Classification Of Organisms Chapter 14 Coach Fults

Taxonomy Biologist can’t memorize all 30 million organisms on earth So there needs to be a way we can effectively group all these organism and be able to easily distinguish between them More than 2,000 years ago, Aristotle grouped plants and animals according to their structural similarities

Taxonomy Later Greeks and Romans grouped those into basic categories such as oaks, dogs, and horses Eventually each unit of classification came to be called a genus “in Latin meaning group” In the middles ages, genera were named in Latin

Taxonomy The science of naming and classifying organisms is called taxonomy Until the mid-1700s, biologist named a particular type of organism by adding descriptive phrases to the name of the genus These phrases could sometimes be 12 words long They were called polynomials; so this made it difficult for all ppl to know

A Simpler System Carl Linnaeus came up with a much simpler system He created 2 word naming system called bi-nomial nomenclature The genus was followed by a species name Ex: Felis domestics

Scientific Names Genus- contains similar species This is always capitalilized and either italicized or underlined Felis is the genus And domesticus is the species The scientific name is Felis domesticus

Classifying Organisms ex: honey bee Domain Eukarya Kingdom Animalia Phylum Arthropoda Class Insecta Order Hymenoptera Family Apidae Genus Apis Species mellifera

What is a Species? In 1942, Ernest Mayr of Havard University proposed a biologically based definition of a species, which is called the biological species concept Biological species- a group of natural populations that are interbreeding or that could interbreed, and that are reproductively isolated from other such groups

What is a Species? Reproductive isolation occurs when a barrier separates 2 or more groups of organisms and prevents them from interbreeding In nature; however, reproductive barriers between sexually reproducing species are not always complete Hybrids can be created, but those 2 parents must be closely related

Evolutionary History Linnaeus’s classification system was based on his observation that organisms have different degrees of similarity A tiger resembles a more like a gorilla than a fish Therefore, classification based on similarities should reflect an organisms phylogeny Phylogeny is its the evolutionary history

Evolutionary History However, not all traits are inherited for common ancestors Wings of a bird vs. insect; both used for flight but their structure is different Fossil evidence shows that they evolved independently of one another Through the process of convergent evolution

Evolutionary History Convergent evolution means they evolved with similar structures because their habitat were similar These similarities are called analogous characters

Cladistics Biologists today study evolutionary relationships using cladistics Cladistics is a method of analysis that reconstructs phylogenies by inferring relationships based on shared characters This is how they figure out how organisms evolved They look for ancestral characters, this is a trait that both groups have

Cladistics Consider a bird and a cow, both have backbones; that is an ancestral character Having feathers is a derived character Feathers evolved in an ancestor of birds and was not also ancestral to mammals Shared derived characters is evidence that 2 groups are relatively closely related

Cladistics Biologists using cladistics constructs a branching diagram called a cladogram Which shows evolutionary relationships among groups of organisms Organisms with shared derived characters are grouped together on the cladogram

Considering Characters Evolutionary success often depends on high-impact events, such as the evolution of feathers

Evolutionary Systematics In evolutionary systematics, taxonomists give varying degrees of importance to characters and thus produce subjective analysis of evolutionary relationships In this type of analysis, relationships are displayed using a phylogentic tree This give more importance to characters like feathers which would place birds and reptiles in totally different groups