IB Biology Standard Level Paper 1A Review

A set of vocabulary flashcards covering the core principles of molecular biology, cytology, human physiology, genetics, evolution, and ecology from IB Biology SL Paper 1A.

Deoxyribose

The five-carbon pentose sugar found in DNA nucleotides, characterized by having a hydrogen atom ($-\text{H}$) instead of a hydroxyl group ($-\text{OH}$) on carbon $2$.

Hydrolysis of Polymers

The biochemical reaction in polymer digestion where water provides $-H$ and $-OH$ groups to split covalent bonds and yield monomers.

Unsaturated Fatty Acids (in oils)

Fatty acids containing one or more double carbon bonds ($\text{C}=\text{C}$), resulting in kinks that lower the melting point and cause oils to remain liquid at room temperature.

Anabolic Reaction

An enzyme-catalysed, energy-consuming metabolic pathway in which complex products are synthesized from simpler reactants, ending at a higher energy level than the initial reactants.

Lactate Accumulation

The rapid increase in blood lactate concentration during high-intensity exercise caused by the anaerobic breakdown of glucose to generate ATP when oxygen availability is limited.

PCR Stage X (Extension)

The stage of the polymerase chain reaction carried out at approximately $72\,^\circ\text{C}$, which provides the optimum temperature for Taq DNA polymerase to synthesize new DNA strands.

Codon

A specific sequence of three consecutive nucleotides in mRNA (such as GGA, GGU, or GGC) that encodes a particular amino acid (such as glycine) during translation.

Freeze-fracture Microscopy

A specialized preparation technique where frozen biological specimens are physically cleaved along the hydrophobic interior of lipid bilayers to examine the internal structure of cell membranes.

Transmembrane Ion Transport

The processes by which charged ions cross the nonpolar interior of plasma membranes, occurring via facilitated diffusion through channel proteins and active transport via pumps.

Resting Membrane Potential

The electrical potential across an axon membrane when not transmitting an impulse, actively maintained by using ATP to pump sodium ions out and potassium ions into the cell.

Metaphase (Mitosis)

The mitotic stage during which condensed chromosomes are attached to and aligned at the spindle equator by microtubule spindle fibres.

Genus

The taxonomic rank preceding the species name in binomial nomenclature; for example, Valeriana officinalis and Valeriana ciliosa share the genus Valeriana.

Expiratory Reserve Volume (ERV)

The extra volume of air that can be forcibly exhaled from the lungs after a normal, quiet tidal exhalation, represented by arrow B on a spirometer trace.

Vein

A thin-walled blood vessel with a relatively large lumen and internal valves that functions specifically to carry deoxygenated or oxygenated blood back towards the heart.

Chemoreceptor Heart Rate Reflex

A regulatory neural pathway where chemoreceptors detect low blood pH, triggering the medulla to send nerve impulses along sympathetic pathways to increase heart rate.

Innate Immune System

The non-specific primary line of biological defence that provides a constant, unchanged response to a broad spectrum of pathogens without forming immunological memory cells.

Incomplete Dominance

A non-Mendelian inheritance pattern where neither allele is fully expressed, resulting in $100\%$ heterozygous offspring showing an intermediate blend (such as purple flowers from homozygous blue and red parents).

Polygenic Inheritance

The additive determination of a phenotypic trait by multiple separate genes, producing a continuous, bell-shaped distribution (such as human height) that is further influenced by environmental factors.

In Situ Conservation

The preservation and management of endangered species within their natural environment, such as protecting Australian coastal forest reserves from fires to safeguard Petaurus gracilis.

Terrestrial Biome Distribution Axes

A Whittaker-style climatic model where the vertical axis (Y) represents mean annual temperature and the horizontal axis (X) represents annual rainfall to determine the distribution of terrestrial biomes.

Heterosphecia tawonoides

A clearwing moth species that utilizes physical adaptations (furry legs, transparent wings) and behavioural adaptations (mud-puddling alongside bees) to mimic bees and evade predation.

Carrying Capacity ($K$)

The maximum population size of a species that an ecosystem can support, causing population growth to level off as seen in the Salish Sea harbour seal (Phoca vitulina) population past the year $2010$.

Allelopathy

A biological phenomenon where an organism releases biochemical secondary metabolites into the surroundings that inhibit neighbouring competing species, used in agriculture to suppress weeds.

Secondary Production

The generation of consumer biomass over time via heterotrophic nutrition, initiated when animals ingest and assimilate organic matter produced by primary producers (green plants).

Keystone Species

A species that exerts a crucial regulatory influence over an entire ecosystem structure, whose removal can precipitate significant ecological disruption and steep population surges of certain taxa.

Permafrost Thaw Feedback Loop

A positive feedback cycle in global warming where melting permafrost exposes ancient peat to decomposition (process H), releasing methane gas (gas J) that traps more terrestrial heat.