Phylogenetics, Macroevolution, and Paleontology

Vocabulary flashcards covering core concepts in phylogenetics, cladistics, macroevolution, origin-of-life hypotheses, paleontology, and early cellular life.

Phylogenetics

The science of figuring out relationships between organisms.

Phylogeny

A hypothesis of evolutionary interrelationships of a group of species or populations, usually shown as a tree.

Systematics

The science of classifying organisms based on their characteristics and relationships.

Taxonomy

The part of systematics concerned with naming organisms.

Cladistics

The classification of organisms based on their order of branching on an evolutionary tree (phylogenetic systematics).

Branch Point

A node on a phylogenetic tree where lineages diverge, representing a speciation event.

Monophyletic Group

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

Paraphyletic Group

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

Polyphyletic Group

A group of organisms that does not include their common ancestor, which is avoided in modern taxonomy.

Homologies

Developmental, structural, and genetic similarities between organisms due to shared ancestry.

Homoplasy

An analogous or convergent characteristic, morphology, or molecular sequence that evolved independently in separate lineages.

Ancestral Characters

Primitive characteristics inherited from ancestors.

Shared Derived Characters (Synapomorphies)

New characters relative to earlier forms that distinguish a group from related ancestral species and are most useful for determining relationships.

Parsimony

A phylogenetic criterion that selects the tree or trees with the fewest evolutionary steps.

Occam's Razor

The scientific principle stating that when competing hypotheses make the same predictions, the simpler hypothesis requiring fewer assumptions is more likely to be correct.

Outgroup

A taxon from an ancestral lineage used as a reference to compare against ingroup taxa.

Punctuated Equilibria

A model of macroevolution formulated by Gould and Eldredge in which long periods of stasis are punctuated by episodes of rapid change.

Molecular Clock

A tool based on parts of the genome accumulating mutations at a relatively steady rate, calibrated using the fossil record or mutation rates over generations.

Primitive Soup Hypothesis

The hypothesis tested by Miller and Urey demonstrating that organic monomers like amino acids could form spontaneously in a reducing early Earth atmosphere using energy from lightning and UV light.

Paleontology

The scientific study of fossil organisms.

Principle of Superposition

A relative dating principle stating that in a sequence of layered sedimentary rocks, any layer is older than the layer above it and younger than the layer below it.

Background Extinction

The normal, slow turnover rate of extinction, accounting for approximately $96\%$ of all extinctions.

Mass Extinction

A rapid, global event that causes the extinction of a broad range of species.

Photoautotrophs

Autotrophic organisms that obtain energy from sunlight using photosynthesis.

Chemoautotrophs

Autotrophic organisms that obtain energy from simple inorganic compounds such as ammonia ($\text{NH}_3$).

Stromatolites

Geological structures composed of many layers of photosynthetic cyanobacteria and sediment, representing Earth's oldest known fossils dating to approximately $3.5\text{ billion}$ years ago.

Endosymbiosis

The evolutionary process by which mitochondria and plastids (such as chloroplasts) originated as formerly small prokaryotes engulfed by host cells.