Biology: Biodiversity, Cell Types, and Phylogeny

Comprehensive vocabulary flashcards covering viruses, endosymbiosis, protist and plant diversity, animal germ layers, phylogenetic trees, taxonomy, archaea, and bacterial morphology and reproduction.

Capsid

A protein coat shell enclosing the viral genome that protects the nucleic acid from the host, aids in attachment, and gives the virus its shape.

Viral envelope

An additional outer structure found on some viruses that can assist with host infection.

Host range

The limited number of host species, tissues, or cells that a virus or other infectious particle can infect.

Lytic cycle

A viral replication cycle in which viruses burst from a host cell, usually killing it, and proceed to attack other cells.

Lysogenic cycle

A viral cycle where viral DNA is incorporated into the host cell's genome and remains dormant (lysogeny) without immediately destroying the cell.

Endosymbiosis

The symbiotic relationship in which one prokaryotic cell engulfed another prokaryotic cell, resulting in the evolution of eukaryotic cells.

Endosymbiont

A cell that is engulfed by another cell during an endosymbiotic event.

Euglena

A plantlike protist that typically possesses an eyespot for light detection, one or two flagella for motility, and a cellulose pellicle instead of a cell wall.

Protozoa

Animal-like, heterotrophic protists, exemplified by Amoeba, which feeds by phagocytosis and moves via pseudopods.

Peroxisomes

Cell structures that transfer hydrogen from a variety of substrates to oxygen, producing and subsequently degrading hydrogen peroxide.

Phragmoplast

A plant cell structure formed when cytoskeletal elements and vesicles align across the midline of a dividing cell.

Cuticle

A plant covering composed of wax and other polymers that helps prevent water loss.

Stomata

Specialized pores in plants that permit the exchange of $CO_2$ and $O_2$ between the interior tissues and the outside air.

Xylem

Vascular tissue in plants responsible for transporting water and minerals upward from the roots.

Phloem

Vascular plant tissue dedicated to transporting larger organic molecules such as sugars (glucose).

Gymnosperms

Cone-bearing plants characterized by 'naked seeds' that are not enclosed in chambers.

Angiosperms

Flowering plants whose seeds develop inside chambers that originate within flowers.

Diploblast

An animal organism that develops from two primary germ layers.

Triploblast

An animal organism that develops from three primary germ layers.

Ectoderm

The outermost primary germ layer in animals; produces skin, nervous tissue, and some sensory organs in humans.

Mesoderm

The middle primary germ layer in animals; gives rise to muscles, blood, kidneys, and reproductive organs in humans.

Endoderm

The innermost primary germ layer in animals; forms the lungs, liver, pancreas, bladder, and stomach lining in humans.

Coelomates

Animals possessing a coelom, a fluid-filled body cavity that provides space for the suspension and development of organs and organ systems.

Acoelomates

Animals that lack a coelom (fluid-filled body cavity).

Sessile

An organism that lacks the capacity for self-locomotion and remains fixed in one place.

Systematics

The scientific discipline focused on classifying organisms and determining their evolutionary relationships.

Clade

A monophyletic group consisting of an ancestral species and all of its descendants.

Cladistics

An approach to biological systematics in which organisms are organized into clades based primarily on common descent.

Sister taxa

Two taxa that share an immediate common ancestor with each other not shared by any other group.

Outgroup

A lineage or species related to the group being studied, but known to be less closely related than any members of the ingroup are to each other.

Ingroup

A species or group of species whose evolutionary relationships are being actively analyzed.

Polytomy

A branch point on a phylogenetic tree from which more than two descendant groups emerge.

Derived traits

Evolutionary traits that arose during the divergence of a lineage and differ from the traits found in the ancestor of that group.

Ancestral traits

Traits present in the common ancestor of a group that have undergone little evolutionary change since.

Homology

Phenotypic or genetic similarities between organisms resulting from shared ancestry.

Analogy

Functional similarities between organisms that evolved independently rather than through a shared ancestor.

Morphological Species Concept

A framework that defines a species primarily by its structural features, body shape, and size.

Biological Species Concept

A framework that defines a species as a group of organisms that can interbreed in nature and produce viable, fertile offspring.

Phylogenetic Species Concept

A framework that defines a species based on its evolutionary history (phylogeny).

Binomial nomenclature

A two-part naming system for species consisting of a capitalized genus name followed by a lowercase species epithet.

Thermophiles

Heat-loving archaea that thrive in high-temperature environments such as hot springs and hydrothermal vents.

Methanogens

Anaerobic archaea that convert $CO_2$ into methane, commonly found in sewage treatment and oxygen-depleted habitats.

Halophiles

Salt-loving archaea that require high salt concentrations to survive, inhabiting locations like salt lakes and the Dead Sea.

Capsule

A sticky external layer of polysaccharide or protein surrounding the prokaryotic cell wall, protecting against dehydration and the host immune system.

Endospore

A tough, multilayered dormant bacterial structure that allows a cell to survive long periods in extreme environmental conditions.

Fimbriae

Hairlike appendages in prokaryotes that allow cells to adhere to substrates or to one another, typically shorter and more numerous than pili.

Pili

Appendages that help bacteria attach to surfaces and facilitate the pulling together of cells during conjugation.

Taxis

A behavioral directional response of a bacterial cell toward or away from an external stimulus.

Peptidoglycan

A polymer mesh in bacterial cell walls that maintains structure, protects against bursting in hypotonic environments, and anchors surface molecules.

Gram-Positive Bacteria

Bacteria that possess cell walls containing a thick layer of peptidoglycan, causing them to stain purple during Gram staining.

Gram-Negative Bacteria

Bacteria that have cell walls containing a thin layer of peptidoglycan, causing them to stain pink during Gram staining.

Binary Fission

Asexual prokaryotic reproduction in which a single cell replicates its DNA and divides to form two genetically identical daughter cells.

Conjugation

A parasexual process in bacteria where DNA is transferred between two cells that are temporarily joined via a pilus and mating bridge.