1442 Laboratory 2Classification and Taxonomy

Heather M Hawkins MICHAELL@uta.edu

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 OutlineLevels of ClassificationDichotomous KeyDefinition of SpeciesToday’s Experiment

Levels of ClassificationCarolus Linnaeus (1707-1778) 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 ClassificationTaxonomy: 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 ClassificationCommon names: Can vary with

culture/region, names familiar to most laymen

Scientific names: Unique to each organismBinomial system first employed by Linnaeus in

the 18th Century (Genus species)

Levels of Classification

Taxonomic KeysUsed to identify organisms within a setUsually 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

Dichotomous Key Examples

Leaf MorphologyBlade (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 MorphologyMargins 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 ExperimentConstruct your own Dichotomous key for the

shapes on the handout.Use page 29 in your text for help.Have a classmate check your key.

AssignmentComplete Web Assignment 1 from the

IntroLabs website for next week.Print out Web Assignment 2Study for next week’s quiz (this week’s

material and new material)

Homework HelpWhat 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 20-22 in the text for ideas.