Notes 2.1
Scientists develop systems for classifying living things.
Scientists classify millions of species.
• Until the 1600s, scientists classified organisms according to their appearance.
• The invention of the microscope allowed scientists to see structures and organisms that were not visible before.
Classification and Taxonomy
• Classification: the process of arranging organisms into groups based on similarities
• Taxonomy: the science of naming and classifying organisms
• The purpose of classification and taxonomy is to make information easier to find and understand.
Classification and Taxonomy
• Until 1700s scientists could not agree on a system
• Both overly long Latin scientific names and common names can be confusing.
Using Classification
• Scientists use similarities and differences among species, including appearance, biology, and genetics.
• The more characteristics 2 organisms share, the more similar their scientific names should be in the classification system.
• See examples on page 45B.
Taxonomists study biological relationships.
• Taxonomists: the scientists who classify and name organisms based on their similarities and differences.
• Taxon: a group of organisms that share certain traits
• Taxons can be broad (animal) or more specific (cat).
• A single species found in a fossil record can be the ancestor of many species on Earth today.
Taxonomists study biological relationships (continued)
• In order to classify organisms, scientists compare a variety of traits.
• Trait: a characteristic or behavior• If 2 organisms share a trait, taxonomists try to
determine if they share that trait because they share an ancestor.
Continued
• Page 47B—the seahorse shares more traits with a leafy sea dragon than the sargassum seaweed or sargassum fish.
• Taxonomists take evidence and try to reconstruct the evolution of a species.
• Then they place the species in the classification system.
Physical Evidence
• Primary devices used—eyes and measuring devices
• Collect samples and note characteristics—size, color, weight, how obtain energy, internal structures, outward appearance
• Individuals of a species have many similarites and some differences.
Physical Evidence
• Skeletons, shells, and other hard parts of organisms fossilize more easily.
• Scientists observe and measure this evidence.• They also compare bones.• All this physical evidence helps scientists see
that all living organisms are related by evolution.
• Those most closely related share a more recent ancestor.
Genetic Evidence
• Scientists can compare the components of a gene from one organism with the components of the same gene from another organism.
• Genetic evidence usually supports physical evidence.
• See p. 49B—Red pandas are more closely related to raccoons than Giant Pandas
Review Questions 49B
• 1. Classification allows taxonomists to organize a great deal of data so that it is easier to find and understand.
Number 2
• Taxonomists study biological relationships to discover how one species evolved as compared with another species.
Number 3
• Scientists look at DNA and compare genes of organisms.
Number 4
• Having a universal naming system allows people speaking different languages to refer to all organisms the same way. It’s easier to understand.
Number 5
A marbled godwit would have marbled feathers, wings, feet, and a beak.
Number 6
• Compare physical traits, such as color, size, weight and how they get energy. Analyze bones; compare to fossils; compare DNA.
Quiz Fill-in Terms
ClassificationEvolutionphysicalSystem taxonsTaxonomy Traitsgenetic
Extended Response
• Explain how scientists may use physical and genetic evidence to determine how closely related two species of birds are.
• Quiz Wednesday!