Exam 2 Biology Study Guide Flashcards

A set of vocabulary flashcards based on the Exam 2 Study Guide covering early cell evolution, phylogenetics, prokaryote biology, and protist diversity.

Protocell

A membrane-enclosed droplet or fluid-filled structure that maintains an internal chemistry distinct from its surroundings, representing an early precursor step to modern living cells.

Radiometric Dating

A technique used to determine the absolute age of rocks and fossils based on the characteristic decay rate of radioactive isotopes contained within them.

Fossil

A preserved remnant, trace, or impression of an organism from a past geological age embedded in Earth's crust.

Endosymbiosis

A evolutionary process in which a unicellular host cell engulfs a prokaryotic cell, which then lives symbiotically within the host and eventually becomes an organelle, such as a mitochondrion or plastid.

Phylogenetics

The study of the evolutionary history and relationships among species or groups of organisms.

Systematics

A scientific discipline focused on classifying organisms and determining their evolutionary relationships.

Taxonomy

The scientific discipline concerned with naming, describing, and classifying organisms into hierarchical groups.

Binomial Nomenclature

The formal two-part system of naming species, consisting of the capitalized genus name followed by the specific epithet, both written in italics or underlined.

Sister Taxa

Groups of organisms that share an immediate common ancestor not shared by any other group, making them each other's closest relatives on a phylogenetic tree.

Basal Taxon

A lineage that diverges early in the history of a group and originates near the common ancestor of the entire tree.

Rooted Tree

A phylogenetic tree that contains a branch point representing the most recent common ancestor of all taxa shown in the diagram.

Branch Point

A node on a phylogenetic tree representing the divergence of two or more evolutionary lineages from a single common ancestor.

Homology

Similarity in characters or structural features resulting from shared evolutionary ancestry.

Analogy

Similarity between organisms due to convergent evolution in response to similar environmental pressure, rather than shared ancestry.

Divergent Evolution

The evolutionary process in which species sharing a common ancestor accumulate differences, leading to the formation of new, distinct species.

Convergent Evolution

The independent evolution of similar functional or structural features in distantly related lineages driven by similar environmental pressures.

Clade

A monophyletic group on a phylogenetic tree consisting of a common ancestral species and all of its evolutionary descendants.

Monophyletic Group

A clade containing an ancestral species and all of its descendants.

Paraphyletic Group

A evolutionary group containing an ancestral species and some, but not all, of its descendants.

Polyphyletic Group

A grouping of taxa that includes distantly related organisms but excludes their most recent common ancestor.

Symplesiomorphy

A shared ancestral character that originated in an ancestor of the taxon and is present in multiple groups.

Synapomorphy

A shared derived character that is unique to a particular evolutionary clade and absent in ancestral groups.

Outgroup

A closely related species or group of species from a lineage known to have diverged before the focus group being studied.

Ingroup

The species or set of species whose evolutionary relationships are being investigated on a phylogenetic tree.

Endospore

A thick-walled, dormant structural cell produced inside certain bacteria to withstand extreme environmental stress.

Transformation

A process of bacterial genetic recombination where a cell takes up external foreign DNA from its surrounding environment.

Transduction

The transfer of prokaryotic genes from one bacterial host cell to another by a bacteriophage virus.

Conjugation

The direct transfer of genetic material between two temporarily joined prokaryotic cells through a pilus.

Photoautotroph

An organism that harnesses light energy to synthesize organic compounds from inorganic carbon dioxide ($\text{CO}_2$).

Chemoautotroph

An organism that obtains energy by oxidizing inorganic substances and uses carbon dioxide ($\text{CO}_2$) as a carbon source.

Photoheterotroph

An organism that uses light for energy generation but must obtain carbon from organic compounds created by other organisms.

Chemoheterotroph

An organism that relies on consuming organic molecules for both its energy requirements and carbon supply.

Extremophile

An organism, frequently belonging to domain Archaea, adapted to live in environmental conditions of extreme temperature, salinity, acidity, or alkalinity.

Excavata

A major eukaryotic protist clade characterized by specialized cytoskeletal structures and often an excavated feeding groove on one side of the cell body.

SAR Clade

A large, diverse eukaryotic protist supergroup defined by DNA evidence, comprising Stramenopiles, Alveolates, and Rhizarians.

Archaeplastida

The monophyletic eukaryotic supergroup containing red algae, green algae, and land plants.

Unikonta

A eukaryotic supergroup including amoebozoans (such as slime molds and tubulinids) along with opisthokonts (animals, fungi, and related protists).