bio207 exam 3

Stromatolites: Masses of carbonate or silicate rock that represent layers of ancient phototrophic microbial communities, specifically cyanobacterial communities, and serve as fossil evidence of early life.

Prebiotic soup: A model proposing that small organic molecules arose non-biologically (abiotically) from simple reduced chemicals (NH3 and CH4) sparked by energy sources like lightning, leading eventually to cells

Photoferrotrophy: A metabolic process for gaining energy, likely used by early microbes, that involved light-driven oxidation of ferrous iron .

Clade: A group of organisms consisting of a single common ancestor and all of its descendants; a monophyletic group.

Phylogeny: The evolutionary history and relationships among a group of organisms, often represented visually by a phylogenetic tree.

Monophyletic group: A group that consists of a common ancestor and all of its descendants; a clade.

Natural selection: The process where organisms better adapted to their environment tend to survive and produce more offspring

Adaptation: An evolutionary process where a population becomes better suited to its habitat; also refers to a trait that is a result of this process.

Drift: Evolutionary change that occurs due to random chance, particularly in small populations (also known as genetic drift).

Molecular clock: The temporal information contained in a macromolecular sequence, based on the principle that random, non-selected mutations accumulate at a steady rate over generations, proportional to the time since divergence. The small subunit rRNA (SSU rRNA) gene (16S for bacteria, 18S for eukaryotes) is the most widely used molecular clock

Horizontal Gene Transfer (HGT): The transfer of genetic material between organisms that are not parent and offspring, contributing to microbial genome evolution and obscuring phylogenetic relationships

Vertical Gene Transfer (VGT): The transfer of genetic material from parent to offspring

Average Nucleotide Identity (ANI): A measure of the genomic similarity between two organisms, calculated by comparing orthologs (genes of the same function). It is a key criterion for defining prokaryotic species, with greater than or equal to 95% ANI generally indicating the same species

Core genome: The set of genes shared by all strains within a species or other taxonomic group.

Pangenome: The total set of genes present in all strains of a species or other taxonomic group.

Mutualism: A type of symbiotic relationship where both organisms benefit.

Parasitism: A symbiotic relationship where one organism (the parasite) benefits at the expense of the other (the host).

Endosymbiosis: The most intimate kind of symbiosis where one partner (the endosymbiont) grows within the body or, more strictly, inside the cells of another organism (the host)