Comprehensive Biology Lecture Notes: Nucleic Acids, Cell Biology, Evolution, and Biodiversity Conservation

Vocabulary practice flashcards covering nucleic acids, properties of water, cellular organization, evolutionary mechanisms, taxonomy, ecological metrics, and biodiversity conservation strategies.

Nucleotide

The structural subunit of nucleic acids consisting of three joined components: a phosphate group, a pentose sugar (deoxyribose or ribose), and a nitrogenous base (adenine, thymine, uracil, guanine, or cytosine).

Sugar-Phosphate Backbone

A strong, repeating structural chain of alternating sugar and phosphate molecules in a nucleic acid strand, linked via covalent phosphodiester bonds between the phosphate group and the $3'$ carbon of the next pentose sugar.

Purines and Pyrimidines

The two categories of nitrogen-containing bases found in nucleotides; purines (adenine and guanine) possess a double-ring structure, whereas pyrimidines (cytosine, thymine, and uracil) have a single-ring structure.

Gene

A specific sequence of DNA nucleotides that contains the biochemical instructions needed to synthesize a particular functional polypeptide chain (protein) or RNA molecule.

Antiparallel Strands

The structural orientation of a double-stranded DNA molecule where the two complementary strands run in opposite directions, with one running $5' \rightarrow 3'$ and the adjacent running $3' \rightarrow 5'$.

Universal Genetic Code

The principle that the same three-nucleotide sequence (codon) translates to the same amino acid across nearly all organisms on Earth, providing powerful evidence for a single common ancestor of all life.

Polar Covalent Bond (Water)

The unequal sharing of electrons between oxygen and hydrogen atoms inside a single water molecule, causing the oxygen atom to hold a partial negative charge ($\delta^-$) and the hydrogen atoms to hold a partial positive charge ($\delta^+$).

Cohesion (Water)

The tendency of water molecules to stick to each other via intermolecular hydrogen bonds, facilitating processes like transpiration pull in xylem vessels.

Adhesion (Water)

The property of water molecules sticking to other polar or charged surfaces, such as cellulose in plant cell walls or the glass walls of a vessel.

Specific Heat Capacity (Water)

The quantity of heat energy required to raise the temperature of $1\text{ g}$ of a substance by $1\,^\circ\text{C}$; water possesses a high specific heat capacity due to extensive hydrogen bonding, stabilizing aquatic habitats and internal body temperatures.

Buoyancy

The upward force exerted by a fluid on an object placed in it, equal to the weight of fluid displaced and caused by pressure differences between depths.

Viscosity

The internal friction or resistance to flow within a fluid; water has a higher viscosity than air due to the continuous breaking and reforming of hydrogen bonds.

Prokaryotic Cell

A structurally simpler cell type that lacks a membrane-bound nucleus and membrane-bound organelles; possesses naked, circular DNA situated within an unpartitioned nucleoid region.

Eukaryotic Cell

A complex cell type compartmentalized by internal membranes, enclosing its linear DNA within a double-membraned nucleus and containing distinct organelles dedicated to specific cellular processes.

Cell Differentiation

The process whereby unspecialized cells (such as stem cells) develop into structurally and functionally distinct cell types through selective gene expression.

Striated Muscle Fibre

An atypical, multinucleated eukaryotic cell structure formed through the fusion of multiple individual precursor cells, surrounded by a single continuous plasma membrane.

Aseptate Fungal Hyphae

Fungal hyphal filaments lacking internal dividing walls (septa), forming continuous tube-like structures that contain multiple nuclei freely distributed within common cytoplasm.

Phloem Sieve Tube Elements

Specialized, atypical plant vascular cells that break down their nucleus and most metabolic organelles during differentiation to reduce resistance to sap flow, sustained by adjacent companion cells.

Micrograph Magnification Formula

$\text{Magnification} = \frac{\text{Image Size}}{\text{Actual Size}}$, which allows calculating the physical size of biological specimens using measured scale bars in identical units.

Cell Theory

The biological principle stating that all living organisms are composed of one or more cells, cells represent the basic unit of life, and all cells arise from pre-existing cells.

Endoplasmic Reticulum (Rough vs. Smooth)

Rough ER is studded with $80\text{S}$ ribosomes that synthesize proteins destined for secretion or lysosomal packaging; Smooth ER lacks ribosomes and synthesizes lipids, phospholipids, and stores calcium ions.

Binomial System

The universal two-part naming convention established by Carl Linnaeus that identifies every organism by its genus name (capitalized) followed by its specific epithet/species name (lowercase).

Biological Species Concept

The definition of a species as a population or group of populations whose members possess the potential to interbreed in nature and produce viable, fertile offspring.

Reproductive Isolation

The presence of biological, geographical, or behavioral mechanisms that prevent members of different species from interbreeding, thereby maintaining distinct gene pools.

Karyotype and Karyogram

A karyotype describes the total number and types of chromosomes present in a cell; a karyogram is an organized visual image displaying homologous chromosome pairs arranged from largest to smallest, followed by sex chromosomes.

Single Nucleotide Polymorphism (SNP)

A single nucleotide site within a specific DNA sequence that exhibits variation among different individuals of the same species.

Lamarckism vs. Natural Selection

Jean-Baptiste Lamarck proposed the inheritance of acquired characteristics during an organism's lifetime (refuted), whereas Charles Darwin demonstrated that evolutionary change occurs via natural selection operating on heritable, pre-existing variation.

Homologous Structures

Similar anatomical features present in different species derived from a common ancestral blueprint, which have diverged structurally and functionally due to differing selection pressures (e.g., the vertebrate pentadactyl limb).

Vestigial Structures

Reduced or rudimentary anatomical structures retained in an organism that have lost all or most of their ancestral functions through adaptive evolution.

Lumpers and Splitters

Two competing philosophies in taxonomy: 'lumpers' emphasize overarching commonalities to group organisms into fewer species, whereas 'splitters' focus on fine differences to classify them into distinct, separate species.

Anthropogenic Species Extinction

The extinction of species caused directly or indirectly by human activities, recognized as driving a sixth mass extinction event through habitat loss, overexploitation, pollution, climate change, and invasive species.

Giant Moa (Dinornis novaezealandiae)

An extinct flightless bird endemic to New Zealand (exceeding $3\text{ m}$ in height and $250\text{ kg}$ in body mass) that suffered rapid anthropogenic extinction due to overhunting and habitat alteration following human settlement.

Simpson's Diversity Index

A quantitative measurement of ecological community diversity that accounts for both richness and evenness, represented by the formula $D = \frac{N(N-1)}{\sum n(n-1)}$, where higher values indicate greater biodiversity and community stability.

Citizen Science

The involvement of the non-professional general public in recording and collecting scientific data across broad spatial scales, requiring verification protocols to control for volunteer sampling bias.

Ex-situ Conservation

The preservation and protective management of threatened organisms outside their natural ecosystems, such as within captive breeding enclosures, botanical gardens, and cryogenic seed or tissue banks.

In-situ Conservation

The conservation and active protection of endangered species directly within their original natural habitats, typically through nature reserves, national parks, and ecological rewilding programs.

EDGE Programme

A global conservation scheme standing for 'Evolutionarily Distinct and Globally Endangered' that identifies and prioritizes threatened species that occupy unique, isolated positions on the evolutionary tree with few close relatives.