11TH BIO CH1 THREE DOMAIN SYSTEM OF CLASSIFICATION AND DOMAIN ARCHAEA

The defining hallmarks of Domain Eukarya are the presence of true, membrane-bound organelles (like mitochondria) and a distinct nucleus containing linear chromosomes.

Organisms capable of anaerobic respiration or fermentation switch to these metabolic pathways to generate ATP when oxygen is unavailable.

The presence of a peptidoglycan cell wall and asexual reproduction via binary fission are defining structural and life-cycle traits of Domain Bacteria.

Treponema pallidum, the causative agent of syphilis, is a classic example of a spirochaete, recognized by its flexible, spiral shape.

The prefix 'staphylo-' translates to "bunch of grapes," perfectly describing the clustered arrangement of Staphylococci bacteria.

The cytoskeleton acts as a dynamic internal scaffolding, maintaining cell shape, organizing organelles, and facilitating motility.

Mutualism is a type of symbiotic relationship where both participating species derive a biological or ecological benefit from the interaction.

Sexual reproduction mixes genetic material from two parents via meiosis and fertilization, greatly increasing the genetic variation within a population.

Peptidoglycan is a component of bacterial cell walls, not the eukaryotic cytoskeleton, which consists of microtubules, microfilaments, and intermediate filaments.

Halophiles (from the Greek word for "salt-loving") are microorganisms that require highly saline environments to survive.

Autotrophs can synthesize their own organic food sources. Anabaena and Spirulina use sunlight to perform photosynthesis.

Prokaryotes (Bacteria) lack a membrane-bound nucleus, so their DNA resides in a nucleoid region, whereas eukaryotes have a defined nucleus.

Plasmids can be transferred horizontally between bacteria, allowing for the rapid spread of beneficial traits like antibiotic resistance.

Chloroplasts contain chlorophyll and are the sites of photosynthesis. They are unique to autotrophic eukaryotes like plants and algae.

The endosymbiotic theory posits that mitochondria and chloroplasts originated as free-living bacteria that were engulfed by early eukaryotic cells.

Histone proteins act like spools, allowing the long linear DNA molecules to wrap around them and condense into compact chromatin.

Unlike bacteria, eukaryotes have their genetic material organized into multiple linear chromosomes tightly packaged within a nucleus.

Anabaena is a genus of filamentous cyanobacteria that are known for their photosynthetic and nitrogen-fixing abilities.

Actinobacteria are a group of Gram-positive bacteria known for their high G+C DNA content, and they include important soil dwellers and pathogens.

Proteobacteria is a major and highly diverse phylum of Gram-negative bacteria that includes E. coli and nitrogen-fixing Rhizobium.

Fimbriae help bacteria attach to host cells or surfaces, while specialized pili are involved in conjugation (the transfer of DNA).

Flagella are long, whip-like appendages extending from the cell surface that act as propellers to provide motility to bacteria.

The prefix 'strepto-' indicates a chain-like arrangement of cells, such as in Streptococcus species.

Cocci (singular: coccus) refer to bacteria that are spherical, round, or ovoid in shape.

Vibrio bacteria, such as Vibrio cholerae, have a distinctive curved or comma-like shape.

Binary fission is a form of asexual reproduction where a parent bacterial cell grows and divides into two genetically identical daughter cells.

Plasmids are extra-chromosomal, circular DNA molecules that can carry advantageous genes, such as those responsible for antibiotic resistance.

Unlike eukaryotes which have linear chromosomes, most bacteria possess a single, circular chromosome located in the nucleoid region.

True bacteria (Eubacteria) have cell walls made primarily of peptidoglycan, which is a structural polymer of sugars and amino acids.

The five-kingdom system proposed by Whittaker placed all prokaryotic organisms, including bacteria, into the single kingdom Monera.

These enzymes evolved in hyperthermophilic environments, meaning they remain stable and do not denature during the boiling cycles required for PCR.

Bacteria and Eukaryotes utilize unbranched fatty acids with ester linkages. Archaea use branched chains with ether linkages.

Acidophilic Archaea can thrive in the highly acidic and toxic environments associated with biomining, helping to leach metals from raw ores.

Methanogens perform anaerobic digestion of organic waste matter, effectively treating the sewage while producing methane biogas.

The combination of an extreme environment, ether lipid linkages, and the absence of peptidoglycan are the exact defining features of Archaea.

Archaea possess transcription and translation machinery (like RNA polymerases and ribosomes) that are much more similar to eukaryotes than to bacteria.

Because they are prokaryotic and morphologically similar under a microscope, they were originally classified as a subset of bacteria.

Peptidoglycan is a defining structural molecule of bacterial cell walls, whereas archaeal cell walls lack it entirely.

The five-kingdom system grouped all prokaryotes in Monera, but phylogenetic analysis shows Archaea and Bacteria are fundamentally distinct evolutionary lineages.

Ether linkages and branched lipid chains provide high chemical and thermal stability, allowing Archaea to survive in extreme heat or acidity.

Molecular and genetic evidence indicates that Archaea share a more recent common ancestor with Eukarya than they do with Bacteria.

Methanogens reside in the human gut and produce methane gas during the anaerobic breakdown of complex carbohydrates.

Archaeal enzymes like Taq polymerase are highly thermostable, making them essential for DNA replication techniques like PCR.

Halobacteria are extreme halophiles, meaning they thrive in environments with very high salt concentrations, like the Dead Sea.

Methanogenesis, the production of methane as a metabolic byproduct, is exclusively performed by certain Archaea known as methanogens.

Unlike bacterial cell walls, archaeal cell walls completely lack peptidoglycan. They often contain pseudopeptidoglycan instead.

Archaea have branched isoprene chains in their membrane lipids, unlike the unbranched fatty acids found in bacteria and eukaryotes.

Archaeal cell membranes are unique because their lipids contain ether linkages, providing high stability in extreme environments.

Archaea reproduce asexually through binary fission, fragmentation, or budding. They do not undergo mitosis or meiosis.

Like bacteria, archaeans are microscopic, typically ranging from 0.1 to 15 micrometers in diameter.

Archaios translates to "ancient," reflecting the idea that these organisms evolved early in Earth's history.

Phylogeny is the study of the evolutionary history and relationships among individuals or groups of organisms.

The three domains are Archaea, Bacteria, and Eukarya. This system divided the former Monera kingdom into two distinct domains.

Carl Woese proposed the three-domain system of life in 1990 based on differences in 16S ribosomal RNA.

Kingdom Monera was the group that contained all unicellular organisms lacking a true nucleus, encompassing all prokaryotes.

Robert Whittaker proposed the five-kingdom system in 1969 to better classify living organisms based on their cellular structure and mode of nutrition.