General Biology: Evolution, Prokaryotes, Viruses, Protists, and Plant Diversity

Vocabulary practice flashcards covering fundamental themes in biology, mechanisms and history of evolution, population genetics, virology, prokaryotic diversity, protist lineages, and plant adaptations.

Emergent Properties

new, unique characteristic that appears when smaller simpler parts interact to form larger, complex systems. (ex: heart and body- can’t work individually, brain/memory: a single brain cell (neuron) can’t store a memory or thing a thought, memory and consciousness work together, life.

Reductionism

The scientific approach of reducing complex biological systems into simpler, individual components (such as genes, cells, or proteins) to make them more manageable to study.

Systems Biology

An approach that explores emergent properties by studying the interactions and dynamic networks of parts within a biological system to predict how the entire system behaves over time.

Negative Feedback

A primary regulatory mechanism that functions to return an organism's internal environment back to homeostasis (e.g., insulin secretion regulating blood glucose levels, sweating).

Positive Feedback

A biological feedback mechanism in which the response drives the system further away from homeostasis (e.g., the physiological process of childbirth).

Scientific Law

what happens in nature under specific conditions, , often expressed as a mathematical equation

Scientific Theory

Expalins why or how it happens (e.g., the theory of natural selection).

Fixity of Species

The historical concept supported by ancient Greek philosophers such as Plato (400 B.C.) and Aristotle (350 B.C.) asserting that biological species do not change over time.

Natural Selection

Differential reproductive success among individuals within a population possessing diverse, heritable phenotypic traits, serving as the primary mechanism for adaptive evolution.

Homologous Structures

Anatomical features in different species that may perform diverse functions but share underlying structural similarity due to inheritance from a common ancestor. (hand bones)

Vestigial Structures

Homologous features inherited from an ancestor that have lost all or most of their original function and are morphologically reduced (e.g., pelvis remnants in whales, reduced eyes in the olm).

Convergent Evolution

The independent evolution of similar adaptations and phenotypic characteristics in unrelated species, driven by exposure to similar environmental selective pressures.

Microevolution

A change in the allelic frequencies within a biological population over successive generations.

Hardy-Weinberg Equilibrium

A theoretical model stating that allelic and genotypic frequencies in a population remain constant across generations if five conditions are satisfied: very large population size, no migration (gene flow), no mutation, random mating, and no natural selection.

Directional Selection

A mode of natural selection that consistently favors individuals exhibiting phenotypes at one end extreme of the spectrum of phenotypic variation.

Disruptive Selection

A mode of natural selection that simultaneously favors individuals at both phenotypic extremes while selecting against intermediate or average phenotypes.

Stabilizing Selection

A mode of natural selection that favors both ends reducing phenotypic variance and selecting against extreme phenotypes.

Virus

An infectious, obligate cellular parasite consisting of genetic material ($\text{DNA}$ or $\text{RNA}$) enclosed within a protective protein shell (capsid).

Virion

The complete, inert, and non-living viral particle (nucleic acid core enveloped in a protein capsid) found outside of a host cell.

Capsomere

An individual morphological protein subunit that polymerizes to form the structural outer shell (capsid) of a virus.

Bacteriophage

A specialized virus that infects bacterial host cells, typically structured with an icosahedral capsid head containing genetic material and an attached protein tail sheath with fibers.

Viroid

The smallest known infectious plant pathogen, composed entirely of a single circular strand of naked $\text{RNA}$ ($200 - 400$ nucleotide bases) lacking a protective protein capsid.

Retrovirus

A virus that carries its genetic information in $\text{RNA}$ and employs a specialized reverse transcriptase enzyme to transcribe its viral $\text{RNA}$ genome into host genomic $\text{DNA}$ (e.g., HIV).

Peptidoglycan

A rigid polymer of sugars and amino acids that forms the mesh-like structural component of bacterial cell walls.

Gram-Positive Bacteria

Bacteria characterized by a single thick peptidoglycan wall layer lacking an outer membrane, which retains crystal violet stain and appears purple under microscopy.

Gram-Negative Bacteria

Bacteria that possess a thin layer of peptidoglycan situated between two lipid bilayers, covered by an outer lipopolysaccharide membrane that stains pink/red.

Endospore

A metabolically dormant and highly resistant internal structure produced by certain bacteria (such as Bacillus anthracis) to survive harsh environmental stress, consisting of a copied chromosome encased in a tough protein coat.

Chemotaxis

The directed movement of an organism or single cell toward or away from a chemical stimulus in its environment.

Extreme Halophiles

Extremophilic archaea adapted to hypersaline environments ($5\%$ to $35\%$ salinity, such as the Dead Sea or Great Salt Lake), often having an obligate requirement for at least $9\%$ salt to survive.

Extreme Thermophiles

Extremophilic archaea possessing heat-stable proteins and $\text{DNA}$ enabling them to thrive in extremely hot environments, such as hot springs and hydrothermal vents ($90^\circ\text{C} - 120^\circ\text{C}$).

Exotoxins

Soluble, toxic proteins actively secreted by living bacterial cells into the surrounding extracellular environment (e.g., cholera toxin secreted by Vibrio cholerae).

Endotoxins

Toxic lipopolysaccharide components located in the outer membrane of gram-negative bacteria that are released primarily upon the death and lysis of the bacterial cell (e.g., Salmonella).

Endosymbiosis Theory

The theory that eukaryotic organelles (mitochondria and plastids) originated when an ancestral eukaryotic cell engulfed specialized prokaryotic cells that became mutually beneficial endosymbionts.

Diplomonads

A group of excavate protists characterized by reduced mitochondria called mitosomes, two equal nuclei, multiple flagella, and an anaerobic or parasitic lifestyle (e.g., Giardia duodenalis).

Parabasalids

A subgroup of excavate protists with modified, anaerobic mitochondria-related organelles called hydrogenosomes and multiple flagella (e.g., Trichomonas vaginalis).

Sporopollenin

A durable biological polymer that encases the zygotes of charophyte algae and the outer walls of plant spores, protecting them from desiccation and mechanical damage.

Apical Meristem

Localized regions of actively dividing cells at the growing tips of plant roots and shoots that drive primary growth and vertical elongation.

Archegonia

Multicellular female gametangia in plants that produce non-motile egg cells and protect the developing embryo after fertilization.

Antheridia

Multicellular male gametangia in plants that produce and release flagellated sperm cells.

Microphyll

A small, spine-shaped leaf containing a single unbranched vascular vein, characteristic of lycophytes.

Megaphyll

A leaf supported by a highly branched vascular network, allowing for larger surface area and enhanced photosynthetic capacity.

Heterospory

A reproductive condition in seed plants and certain lycophytes wherein the sporophyte produces two distinct types of spores: microspores (developing into male gametophytes) and megaspores (developing into female gametophytes).