Semester 2 Comprehensive Biology Vocabulary

A comprehensive set of vocabulary flashcards covering key concepts from plant biology, ecology, cellular energetics, cell structure, microbiology, evolution, and taxonomy for the Semester 2 Final.

Charophycean green algae

Group of freshwater green algae considered the closest living relatives of land plants.

Cellulose

Structural polysaccharide that makes up plant and many algal cell-walls.

Chlorophyll a

Primary green photosynthetic pigment that directly converts light energy to chemical energy.

Chlorophyll b

Accessory green pigment that broadens the spectrum of light usable in photosynthesis.

Alternation of generations

Plant life-cycle that alternates between a multicellular diploid sporophyte and a multicellular haploid gametophyte.

Sporophyte generation

Diploid (2n) plant stage that produces haploid spores by meiosis.

Gametophyte generation

Haploid (n) plant stage that produces gametes by mitosis.

Bryophytes

Seedless, non-vascular plants such as mosses whose dominant stage is the gametophyte.

Waxy cuticle

Waterproof coating on aerial plant surfaces that reduces water loss.

Pterophytes

Seedless vascular plants (e.g., ferns) whose dominant stage is the sporophyte.

Vascular tissue

Bundles of conductive tubes (xylem and phloem) that transport materials in plants.

Xylem

Vascular tissue that moves water and minerals upward from roots.

Phloem

Vascular tissue that distributes sugars throughout a plant.

Lignin

Rigid polymer that strengthens and supports vascular plant cell walls.

Gymnosperms

Vascular plants with "naked" seeds produced on cones (e.g., pines).

Ovulate cone

Female gymnosperm cone containing ovules and eggs.

Pollen cone

Male gymnosperm cone that produces pollen grains.

Pollination

Transfer of pollen to the receptive part of a seed plant (stigma or cone).

Pollen tube

Tube grown by a pollen grain to deliver sperm to the ovule.

Seed

Dormant plant embryo with food supply enclosed in a protective coat.

Angiosperms

Flowering plants whose seeds are enclosed within fruits.

Embryo sac

Female gametophyte of an angiosperm, containing the egg and two polar nuclei.

Double fertilization

Angiosperm event in which one sperm fertilizes the egg (zygote) and a second fuses with two nuclei to form triploid endosperm.

Endosperm

Triploid nutritive tissue in angiosperm seeds that feeds the embryo.

Fruit

Mature ovary of a flower that aids in seed protection and dispersal.

Ecology

Study of interactions between organisms and their environment.

Organism level

Ecological study focusing on an individual’s adaptations to its environment.

Population level

Ecological study of individuals of one species in one place, emphasizing intra-specific interactions.

Community level

Ecological study of interacting populations of different species in an area.

Ecosystem level

Ecological study that includes all biotic and abiotic factors and their energy/nutrient flows.

Biome

Large regional ecosystem characterized by climate and dominant vegetation (e.g., tundra).

Biosphere

Zone of life on Earth; sum of all biomes.

Niche

Sum of biotic and abiotic resources a species requires for survival and reproduction.

Carrying capacity

Maximum population size an environment can sustainably support.

Competitive exclusion

Principle stating that no two species can occupy exactly the same niche indefinitely.

Trophic pyramid

Diagram showing feeding relationships and energy distribution across trophic levels.

Decomposers

Organisms (bacteria, fungi) that break down dead matter and recycle nutrients.

Nitrogen cycle

Biogeochemical cycle that converts nitrogen among atmospheric, terrestrial, and biotic forms.

Carbon cycle

Movement of carbon through photosynthesis, respiration, decomposition, and combustion.

Quaternary consumer

Predator at the fourth consumer level atop a food chain.

10 percent rule

Approximate 10 % of energy at one trophic level is transferred to the next level.

Numbers pyramid

Graphic showing decreasing numbers of organisms at successive trophic levels.

Biomass pyramid

Graphic depicting decreasing total living mass at higher trophic levels.

Redox reaction

Paired oxidation–reduction chemical reaction involving electron transfer.

Oxidation

Loss of electrons or H⁺; often releases energy.

Reduction

Gain of electrons or H⁺; often stores energy.

Cellular respiration

Exothermic redox pathway that oxidizes glucose to CO₂ and reduces O₂ to H₂O, producing ATP.

Electron shuttle

Molecule that temporarily carries high-energy electrons between metabolic stages.

NAD⁺

Oxidized form of nicotinamide adenine dinucleotide; can accept 2 e⁻ + H⁺ to become NADH.

