Biology: Prokaryotes, Early Life, and Endosymbiosis

Flashcards covering the characteristics, morphology, reproduction, gene transfer, and evolutionary significance of prokaryotes, as well as the endosymbiotic theory.

Anaerobic organisms

Organisms that can grow without oxygen, representing the earliest forms of life on Earth.

Cyanobacteria

Photosynthetic organisms (also known as blue-green algae) that evolved and added oxygen to Earth's early atmosphere.

Stromatolite

A sedimentary structure formed when minerals are precipitated from water by prokaryotes in a microbial mat, providing evidence of the oldest bacterial life ($3.9\text{ to }3.6\text{ billion years ago}$).

Age of the Earth

Approximately $4.54\text{ billion years old}$, with the first prokaryotes appearing around $3.9\text{ billion years ago}$.

Thermophiles

Organisms adapted to survive and thrive in extreme temperatures.

Halophiles

Organisms adapted to live in highly salty environments.

Cocci

Prokaryotes with a spherical basic shape.

Bacilli

Prokaryotes with a rod-like basic shape.

Spirilla

Prokaryotes with a spiral or corkscrew basic shape.

Spirochetes

Spiral bacteria that can burrow into host tissue, avoid antibiotics, and lie dormant for years (such as the causative agent of syphilis).

Capsule

A specialized third protective layer in some prokaryotes that enables surface attachment and protects against dehydration.

Flagella

Tail-like appendages in prokaryotes primarily utilized for locomotion and swimming.

Pili

Hair-like surface appendages on prokaryotes used for attaching to surfaces and for the transfer of genetic material during conjugation.

Plasmids

Small, circular pieces or extra fragments of DNA present in prokaryotes separate from the main circular chromosome.

Binary fission

An asexual mode of reproduction in prokaryotes wherein the cell replicates its circular chromosome and divides directly in half.

Transformation

A mechanism of horizontal gene transfer where a bacterial cell imports and incorporates free DNA from its surrounding environment (from alive or dead bacteria).

Transduction

A process of horizontal gene transfer in which viruses that infect bacteria transfer DNA from one bacterium to another.

Conjugation

The transfer of DNA (typically a plasmid) from one bacterium to another through a direct cytoplasmic connection via a pilus.

Pathogenic prokaryotes

Disease-causing prokaryotes, all of which belong to domain Bacteria (Archaea do not cause disease).

Microbial bioremediation

The deliberate application and use of prokaryotes to break down and remove pollutants from the environment.

Commensalism

A symbiotic relationship in which a bacterium benefits from its association with a human host while the host is neither helped nor harmed.

Endosymbiotic theory

The evolutionary theory stating that eukaryotes evolved from one prokaryotic cell engulfing another, which then lived inside the host and coevolved until the cells became inseparable.