Evolution/Classification/Taxonomy Unit Learning Target Objectives: (I can…) • Explain the need for grouping organisms and for assigning a name using binomial nomenclature. • List 4 types of evidence used to classify/group organisms. • Create and accurately use phylogenic (evolutionary) trees and dichotomous keys. • Identify 5 kingdoms and 7 levels of classification from largest to smallest (kingdom to species). • Explain how the environment/natural selection affects both divergent and convergent evolution.
Vocabulary Taxonomy * binomial nomenclature * Carolus Linnaeus * Kingdom, phylum, class, order, family, genus, species * subspecies/variety * morphology * biochemistry * embryology * chromosomes * analogous organs * homologous organs * evolution (divergent & convergent) * natural selection * herbs * shrubs * John Ray * Charles Darwin * phylogeny * dichotomous key * Monera * Protista
Classification Taxonomy (aka “classifying”) - grouping of organisms according to their natural “relatedness.” (Ex: dogs, wolves, and coyotes are similar in structure and DNA makeup.) The earliest divisions were just “plant” or “animal but many organisms (Ex: mushrooms, bacteria, paramecium) don’t fit into either group. Problem Areas When Naming Organisms Confusion over names was a problem: 1) Sometimes many organisms had the same common name, AND 2) Sometimes the same organism has many, different, common names.
Binomial Nomenclature – using 2 names, the Genus and species (unique), to identify organisms. Carolus Linnaeus – developed groupings at different levels (hierarchy), including using the binomial nomenclature system. Kingdom (Animals) PhylumDivision (Plants) Class Order Family * Genus * Species Subspecies Variety
Hint: Remember the order from the broadest level, Kingdom, to the most restrictive level, species, with: Kings play cards on fat green stools. Species- members within a species or its subgroups can breed with each other. Members of different species cannot interbreed (or will produce sterile offspring in some cases.) *Genus and *species are used in the binomial nomenclature. The Genus is always capitalized and the species name is always lower case. Occasionally, the subspecies or variety is added to increase specific understanding. Examples: Genusspeciessubspecies Homo sapiens Canis lupus occidentalis Prunus persica nectarina
Evidence used in classification: 1) Morphology – shape, appearance Many related organisms look alike. However, many unrelated organisms also look similar. 2) Embryology – comparing embryos. All vertebrate embryos have similar characteristics, including gill slits. 3) Chromosomes – similar genetic make-up shows close relationship. 4) Biochemistry – production of certain proteins, toxins, etc. may indicate a close relationship. (Especially with bacteria.)
There are problems when using morphology: 1) Structures that appear similar may not be related at all. Ex: Analogous organs – organs that serve the same function but do NOT come from the same embryonic structures. Bird’s wing versus butterfly wing Panda’s thumb vs. human thumb 2) Structures appear very different but do come from the same embryonic tissues. Ex: Homologous organs Bird’s wing / human hand / whale’s flipper
Analogous Organs: Homologous Organs:
Why do some unrelated organisms look so similar while some related organisms look quite different? Evolution – species change (adapt) over time to better fit their environment. Divergent evolution – related species become more and more dissimilar – usually because they live in different environments. Convergent evolution – unrelated species appear more and more alike as they adapt to living in the same sort of environment. Natural selection – organisms with a mutation or a phenotype that is beneficial will survive and reproduce. This drive evolution.
Early Classification Schemes: Aristotle – classified all organisms as either plants or animals. Divided animals into: LandWaterAir Exs: Kangaroo Fish Butterfly Ostrich Whale Bird Reptiles Jellyfish Beetles Theophrastus – divided plants by size and type of stem. 1) herbs – small plants with soft stems 2) shrubs – medium sized with many woody stems 3) trees – large plants with one woody stem John Ray – called each group of different living things a species. species – organisms that look alike and can reproduce themselves.
Phylogeny – evolutionary history, or “family tree” This type of classification didn’t occur until after Charles Darwin convinced scientists that different species of organisms evolved from a common ancestor. Base of “tree” = common ancestor Tips of branches = most recently developed species in that line Closely spaced branches = closer relationship than distantly spaced branches.
Grouping organisms can be achieved by using a … Dichotomous Key = a written set of choices that leads to the identification of an organism. Ex: 1) simple leaf (go to #2) compound leaf (go to #3) 2) blade entire (go to #4) blade lobed (go to #5) This all leads to a binomial name: Genus and species
The 5 Kingdom Classification System: (Robert Whittaker, 1969) 1) Kingdom Monera (monerans) - single-celled, microscopic - No nuclear membrane (prokaryotes) - other organelles have no membrane - most absorb nutrients - reproduce asexually (However they may exchange genetic information through pilli.) Ex: bacteria 2) Kingdom Protista (protists) - single-celled or simple multicellular - have a membrane bound nucleus and organelles (eukaryotes) -live in moist habitats - reproduce sexually or asexually Ex: algae, protozoa
3) Kingdom Fungi - usually multicellular (except yeasts) - eukaryotes - heterotrophs (absorb food) - sexual or asexual reproduction (spores versus budding) - most have cell walls made of chitin Exs: yeasts, molds, mushrooms 4) Kingdom Plantae - multicellular - eukaryotes - autotrophs (chloroplasts) - sexual and asexual reproduction - cell walls of cellulose Ex: mosses, ferns, gymnosperms, angiosperms
5) Kingdom Animalia - multicellular - eukaryotic - hetertrophs (ingestion) - usually sexual reproduction (exceptions include seastars, etc) - No cell walls