NADH

Reduced, energy-rich form of NAD⁺ that donates electrons to the ETC.

FAD

Oxidized flavin adenine dinucleotide that becomes FADH₂ when reduced.

FADH₂

Reduced FAD carrying high-energy electrons to the ETC.

Glycolysis

Anaerobic pathway in cytoplasm that splits glucose into two pyruvate, yielding 2 ATP and 2 NADH.

Energy investment phase

First stage of glycolysis in which 2 ATP are spent to phosphorylate glucose.

Energy harvest phase

Second stage of glycolysis producing 4 ATP, 2 NADH, and 2 pyruvate.

Fermentation

Anaerobic process that regenerates NAD⁺ by reducing pyruvate to lactate or ethanol.

Pyruvate fixation

Conversion of pyruvate to acetyl CoA, producing CO₂ and NADH in the mitochondrial matrix.

Krebs cycle

Cyclic matrix pathway oxidizing acetyl CoA to CO₂ and generating NADH, FADH₂, and ATP.

Electron transport chain

Series of membrane proteins that pass electrons, pumping H⁺ to build a gradient.

Chemiosmosis

ATP production using energy stored in a proton gradient across a membrane.

ATP synthase

Rotary enzyme that synthesizes ATP as protons flow through it down their gradient.

Photosynthesis

Endothermic redox process that converts light energy, CO₂, and H₂O into glucose and O₂.

Light reactions

Thylakoid events that convert light energy to ATP and NADPH, releasing O₂.

Calvin cycle

Stroma reactions that use ATP and NADPH to reduce CO₂ into sugars.

Photolysis

Light-driven splitting of water to provide electrons, H⁺, and O₂.

Photosystem II

Water-splitting photosystem that feeds electrons to a long ETC and pumps H⁺.

Photosystem I

Photosystem that re-energizes electrons to reduce NADP⁺ to NADPH.

Antenna complex

Array of pigments that capture light and funnel energy to the reaction center.

Reaction center chlorophyll

Special chlorophyll that loses excited electrons to the primary acceptor.

Primary electron acceptor

Molecule that first receives high-energy electrons from the reaction center.

Chloroplast

Plant organelle where photosynthesis occurs; contains thylakoids and stroma.

Thylakoid

Flattened chloroplast sac housing photosystems and ETCs; internal space accumulates H⁺.

Stroma

Chloroplast fluid outside thylakoids where the Calvin cycle operates.

Proton gradient

Difference in H⁺ concentration across a membrane storing potential energy.

RuBP

Five-carbon sugar that combines with CO₂ in the Calvin cycle.

Rubisco

Enzyme catalyzing CO₂ fixation to RuBP; Earth’s most abundant protein.

G3P

Three-carbon sugar product of the Calvin cycle; two G3P make one glucose.

Carbon fixation

Phase of Calvin cycle attaching CO₂ to RuBP to form PGA.

Reduction (Calvin)

Phase using ATP and NADPH to convert PGA to G3P.

Regeneration

Phase reforming RuBP from G3P so the Calvin cycle can continue.

Potential energy

Stored energy due to position or chemical composition.

Kinetic energy

Energy of motion, including heat, light, and movement.

First law of thermodynamics

Energy cannot be created or destroyed, only transformed.

Second law of thermodynamics

Spontaneous energy changes increase the universe’s entropy (disorder).

Entropy

Measure of disorder; higher entropy equals greater stability.

ATP

Adenosine triphosphate; universal cellular energy currency with high-energy phosphate bonds.

ADP

Adenosine diphosphate; ATP after losing one phosphate during energy release.

High-energy phosphate

Free phosphate group retaining released bond energy; used in phosphorylation.

Phosphorylation

Transfer of a phosphate group to a molecule, often energizing it.

Chemical work

Cellular work that forms or breaks chemical bonds.

Transport work

Pumping substances across membranes against gradients.

Mechanical work

Movement of cell structures or the whole cell.

Metabolism

Sum of all chemical reactions in an organism.

Catabolism

Exothermic, bond-breaking metabolic pathways that release energy.

Anabolism

Endothermic, bond-forming metabolic pathways that require energy.

Energy coupling

Using energy released from exergonic reactions to drive endergonic ones.

Activation energy

Initial energy input needed to start a chemical reaction.

Catalyst

Substance that speeds a reaction by lowering activation energy without being consumed.

Enzyme

Protein catalyst that is substrate-specific and reusable.

Substrate

Reactant molecule that binds to an enzyme’s active site.