The Diversity of Life n Biologists have identified about 1.5 million organisms. n Thousands more remain to be found. n Great variation in organisms exists.

Diversity continued n Some organisms are clearly plant or animal. n Other organisms are more difficult to classify. n Thus we need a classification system!

Plant and Animal Characteristics n As previously discussed, it is relatively simple to distinguish plants from animals. n See handout.

Classification Categories n The categories used by biologists to classify an organism are: Kingdom, Phylum,Class, Order, Family, Genus, and Species. n See Table 6.1 on page 95.

Nomenclature n Nomenclature is a system for naming organisms. n Linnaeus developed the binomial system of nomenclature.

Nomenclature continued n Binomial means two names. n The names must be in Latin. n The first name is the Genus and the second name is the Species. n For example for a human it is Homo sapiens and for the frog Rana pipiens.

Modern Taxonomy n In the mid 1800’s the common belief was that species did not change. n Biologists collected single specimens that were used to represent all species of that one organism. n They called these type specimens. n Variations were ignored. n Later in 1859 it was noted that over long periods of time a species will change in response to the environment.

Species n The term species refers to a similar population of organisms that can interbreed in nature. n Over time, species may interbreed, evolve and form new species. n This phenomenon further supports the need for a classification system.

Classification of Living Organisms Handout n This handout, shows us that we have two broad categories of living things: n Prokaryotes and Eukaryotes

The Prokaryotes n Cells are called prokaryotic. n Lack a nucleus. n Lack membrane bound organelles. n Ribosomes are smaller than those in eukaryotic cells. n DNA lacks histones (Special protein) n Flagella are twisted strands of protein. Ex. Bacteria

Eukaryotes n Cells are called eukaryotic n Cells have a well defined nucleus, with DNA containing histones. n Membrane bound organelles are present(mitochondria, etc.) n Flagella have microtubules in the 9+2 pattern.

Three Domain System n Latest system to classify living things. n Developed in the last 20 years by microbiologists who believe that microbes dominate the diversity of life on Earth. n This system is based on gene studies and in particular on rRNA, which is found in all living things.

Three Domain System continued n The three domains include 2 groups for bacteria and 1 for the rest of the living things. n 1. Archaea Bacteria: includes ancient bacteria that can be found in very harsh environments. n Ex. Methane producers, salt lovers,and heat lovers.

Three Domain System continued n 2. Eubacteria: This domain includes the true bacteria that are found in various environments such as E.coli that is found in the intestines of warm blooded animals. Blue - green algae are also included in this group. n 3. Eucharya: All remaining organisms. Cells have distinct nuclei and organelles.