Biodiversity Unit 1 Classification and Diversity What you ought to know

Why Classify? Huge diversity among organisms 1 organism can have different names (>1) 1 name can be given to different organisms Avoids confusion due to language/cultural variation

Describe a situation where classification has affected your life. Classification systems provide a framework for examining existing living organisms and a method for comparing modern organisms with extinct forms

Importance of Classification Recognition - organize and group things to avoid confusion between objects, ideas, and events. Serves as a basis for identifying known organisms and unfamiliar organisms newly discovered Gives order and logic to groups of related objects Groups/categories are called taxa The science of classification is taxonomy Scientists who carry out this work are taxonomists

Modern Taxonomy Binomial Nomenclature – Devised by Carolus Linnaeus ( ) – System of rules for naming organisms based on physical and structural features of the organism – The more features organisms have in common the closer the relationship

Binomial Nomenclature Two-part latin name Genus + species Noun + adjective Ex) Ursus horribilis *species is never used alone Basic unit of classification

Which organisms are most closely related?

Advantage to binomial nomenclature: Indicates similarities in anatomy, embryology, and likely evolutionary ancestry Ex)grizzly bear Ursus horribilis polar bear Ursus maritimus *koala bear Phascolarctus cinereus * not considered a true bear

Dichotomous Keys Used in identification of organisms The key is constructed so a series of choices leads to a specific branch of the key. If the choices are made accurately the taxonomist is led to the name of the organism being identified

Example

Levels of Classification Kingdom Phylum Class Order Family Genus Species

Example: Butterflyweed (Asclepias tuberosa) Kingdom: Plantae (All plants) Phylum: Angiospermophyta (All flowering plants) Class: Magnoliopsida (Dicotyledons) Order: Gentianales (All plants with united petals and fused reproductive parts) Family: Asclepiadaceae (Plants with a specific pattern of fused repro. floral parts) Genus: Asclepias (All milkweeds ) Species: tuberosa (a specific kind (species) of milkweed with orange flowers and tuberous roots)

How many kingdoms should there be? Historically, biologists used a two kingdom system PLANTS and ANIMALS This worked well until microscopic organisms were discovered that displayed characteristics of both kingdoms Kingdom Protista was added

And then there were six…. Not long after, it was noted that bacteria and blue-green algae lacked a true nucleus Kingdom Monera was established as the only kindgom of prokaryotic organisms (all other kingdoms contain eukaryotes) In the 1970’s work by Carl Woesz on the RNA of bacteria led to a general agreement that the Monerans be divided into two separate kingdoms, the Bacteria and Archaea The scientific community’s acceptance of this is still cautious.

There’s a fungus amoung’us! In the plant and animal kingdom system, anything that was not an animal was a plant Recently taxonomists established the kingdom for Fungi due to significant differences from plants: – Life cycle – Structure – Reproduction

Phylogeny and Modern Taxonomy Early biologists believed that living things were fixed and unchanging The modern view is that organisms changed over time and evolution is accepted as the basis for classification Phylogeny is the evolutionary history of an organism determined by radioactive dating, comparative biochemistry, physiology and DNA studies.

Phylogenetic tree (Nelson p.423)

5 Kingdoms versus 3 Domains??? The three domain system of biological classification was introduced by Carl Woesz to reflect his discovery that the prokaryotes comprise two very different groups of organisms.Carl Woes In it, all living things are grouped into three domains. – Two of these, the Bacteria and Archaea (originally Eubacteria and Archaebacteria), include prokaryotes.BacteriaArchaea – The third, the Eukarya or Eukaryota, includes all eukaryotes, including the older kingdoms Animalia, Plantae, Fungi, and Protista. eukaryotesAnimalia PlantaeFungiProtista

These domains are typically divided into kingdomskingdoms Other ranks higher than kingdom had been used earlier (for instance empires) to group together the eukaryotes, but in these schemes the prokaryotes were retained as a single group. Some have argued that such systems are actually preferable and that the differences between Bacteria and Archaea are not sufficient to warrant such a level of separate treatment.

Resources Classification website Taxonomy