Biological Diversity – Taxonomy & Microbial Physiology

A set of vocabulary flashcards covering taxonomic hierarchy, microbial oxygen requirements, Gram staining, cell structures, metabolic categories, and key molecular features in prokaryotes and eukaryotes.

Taxonomic Rank

Hierarchical system of classification that arranges taxa from most general to most specific.

Microbiome

The total community of microorganisms (bacteria, fungi, etc.) living in and on the human body.

Obligate Aerobe

Microbe that requires molecular oxygen for survival and metabolism.

Obligate Anaerobe

Microbe that cannot survive in the presence of molecular oxygen.

Facultative Anaerobe

Organism that grows in oxygen but can switch to anaerobic metabolism when oxygen is absent; common in mammals.

Gram-Positive Bacterium

Bacterium that stains purple, has a thick peptidoglycan cell wall, lacks an outer membrane, and contains teichoic acids but no endotoxins.

Gram-Negative Bacterium

Bacterium that stains pink, possesses a thin peptidoglycan layer plus an outer membrane rich in LPS, and releases endotoxins upon lysis.

Endotoxin

Toxic substance (often LPS) released when Gram-negative bacteria are broken down, causing inflammatory responses.

Lipopolysaccharide (LPS)

Component of the outer membrane of Gram-negative bacteria that provides structural integrity and endotoxin activity.

Peptidoglycan

Mesh-like polymer forming the bacterial cell wall; thick in Gram-positive, thin in Gram-negative cells.

Endospore

Durable, dormant structure some bacteria produce to survive extreme environmental conditions.

Prokaryotic Cell

Cell lacking a membrane-bound nucleus/organelles; contains circular DNA in a nucleoid region.

Eukaryotic Cell

Cell with membrane-bound nucleus, multiple linear chromosomes, and specialized organelles.

Domain Archaea

Prokaryotic domain whose members have histones and introns, pseudomurein cell walls, and often inhabit extreme environments.

Domain Bacteria

Prokaryotic domain lacking histones and introns, characterized by peptidoglycan cell walls.

Heterotroph

Organism that obtains both energy and carbon by consuming organic compounds produced by other organisms.

Autotroph

Organism that synthesizes organic molecules from inorganic carbon sources such as CO₂.

Chemoheterotroph

Organism that uses organic compounds as both an energy source and a carbon source.

Chemoautotroph

Organism that obtains energy from inorganic chemicals (e.g., NH₃, H₂S) and fixes CO₂ into biomass.

Photoheterotroph

Organism that harnesses light energy but obtains carbon by consuming organic compounds.

Photoautotroph

Organism that uses light energy to convert inorganic CO₂/HCO₃⁻ into organic molecules via photosynthesis.

Histones

DNA-wrapping proteins present in eukaryotes and archaea but absent in bacteria.

Introns

Non-coding sequences within genes found in eukaryotes and archaea, generally absent in bacterial genes.

Pseudomurein

Polysaccharide component of some archaeal cell walls, structurally similar to but chemically distinct from peptidoglycan.

Decomposer

Organism that breaks down dead organisms and non-living organic material, recycling nutrients into the ecosystem.