The History of Life on Earth & Phylogeny and the Tree of Life

Flashcards covering key vocabulary terms from lectures on 'The History of Life on Earth' and 'Phylogeny and the Tree of Life'.

Macroevolution

Large-scale evolutionary changes, such as the origin of terrestrial vertebrates or mass extinctions.

Abiotic synthesis of small organic molecules

The first stage in the chemical and physical processes on early Earth that may have produced very simple cells.

Protocells

Packages of molecules that may have been fluid-filled vesicles with a membrane-like structure, exhibiting replication and metabolism.

Oparin and Haldane

Scientists who proposed in the 1920s that Earth's early atmosphere was a reducing environment, suitable for organic molecule formation.

Miller and Urey

Scientists who conducted experiments in 1953 demonstrating the abiotic synthesis of organic molecules in a simulated reducing atmosphere.

RNA monomers

Simple molecules that can spontaneously form into polymers without the aid of enzymes or cells under certain conditions.

Ribozymes

RNA molecules that function as catalysts, capable of catalyzing various biochemical reactions.

Fossil Record

The chronological collection of life's remains preserved in sedimentary rock layers (strata), biased toward species that existed for a long time, were abundant, widespread, and had hard parts.

Sedimentary rocks

Rocks formed from accumulated layers of sediment, which are the richest source of fossils.

Radiometric dating

A method used to determine the absolute ages of fossils based on the constant decay rate of a 'parent' isotope to a 'daughter' isotope.

Half-life

The time required for half of a radioactive 'parent' isotope to decay into its stable 'daughter' isotope.

Geologic record

A timeline of Earth's history divided into eons (Archaean, Proterozoic, Phanerozoic) and eras (Paleozoic, Mesozoic, Cenozoic).

Phanerozoic Eon

The eon encompassing multicellular eukaryotic life, divided into the Paleozoic, Mesozoic, and Cenozoic eras.

Stromatolites

The oldest known fossils, dating back 3.5 billion years, formed by the accumulation of sedimentary layers on bacterial mats.

Oxygen revolution

The period from 2.7 to 2.3 billion years ago when atmospheric O2 levels dramatically increased due to oxygenic photosynthesis, leading to the extinction of many prokaryotic groups.

Endosymbiont theory

Proposes that mitochondria and plastids (like chloroplasts) were formerly small prokaryotes living as endosymbionts within larger host cells.

Endosymbiont

A cell that lives within another host cell.

Multicellularity

The evolutionary development of organisms composed of multiple cells, leading to a second wave of diversification among eukaryotes, giving rise to algae, plants, fungi, and animals.

Vascular tissue

Specialized plant tissue that transports materials internally, appearing in plants by about 420 million years ago.

Tetrapods

Vertebrates with four limbs, which evolved from lobe-finned fishes around 365 million years ago and were among the first animals to colonize land.

Plate Tectonics

The scientific theory describing the large-scale motion of Earth's lithosphere, leading to continental drift, mountain formation, island creation, and earthquakes.

Pangaea

A supercontinent that formed about 250 million years ago, leading to significant global environmental changes and mass extinctions.

Mass extinction

A period of disruptive global environmental changes resulting in the disappearance of a large percentage of Earth's species, with more than 50% going extinct in each of the five major events.

Permian extinction

The most severe mass extinction event, occurring 251 million years ago, causing the extinction of about 96% of marine animal species, linked to intense volcanism and global warming.

Cretaceous mass extinction

Occurred 65.5 million years ago, leading to the extinction of half of all marine species and many terrestrial plants and animals, including most dinosaurs, likely caused by a meteorite impact (Chicxulub crater).

Adaptive radiation

The rapid evolution of diversely adapted species from a common ancestor, often following mass extinctions, the evolution of novel characteristics, or the colonization of new regions.

Heterochrony

Evolutionary change in the rate or timing of developmental events, which can significantly impact an organism's body shape.

Paedomorphosis

A type of heterochrony where the rate of reproductive development accelerates compared with somatic development, resulting in sexually mature species retaining juvenile body features.

Homeotic genes

Genes that control the placement and organization of body parts during development.

Hox genes

A class of homeotic genes that provide specific positional information during an organism's development, influencing where body parts are formed.

