The Process of grouping things based on their similarities. Classification The Process of grouping things based on their similarities.

Why do Scientists Classify? Today, scientists have identified at least 1.7 million kinds of organisms here on Earth. It is important for biologists to have all of these things organized. Biologists use classification to organize living things into groups so that organisms are easier to study!

Early Classification Systems The first scientist to develop a classification system was the Greek Scholar Aristotle, who observed many animals. He recorded each animal’s appearance, behavior and movement. He then divided the animals into 3 groups: Those that fly Those that swim Those that walk, crawl, or run

Aristotle He could see that even though all the organisms in a group moved in a similar way, they were different in many other ways. He used these differences to further divide each group into subgroups-smaller groups of organisms that shared other similarities. Aristotle’s method of using careful observations as the basis for classification and his idea of subgroups are still used today!

Classification System of Linnaeus Like Aristotle, Linnaeus used observations as the basis of his system. He also uses his observations to devise a naming system for organisms. Binomial Nomenclature-a naming system in which each organism is given a 2 part name.

Binomial Nomenclature The first part of an organism’s name is its genus-a classification grouping that contains similar, closely related animals. The second part of an organism’s name is its species- a group of similar organisms that can a mate and produce fertile offspring in nature. To write a scientific name: Genus goes first- CAPITALIZE the first letter. Species goes second with a lowercase first letter. We use Latin words when giving an organism its scientific name.

Genus species Genus-Canis Wolfs and dogs belong to the same genus-Canis. Canis familiaris Canis lupus Genus species

Classification Today The theory of evolution (Darwin!) changed the way biologists think about classification. Today, scientists understand that certain organisms are similar because they share a common ancestor. When organisms share a common ancestor, they share an evolutionary history. Species with similar evolutionary histories are classified more closely together.

Levels of Classification There is a series of 7 levels to classify organisms today. Organisms are grouped by their shared characteristics. A kingdom is the broadest level, then phyla, classes, orders, families, genus and then species. The more classification levels that 2 organisms share, the more characteristics they have in common.

Ken poured coffee on Fred’s good shirt! The 7 Kingdoms Ken poured coffee on Fred’s good shirt!

Using the Classification System Dichotomous Key- a series of paired statements that describe the physical characteristics of different organisms. This is sometimes also called a Taxonomic key.

Dichotomous Key