General Biology Review: Phylogenetics, Diversity, Anatomy, and Physiology

Comprehensive vocabulary flashcards covering evolutionary systematics, virology, prokaryotes, protists, fungi, animal diversity, plant morphology and transport, endocrinology, reproductive biology, animal development, and neurophysiology.

Systematics

The study of the diversity of organisms and their evolutionary relationships, comprising taxonomy and phylogenetics.

Taxon

A taxonomic grouping or unit of organisms at any particular level of the hierarchical classification system (plural: taxa).

Homologous Characters

Anatomical traits or character states that share a common evolutionary history and are inherited from a common ancestor, exhibiting the same basic anatomical patterns despite potentially differing functions.

Analogous Characters

Independently acquired characteristics that perform similar functions due to similar selective pressures and environments rather than shared ancestry; a result of convergent evolution.

Basal Taxon

A lineage that diverged early in the evolutionary history of a group and lies on a branch originating near the common ancestor of the group.

Shared Derived Character (SDC)

An evolutionary novelty or character state that is unique to a particular clade and not found in its ancestral lineage.

Monophyletic Group

A valid clade consisting of an ancestral species and all of its descendants.

Paraphyletic Group

An evolutionary grouping that consists of an ancestral species and some, but not all, of its descendants.

Polyphyletic Group

A grouping of distantly related species that does not include their most recent common ancestor.

Capsid

The protein shell that encloses a viral genome, built from protein subunits called capsomeres, which determines viral shape and aids in host cell attachment.

Virulent Phage

A bacteriophage that reproduces exclusively by a lytic cycle, leading to the destruction and lysis of the host bacterial cell at the end of infection.

Temperate Phage

A bacteriophage capable of reproducing using both the lytic and lysogenic cycles, allowing its DNA to integrate into the bacterial chromosome as a prophage without destroying the host.

Peptidoglycan

A mesh-like polymer of sugars and polypeptides found in the cell walls of domain Bacteria that maintains cell shape and prevents osmotic bursting in hypotonic environments.

Taxis

An oriented movement toward (positive) or away from (negative) a stimulus, such as light (phototaxis).

Conjugation

The transfer of genetic material between two prokaryotic cells that are temporarily joined by a mating bridge formed via a pilus, requiring an F (fertility) factor plasmid.

Extremophile

Prokaryotes adapted to severe environmental conditions, such as acidophiles ($\text{pH } 3$ or below), alkaliphiles ($\text{pH } 9$ or above), thermophiles ($60\text{--}80\,^\circ\text{C}$), hyperthermophiles ($80\text{--}122\,^\circ\text{C}$), psychrophiles ($-15\text{ to }10\,^\circ\text{C}$ or lower), and halophiles ($\ge 0.2\text{ M}$ salt).

Primary Endosymbiosis

The evolutionary process wherein a eukaryote engulfed an aerobic proteobacterium to form mitochondria, or a photosynthetic cyanobacterium to form primary plastids (chloroplasts).

Phycoerythrin

A red photosynthetic accessory pigment found in red algae that absorbs blue and green wavelengths, enabling them to survive in deeper ocean habitats.

Chitin

A tough, nitrogen-containing polysaccharide that forms the structural cell walls of fungi and the exoskeletons of arthropods.

Plasmogamy

The fusion of the cytoplasm of two individual fungal mycelia without the immediate fusion of their nuclei, producing a heterokaryotic ($n+n$) stage.

Karyogamy

The fusion of two haploid nuclei within a heterokaryotic fungal cell, producing a diploid ($2n$) zygote that subsequently undergoes meiosis.

Extracellular Matrix (ECM)

A complex network of extracellular macromolecules, primarily composed of collagen, that provides structural support and connectivity to animal cells in the absence of a cell wall.

Diploblastic

Having a body plan derived from only two embryonic germ layers: ectoderm and endoderm.

Triploblastic

Having a body plan derived from three embryonic germ layers: ectoderm, mesoderm, and endoderm.

Coelom

A fluid-filled body cavity located between the body wall and the digestive tract, found exclusively in triploblastic animals and classified as acoelomate, pseudocoelomate, or eucoelomate based on its mesodermal lining.

Protostome Development

A developmental pattern characterized by spiral and determinate cleavage, the splitting of solid masses of mesoderm to form the coelom, and the development of the mouth from the blastopore.

Deuterostome Development

A developmental pattern characterized by radial and indeterminate cleavage, the folding and outpocketing of the archenteron to form the coelom, and the development of the anus from the blastopore.

Choanocytes

Flagellated collar cells lining the spongocoel of sponges (Porifera) that generate water currents with their flagella and filter food particles via phagocytosis.

