FTCE Biology 6-12 cheat sheet

Controlled investigation sequence: observation → question → testable and falsifiable hypothesis → prediction → controlled experiment → data analysis → conclusion.

Independent variable = factor the researcher manipulates; dependent variable = factor measured; standardized (controlled) variables are held constant to prevent confounding.

A control group receives no treatment or a placebo and supplies the baseline needed to attribute observed changes to the independent variable.

Reliability increases with replication and larger samples; validity means the procedure measures what it claims (internal validity = free of confounds, external validity = generalizable).

p < 0.05 conventionally means a result this extreme would occur by chance less than 5% of the time if the null hypothesis were true; the null is rejected, not the hypothesis 'proven'.

Chi-square compares observed with expected categorical frequencies; a t-test compares two means; standard deviation measures spread; standard error of the mean = SD/√n.

A scientific theory is a well-tested explanation supported by multiple independent lines of evidence; a scientific law describes a consistent, often mathematical, relationship.

Correlation does not establish causation; causal claims require controlled or randomized experiments that rule out confounds.

Total microscope magnification = ocular lens power × objective lens power; resolution improves as wavelength shortens, so electron microscopes resolve structures invisible to light microscopes.

Cell theory: all organisms consist of one or more cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.

Prokaryotic cells lack a nucleus and membrane-bound organelles and have 70S ribosomes; eukaryotic cells have a nucleus, membrane-bound organelles, and 80S ribosomes.

Passive transport (diffusion, facilitated diffusion, osmosis) moves materials down gradients without ATP; active transport moves materials against gradients and requires ATP.

Osmosis: water crosses a selectively permeable membrane from higher water potential (lower solute concentration) to lower water potential; aquaporins accelerate the flow.

Enzymes lower activation energy by stabilizing the transition state; activity peaks at an optimal pH and temperature and falls when the enzyme denatures.

Respiration ATP yield per glucose: glycolysis in the cytoplasm (net 2 ATP, 2 NADH), Krebs cycle in the matrix, electron transport chain on the inner mitochondrial membrane - about 30–38 ATP aerobically; fermentation yields only 2 ATP.

Cell cycle: G1 growth, S phase DNA replication, G2 preparation, M phase mitosis (prophase, metaphase, anaphase, telophase); checkpoints at G1, G2, and M verify DNA integrity.

Photosynthesis: light reactions in thylakoid membranes split water, release O2, and produce ATP and NADPH; the Calvin cycle in the stroma uses RuBisCO to fix CO2 into sugar.

Gene expression: transcription (DNA → mRNA in the nucleus) followed by translation (mRNA codons matched to tRNA anticodons at ribosomes) to build a polypeptide.

Law of segregation: allele pairs separate during meiosis I so each gamete carries one allele; law of independent assortment: alleles of different genes assort independently when the genes lie on different chromosomes.

A monohybrid cross of two heterozygotes gives a 3:1 phenotypic and 1:2:1 genotypic ratio; a dihybrid heterozygote cross gives 9:3:3:1 with independent assortment.

Genotype = allele combination; phenotype = observable trait; homozygous = identical alleles; heterozygous = different alleles; a testcross reveals an unknown dominant genotype.

Incomplete dominance gives an intermediate phenotype (red × white → pink); codominance expresses both alleles fully (AB blood type); multiple alleles and polygenic inheritance add further variation.

X-linked recessive traits appear more often in males because males carry a single X; an affected father passes the allele to all daughters but no sons.

Nondisjunction during meiosis produces gametes with extra or missing chromosomes, causing aneuploidy such as trisomy 21 or monosomy.

Hardy-Weinberg: p + q = 1 and p² + 2pq + q² = 1; frequencies stay constant only with no mutation, no migration, no selection, an infinitely large population, and random mating.

Natural selection requires heritable variation and differential reproductive success; fitness is relative reproductive output, and selection acts directly on phenotypes rather than genotypes.

Speciation occurs by geographic isolation (allopatric) or by reproductive isolation without geographic separation (sympatric, e.g., polyploidy); evidence for common descent includes fossils, homologous structures, biogeography, embryology, and molecular sequences.

