Scientists Develop Systems For Classifying Living Things

• Scientists Classify Millions of Species: – CLASSIFICATION & TAXONOMY

• Classification = process of arranging organisms into groups based on similarities.

• Taxonomy = science of naming and classifying organisms

– USING CLASSIFICATION

• Taxonomists study biological relationships– PHYSICAL EVIDENCE– GENETIC EVIDENCE

Classification & Taxonomy• A good system of classifying lets you organize a large

amount of information so its easy to find & understand. • A good system of taxonomy lets people communicate about

organisms.• Common names (like daddy longlegs) can mean a relative of

the spider (in U.S.) or the mosquito (in England). • Biologists need both a system for organizing and a system for

naming. Each name should refer to one specific type of organism. (use species name so everyone knows which organism they are talking about)

Using Classification• Classification system can help identify unfamiliar organisms.

A caracal may be unfamiliar, but if its was a cat, you know it has: fur, fangs, claws, meat eater… all characteristics of cat family.

• The more characteristics 2 organisms share, the more similar their names should be in the classification system. The cats below, all belong to the cat family, Felidae.

Taxonomists study Biological Relationships

• Scientists need a simple, standard way of arranging all of the different species. The science of taxonomy is related to the Greek word taxis (arrangement). – Taxonomists are scientists who classify & name

organisms based on their similarities and differences. – Taxon = group of organisms that share certain traits.– Species that share ancestors are grouped together.

• To determine how to classify, scientists compare many traits (a characteristic or behavior that can be used to tell 2 species apart, like size or bone structure. If 2 organisms share a trait, taxonomists will try to discover if they shared a common ancestor.

Taxonomists• The leafy sea dragon shares traits with all the organisms

pictured. (but sea dragon is animal that moves, gets food from other organisms & breathes air, while sargassum seaweed is an algae). Sargassum fish shares traits with sea dragon, but looks very different. Sea dragon is actually closely related to sea horse.

• Taxonomists use physical evidence (fur, bone, teeth) and genetic evidence (DNA) to place organisms in the classification system.

Physical Evidence• The early tools taxonomists used to

classify were eyes & measuring devises. Collected examples of organisms and noted characteristics (color, size, weight, internal structure, etc.)

• 2 jay birds have common ancestor but also some difference. Blue jay is Cyanocitta cristata and the Steller’s Jay is Cyanocitta stelleri.

• Scientists can study bones & fossils to compare organisms too.

• Physical evidence gives clues how an organism may have lived,moved and what type of food it ate.

Genetic Evidence• Today, scientists can use lab machines to catalog each

component of an organism’s DNA. They can compare a gene from one organism with the gene of another organism. Usually genetic evidence supports physical evidence, but not always.

• For years scientists classified the “Red Panda” as a close relative of the Giant Panda (both from China); they both had similar appearances and ate bamboo. Molecular evidence showed that the red panda is closer to a Raccoon, while a Giant Panda is closer to a Spectacled Bear.