Classification and Taxonomy Heather M Hawkins Office Hours: 11-2 LS 464

Tuesday Choose 5 questions to answer: 1. True/False Within an experiment the independent variable is measured. 2. The first step in testing a hypothesis is making a ___________________about the observations one would expect to make if the hypothesis is correct. 3. True/False Systematics is the science of using phylogenetic relationships to classify organisms. 4. The basic units of mass in the metric system is____________________. 5. What is the name of the prefix for 10^-6 that is applied to all SI units? 6. List two of the principle parts of the microscope we studied?

Wednesday Choose 5 questions to answer: 1. True/False Within an experiment the independent variable is manipulated. 2. The first step in testing a hypothesis is making a ___________________about the observations one would expect to make if the hypothesis is correct. 3. True/False Taxonomy is the science of naming organisms. 4. The basic units of volume in the metric system is____________________. 5. What is the name of the prefix for 10^-9 that is applied to all SI units? 6. List two of the principle parts of the microscope we studied? 7. Magnification is determined by this formula: _____ X objective = total magnification.

Today’s Outline Levels of Classification Dichotomous Key Definition of Species Today’s Experiment

Levels of Classification Carolus Linnaeus ( ) a Swedish physician and botanist contributed two fundamental ideas to science: Developed a two part system (binomial) of naming organisms according to genus and species. Also developed a system to group similar species into a hierarchy of increasing general categories.

Levels of Classification Taxonomy: the science of naming and classifying organisms Systematics: the science of using phylogenetic relationships to classify and name organisms Phylogenetics: the study of evolutionary relatedness among various groups of organisms

Levels of Classification Common names: Can vary with culture/region, names familiar to most laymen Scientific names: Unique to each organism Binomial system first employed by Linnaeus in the 18 th Century (Genus species)

Levels of Classification

Taxonomic Keys Used to identify organisms within a set Usually limited to region or taxa Examples: Key to the trees of New England Key to Lizards of Texas Example in your lab manual (pp 20-23) Dividing organisms based upon phenotypic characteristics Dichotomous keys are arranged choices with two alternatives

Dichotomous Key Examples

Leaf Morphology Blade (or leaf) is connected to the branch at the node. Internode defines the space between nodes. A simple leaf had only one blade per auxiliary bud, while a compound leaf has several.

Leaf Morphology Margins or leaf edges: entire (smooth), serrate (toothed), or lobed Leaf attachments to the branch: opposite (nodes are directly across from each other), alternate (nodes are offset), or whorled (greater than three nodes are attached to one position on a branch) Venation patterns: pinnate (feather like pattern) or palmate (hand like)

Leaf Morphology

What is a Species? Species is a Latin word meaning “kind” and “appearance.” Linnaeus described species in terms of their physical form. Basic concept: group of organisms and a single species represents all the individuals make that group Most common definition from Ernest Mayr (1942): Species are a group of actually or potentially interbreeding natural populations which are reproductively isolated from other groups. (Biological Species Concept)

What is a Species? Biological Species Concept: Can be defined in another way, a species represents a population whose members can interbred in nature to produce viable offspring but cannot with other species. This concept is more interested in reproductive compatibility rather than physical similarities and hinges on reproductive isolation. Limitations: How do you group extinct life forms, normally they are grouped based on physical characteristics? Definition based on interbreeding, how do you group organisms that reproduce asexually?

What is a Species? Morphological species concept: Species are defined by measurable physical attributes, not by reproductive isolation. Recognition species concept: Species are defined by molecular, morphological, and behavioral characteristics that maximize successful mating, these characteristics are affected by natural selection. Ecological species concept: Species are defined by where they live and what they do, morphology is irrelevant.

What is a Species? Evolutionary species concept: Species are defined as a sequence of ancestral and descendant populations that are evolving independently of other groups. Many more species concepts exist than presented here. Unlikely that a single definition can be created to define all species. Remember, in defining a species we are talking about a genetically discrete unit in nature. To create these units processes must occur to initiate and perpetuate the isolation of the population’s gene pool from others.

Today’s Experiment Construct your own Dichotomous key for the shapes on the handout. Use page 29 in your text for help. Have a classmate check your key.

Assignment Complete Web Assignment 1 from the IntroLabs website for next week. Print out Web Assignment 2 Study for next week’s quiz (this week’s material and new material)

Homework Help What is a species? Review the various species concepts presented attempt to merge two or three of them into a single definition. Dichotomous Key for Leaves: Try beginning with dividing between simple and compound leaves? See page in the text for ideas.