Life in General Living matter is organized into complex structures based on organic molecules. They have cells. Homeostasis is maintained by Living organisms. Growth and development. Reproduction and transmission of genetic information. Living Organisms are capable of replicating themselves and Continuing their Genetic lines.

Life in General (cont’d) Acquisition and conversion of matter and energy from the external environment. Living Organisms are capable of integrating material from the external environment and making it a part of themselves. They are able to synthesize their own organic materials On this planet (at least) their is a requirement for water. Response to stimuli from the environment Evolution.

Classification Systems classification is a method for organizing information ARISTOTLE ( BC) is often called the father of biological taxonomy. His scheme referred to common groups, such as birds, fishes, whales, and bats, he recognized the need for groups and group names in the study of animals. his system was based on the knowledge that he possessed at the time.

Classification Systems (cont’d) John Ray ( ) used differences in anatomy as the prime rule for classification, bringing out both the similarities and differences between groups--for example, fins or feathers. This is still the preferred method

Classification Systems (cont’d) Similar things are grouped together. However, there are many reasonable ways of defining similarity, and as a result many different classifications for the same things.

Classification Systems (cont’d) key property of classifications is that they can be nested within one another, creating an ever increasing leveled system. As a result any group within a classification can be split in still smaller groups. There is no limit to the depth of a layered classification.

Carl Linnaeus Linnaeus defined the biological classification system that we still use for plants and animals, and, with relatively minor changes, for fungi and microorganisms. It is a layered system that starts with a few categories at the highest level, and further subdivides them at each lower level. In the Linnaean system, to uniquely name a species it is necessary to supply both genus and species. In the case of animals, Linnaean classifications often reflect our "gut reactions" regarding whether an animal is similar or not.

Linnaeus (cont’d) biologists also classify organisms into different categories mostly by judging the levels of apparent similarity and difference that they can see. The assumption is that the greater the similarity, the closer they are related in a biological sense.

Classifying Organisms If an unknown organism is discovered, researchers begin their classification by looking for features that seem to have the same purpose as those found on other species. Next it will have to be determined whether or not the similarities are due to a separate evolutionary development or to a common ancestor. If there is a common ancestor then the two species are probably closely related and should be classified into the same or near biological categories.

Classifying Organisms (cont’d) Homologous structures are physical features, of different organisms, that have a similar appearance or function because they were inherited from a common ancestor that also had them. For example, the forelimb of a sloth, the wing of a crow, and your arm have the same functional types of bones as did our shared reptilian ancestor--these are homologous structures. The more such structures two organisms possess, the more likely it is that they have a close relationship.

Classifying Organisms (cont’d) Listing features that separate one species from another has the effect of making it look like the species and their distinctive features are fixed and eternal. We need to remember that they were brought about by evolutionary changes that operated not only at some time in the past, but which also continue to operate today and will surely give rise to new forms in the future. We also need to realize that most species are genetically varied

Biological Classification Biological classification is the grouping of organisms into categories that express their PHYLOGENY, or line of descent, based on information such as structure, development, biochemical functions, and evolutionary history of organisms. The purpose of such a classification is to provide a clear and practical way to organize and communicate information about organisms. Classification can show relationships between different ancient and modern groups, indicate the evolutionary pathways along which present-day organisms may have developed, and provide a basis for comparing experimental data about different plant and animal groups.

Biological Classification Organisms included in a group share a common genetic heritage in their genetic material, and they must be more closely related to each other than they are to the members of other groups of the same rank. However, classifications of organisms are modified as new information comes forward and as a result the phylogeny would change. Taxonomy is the method we use to group organisms. The first scheme for classifying animals into logical groupings may have been brought forward by Aristotle over 2,000 years ago. Since then many new systems have been proposed; none, however, has succeeded in fitting all plants, animals, and microorganisms into a single, completely satisfactory scheme.

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