Biology 11 Citadel High School 2010 Classification Biology 11 Citadel High School 2010

What is classification and why do we classify? Classification is the action of grouping objects in useful units. Scientists are always discovering new species of organisms. We classify organisms in order to better understand them and how they relate to other organisms.

What is the science of classifying? Taxonomy is the science of classifying organisms. It consists in classifying organisms according to similar and different characteristics. The characteristics used in classification can vary.

The history of classification Aristotle (384-322 BC) was one of the first taxonomists. He classified the plants into grasses, bushes, and trees. He classified the animals depending on whether they lived on the earth, in water, or in air. (It didn't explain the fact that some birds were in water and air.)

Natural Classification One of the objectives of the modern taxonomy is to establish a natural classification founded on evolution. Related organisms have more features in common than the distantly related organisms.

Carolus Linnaeus A Swedish botanist who elaborated a classification that is used again today. Linnaeus established binomial nomenclature.

Binomial Nomenclature The binomial nomenclature is a set of scientific names formed of two words. The first name designates the Genus (a group of similar species), and the second designates the species. Ex. sugar maple  Acer saccharum

Binomial Nomenclature Ex. sugar maple  Acer saccharum The Genus is written with a capital and the species with a lower-case letter and the two names are in italic or underlined. As binomial nomenclature is in Latin, scientists all over the world can understand it, whatever their maternal language.

Why dont we use common names? Common names are not used because they are not precise. Ex: cougar, puma and mountain lion are all the same animal! Merle: is a different bird in different Canada and in France.

The groups … Categories Example English kingdom Animalia Animal phylum Chordata Chordates sub-phylum Vertebrata Vertebrates class Mammalia Mammalian order Primates family Pongidae Pongidae (big monkeys) genus Gorilla species Gorilla Gorilla subspecies Gorilla Gorrilla beringei mountain Gorilla

Phylogeny Phylogeny is the history of the evolution of the species. Scientists compared some modern shapes to fossils of similar shapes. According to the biologists, new species appeared as the organisms adjusted (evolved) and the populations changed.

Phylogenetic Trees (pg The representation of this classification looks like a tree, the modern species are indicated at the end of the branches. The groups closer in the tree have a lot of common features ; the distant groups are very different and they are probably not closely related.

To determine the relations Taxonomists compare the appearance, the internal structures, the stages of development, the chemical composition, etc. All organisms are related either closely or quite distantly.

http://4e.plantphys.net/images/ch01/wt0101a_s.png http://ionetics.blogspot.com/2006_05_01_archive.html

Ernst Haeckel middle of the 19th century                                               One of the first to describe the evolutionary relationships between living organisms.