Classification Chapter 18

Why Classify? Think of all the things around you – they can easily be put into organized groups, such as food types at a grocery store, clothing at a department store, books, CD’s, etc. Think of all the things around you – they can easily be put into organized groups, such as food types at a grocery store, clothing at a department store, books, CD’s, etc. This organized grouping is called classification This organized grouping is called classification Purpose; To find things, place things, identify things in an orderly way that makes sense Purpose; To find things, place things, identify things in an orderly way that makes sense Scientists call this taxonomy Scientists call this taxonomy

But how to make sense of it all… Aristotle; Classified organisms based on where they lived:

Animals: Air LandWater

Does where an organism lives seem like a good method for grouping? How about what they look like (body structures, etc)? Carolus Linnaeus; more similar species share more traits and characteristics Pg. 450 in textbook…the more similar two organisms are, the more taxonomic groups they share.

Linnaeus’s System A hierarchy A hierarchy Various levels – each level is called taxon Various levels – each level is called taxon

Scientific Names Common names are confusing – language is an issue, several names can mean one animal – puma, cougar, panther Common names are confusing – language is an issue, several names can mean one animal – puma, cougar, panther Latin, Greek is used Latin, Greek is used First attempts used physical characteristics – names too long, different scientists name things differently First attempts used physical characteristics – names too long, different scientists name things differently Binomial nomenclature – Carolus Linnaeus, Swedish botanist – two name system: Binomial nomenclature – Carolus Linnaeus, Swedish botanist – two name system: Homo sapiens Homo sapiens First name is genus, second name is species First name is genus, second name is species Ursa martimus, Ursa arctos – same genus or species??? Ursa martimus, Ursa arctos – same genus or species???

What problems do we now run into? Just because two species look alike doesn’t always mean that they’re closely related…they may have just evolved in very similar environments (think convergent evolution and analogous structures). Just because two things don’t look alike doesn’t necessarily mean they’re NOT closely related (bats and whales are both mammals…think divergent evolution and homologous structures)

So who gets to decide which structures are important enough to use in classification and which ones aren’t? When you did your Modes of Transportation Taxonomy, did your group have the same categories as everyone else? Which group did it the “right” way? Horseshoe crabs…Crustaceans??? This was a great source of conflict among scientists

The Dichotomous Key A key used by scientists to classify organisms A key used by scientists to classify organisms Uses a two-choice method to group organisms based upon their physical attributes Uses a two-choice method to group organisms based upon their physical attributes Many field guides use this type of key Many field guides use this type of key Let’s try one!!! Let’s try one!!!

Footwear 1. a. Has laces – go to #2 b. No laces – go to #3 b. No laces – go to #3 2. a. Sneaker? – go to #4 b. Shoe? – go to #5 b. Shoe? – go to #5 3. Your footwear is a loafer or a slip-on 4. a. Sneaker white? - go to #6 b. Sneaker colored – go to #7 b. Sneaker colored – go to #7 5. a. Heels? - go to #8 b. Flats? - go to #9 b. Flats? - go to #9 6. Your footwear is a tennis sneaker 7. Your footwear is a running sneaker 8. Your footwear is a dress shoe 9. Your footwear is a casual shoe