1 tree of life BIO II

Genetic marker for domain classification

Molecular characteristic

Circular chromosome

DNA molecule that forms a closed loop

Phylogenetic tree

Diagram that depicts hypothesized evolutionary relationships among species based on shared characteristics

Histone proteins

Basic proteins around which DNA is wound to form nucleosomes

Archaeal lack of known pathogens

No documented cases of archaea directly causing disease in humans

Modified vs. unmodified methionine distinction

Presence of a chemically altered start amino acid indicates a bacterial lineage

Biotechnological applications of microbes

Use of microorganisms in processes like food fermentation

Antibiotics

Chemical agents that inhibit or kill bacterial cells by targeting structures or pathways absent in eukaryotes

Nutrient cycling

Repeated movement of elements like carbon and nitrogen through biological and geological processes

Endosymbiotic origin of mitochondria

Theory that mitochondria originated from a free‑living bacterium that entered into a mutualistic relationship with an ancestral eukaryotic cell

Methane release from thawing permafrost

Emission of this greenhouse gas by archaeal methanogens as frozen soils warm

Membrane lipid ester linkage

Bond type that joins fatty acid chains to glycerol in bacterial and eukaryotic membranes

Eukaryotes

Organisms that have membrane‑bound organelles

Monophyletic group

A set of organisms that includes an ancestor and all of its descendants

LUCA

The hypothesized common ancestor from which all known life on Earth descended

Linear chromosome

DNA molecule with two distinct ends

Modified methionine (initiation)

A chemically altered form of methionine that serves as the first amino acid during translation in many bacteria

Broad‑spectrum antibiotics

Drugs that affect a wide range of bacterial species

Unmodified methionine (initiation)

The standard methionine residue that serves as the first amino acid during translation in many organisms

Side effects of broad‑spectrum antibiotics

Unintended disturbances of normal microbial communities

Nucleus

Membrane‑enclosed compartment that houses genetic material in eukaryotic cells

Cell wall (bacterial)

Rigid outer layer composed primarily of peptidoglycan

Membrane lipid ether linkage

Bond type that attaches isoprenoid chains to glycerol in certain archaeal membranes

Methanogen

Archaeal microorganisms that generate methane as a metabolic by‑product

Ether‑linked isoprenoid lipids

Membrane phospholipids composed of isoprene units joined by ether bonds

Decomposition (microbial role)

Breakdown of dead organic material by microorganisms

Primary production (by microbes)

Conversion of inorganic carbon into organic compounds through photosynthesis

Pathogenic bacteria

Bacterial species capable of causing disease in humans

Human microbiome (beneficial role)

Community of microorganisms living on and inside the human body that generally aid digestion

Peptidoglycan

A polymer of alternating sugars and peptide cross‑links that provides rigidity to certain prokaryotic cell walls

S‑layer

Proteinaceous surface layer that can replace a traditional cell wall in some prokaryotes

Cyanobacteria

Photosynthetic prokaryotes that produce oxygen and fix carbon dioxide

Carbon fixation by cyanobacteria

Process by which these photosynthetic microbes convert atmospheric carbon dioxide into organic matter

Archaea

Unicellular prokaryotes possessing a single circular chromosome

Bacteria

Unicellular prokaryotes with a single circular chromosome and a cell wall containing a sugar‑lattice cross‑linked by amino‑acid chains

Extremophile

Organism that thrives in conditions considered hostile to most life

Synapomorphy

A shared derived trait that distinguishes a particular clade from others