notes 2.1 scientists develop systems for classifying living things

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!