Honors Biology Exam Study Guide: Units 1, 2, and 3

Comprehensive vocabulary flashcards covering Experimental Design, Characteristics of Life, Properties of Water, Macromolecules, Enzymes, Evolutionary Theory, Population Genetics, and Speciation from Honors Biology Units 1, 2, and 3.

Alternative Hypothesis ($H_1$ or $H_a$)

A testable prediction stating that there will be a measurable effect or relationship between variables (e.g., "Increasing fertilizer concentration will increase plant growth").

Null Hypothesis ($H_0$)

A testable prediction stating that there will be no effect or relationship between variables (e.g., "Changing fertilizer concentration will not affect plant growth").

Independent Variable (IV)

The factor in an experiment that the researcher deliberately changes or manipulates.

Dependent Variable (DV)

The factor in an experiment that is measured or observed; it responds to changes made to the independent variable.

Constants (Controlled Variables)

Conditions kept identical across every group in an experiment to ensure that only the independent variable affects the outcome.

Control Group

A group used as a standard for comparison that does not receive the experimental treatment being tested.

Experimental Group

The group in an experiment that receives the treatment or the altered independent variable.

Negative Control

A control group expected to show no response because it lacks the active treatment, helping determine whether an effect is truly caused by the treatment.

Positive Control

A control group that receives a treatment known to produce the expected response, demonstrating that the experimental system and procedure are functioning properly.

Scientific Theory

A broad, well-supported explanation of many observations that is substantiated by extensive evidence; theories explain why or how phenomena occur.

Scientific Law

A statement describing a consistent natural pattern or relationship, often expressed mathematically, without explaining the underlying cause.

Quantitative Data

Numerical measurements or counts, such as $18.5\,\text{cm}$, $42$ cells, or $75\%$.

Qualitative Data

Descriptive, non-numerical observations that describe qualities or characteristics, such as color changes or movement toward light.

Metabolism

The sum of all chemical reactions occurring within an organism, including reactions that synthesize molecules and those that break molecules down to release or use energy.

Homeostasis

The maintenance of relatively stable internal conditions within suitable ranges despite external changes (e.g., regulation of body temperature, blood glucose, or water balance).

Adaptation

A heritable characteristic that becomes common in a population over generations because it increases survival or reproductive success in a particular environment.

Polar Covalent Bond

The type of bond within a single water molecule holding oxygen and hydrogen together due to unequal sharing of electrons.

Hydrogen Bond

A weak attraction formed between separate water molecules, where the partial positive hydrogen of one molecule is attracted to the partial negative oxygen of another.

Cohesion

The attraction between water molecules of the same kind, which helps water form continuous columns.

Adhesion

The attraction between water molecules and other surfaces.

Capillary Action

The movement of water through narrow spaces caused by the combined effects of adhesion and cohesion (critical in plant xylem).

Surface Tension

The resistance of a water surface to being broken or stretched, caused largely by cohesion between water molecules.

Universal Solvent

A term describing water's ability to dissolve many ionic and polar substances due to its polarity.

High Specific Heat Capacity

The property of water requiring a large amount of energy to change its temperature, which stabilizes temperatures in organisms and environments.

Hydrophilic

"Water-loving"; describes polar or charged substances that interact well with and dissolve in water.

Hydrophobic

"Water-fearing"; describes nonpolar substances that do not mix well with water, such as oils.

Dehydration Synthesis

A chemical reaction that builds a larger polymer from smaller monomers by removing a molecule of $\text{H}_2\text{O}$, forming a covalent bond.

Hydrolysis

A chemical reaction that breaks bonds within a polymer into smaller subunits by adding a molecule of $\text{H}_2\text{O}$.

Carbohydrates

Biological macromolecules composed mainly of carbon, hydrogen, and oxygen (often in a $1:2:1$ ratio); monosaccharides serve as monomers to build polysaccharides used for short-term energy and structural support.

Lipids

Hydrophobic macromolecules composed mainly of carbon, hydrogen, and oxygen (some contain phosphorus) that provide long-term energy storage, insulation, cushioning, waterproofing, and membrane structure.

Saturated Fats

Lipids containing fatty acid chains with no carbon-carbon double bonds, allowing chains to pack tightly and typically remain solid at room temperature.

Unsaturated Fats

Lipids containing one or more carbon-carbon double bonds, which create bends in fatty acid chains that prevent tight packing and keep them liquid at room temperature.

Phospholipids

Molecules that form cell membrane bilayers, consisting of a hydrophilic, polar phosphate-containing head and two hydrophobic, nonpolar fatty-acid tails.

Proteins

Macromolecules composed of amino acid monomers folded into polypeptide chains that perform functions including enzymatic catalysis, transport, structure, movement, defense, and signaling.

Nucleic Acids

Macromolecules composed of nucleotide monomers (carbon, hydrogen, oxygen, nitrogen, and phosphorus) that store (DNA) and transmit (RNA) genetic information.

Enzymes

Biological catalysts, typically proteins, that accelerate chemical reactions by lowering their activation energy without being permanently consumed.

Activation Energy

The minimum energy input required to initiate a chemical reaction and reach the transition state.

Substrate

The specific reactant molecule upon which an enzyme acts.

Active Site

The specific region of an enzyme whose shape and chemical properties complement the substrate, allowing binding and conversion to products.

