Finding Order in Diversity Classification

Why do we need to classify? Imagine a store…..how do you know where to find the milk or the cereal? Are they in the same aisle? How is the store “organized”? Are all stores similar? Imagine your computer or mp3 player…..are all of your songs and files in a single folder or do you have them grouped in some way?

When you have a lot of information, it is best to organize and group items so that you can find them easier or easily see their relationship to other items ….this is why we CLASSIFY Even websites must organize their products

Evolution overview All life on earth began about 3.5 billion years ago with organisms that were a single cell Then one billion years ago organisms that are made of many cells appeared as a result of evolution During evolution traits that do not help organisms survive disappear while good traits that help with survival remain

Classification As a result of evolution earth is populated by many different organisms with different traits. We group these organisms according to their similar characteristics Classification – grouping and naming of organisms according to their evolutionary relationships and shared characteristics

Taxonomy Branch of biology that deals with classification of life forms Taxonomist – use the tools of classification to identify and find relationships among organisms Taxonomists classify organisms based on their (1)biochemical and genetic information (DNA, proteins),(2) embryological development, (3)fossil record – (1)+(2)+(3)=evolutionary relationships, (4) in addition to their body structure

Early Classification and naming systems Aristotle – Greek philosopher – Invented the first classification system – He classified organisms into two major groups plants and animals Land Water Shrubs Herbs PlantsAnimals Air Trees

Early Classification and naming systems continued... Carolus Linnaeus – Swedish botanist – In the 18 th century developed a new classification system – He also grouped them into plants and animals – He classified animals based on their similar body structures and not where they lived Example: bats were grouped with mammals not with birds

Binomial Nomenclature Linnaeus also gave each organism a two-word, Latin scientific name – This is called binomial nomenclature – still used today Binomial – consisting of two terms Nomenclature – a system of names

Bi-Nominal – two terms, two names How many names do you use to identify yourself? – Example: Karen Wood – But why do we need this? Can we just call her Karen or simply that girl over there?

Scientists also need a way to *NAME* organisms The “common names” used by people can sometimes be misleading or confusing In order to communicate effectively, biologists need a CONSISTENT naming protocol. *Check out these slides of confusing names…..

Photo Credits Sea Lion: Bill Lim Ant Lion: Amphioxus Lion: law_keven Sea Lion? Ant lion? Lion?

Which one of these is NOT actually a bear? Photo Credits Panda: Chi King Koala: Belgianchocolate Black Bear: SparkyLeigh

Bi-Nominal – two terms, two names: Genus and Species The first word in binomial nomenclature is called the genus which is a group that has one or more different species classified within it – Closely related species that come from a common ancestor The second word is species or a group of similar organisms that are capable of producing fertile offspring with each other

Genus and Species Example: Panthera leo – lion and Panthera tigris – tiger Both species are classified in the same genus Panthera along with other big cats however they are each a different species because they can’t reproduce with each other Genus and species names are always italicized. First letter of the genus is always capitalized and the first letter of the species is always lower case.

Taxonomic Groupings Taxonomists classify things into seven major groups or taxa They are: Kingdom – largest group of living things (broadest) Phylum – largest group within a kingdom Class – largest group within a phylum Order – largest group within a class Family – largest group within an order Genus – largest group within a family Species – smallest group of living thing (most specific) HINT for remembering the order of the levels of classification: King Phillip Came Over For Great Spaghetti King Phillip Cried Out For Great Soup

To help you remember the list KING PHILIP CAME OVER FOR GREAT SOUP Kingdom, Phylum, Class, Order, Family, Genus, Species

KingdomAnimalia PhylumChordata ClassMammalia OrderPrimate FamilyHominidae GenusHomo Speciessapiens The scientific name is always the genus + species Humans = Homo sapiens Photo by atomicshark

LionTigerPintail Duck KingdomAnimalia PhylumChordata ClassMammalia Aves OrderCarnivora Anseriformes FamilyFelidae Anatidae GenusPanthera Anas SpeciesLeoTigrisacouta What are the scientific names of each of these organisms?

What is a species? Defined as organisms that can interbreed with one another, and produce fertile offspring

When two organisms of different species interbreed, the offspring is called a HYBRID Example: ligers and mules Is offspring fertile?

Tree of Life Shared characteristics or evolutionary relationships?