Taxonomic hierarchy: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species; species is the only rank with a biological definition.

Three domains: Bacteria, Archaea (no peptidoglycan, ether-linked membrane lipids, many extremophiles), and Eukarya; binomial names italicize genus plus species epithet.

Viruses are acellular obligate intracellular parasites (capsid plus DNA or RNA); they are excluded from the kingdoms and replicate only with host machinery.

Bacterial shapes: cocci (spheres), bacilli (rods), spirilla (spirals); peptidoglycan walls distinguish gram-positive (thick layer) from gram-negative (thin layer plus outer membrane).

Fungi: chitin cell walls, heterotrophic absorption after extracellular digestion, body of hyphae forming a mycelium; ecological roles include decomposers, parasites, and mutualists (lichens, mycorrhizae).

Plant phylogeny: bryophytes (nonvascular, gametophyte dominant) → seedless vascular ferns → gymnosperms (naked seeds, cones) → angiosperms (flowers, fruit, double fertilization).

Land adaptations in plants: cuticle, stomata, vascular tissue (xylem and phloem), lignin, protected embryos, seeds, and pollen, each reducing dependence on external water.

Animal classification features: symmetry (radial vs. bilateral), body cavity (acoelomate, pseudocoelomate, coelomate), segmentation, and protostome vs. deuterostome development.

Protists are mostly unicellular eukaryotes; the group is paraphyletic and includes algae, protozoa, and slime molds.

Ecological hierarchy: organism → population → community → ecosystem → biome → biosphere.

Energy flows one way while matter cycles; roughly 10% of energy passes to the next trophic level, so energy and biomass pyramids are widest at the producer level.

Biogeochemical cycles: carbon (photosynthesis, respiration, combustion), nitrogen (fixation, nitrification, denitrification), water (evaporation, condensation, precipitation), phosphorus (no atmospheric phase; released by rock weathering).

Exponential growth (J-curve) occurs with unlimited resources; logistic growth (S-curve) slows near carrying capacity: dN/dt = rN(K − N)/K.

Density-dependent factors (food, disease, predation, space) intensify as density rises; density-independent factors (fire, drought, storms) act regardless of density.

Species interactions: competition (−/−, competitive exclusion), predation and parasitism (+/−), mutualism (+/+), commensalism (+/0).

Primary succession begins on bare substrate lacking soil (lichens, mosses); secondary succession begins where soil remains after a disturbance, as in old-field succession.

Human impacts include habitat fragmentation, invasive species, eutrophication from nutrient runoff, biomagnification of fat-soluble toxins, and greenhouse-gas-driven climate change.

Biodiversity peaks in tropical regions and hotspots; keystone and foundation species exert influence on community structure far beyond their abundance.

Homeostasis relies on negative feedback to reverse deviations from a set point (insulin lowers glucose, ADH conserves water); positive feedback amplifies change, as oxytocin does in labor.

Resting potential is about −70 mV, maintained by the Na⁺/K⁺ pump (3 Na⁺ out, 2 K⁺ in); threshold triggers an all-or-none action potential via Na⁺ influx followed by K⁺ efflux.

Synaptic transmission: neurotransmitter released from axon terminals crosses the cleft, binds postsynaptic receptors, and is cleared by reuptake or enzymatic breakdown.

Circulation: arteries carry blood away from the heart, veins carry it back (valves prevent backflow), and one-cell-thick capillaries permit exchange.

Respiration: alveoli give a thin, moist, large surface area for gas exchange; negative-pressure breathing fills the lungs when the diaphragm contracts and flattens.

Digestion: amylase digests starch, pepsin digests protein in the acidic stomach, lipase digests fats; villi and microvilli of the small intestine absorb nutrients.

Nephrons filter, reabsorb, and secrete; ADH raises water reabsorption and aldosterone raises Na⁺ reabsorption, regulating blood volume and pressure.

Muscle contraction follows the sliding filament model: myosin heads bind actin and pull using ATP, while Ca²⁺ released from the sarcoplasmic reticulum exposes binding sites.

Behaviors are innate (fixed action patterns, taxes, kineses) or learned (habituation, classical and operant conditioning, imprinting); communication and circadian rhythms are shaped by natural selection.