ЦТ Biology cheat sheet

Levels of organization, ascending: molecular → cellular → tissue → organ → organism → population-species → biogeocenotic → biospheric.

Scientific method sequence: observation → hypothesis → controlled experiment → data analysis → conclusion → theory.

A controlled experiment requires an experimental group and a control group differing in exactly one variable.

Comparative-descriptive, experimental, modelling, and monitoring methods are the main research methods in biology.

A population-species level is the elementary unit of evolution; a biogeocenosis is the elementary unit of the biosphere cycle.

Homeostasis is the property of biological systems at cellular, organism, and population levels to maintain a stable internal state.

A hypothesis becomes a theory only after repeated verification by independent researchers; a law is a theory with a mathematical formulation.

Inorganic ions: K+ high inside cells, Na+ high outside; Ca2+ participates in muscle contraction and blood clotting.

Water constitutes 70-80% of cell mass and is the universal solvent due to its polarity and hydrogen bonds.

Proteins: primary structure is a peptide sequence; secondary is alpha-helix or beta-sheet; tertiary is a globule; quaternary is a multimer.

Nucleic acids: DNA is a double helix with A-T, G-C pairs; RNA is single-stranded with A-U pairs.

Mitochondria: double membrane, cristae, own DNA and ribosomes; function is ATP synthesis by oxidative phosphorylation.

Chloroplasts: double membrane, thylakoid grana, stroma; function is photosynthesis; contain chlorophyll a and b.

Ribosomes synthesize protein; the large subunit catalyzes peptide bond formation; the small subunit binds mRNA.

Lysosomes contain hydrolytic enzymes at acidic pH and carry out intracellular digestion; the Golgi apparatus packages and secretes substances.

Photosynthesis summary: 6CO2 + 6H2O + light → C6H12O6 + 6O2; light reactions occur in thylakoids, the Calvin cycle in the stroma.

Light reactions split water (photolysis), producing O2, ATP, and NADPH; the Calvin cycle fixes CO2 using ATP and NADPH.

Chemosynthesis: nitrifying bacteria oxidize NH3 to NO2- and NO3-; sulfur bacteria oxidize H2S; energy is used to fix CO2.

Glycolysis: glucose → 2 pyruvate + 2 ATP + 2 NADH; occurs in the cytoplasm; anaerobic.

Aerobic respiration: pyruvate → acetyl-CoA → Krebs cycle → electron transport chain; total up to 38 ATP per glucose.

Alcoholic fermentation: glucose → 2 ethanol + 2 CO2 + 2 ATP; lactic acid fermentation: glucose → 2 lactate + 2 ATP.

Plastic exchange (biosynthesis) is endergonic and requires ATP; energy exchange (catabolism) is exergonic and produces ATP.

Transcription occurs in the nucleus; translation occurs on ribosomes; the genetic code is triplet, non-overlapping, and degenerate.

Mitosis phases: prophase (chromosome condensation), metaphase (alignment at the equator), anaphase (sister chromatid separation), telophase (nuclear envelope restoration).

Mitosis produces two diploid daughter cells genetically identical to the parent cell.

Meiosis: two divisions produce four haploid cells; crossing over occurs in prophase I; independent assortment occurs in metaphase I.

Spermatogenesis produces four sperm from one spermatogonium; oogenesis produces one ovum and three polar bodies.

Ontogenesis: embryonic (cleavage, gastrulation, organogenesis) and postembryonic (direct or indirect development) periods.

Cleavage of a zygote produces blastomeres; the blastula has a blastocoel; the gastrula has ectoderm, endoderm, and mesoderm.

Double fertilization in angiosperms: one sperm fuses with the egg (2n zygote), the other with two polar nuclei (3n endosperm).

Mendel's first law: monohybrid cross of homozygotes gives uniform F1; second law: F2 phenotypic ratio 3:1 in a monohybrid cross.

Law of independent assortment applies to genes on different chromosomes; linked genes violate it and show recombination frequency.

Test cross: crossing with a recessive homozygote reveals the genotype of the dominant phenotype.

Incomplete dominance gives an intermediate phenotype; codominance gives both traits expressed simultaneously (AB blood group).

Human sex determination: XX female, XY male; the SRY gene on the Y chromosome initiates male development.

Sex-linked traits (e.g., hemophilia, color blindness) are located on the X chromosome and appear more often in males.

