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Modern Classification

Modern Classification. 17.2. What is a species. It used to be thought that anything that looked different were considered to be different species. We now know that any given species has variation .

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Modern Classification

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  1. Modern Classification 17.2

  2. What is a species • It used to be thought that anything that looked different were considered to be different species.

  3. We now know that any given species has variation. • In the 1940’s scientists defined a species as a group of organisms that can interbreed and produce fertile offspring

  4. Phylogenic Species Concept • Phylogeny- the evolutionary history of a species • The phylogenic species concept defines a species as a cluster of organisms that is distinct from other clusters and shows evidence of a pattern of ancestry and descent

  5. But like all things they add to it • Phylogenetic species concept. This deals with species in terms of populations and ancestry. • It says two or more groups that evolve independently are classified as different species.

  6. What's that funny P word mean? • Phylogeny- the evolutionary history of a species.

  7. Remember all this classification starts with identifying characters • A Character is a inherited feature that can vary in a species.

  8. There are 2 types of Characters you need to know. • Morphological Characters-The size, shape, and structure of an organism or one of its parts. Bone structure, coloration. • Biochemical Characters-molecular similarities and differences among organisms. Ex DNA, RNA

  9. Quick Check! • What's a species? • We classify things based on their….? • What are the different types of characteristics? • Ok now I have all this classification stuff down what do I do with it??

  10. Taxonomic Devices Phylogenetic Trees - a tree showing the evolutionary relationships among groups Cladograms - a diagram that represents the evolutionary tree of life - also includes characteristics Dichotomous Keys - a device used to identify organisms - uses couplets, which are pairs of highly organized statements

  11. Cladistics • Cladistics is the method that classifies organisms according to the order that they diverged from a common ancestor.

  12. CLADOGRAM “clade” a group of organisms that includes an ancestor and all descendants

  13. Scientists use Cladistics to make a cladogram. • Cladistics-a method of classifying according to when they diverged from a ancestor. • A cladogram (aka phylogenetic tree)- is a branching diagram that shows a proposed evolutionary history.

  14. What taxon is most closely related to birds? • Which taxon is least closely related to humans? • Which taxon has the least recent shared ancestors with humans?

  15. DO: What are the relationships between A, B, C, D, and E?

  16. Character types • Ancestral- a character found within the entire line of decedents • Derived-characters that are present in one group but not the ancestor

  17. How to read a cladogram

  18. How to Build a cladogram. • http://ccl.northwestern.edu/simevolution/obonu/cladograms/Open-This-File.swf

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