Phylogenies, The Cell, and Bacteria lecture notes

Flashcards covering systematics, phylogeny, cell theory, prokaryotic and eukaryotic differences, and the classification/shapes of bacteria.

Systematics

The study of evolutionary relationships using evidence to establish the best hypothesis of how species are related.

Phylogeny

A hypothesis or representation of the evolutionary history and branching relationships of organisms, often viewed as Darwin's branching tree of life.

Convergent Evolution

A pattern where unrelated species, such as icthyosaurs, sharks, and dolphins, independently evolve similar traits.

Divergent Evolution

A pattern of evolution where species sharing a common ancestor accumulate differences, leading to speciation.

Cladogram

A diagram that depicts a hypothesis of evolutionary relationships among species.

Clade

A group consisting of a species and all its descendants that share a common ancestor, indicated by shared derived characters.

Synapomorphy

A derived character that is shared by members of a specific clade.

Homoplasy

A shared character state that was not inherited from a common ancestor, often resulting from convergent evolution.

Taxonomy

The science of classifying living things into a hierarchical system.

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

Taxonomic Classification Hierarchy

Binomial Nomenclature

A two-part naming system for species consisting of the Genus and the species (e.g., $Homo \text{ } sapiens$).

Monophyletic group

A group that includes the most recent common ancestor and all of its descendants, also known as a clade.

Paraphyletic group

A group that includes the most recent common ancestor but does not include all of its descendants.

Polyphyletic group

A group that does not include the most recent common ancestor of all its members.

3 Domains of Life

The classification of organisms into Bacteria, Archaea, and Eukarya based on RNA sequences, cell membrane components, and antibiotic sensitivity.

Domain Bacteria

Simple cells with no nucleus, containing a peptidoglycan cell wall and sensitivity to antibiotics.

Domain Archaea

Simple cells with no nucleus, lacks a peptidoglycan cell wall, and is not sensitive to antibiotics.

Domain Eukarya

Complex cells characterized by the presence of a nucleus and membrane-bound organelles.

Model Systems

Organisms used in research to generalize discoveries, such as $C. \text{ } elegans$ (roundworm) and $D. \text{ } melanogaster$ (fruit fly).

The Cell Theory

States that the cell is the basic unit of life, all living organisms are made of one or more cells, and all cells come from preexisting cells.

Common Cell Characteristics

Features shared by all cells: Cell Membrane, Cytoplasm, Ribosomes, and DNA.

Prokaryotic Cells

Small cells ($1-10 \text{ } \boldsymbol{\mu} \text{m}$) with circular DNA in a nucleoid, a cell wall, and no membrane-bound organelles.

Eukaryotic Cells

Large cells ($10-100 \text{ } \boldsymbol{\mu} \text{m}$) with linear DNA housed in a nucleus and containing membrane-bound organelles.

Endosymbiotic Theory

The theory that eukaryotic organelles like mitochondria and chloroplasts formed when free-living prokaryotic cells were engulfed by other cells.

Evidence for Endosymbiosis

Mitochondria and chloroplasts are the same size as bacteria ($1-10 \text{ } \boldsymbol{\mu} \text{m}$), contain circular DNA and their own ribosomes, and divide by binary fission.

Cyanobacteria

The first photo-synthesizers; examples include $Oscillatoria$, $Nostoc$, and $Anabaena$.

Extremophiles

Prokaryotes that thrive in extreme conditions, such as thermophiles in hot springs or halophiles in hypersaline environments like the Dead Sea.

Osmophiles

Bacteria that thrive in environments with a high sugar concentration.

Microbial Mats (Biofilms)

Colonies of bacteria, often around hydrothermal vents, that help retain microbial nutrients.

Coccus

A spherical-shaped bacterial cell.

Bacillus

A rod-shaped bacterial cell.

Spirilla

Helical-shaped or corkscrew-form bacterial cells.

Gram-positive

Bacteria with a thick peptidoglycan cell wall that traps crystal violet dye, appearing dark purple.

Gram-negative

Bacteria with a thin peptidoglycan layer and an outer membrane; they appear red after staining with safranin.