Chapter 18 Classification

Every year, thousands of new species are discovered Biologists classify them with similar organisms The ways we group organisms continue to change Today’s methods reflect an organism’s evolutionary history

Classification Taxonomy- The branch of biology that names and groups organisms according to their characteristics and evolutionary history This allows us to keep track of all of the millions of different species. Between 2-25 million!! Most extinct now.

History of Classification Aristotle first classified organisms over 2,000 years ago Grouped them as: –Animals Land, water, or air dwellers –Plants 3 types based on stems

History of Classification As more and more species were discovered, the existing categories weren’t adequate –Common names – not accurate (jellyfish is really not a fish) –Common names varied from country to country –Some early scientific names were too long and complicated

History of Classification Swedish naturalist Carolus Linnaeus ( ) – devised a system of grouping organisms into hierarchical categories He used an organism’s form and structure (morphology) to classify it

Classification 7 levels –Kingdom –Phylum –Class –Order –Family –Genus –Species *King Phillip Came Over For Good Spaghetti

Binomial Nomenclature Two part name 1 st name capitalized 2 nd name lowercase underlined or italicized 1 st name is the genus, the second is a describer word –Example: Homo sapiens which means (wise)

Phylogeny Modern taxonomists consider: –1. morphology –2. chromosomal characteristics –3. nucleotide and amino acid sequences –4. embryological development –5. fossil record

Phylogenic Tree Phylogenic tree – a family tree that shows the evolutionary relationships thought to exist among groups of organisms

Fossil Record Provides clues to evolutionary relationships But, some organisms have incomplete fossil records There may be strata where no fossils of an organism appear Need other evidence to support the phylogenetic tree

Morphology Study organism’s structure and compare it to other living organisms Homologous features suggest a common ancestor The greater the number of homologous features, the more closely related the organisms

Embryological Development Early patterns of embryological development provide evidence of phylogeny –Egg is fertilized and zygote starts to divide by mitosis –Hours later a ball of cells called a blastula is formed –Soon after, an indentation called a blastopore forms –Blastopore becomes the mouth in most animals, but the other end in echinoderms (starfish, sand dollars)

Chromosomes & Macromolecules Taxonomists use comparisons of macromolecules such as DNA, RNA, and proteins as a kind of molecular clock The number of differences is a clue to how long ago the species diverged Biologists can also compare karyotypes or patterns of chromosomes In our human history lab, we saw how similar the amino acid sequences were between humans and chimps

Cladistics Cladistics – a system of phylogenic classification using shared derived characters A derived characters is a feature that only evolved in a specific group (birds have feathers) A group of shared derived characters is strong evidence for common ancestry Cladograms - Ancestry diagrams

Six Kingdoms 1) Archaebacteria 2) Eubacteria 3) Protista 4) Fungi 5) Plantae 6) Animalia

Archaebacteria Unicellular prokaryotes Some are autotrophic (chemosynthesis) –Waste products may include flammable gasses – methane) Many live in harsh environments –Sulfurous hot springs, salty lakes, anaerobic conditions (intestines) Directly descended from the first organisms on earth (before oxygen and photosynthesis)

Eubacteria Unicellular prokaryotes Most are aerobic True bacteria – can affect your life: –Cause tooth decay –Make yogurt –Cause food poisoning

Protista Eukaryotic Mostly single celled (amoeba, euglena) Some multicellular (giant kelp) All eukaryotes that are not plants, animals or fungi Some look like plants, but lack specialized tissues

Fungi Heterotrophic Can be unicellular or multicellular They absorb nutrients rather than ingesting them There are over 100,000 species: –Mushrooms –Mildews –Molds –rusts

Plantae Use the term Division instead of Kingdom Eukaryotic and Multicellular Most are autotrophic and use photosynthesis to get energy There are over 350,000 species: –Mosses –Ferns –Conifers –Flowering plants

Animalia Eukaryotic Multicellular Heterotrophic Most have symmetrical bodies and are able to move around their environment Examples: –Humans –Dogs –Fish –Insects