Exam 2: Prokaryotes, Protists, and Plant Evolution

Vocabulary practice flashcards covering prokaryotic structure, genetics, extremophiles, protist diversity, endosymbiosis, and the evolutionary transition to seed and flowering plants.

Hydrothermal Vent Prokaryotes

Prokaryotes discovered near deep-sea hydrothermal vents that serve as the best biological model for the earliest living organisms on Earth.

Alpha Proteobacteria

The specific bacterial lineage from which modern mitochondria are thought to have descended via endosymbiosis.

Endosymbiosis

The evolutionary process in which an engulfed prokaryotic cell established a permanent mutualistic relationship inside a host cell, accounting for the relocation of organelle genes to the nuclear genome.

Archaea

The domain of prokaryotic extremophiles that includes organisms capable of living in high-temperature environments, such as hot springs at $95^\circ\text{C}$.

Symbiotic Pathogen

A symbiotic bacterium that lives within a host organism (such as the human intestine) and causes disease.

Cyanobacteria

Photosynthetic prokaryotes that release oxygen and are the evolutionary ancestors of chloroplasts found in green algae and land plants.

Gram-Negative Cell Wall

A bacterial cell wall containing relatively little peptidoglycan and an outer membrane, which enables survival in the presence of penicillin.

Bacterial vs. Eukaryotic Flagella

Flagella in eukaryotes and bacteria that evolved independently as an example of convergent evolution, distinguished by different protein structures and distinct mechanisms of movement.

Endospore

A durable, dormant bacterial structure capable of surviving boiling; when regenerating without original plasmids, it lacks plasmid-borne antibiotic-resistance genes.

Transduction

A horizontal gene transfer mechanism in prokaryotes that specifically relies on bacteriophages (viruses) to carry DNA between cells.

Transformation

A horizontal gene transfer mechanism in which a bacterial cell takes up foreign DNA directly from the surrounding environment without viral participation.

Conjugation

A prokaryotic horizontal gene transfer process where genetic material, such as plasmids, is transferred directly between two cells temporarily connected by a mating bridge or pilus.

Horizontal Gene Transfer

The umbrella term for the non-reproductive movement of genetic material between independent organisms, encompassing transformation, transduction, and conjugation.

Secondary Endosymbiosis

The evolutionary event in which a heterotrophic eukaryotic host engulfs a photosynthetic eukaryote, confirmed when the resulting plastids are enclosed by multiple membranes.

Protists

A highly diverse group of mostly single-celled organisms unified by the shared fundamental characteristic of being eukaryotic.

Gametic Life Cycle

A life cycle in which diploid ($2n$) cells undergo meiosis to directly produce haploid ($1n$) gametes.

Plasmodium

The apicomplexan protist parasite responsible for malaria, which immediately infects human liver cells after entering the bloodstream from a mosquito bite.

Dinoflagellates

Aquatic protists characterized by possessing two flagella, often exhibiting mixotrophic or photosynthetic lifestyles.

Diatoms

Photosynthetic protists characterized by unique, glass-like tests (cell walls) composed of silicon dioxide.

Blade

The leaf-like photosynthetic anatomical structure characteristic of brown algae.

Convergent Evolution in Protists

The independent evolution of similar morphological traits and lifestyles in unrelated lineages, exemplified by the historical grouping of slime molds with true fungi.

Plant-Fungal Colonization Association

The symbiotic partnership between early terrestrial plants and soil fungi that aided early plants in extracting essential mineral nutrients from soil.

Embryophytes

The plant taxon (Plantae) defined by the retention and nourishment of the developing diploid zygote/embryo within maternal gametophyte tissues.

Sporopollenin

A durable, resistant biological polymer that coats plant spores and pollen grains, preventing them from drying out and sustaining structural integrity.

Alternation of Generations

A life cycle shared by all land plants that alternates between a multicellular haploid ($1n$) gametophyte and a multicellular diploid ($2n$) sporophyte.

Sporophyte

The diploid ($2n$) multicellular generation of a plant that develops from a zygote and produces spores via meiosis.

Gametophyte

The haploid ($1n$) multicellular generation of a plant that produces haploid gametes through mitosis.

Sporophylls

Modified leaves in vascular plants, such as ferns, that bear sporangia which produce spores.

Flagellated Sperm

Motile reproductive cells requiring water to reach the female gamete, making the desert persistence of true mosses and ferns ecologically remarkable.

Micropyle

A small opening in the integuments of an ovule through which a pollen grain or pollen tube enters to reach the female gametophyte.

Seed

A protective dispersal unit unique to seed-producing plants, consisting of an embryo packaged alongside a nutrient store within a durable outer coat.

Pollen

A protective structure encasing the male microgametophyte, enabling fertilization without the need for environmental water.

Stigma

The receptive surface located at the tip of the angiosperm carpel that is specialized for receiving pollen grains.

Fruit

The mature, thickened ovary wall directly produced by the female sporophyte of an angiosperm, whose yield can be measured to assess pollination success.

Stomata

Specialized microscopic pores on plant leaves and stems that regulate photosynthetic gas exchange and control transpiration water loss.

Phototrophs

Organisms that utilize light as their primary source of energy for metabolic processes.

Chemotrophs

Organisms that obtain energy through the oxidation of environmental chemical compounds rather than from sunlight.

Fimbriae

Short, hair-like protein appendages on bacterial cell surfaces that function primarily in adhering to substrates or host tissues.

Pili

Bacterial surface appendages that are typically longer than fimbriae and participate in cell-to-cell contact and DNA transfer during conjugation.

Endosperm

A nutrient-rich, typically triploid ($3n$) tissue inside angiosperm seeds that nourishes the developing embryo sporophyte.

Carpel

The female reproductive organ of a flower composed of the stigma, style, and ovary containing one or more ovules.

Stamen

The pollen-producing male reproductive organ of a flower, consisting of a terminal anther supported by a filament.