Exaptations

Structures that evolve in one context or for one function but are later co-opted or adapted for a different function.

Phylogeny

The evolutionary history of a species or a group of related species.

Systematics

A scientific discipline focused on classifying organisms and determining their evolutionary relationships, using fossil, molecular, and genetic data.

Taxonomy

The ordered division and naming of organisms.

Binomial Nomenclature

The two-part naming system for species established by Linnaeus, consisting of the Genus and specific epithet.

Genus

The first part of a scientific species name, which is capitalized and groups closely related species.

Specific epithet

The second part of a scientific species name, unique for each species within its genus.

Taxon

A formal taxonomic unit at any level of the hierarchical classification system (e.g., domain, kingdom, phylum, class, order, family, genus, species).

Phylogenetic Tree

A diagram representing a hypothesis about the evolutionary relationships among organisms, with branches representing the divergence of lineages.

PhyloCode

A proposed system of biological nomenclature that only recognizes groups consisting of a common ancestor and all its descendants (clades).

Sister taxa

Groups of organisms that share an immediate common ancestor and are each other's closest relatives on a phylogenetic tree.

Rooted tree

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

Basal taxon

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

Polytomy

A branch point in a phylogenetic tree from which more than two descendant groups emerge, indicating an unresolved pattern of divergence.

Homologies

Similarities between organisms (phenotypic or genetic) that are due to shared ancestry.

Analogy

Similarity between organisms that is due to convergent evolution rather than shared ancestry.

Convergent evolution

The independent evolution of similar features in different lineages, often as a result of similar environmental pressures or natural selection.

Homoplasies

Analogous structures or molecular sequences that evolved independently in different lineages.

Molecular systematics

A field that uses DNA and other molecular data to determine evolutionary relationships among organisms.

Cladistics

A phylogenetic approach that groups organisms by common descent, forming clades.

Clade

A group of species that includes an ancestral species and all of its descendants; a monophyletic group.

Monophyletic group

A valid clade consisting of a common ancestral species and all of its descendants.

Paraphyletic grouping

A grouping that consists of an ancestral species and some, but not all, of its descendants.

Polyphyletic grouping

A grouping that consists of various species that lack a common ancestor within the group.

Shared ancestral character

A character that originated in an ancestor of a particular taxon.

Shared derived character

An evolutionary novelty that is unique to a particular clade.

Maximum parsimony

A principle that assumes the most likely phylogenetic tree is the one that requires the fewest evolutionary events (e.g., character changes or genetic mutations).

Maximum likelihood

A method for inferring phylogenetic trees that, given certain rules about how DNA changes over time, identifies the tree reflecting the most probable sequence of evolutionary events.

Phylogenetic bracketing

An approach that allows the prediction of features of an ancestor by inferring that all descendants in a clade share similar traits unless evidence suggests otherwise.

rRNA genes

Genes that code for ribosomal RNA, which change relatively slowly and are useful for investigating ancient branching points in evolutionary history.

mtDNA

Mitochondrial DNA, which evolves rapidly and is therefore useful for exploring more recent evolutionary events.

Gene duplication

A process that increases the number of genes in a genome, providing more opportunities for evolutionary change and often leading to gene families.

Orthologous genes

Homologous genes found in different species due to speciation, typically present as a single copy in each genome.

Paralogous genes

Homologous genes within a single species that arise from gene duplication, often evolving new functions.

Molecular clock

A method using constant rates of evolution in some genes to estimate the absolute time of evolutionary change between species or gene duplication events.

Neutral theory

A theory suggesting that much evolutionary change at the molecular level, particularly in noncoding DNA or at third base positions of codons, has no effect on fitness and is not influenced by natural selection.

Three-domains

A classification system (Bacteria, Archaea, and Eukarya) reflecting broad distinctions in ribosomal RNA, indicating that eukaryotes and archaea are more closely related to each other than to bacteria.

Horizontal gene transfer

The movement of genes from one genome to another, not through parent-offspring inheritance, but via mechanisms like plasmids, viral infection, or fusion of organisms.

Ring of life

A proposed model for depicting early evolutionary relationships, suggesting that eukaryotes arose as a fusion between a bacterium and an archaean, rather than a single common ancestor for all life.