Cnidocytes

Specialized stinging cells unique to the tentacles of phylum Cnidaria that contain capsule-like organelles used for defense and prey capture.

Radula

A straplike raspy organ equipped with chitinous teeth found in the mouth of most molluscs, used to scrape up food.

Ecdysis

The periodic process of molting or shedding an external cuticle or exoskeleton during growth, which defines the clade Ecdysozoa.

Water Vascular System

A network of hydraulic canals unique to echinoderms that branches into tube feet, functioning in locomotion, feeding, and gas exchange.

Notochord

A firm, flexible, longitudinal skeletal rod located between the digestive tube and nerve cord in all chordate embryos, serving as the forerunner of the vertebral column.

Mammalian Lineages

The three major clades of mammals: Monotremes (egg-laying), Marsupials (pouched mammals with simple placentas), and Eutherians (placental mammals completing embryonic development in the uterus).

Alternation of Generations

A plant life cycle in which a multicellular haploid gametophyte ($n$) produces gametes by mitosis, and a multicellular diploid sporophyte ($2n$) produces spores by meiosis.

Cohesion-Tension Theory

The mechanism explaining the upward movement of water through xylem, driven by negative pressure (tension) generated by transpiration in leaves and transmitted downward via hydrogen-bonded water molecules (cohesion and adhesion).

Pressure-Flow Hypothesis

The model describing phloem translocation, where active transport of sucrose into phloem sieve tubes creates a hypertonic environment, drawing water from xylem and building positive bulk pressure that drives sap toward the sink.

Heterospory

The production of two distinct types of spores: megaspores that give rise to female megagametophytes, and microspores that develop into male microgametophytes.

Flower

The specialized reproductive shoot of an angiosperm consisting of up to four whorls of modified leaves: sepals, petals, stamens (filament and microsporangia-bearing anther), and carpels (stigma, style, and ovule-bearing ovary).

Double Fertilization

A mechanism in angiosperms wherein one sperm fertilizes the egg to form a diploid ($2n$) zygote, while a second sperm fuses with the two nuclei of the central cell to produce triploid ($3n$) endosperm.

Tropic Hormone

A hormone that regulates the function of other endocrine cells or glands by stimulating the synthesis and release of subsequent hormones.

Neuroendocrine Signaling

A mode of intercellular communication in which neurosecretory cells secrete neurohormones directly into the bloodstream to reach target tissues throughout the body.

Spermatogenesis

The production of mature sperm cells within the seminiferous tubules, where diploid ($2n$) spermatogonia undergo mitosis and meiosis to produce four haploid ($n$) spermatids that differentiate into mature sperm.

Oogenesis

The developmental process producing female gametes, starting with oogonia ($2n$) forming primary oocytes arrested at prophase I, which resume at puberty to produce a secondary oocyte ($n$) arrested at metaphase II until fertilization.

Acrosomal Reaction

The discharge of hydrolytic enzymes from the acrosome of a sperm upon contact with the egg's jelly coat or zona pellucida, allowing the acrosomal process to penetrate egg coverings and bind receptors on the plasma membrane.

Cortical Reaction

The slow block to polyspermy triggered by intracellular $\text{Ca}^{2+}$ release, which causes cortical granules to release enzymes that harden the vitelline layer or zona pellucida into a permanent fertilization envelope.

Holoblastic Cleavage

A pattern of embryonic cleavage in which division furrows pass entirely through the egg due to the presence of little or moderate yolk, seen in echinoderms, mammals, and amphibians.

Meroblastic Cleavage

An incomplete pattern of cleavage typical of heavily yolked eggs (such as in birds), where division is restricted to a small disc of yolk-free cytoplasm.

Induction

The developmental process by which one group of embryonic cells stimulates or influences the differentiation pathway of adjacent target cells, such as the notochord inducing neural plate formation.

Autonomic Nervous System

The efferent division of the peripheral nervous system that involuntarily regulates smooth muscle, cardiac muscle, and glands, divided into sympathetic, parasympathetic, and enteric branches.

Reflex Arc

An automatic, involuntary neural circuit in which sensory information detected by a receptor travels along an afferent neuron to the spinal cord and rapidly triggers motor output along an efferent neuron to an effector.

Resting Potential

The steady-state membrane potential of an unexcited neuron (typically $-70\text{ mV}$), maintained by the active transport of the $\text{Na}^+/\text{K}^+$ pump and passive diffusion through open ungated $\text{K}^+$ channels.

Saltatory Conduction

The rapid propagation of action potentials along a myelinated axon, where depolarization events jump from one unmyelinated node of Ranvier to the next, increasing conduction speed up to 50-fold.