2 The study of organisms requires the use of both large and small categories of organisms. Scientists assign each type of organism a universally accepted name in the system known as binomial nomenclature.For many species, there are often regional differences in their common names.
3 Scientists have identified and named a fraction of all species. In the scientific version of a species name, the first term is capitalized only.Example:Craspedacusta sowerbyiBased on their names, you know that the baboons Papio annubis and Papio cynocephalus belong to the same genus, but to different species.Genus NameCraspedacustasowerbyispecies name
4 Binomial , or two-part, names are much shorter than early versions of scientific names. Carolus Linnaeus developed a system of classification using 7 taxonomic categories:KingdomPhylumClassOrderFamilyGenusspecies
5 A Kingdom is composed of a number of related phyla. A Phylum contains a number of classes.A Class contains a number of orders.An Order contain a number of families.A Family contains a number of genera.A Genus contains one or more species.Often, the species (second part) name of a scientific name is a Latinized description of a particular trait.
6 Traditional classification tended to take into account primarily general similarities in appearance. Carolus Linnaeus recognized only two kingdoms: Plants and AnimalsThe Kingdom is the largest and most general category of classification.Evolutionary classification is grouping organisms based on their evolutionary history.
7 In evolutionary classification, species within one genus should be more similar to one another than they are to species in other genera.In biology, an evolutionary innovation is also referred to as a derived character.An analysis of derived characters is used to generate a cladogram.When scientists perform cladistic analysis, they consider derived characters.
8 Cladistic analysis shows the order in which derived characters evolved. Similar genes are evidence of common ancestry.The degree of relatedness can be determined from the genes of dissimilar organisms such as a cow and a yeast?Humans and yeasts have similar genes for the assembly of certain proteins.All organisms in the kingdoms Protista, Plantae, Fungi, and Animalia are eukaryotes.
9 Neutral mutations accumulate at a steady rate is the main idea of the model of a molecular clock. In the late 1800s a three-kingdom classification system was used. This system contained animals, plants, and protists.Fungi was once grouped with plants in earlier classification systems.Protista contains very diverse organisms that do not fit into the other kingdoms.
10 The domain that contains unicellular organisms that live in extreme environments is Archaea. The two domains composed of only unicellular organisms are Archaea and Bacteria.The three-domain system arose when scientists grouped organisms according to how long they have been evolving independently.The three-domain system recognizes fundamental differences between two groups of prokaryotes.
11 It is thought that the three domains of living things diverged from a common ancestor before the evolution of the main groups of eukaryotes.When scientists use a scientific name for an organism, they can be certain they are all discussing the same organism.The domain Bacteria is composed of the kingdom Eubacteria.The domain Eukarya contains plants, fungi, protists, and animals—which are all eukaryotes.
12 The animals Panthera leo (lion) and Panthera tigris (tiger) belong to the same genus. The use of a two-part scientific name for organisms is called binomial nomenclature.In taxonomy, different classes of organisms might be grouped into a phylum, which is the next (larger) category.
13 In Linnaeus’s system of classification, the two smallest categories are genus and species. In taxonomy, the class Mammalia is grouped with the classes Aves, Reptilia, Amphibia, and several classes of fishes into the phylum Chordata.Traditional classification is based on general similarities of body structure among organisms.In traditional classification, some similarities that were used to group organisms were based on convergent evolution instead of a shared evolutionary history.
14 In cladistic analysis, a characteristic that arises as a lineage of organisms evolves over time is called a derived character.DNA analyses show that the genes of many dissimilar organisms show important similarities at the molecular level.Evidence shows that very dissimilar organisms, such as yeasts and humans, have some genes in common, indicating that they share a common ancestor.
15 The six kingdoms of life include bacteria that have cell walls with peptidoglycan, bacteria that have cell walls without peptidoglycan, protists, fungi, animals, and plants.Unlike the five-kingdom system of classification, the six-kingdom system breaks Monera into two groups.