Phylogenetic Taxonomy Taxonomists use two different approaches to place an organism into the correct taxonomic category: – Systematics: a phylogenetic tree or family tree is used to show the evolutionary relationships between different groups of organisms This process stresses common ancestors and relies on the amount of differences within a group to construct the tree Tree is based on evidence from the fossil record, morphology, embryological development, biochemistry and genetic studies

Phylogenetic Taxonomy Continued... Second approach used to place an organism into the correct taxonomic category is called cladistics – Scientists construct a diagram based on specific characteristics of an organism – This is called a cladogram and its used to show evolutionary relationships among the different groups based on traits called shared derived characteristics – Derived characteristics – a trait that evolved only within the specific group under study Example: Feathers in birds

Phylogenetics A cladogram has CLADES Clade – a monophylletic group - a grouping that includes a common ancestor and all the descendants (living and extinct) of that ancestor Using a phylogeny, it is easy to tell if a group of lineages forms a clade. Imagine clipping a single branch off the phylogeny — all of the organisms on that pruned branch make up a clade.

What's in a Clade

Clades are nested within one another — they form a nested hierarchy. A clade may include many thousands of species or just a few. A clade may include species that are no longer living (extinct)

How are we related to Chimps?

Dichotomous Key Precise method that helps taxonomists classify and identify unknown organisms Made up of a list of observable, alternative characteristics, that leads, step by step, to the correct identification of an organism Dichotomous means dividing in two because there are always two choices at each step At each step the organism will have only one of the traits described and that is the path you follow

Example: A dichotomous key for a plant would have one step where you chose between spores and seeds as a method of reproduction Then it might ask for seeds if its cones or flowers There would also be steps asking about leave structure and the stem

Molecular Phylogenetics and what it all means......

How would you group these?

They are both Mammals – have a common ancestor BUT Have markedly different physical characteristics

Fossil Records and DNA comparison

Molecular Phylogenetics Constructing trees based on DNA sequence comparisons In certain stretches of DNA mutations occur at reliable rates - the more mutations the DNA has accumulated, the longer since it split off from its ancestral sequence May use RNA (for RNA viruses) or protein sequences

Molecular Phylogenetics Made possible by the availability of whole genome sequencing; new technologies make this faster – more organisms genomes sequenced Many species genomes have been sequenced Requires "Bioinformatics" – computer algorithms that compare sequences from multiple organisms Comparison: align sequences, determine (1)similarities, (2)differences, (3)gaps in alignment

Allignment

Adding time to a tree

How do we know the time? Life began 3.8 billion years ago, and insects diversified 290 million years ago, but the human and chimpanzee lineages diverged only five million years ago. How have scientists figured out the dates of long past evolutionary events? Here are some of the methods and evidence that scientists use to put dates on events: Radiometric dating; stratigraphy; molecular clocks

Molecular Clocks Evolutionary changes may occur in a clock-like fashion Changes in DNA sequence can build up over the course of million years at a reliable rate Example: Alpha-globin gene experiences base changes at a rate of.56 changes per base pair per billion years - IF this rate is reliable, the gene could be used as a molecular clock.

Evolution and Trees beyond Taxonomy Phylogenetics can be used to build NEW scientific knowledge: – Identifying the source of new human diseases; – Setting Conservation priorities – Agriculture – Investigating alleged crimes – Use of 'model' organisms in biomedical science

Video

Evolution is an inseparable part of ALL Life Science – Medicine -Agriculture

The Kingdoms There are currently 6 kingdoms

Classification into a kingdom is based on certain criteria - Number of cells (unicellular or multicell ular) - How it obtains energy (hetero troph or autotroph) - Type of cell (eukaryot e or prokaryote)

Kingdom Animalia Multicellular Heterotrophic Most can move Examples: birds, insects, worms, mammals, reptiles, humans, anemones Photo by Eduardo Amorim Photo by Tambako the Jaguar

Kingdom Plantae Multicellular Autotrophic Eukaryotic Cannot move (due to cell walls)

Kingdom Fungae Multicellular (most) Heterotrophic (mainly decomposers) Eukaryotic Photos by nutmeg66

Kingdom Protista Most are unicellular Can be heterotrophic or autotrophic Eukaryotes (all have nucleus) Examples: Ameba, paramecium, euglena, algae Most live in water Photo of Ameba by PROYECTO AGUA **/** WATER PROJECT

Kingdom Eubacteria & Kingdom Archaebacteria Unicellular Can be autotrophic or heterotrophic Prokaryotes (do not have a nucleus) Eubacteria = common bacteria (E. coli, Salmonella) Archaebacteria = “ancient bacteria”, exist in extreme environments

Three Domain System Recently, scientists have added a group above Kingdom. Three groups, called DOMAINS, contain each of the six kingdoms. Domain Eukarya - includes organisms composed of eukaryotic cells (plants, animals, fungi, protists – 4 kingdoms) Domain Bacteria - includes all prokaryotic cells, Kingdom Eubacteria Domain Archaea - includes only "ancient" bacteria, Archaebacteria (1 kingdom)