Three-Domain System and Molecular Classification (Notes Review)

Flashcards cover molecular-based classification (three-domain system), LUCA, Asgard archaea, prokaryotes vs. eukaryotes, ribosomes and rRNA, cell size implications, protein processing, and horizontal gene transfer.

What is the correct order of taxonomic groups from most inclusive to least inclusive?

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

What system classifies life based on molecular information, comparing genetic material across organisms?

The three-domain system (Bacteria, Archaea, Eukarya).

Which molecular feature is primarily used to classify organisms into the three domains?

Ribosomal RNA (rRNA) gene sequences.

Under the three-domain system, into which two domains is Kingdom Monera split?

Bacteria and Archaea.

What does LUCA stand for and represent?

Last Universal Common Ancestor; the most recent common ancestor of all current life.

What notable group discovered in 2017 links Archaea to potential origins of Eukarya, and what genes does it carry?

Asgard archaea; they carry eukaryotic signature genes related to the cytoskeleton and phagocytosis, suggesting a link to eukaryotes.

Which domains are prokaryotes and which domain contains eukaryotes?

Bacteria and Archaea are prokaryotes; Eukarya are eukaryotes.

What is a key difference between bacterial and archaeal cell walls?

Bacteria have peptidoglycan in their cell walls; Archaea lack peptidoglycan and have different cell wall chemistries.

What is the nucleoid in a prokaryotic cell?

The region containing the circular chromosome, not enclosed by a membrane.

Why is the surface area to volume ratio important for cells?

It governs exchange of nutrients and wastes across the membrane; as cells grow, SA:V decreases, making exchange less efficient.

Where is energy production localized in living cells, and why does size matter?

Energy production largely occurs on membranes; smaller cells have a higher SA:V, aiding efficient energy and substance exchange.

What is the pathway of protein processing in eukaryotic cells after translation?

Rough endoplasmic reticulum → Golgi apparatus → vesicles to final destinations; post-translational modifications occur along the way.

What is horizontal gene transfer?

The movement of genetic material between organisms other than by vertical descent, contributing to mosaic genomes.

What are ribosomes made of?

Proteins and ribosomal RNA (rRNA) components.

Why are ribosomal RNA sequences useful for assessing evolutionary relationships?

They are conserved and can be compared across species to infer relatedness and build phylogenies.

What evidence supports a close relationship between Asgard archaea and Eukarya?

Asgard archaea possess genes related to the cytoskeleton and phagocytosis, implying a link to the origin of eukaryotes.

What is the nucleoid compared to the nucleus?

Nucleoid is the DNA-containing region in prokaryotes without a membrane, unlike the membrane-bound nucleus in eukaryotes.