills of our fishy ancestors.

Vestigial Structures It takes a 15 FOOT detour in giraffes! It takes a 92 FOOT detour in supersaurus!

Vestigial Structures

Embryology Embryology is the study of patterns of development of embryos from fertilization to birth.

Embryology The more closely related species are, the more features they share during development.

Embryology Shared similarities are best explained by the theory of common ancestors and evolution through natural selection.

Embryology Pharyngeal pouches are a structure shared as embryos by fish, reptiles, birds, and humans.

Molecular Biology Molecular biology is the branch of biology that deals with life at the molecular level (DNA, RNA, proteins).

Molecular Biology Proteins of all organisms are built by combining just 20 different amino acids.

Molecular Biology “Cytochrome c” is a small protein found in the mitochondrion.

Molecular Biology There are slight differences in “Cytochrome c” molecules of organisms.

Molecular Biology Fewer differences mean organisms share a more recent common ancestor.

Molecular Biology More differences mean organisms share a distant common ancestor (long ago).

What describes the wings of an insect and a bird? Aanalogous structures Bvestigial structures Chomologous structures Dembryology 6.2 Biological Evidence

Which types of structures have no function in their present-day form? Ahomologous structures Bvestigial structures Canalogous structures Dpharyngeal pouches 6.2 Biological Evidence

What do embryologists compare when studying embryos? Aphysical structures Bproteins CDNA sequence Dpatterns of development 6.2 Biological Evidence

What describes the study of similarities and differences in the structure of organisms? Aembryology Bsystematics Cmolecular biology Dcomparative anatomy