Systematics and Taxonomy

Gen Bio 2, Unit 3: Macroevolution

Taxonomy

Taxonomy

• The science of describing, naming, and classifying living and extinct organisms and viruses

• Hierarchical system involving successive levels

Taxon (plural: taxa)

• Taxonomy

• Each group at any level is called a …

Systematics

• The study of biological diversity and the evolutionary relationships among organisms, both extinct and modern

• Its goal is to identify the story behind the common ancestor and present-day organisms throughout evolutionary time

  • The story behind each diversity of life

1. hypotheses

2. evolutionary relationships

Taxonomic groups are now based on (1) regarding (2) derived from systematics

Domain

The highest taxon

1. Bacteria

2. Archaea

3. Eukarya

All of life belongs to three domains. What are they?

1. Domain

2. Supergroup

3. Kingdom

4. Phylum

5. Class

6. Order

7. Family

8. Genus

9. Species

Taxonomic groups from highest to lowest

Binomial nomenclature

A system created by Carolus Linnaeus to name different types of organisms (scientific names)

Genus

• Binomial nomenclature

• Which name’s first letter is always capitalized?

1. italicized

2. underlined

• Binomial nomenclature

• If typewritten, both the genus and the species (1)

• If handwritten, both names are (2)

international organizations

Rules for naming organisms are established and regulated by …

Dichotomous key

• A tool that helps identify unknown organisms to some taxonomic level

• The key is constructed in such a way that a series of choices is made that leads the user to the correct identity of a sample organism

• Always offers two choices for each step, each of which describes key characteristics of a particular organism or group of organisms

Dichotomous

The word that means “divided into two parts”

Phylogeny

• All organisms came from a common ancestor

  • The idea of common descent

• The evolutionary history of organisms

• Provides important information about similar characteristics in closely related species

Phylogenetic trees

• Phylogenies can be reconstructed using _____

• Don’t show patterns of decent

• Don’t indicate when species evolved or how much genetic change occurred in a lineage

1. morphological similarities

2. genetic data

Phylogenetic trees are constructed by comparing (1) of organisms, or, more accurately, using (2) from organisms.

1. Monophyletic grouping

2. Paraphyletic grouping

3. Polyphyletic grouping

The types of phylogenetic grouping.

Monophyletic grouping

• Phylogenetic grouping

• Clade

• Signifies that it consists of the ancestor species and all its descendants

Paraphyletic grouping

• Phylogenetic grouping

• Consists of an ancestral species and some of its descendants

  • Not complete, but all are still connected to one point

Polyphyletic grouping

• Phylogenetic grouping

• Consists of various species that lack a common ancestor

  • They’re connected to at least two different points

1. homology

2. analogy

When constructing a phylogenetic tree, systematists need to distinguish whether a similarity is the result of (1) or (2)

Homology

• Similarly derived structures from the same ancestral structures

• Same structure, different function

  • Human arms for grasping, bird wings for flying, lizard limbs for digging and whale fins for swimming

    • All have the similar bone structure

Analogy

• Similar in function but not derived from same ancestral structures

• Different structure, same function

  • Whale fins, turtle limbs, fish fins and penguin flippers are all for swimming

    • All have different bone structure

Cladistics

The study and classification of species based on evolutionary relationships

Cladistic approach

• It discriminates among possible phylogenetic trees by considering the various possible pathways of evolutionary changes and then choosing the tree that requires the least complex explanation for all of the available data

• Its challenge is to determine the correct polarity of events

  • It may not always be obvious which traits are primitive and came earlier and which are derived and came later in evolution

  • Fossils may be analyzed

characters

The cladistic approach compares homologous traits, also called _____, which may exist in two or more character states

1. Apomorphy

2. Synapomorphy

3. Plesiomorphy

4. Symplesiomorphy

5. Autapomorphy

• Cladistics

• The different character states

Apomorphy

• Cladistics

• A derived character state

• This is anything that is an innovation along an evolutionary linage

• Anything that is different from the ancestral character state

Synapomorphy

• Cladistics

• A shared, derived character state

• An apomorphy that two taxa share and that is assumed to have been present in the common ancestor of those two taxa

Plesiomorphy

• Cladistics

• An ancestral character state

• Any trait that was inherited from the ancestor of a group

Symplesiomorphy

• Cladistics

• A shared, ancestral character state

• Any trait that was inherited from the ancestor of a group and has been passed on into more than one descendant lineage

Autapomorphy

• Cladistics

• A derived trait that is unique to a particular taxon

Branch point

• Cladogram

• 2 species differ in shared derived characters

Ingroup

• Cladogram

• Group interested in

Outgroup

• Cladogram

• Species or group of species that is assumed to have diverged before the species in the ingroup

• It will lack one or more shared derived characters that are found in the ingroup

Principle of Maximum Parsimony

The preferred hypothesis is the one that is the simplest for all the characters and their states

1. rare

2. eliminated

• Molecular clocks

• Favorable mutations are (1) and detrimental mutations are (2)

neutral

• Molecular clocks

• Most mutations are …

evolutionary time

• Molecular clocks

• If neutral mutations occur at a constant rate they can be used to measure _____

mutations

• Molecular clocks

• Longer periods of time since divergence allows for a greater accumulation of …

not perfectly linear

• Molecular clocks

• If graphed, it is _____ over long periods of time

• Not all organisms evolve at the same rate

• There are differences in generations times