Modification (non-heritable) variability is environmental; mutational variability is heritable and includes gene, chromosomal, and genomic mutations.

Selection methods: mass selection for cross-pollinators, individual selection for self-pollinators; heterosis appears in F1 hybrids.

DNA replication is semiconservative; DNA polymerase adds nucleotides 5'→3'; helicase unwinds the double helix.

Transcription: RNA polymerase reads the template strand 3'→5' and synthesizes mRNA 5'→3'.

Translation: mRNA codons are read by tRNA anticodons; the start codon is AUG (methionine); stop codons are UAA, UAG, UGA.

Restriction endonucleases cut DNA at specific palindromic sequences; DNA ligase joins fragments.

Recombinant DNA construction: vector (plasmid) + insert → transformation into host → selection of clones.

PCR cycles: denaturation (~95°C), primer annealing (~55°C), extension (~72°C) by Taq polymerase.

Biotechnology applications: insulin production in E. coli, gene therapy, transgenic plants, monoclonal antibodies.

Bacteria are prokaryotes without a nucleus or membrane-bound organelles; they reproduce by binary fission.

Fungi are heterotrophic eukaryotes with a chitin cell wall; they reproduce by spores and consist of hyphae forming a mycelium.

Lichens are a symbiosis of fungi (mycobiont) and algae or cyanobacteria (photobiont); they are indicators of air pollution.

Algae are photosynthetic autotrophs; green algae have cellulose walls and starch; brown algae contain laminarin.

Mosses lack true roots, have a gametophyte-dominant life cycle; ferns have a sporophyte-dominant life cycle with sori.

Angiosperms: double fertilization, flowers, fruit with seeds; monocots have one cotyledon, parallel venation; dicots have two cotyledons, net venation.

Plant tissues: meristem (growth), parenchyma (storage), xylem (water conduction), phloem (organic transport).

Sponges: no true tissues; choanocytes create water flow; reproduction is sexual and asexual (budding).

Coelenterates (Cnidaria): radial symmetry, two germ layers, nematocysts; polyp and medusa forms.

Arthropods: chitin exoskeleton, jointed appendages, segmented body; insects have three body parts and six legs.

Mollusks: soft body, mantle, muscular foot; cephalopods have a closed circulatory system and high intelligence.

Chordates: notochord, dorsal hollow nerve cord, pharyngeal slits, post-anal tail at some stage of development.

Fish: gills, two-chambered heart, external fertilization; amphibians: three-chambered heart, cutaneous respiration, metamorphosis.

Birds: four-chambered heart, feathers, air sacs, endothermy; mammals: mammary glands, hair, diaphragm, four-chambered heart.

Blood: plasma ~55%, formed elements ~45%; erythrocytes transport O2 via hemoglobin; leukocytes provide immunity; platelets clot blood.

Heart: four chambers; the left ventricle pumps blood into the systemic circulation; the right ventricle into the pulmonary circulation.

Digestion: amylase in the mouth, pepsin in the stomach (acidic pH), trypsin and lipase in the small intestine (alkaline pH).

Nephron: filtration in the glomerulus, reabsorption in the proximal tubule, secretion in the distal tubule; urine formation maintains water-salt balance.

Nervous system: somatic (voluntary) and autonomic (sympathetic/parasympathetic); the reflex arc includes receptor, afferent, center, efferent, effector.

Higher nervous activity: conditioned reflexes form in the cerebral cortex; Pavlov's laws of excitation and inhibition.

Hygiene rules: hand washing, food sanitation, vaccination, ventilation, and physical activity prevent infectious and non-communicable diseases.

Darwin's theory: heritable variation + struggle for existence + natural selection → adaptation and speciation.

Evidence for evolution: paleontological, comparative-anatomical (homologous organs), embryological, biogeographical, molecular.

Population genetics: Hardy-Weinberg equilibrium p² + 2pq + q² = 1 holds for large, random-mating populations without selection or mutation.

Ecological factors: abiotic (light, temperature, water), biotic (predation, competition), anthropogenic.

Food chain: producers → consumers → decomposers; energy transfer between trophic levels is about 10%.

Biogeocenosis: stable self-regulating community of organisms interacting with the abiotic environment.

Biosphere: the shell of Earth inhabited by life; Vernadsky's concept of living matter driving biogeochemical cycles.