Biology 151 Chapter 4

Place the following in order from the most inclusive to the least inclusive taxonomic levels: 1) Class 2) Domain 3) Family 4) Species 5) Kingdom 6) Order 7) Phylum 8) Genus

1) Domain 2) Kingdom 3) Phylum 4) Class 5) Order 6) Family 7) Genus 8) Species

If a characteristic is found in an _____(1) group it is considered a shared ancestral character, while if only some of the organisms within a tree share a characteristic it is considered a shared _____(2) character

1) ancestral 2) derived

This pattern repeats over and over as one goes through the phylogenetic tree of life:

1. A change in the genetic makeup of an organism leads to a new trait that enhances fitness and as a result becomes more prevalent in the group. 2. Many organisms descend from this point and have this trait. 3. New variations may arise after that branch point: some are adaptive and persist, leading to new traits. 4. With new traits, a new branch point is determined (go back to step 1 and repeat).

Binomial Nomenclature

Classification system in which each species is assigned a two-part scientific name

"Unrooted" Trees

Don't show a common ancestor but do show relationships among species.

Branch Point

A point in the phylogenetic tree that indicates the last common ancestor of different groups or a single lineage evolved into a distinct new one.

Cell Theory

- Cells are the smallest living thing - Therefore all living things are composed of cells - All cells come from other cells

phylogenetic tree

A diagram used to reflect evolutionary relationships among organisms or groups of organisms. Scientists consider phylogenetic trees to be hypotheses of the evolutionary past since one cannot go back to confirm the proposed relationships. In other words, a "tree of life" can be constructed to illustrate when different organisms evolved and to show the relationships among different organisms. Unlike a taxonomic classification diagram, a phylogenetic tree can be read like a map of evolutionary history. Additionally, phylogenetic tree structure rotation at branch points does not change the information.

Basal Taxon

A lineage that evolved early from the root and remains unbranched or a branch on a phylogenetic tree that has not diverged significantly from the root ancestor

Cladistics

A system that organizes the homologous traits by sorting organisms into clades: groups of organisms that descended from a single ancestor.

The taxonomic classification system (Linnaean system)

Called the Linnaean system after its inventor, Carl Linnaeus, uses a hierarchical model. Moving from the point of origin, the groups become more specific, until one branch ends as a single species.

Specific Epithet

Second part of a scientific name.

Systematics

Information is used to organize and classify organisms based on evolutionary relationships in a scientific field.

"Rooted" Trees

Means there is a single ancestral lineage to which all organisms represented in the diagram are related. *In a rooted tree, the branching indicates evolutionary relationships.*

Polytomy

Multiple lineages that arise from a common branch point and serves to illustrate where scientists have not definitively determined all of the relationships.

Convergent Evolution

Occurs when organisms that are NOT closely related become more similar over long periods of time.

Maximum Parsimony

This concept predicts that the pathway with the least number of events that could have occurred is the most likely one. Scientists apply this concept to aid in figuring out the most likely evolutionary relationships

Phylogeny

Phylogeny describes the relationships of an organism, which organisms from which it is thought to have evolved, to which species it is most closely related, and so forth.

Phylogenetic Relationships

Provide information on shared ancestry but not necessarily on how organisms are similar or different.

Homoplasy

similar (analogous) structure or molecular sequence that has evolved INDEPENDENTLY in two species.

Plesiomorphy

Shared Ancestral Characteristic

Synapomorphy

Shared Derived Characteristic

Homologous Structures

Structures that have the same evolutionary origin even though they may now look different or have different functions due to shared common ancestry.

What are somethings that you cannot determine from looking at a phylogenetic tree?

The actual evolutionary ages of the species in the tree. Patterns of phenotypic similarities. Whether sister taxa evolved from each other.

Taxonomy

The study of the classifications in order to classify them into the appropriate taxonomic groups, such as kingdom, phylum, class etc. ("Arrangement Law")

Analogous Structures

Traits are the result of similar selection pressures (a similar environment) due to convergent evolution.

Analogy

When characteristics bearing similar functions occur because of environmental constraints.

Sister Taxa

When two lineages stem from the same branch point or groups of organisms that are more closely related to each other than other groups.

Divergent Evolution

When two or more species sharing a common ancestor become more different over time.

Clades

groups of organisms that shared ancestry in a branch(descended from a single ancestor.