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Comparative Anatomy Scientists can compare the anatomy of different organisms to figure out how closely they are related. Anatomy structure = body Homologous Structures Similar in Origin Different in Function (bird wing/human arm) Recent common ancestor May appear in embryonic development and disappear before birth. Key Point #1: Homologous features are those that have similar structure but different functions. Homologous Structures=recent common ancestor!! Analogous Structures Analogous structure: Parts of different species that have the same function, but EVOLVED SEPARATELY Key Point #2: Analogous structures show that unrelated* species will evolve similar adaptations in response to similar environmental pressures Natural selection selects for (keeps around) mutations that increase fitness in the specific environment. If organisms they live in similar environments, they will evolve similar structures. Insect, bird, and bat wings evolved completely separately. Unrelated organisms will evolve similar adaptations in response to similar environmental pressures! No recent common ancestor!!! Seals and penguins both have streamlined bodies, and store fat to keep them warm in the cold water. Unrelated organisms will evolve similar adaptations in response to similar environmental pressures! Vestigial Structures Vestigial structure: Part of an organism that is no longer used for anything Key Point #3: Vestigial structures show that a species used to live in a different environment. Organism moved into a new environment, where the vestigial structure decreases fitness No longer needed, waste of energy Risk of disease Letter “c” = hind legs of a baleen whale skeleton Vestigial = no longer used!!! Blind salamanders have eye sockets!?!? So, what about me? Guided Practice – Notes Reflection How do analogous structures provide evidence for evolution? Analogous structures show that unrelated* organisms will evolve similar adaptations in response to similar environmental pressures If you can’t find the answer… ADD IT!!! Guided Practice – Notes Reflection How do vestigial structures provide evidence for evolution? Vestigial structures show that the species used to live in a different environment Organism moved into a new environment where the vestigial structure decreased fitness… so it started to degrade If you can’t find the answer… ADD IT!!! Guided Practice (GP) Are these structures… (A) Homologous, (B) Vestigial, (C) Analogous? Human embryos and cat embryos both have gill slits. HOMOLOGOUS Guided Practice (GP) Are these structures… (A) Homologous, (B) Vestigial, (C) Analogous? Birds and insects both have wings, but they developed in completely different ways. ANALOGOUS Guided Practice (GP) Is this structure… (A) Homologous, (B) Vestigial, (C) Analogous? Snakes don’t have legs, but they do have hip and leg bones. VESTIGIAL Guided Practice (GP) Is this structure… (A) Homologous, (B) Vestigial, (C) Analogous? The human appendix – a small organ next to the intestines – doesn’t seem to do anything at all. VESTIGIAL Guided Practice (GP) Are these structures… (A) Homologous, (B) Vestigial, (C) Analogous? Cat embryos and human embryos both have tails. HOMOLOGOUS Guided Practice (GP) Are these structures… (A) Homologous, (B) Vestigial, (C) Analogous? Dolphins and sharks both have fins, but they evolved completely differently. ANALOGOUS Guided Practice (GP) Are these structures… (A) Homologous, (B) Vestigial, (C) Analogous? Alligators and bats have the same bone structure in their forelimbs (front legs for alligators, wings for bats). HOMOLOGOUS Guided Practice (GP) Is this structure… (A) Homologous, (B) Vestigial, (C) Analogous? Humans have wisdom teeth (third molars), even though they are not needed to chew up food. VESTIGIAL Guided Practice (GP) Are these structures… (A) Homologous, (B) Vestigial, (C) Analogous? Humans and squids both have eyes, but they evolved in completely different ways. ANALOGOUS Embryo An early stage in the development of an organism Often embryo’s have structures that are not present after the organism is born Human Embryo Cat Embryo All the above have folds called gill pouches in the neck region. All similar by the fact they are all vertebrates. Embryology The study of embryos. The chemical make-up of organisms also provides clues to common ancestry. Example: Scientist compare the sequences of the nucleotides in DNA and the amino acids making up certain proteins in different organisms. The more similarities found in 2 DNA or amino acid sequences, the more closely related the organisms are. Example: Hemoglobin blood in chimpanzee’s is more similar to human hemoglobin than a cats hemoglobin is to a human. ( Chimpanzees and humans are more closely related) Exit Question: Choose one option A All humans have a tail bone, but we don’t have tails. What type of structure is this? EXPLAIN how this structure provides evidence for evolution. B Write in complete sentences! Dogs and alligators both have long snouts that allow their jaws to open wide. However, they evolved in completely different ways. What type of structure is this? EXPLAIN how these structures provide evidence for evolution.