Denaturation

A conformational change in a protein's three-dimensional structure—commonly caused by extreme temperature or extreme pH—that destroys or reduces its biological activity.

Competitive Inhibition

A mechanism of enzyme inhibition where an inhibitor binds directly to the active site, blocking the substrate from entering.

Noncompetitive (Allosteric) Inhibition

A mechanism of enzyme inhibition where an inhibitor binds to a site other than the active site, altering the enzyme's conformation and reducing its activity.

Endosymbiotic Theory

The theory proposing that eukaryotic organelles, notably mitochondria and chloroplasts, originated as free-living prokaryotic cells engulfed by larger prokaryotes, eventually establishing a mutualistic relationship.

Evolution

A heritable change in the inherited characteristics or allele frequencies of a population over successive generations.

Jean-Baptiste Lamarck's Evolutionary Hypothesis

An early, invalid hypothesis stating that organisms develop changes through the use or disuse of body parts during their lifetimes and pass these acquired traits directly to their offspring.

Natural Selection

The evolutionary mechanism where individuals with heritable adaptations that improve survival and reproduction leave more offspring, increasing the frequency of advantageous traits over generations.

Survival of the Fittest

The concept that individuals best suited to their specific environment have greater reproductive success and survival, where "fittest" refers to evolutionary fitness rather than physical strength.

Directional Selection

A type of natural selection that favors one extreme phenotype, shifting the population distribution toward that extreme.

Stabilizing Selection

A type of natural selection that favors intermediate (average) phenotypes and selects against extreme phenotypes.

Disruptive Selection

A type of natural selection that favors both extreme phenotypes while selecting against intermediate phenotypes.

Biological Resistance

The natural or genetic capacity of organisms or populations to withstand or repel biotic attacks or abiotic controls (e.g., antibiotic resistance in bacteria, pesticide resistance in insects).

Taxonomy

The scientific discipline of naming, describing, and classifying organisms based on evolutionary relationships and shared characteristics.

Binomial Nomenclature

A two-part scientific naming convention developed by Carl Linnaeus consisting of a capitalized Genus name followed by a lowercase specific epithet (e.g., Homo sapiens).

Taxonomic Hierarchy

The ranked levels of biological classification from broadest to most specific: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Phylogeny

The evolutionary history and genealogical lineage of a group of organisms.

Cladogram

A branching diagram depicting evolutionary relationships among organisms based on shared derived characteristics.

Clade

A monophyletic group on a phylogenetic tree or cladogram that includes an ancestral organism and all of its evolutionary descendants.

Derived Characteristic

A novel trait that arose in a common ancestor and is shared by all of its descendant lineages.

Node

A branching point on a phylogenetic tree or cladogram representing a common ancestor that split into descendant lineages.

Homologous Structures

Anatomical structures that share a common ancestral origin and similar underlying skeletal/tissue patterns, even if their current functions differ.

Analogous Structures

Structures that perform similar functions but evolved independently through convergent evolution and do not indicate close common ancestry.

Vestigial Structures

Reduced or nonfunctional remnants of structures that served functional roles in ancestral organisms.

Allele Frequency

The proportion or percentage of a specific allele relative to all alleles for that gene within a population's gene pool.

Gene Pool

The total collection of all alleles present among all individuals within a reproducing population.

Hardy-Weinberg Principle

The theoretical model stating that allele frequencies remain constant ($p + q = 1$ and $p^2 + 2pq + q^2 = 1$) across generations in the absence of evolutionary forces, requiring an infinitely large population, random mating, no mutation, no gene flow, and no natural selection.

Genetic Drift

Unpredictable fluctuations in allele frequencies from one generation to the next caused by random chance events, impacting small populations most significantly.

Founder Effect

A type of genetic drift that occurs when a small group of individuals colonizes a new habitat, establishing a population with reduced genetic variation compared to the original gene pool.

Bottleneck Effect

A type of genetic drift that occurs when a population size is drastically reduced by an environmental catastrophe or event, leaving a surviving gene pool with decreased genetic diversity.

Gene Flow

The transfer of alleles into or out of a population resulting from the movement of fertile individuals or gametes (migration).

Artificial Selection

The selective breeding of domesticated plants and animals by humans to encourage the perpetuation of desirable phenotypic traits.

Speciation

The evolutionary process by which biological populations diverge to form distinct, reproductively isolated species.

Gradualism

The model of evolutionary pacing proposing that species evolve gradually through the slow, steady accumulation of small genetic changes over long geologic timescales.

Punctuated Equilibrium

The model of evolutionary pacing characterized by prolonged periods of stasis (little morphological change) interrupted by rapid evolutionary divergence.

Divergent Evolution

The evolutionary pattern in which related species become increasingly distinct over time as they adapt to different ecological niches, often producing homologous structures.

Convergent Evolution

The independent evolution of similar ecological adaptations and analogous structures in unrelated evolutionary lineages exposed to similar environmental pressures.

Coevolution

The process by which two closely interacting species exert reciprocal selective pressures on each other, evolving in response to one another.

Allopatric Speciation

The formation of new species occurring when biological populations become geographically isolated by physical barriers such as mountains or water bodies.

Sympatric Speciation

The emergence of new species within the same geographic area without physical isolation, often mediated by polyploidy, behavioral divergence, or ecological niche partitioning.