Classification Unity and Diversity of Life

Why Classify? Books in a library Food in a grocery store You’ve been asked to organize these things into categories that make sense. How would you do it?

Classifying Sort things into a meaningful order Natural system Using important features Shared Characteristics – shared by all members of the group Birds – all have feathers, wings, beak Reptiles – all have scales, cold blooded (exothermic) Plants – vascular vs. nonvascular system

Why is it important for all scientists to use the same system? Certainty Makes it easier to document new species when everyone uses the same scientific information Makes certain scientists are discussing the same organism

Explain how Earth’s biodiversity relates to classification. Earth contains a great variety of organisms. Scientists have worked to identify approximately 1.8 million species. There are many more species that remain unidentified (estimated 10 -100 million total). Classification is used to organize diverse species in a way that makes sense. Click HERE for a good intro to classification video!

Aristotle’s Classification system 2400 years ago, Aristotle classified organisms using two taxa, plant and animal. He then grouped them according to where they lived; land, sea or air (Think analogous traits). He grouped plants by their stems. Scientists quickly discovered that there were many organisms that fell between Aristotle’s groups. The system was inadequate.

The Linnaean System Carolus Linnaeus (1701-1778) – Swedish botanist Binomial nomenclature 2 part scientific name; genus and species Organisms grouped according to form and structure. Much more specific categories. Groups called taxa (singular: taxon) Science of naming groups is called taxonomy

8 Levels in Linnaeus’ system Domain – Most Broad (added later) Kingdom Phylum Class Order Family Genus Species – Most Specific

Binomial Nomenclature A system for naming things Same in all languages, indicates relationships Two words – genus and species, both are italicized, underlined if written Genus is capitalized Example: Homo sapien, Escherichia coli

Taxonomy Scientists who classify things are called taxonomists. It is their job to look at every kind of living thing and determine how they are alike and how they are different to other living things.

Cladistics Method of classifying organisms into groups of related organisms Clade: a group of related organisms with shared derived traits Derived traits: “new” traits that related species share through their immediate ancestor

Cladogram

Three Domains Bacteria – Prokaryotic. Aligns with the Kingdom Eubacteria Archaea – Prokaryotic. Aligns with the Kingdom Archaebacteria. Eukarya – Consists of all the eukaryotic organisms. Kingdoms in this domain are Protista, Fungi, Plantae, and Animalia.

Six Kingdoms Eubacteria Archaebacteria Protista Fungi Plantae Animalia How are organism placed into their kingdoms? Cell type, complex or simple Their ability to make food The number of cells in their body

Kingdom Eubacteria Eubacteria are single celled and prokaryotic. Most bacteria are in the EUBACTERIA kingdom. They are the kinds found everywhere and are the ones people are most familiar with. Most eubacteria are helpful. Some produce vitamins and foods like yogurt. However, some eubacteria, like Streptococci, can give you strep throat!

Bacteria (Kingdom Eubacteria) are unicellular microorganisms that have, despite their extremely small size, significant beneficial and harmful effects on humans. This scanning electron micrograph shows the bacteria known as Streptococcus pyogenes, which causes strep throat, a common illness in humans. Streptococcus pyogenes. Photograph. Encyclopædia Britannica Online. Web. 9 Jul. 2011. <http://www.britannica.com/EBchecked/media/106347/Bacteria-are-unicellular-microorganisms-that-have-despite-their-extremely-small>.

Kingdom Archaebacteria 1983 - scientists took samples from a spot deep in the Pacific Ocean where hot gases and molten rock boiled into the ocean from the Earth’s interior. To their surprise they discovered unicellular (one cell) organisms in the samples. These organisms are today classified in the kingdom, Archaebacteria. Archaebacteria are found in extreme environments such as hot boiling water and thermal vents under conditions with no oxygen or highly acid or salty environments.

Archaea are found in a diverse range of extreme environments, including the salt deposits on the shores of the Dead Sea. Dead Sea: salt deposits. Photograph. Encyclopædia Britannica Online. Web. 9 Jul. 2011. <http://www.britannica.com/EBchecked/media/122136/Archaea-are-found-in-a-diverse-range-of-extreme-environments>.

Kingdom Protista A diverse group of eukaryotes that are not plants, fungi, or animalia. Unicellular or simple multicellular Heterotrophic and autotrophic Reproduce sexually or asexually Examples: Algae, Protozoa, Slime molds

Kingdom Protista

Kingdom Fungi Eukaryotic Cell walls contain chitin (a carbohydrate) Decomposers – important in the recycling of nutrients Unicellular or multicellular Examples: Yeast, molds, mushrooms

Kingdom Fungi

Kingdom Plantae Eukaryotic Multi-cellular Cell walls contain cellulose Autotrophic, very few heterotrophic Sexual and asexual reproduction Examples: Ferns, grasses, trees, flowers.

Kingdom Plantae

Kingdom Animalia Eukaryotic Multicellular and unicellular Heterotrophic No cell walls Mostly sexual reproduction Examples: jellyfish, coral, worms, insects, mammals

Kingdom Animalia