Classification Systems - Taxonomy

Why Classify? 2.5 million kinds of organisms Not complete- 20 million organisms estimated Must divide into manageable groups To work with the diversity of life we need a system of biological classification that names and orders organisms in a logical manner

Why Classify? Assign a universally accepted name to each organism Place organisms into groups that have real biological meaning Organisms share important traits with members of the same groups

Biological Classification Eighteenth century European scientists used Latin or Greek words to name organisms instead of local languages Very long descriptive names Difficult to standardize – different names

Carolus Linnaeus Developed a system of naming plants and animals that we use today Swedish botanist Binomial nomenclature – gave each organism a two-part scientific name Genus and species - Acer rubrum – red maple Acer is genus of all maple trees Red in Latin is rubrum

Classification System of Linnaeus Universally accepted Groups that have shared characteristics are grouped into the same taxa Taxonomy – the science of naming organisms and placing them into taxa – taxon is singular

Taxonomy The smallest taxon is species – a population of organisms that share similar characteristics and can breed with one another. Kingdom – Phylum- Class – Order- Family – Genus – species Each taxa may also have sub groups or super groups

Geographic Isolation – physical barrier Reproductive Isolation- reproductive barrier – not always complete and can result in hybrids

Taxonomy Today A very difficult science Has changed greatly since Linnaeus The only taxon with clear biological meaning is the species – share a common gene pool – because they interbreed All other taxa are determined by scientists

Taxonomy Today Living species have evolved from earlier species Guiding philosophy for classification Organisms grouped to show evolutionary relationships Homologous structures Developing embryos fossils

Phylogeny Evolutionary history of a species Overall similarity between characteristics of different kinds of organisms Relates extant and extinct species Looks at homology- similar characteristics from a common ancestor.

Convergent evolution – similar traits that evolve independently such as wings-these characters are called analogous characters This can confuse taxonomy

Cladistics System of taxonomy that reconstructs phylogenies by inferring relationships based on similarities Used to determine the sequence in which different groups of organisms have evolved

Focuses on a set of unique characteristics found in a particular group of organisms or derived traits. Looking at shared derived traits a cladogram is made Morphology, physiology, molecular traits, and behavioral traits are studied

Species shown to be closely related are classified together Other species that may look alike but possess analogous structures are classified in diff groups

Morphology Comparitive morphology – (includes embryology) – examines the varying shapes and sizes of organismal structures – includes developmental origins Variations in skull bones, limb bones, scales, feathers hair etc.

Comparitive biochemisry Amino acids Proteins Nucleotides Cytochrome C is slightly different in different organisms.

Comparitive cytology Variation in numbers, shape, sizes of chromosomes Used on living organisms

The Kingdoms of Life Eubacteria – bacteria Protista – one celled organisms Fungi – mushrooms, mold, ringworm, Plantae- plants Animalia – animals Archaebacteria – new kingdom previously part of monera

Eubacteria Prokaryotes – have no nucleus 0ne celled prokaryotes Mostly heterotrophic – does not make own food Cell wall – made of lipid and carbohydrates 3 cell shapes – spirilla, cocci, and bacilli

Protista Eukaryotic – cells have a nucleus Can be heterotrophic or autotrophic Animallike, plantlike, or funguslike Amoeba, paramecium, euglena Single celled organisms

Fungi Heterotrophic – do not make their own food Cell walls – made of chitin Eukarotic – have a nucleus multicellular

Plantae Autotrophic – make own food – photosynthesis Eukaryotic – have a nucleus Multicellular Cell wall – made of cellulose

Animalia Heterotrophic – do not make own food Eukarotic – have a nucleus No cell walls Multicellular