OGE Biology cheat sheet

Biology is the science of living nature; its branches include botany, zoology, anatomy, physiology, microbiology, genetics, and ecology.

Levels of organization (small to large): molecular, cellular, tissue, organ, organism, population-species, biogeocenotic, biospheric.

A scientific method sequence: observation → hypothesis → experiment → analysis of results → conclusion.

Comparative-descriptive method reveals similarities and differences between organisms; historical method explains origins of traits; modelling studies processes that cannot be reproduced directly.

Key signs of living things: cellular structure, metabolism and energy conversion, growth, development, reproduction, heredity, variability, irritability, adaptation, and evolution.

Irritability is a universal property of living things; in animals it appears as reflexes and instincts.

Living systems are open systems: they exchange matter and energy with the environment and maintain relative constancy of internal composition (homeostasis).

A population is the unit of evolution; a species is the basic unit of classification; a biogeocenosis is the unit of the biosphere.

Inorganic substances: water (60–80% of cell mass) is the solvent and reaction medium; mineral salts maintain pH and osmotic pressure.

Organic substances: proteins (monomers - amino acids), carbohydrates (monomers - monosaccharides), lipids (glycerol + fatty acids), nucleic acids (monomers - nucleotides).

Proteins perform enzymatic, structural, transport, protective, contractile, and signalling functions; their function depends on spatial structure.

DNA is a double helix of nucleotides A, T, G, C; RNA is single-stranded with U instead of T; ATP is the universal energy carrier.

Prokaryotic cells (bacteria) lack a nucleus and membrane organelles; eukaryotic cells (plants, fungi, animals) have a nucleus and membrane-bound organelles.

Plant cell features: cellulose cell wall, chloroplasts, large central vacuole, no centrioles in higher plants.

Fungal cell features: chitin cell wall, no chloroplasts; animal cells have no cell wall and contain centrioles.

Organelles: mitochondria - energy; ribosomes - protein synthesis; chloroplasts - photosynthesis; the nucleus stores hereditary information.

Mitosis phases: prophase (chromosomes condense, nuclear envelope breaks down), metaphase (chromosomes align at the equator), anaphase (chromatids move to poles), telophase (nuclei reform).

Mitosis produces two daughter cells with a chromosome set identical to the parent cell; it underlies growth, regeneration, and vegetative reproduction.

Meiosis has two divisions and yields four haploid cells; it occurs during gamete formation.

Meiosis consequence: halving of chromosome number and recombination of hereditary material, which maintains species chromosome constancy at fertilization.

Crossing over occurs in prophase I; independent chromosome assortment occurs in anaphase I.

Interphase precedes division and includes DNA replication (chromosome doubling).

A diploid set is designated 2n, a haploid set n; in humans 2n = 46, n = 23.

Direct division (amitosis) and endomitosis are exceptions; the standard somatic division is mitosis.

Bacteria are prokaryotes: no nucleus, circular DNA, cell wall with murein; they reproduce by simple division; bacterial spores are a survival form, not a reproduction form.

Bacteria by nutrition: autotrophs (cyanobacteria) and heterotrophs (saprotrophs, parasites); by respiration: aerobes and anaerobes.

Fungi are heterotrophs with a chitin wall, reproduce by spores; moulds (penicillium, mucor), yeasts (single-celled, budding), cap fungi (symbiosis with roots - mycorrhiza).

Plant organs: root (anchor, absorption), shoot (stem, leaves, buds); a flower is a reproductive organ; fruit and seed develop after pollination and fertilization.

Photosynthesis equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ in chloroplasts, using light energy; it produces organic matter and oxygen.

Plant groups in ascending complexity: algae, mosses, ferns, gymnosperms, angiosperms; only angiosperms form flowers and fruits.

Transpiration moves water through vessels; mineral salts rise with the root pressure; phloem conducts organic substances.

Vegetative reproduction uses roots, stems, leaves, tubers, bulbs, and runners; sexual reproduction involves gametes and pollination.

Animal kingdom: invertebrates (sponges, coelenterates, worms, molluscs, arthropods, echinoderms) and vertebrates (fish, amphibians, reptiles, birds, mammals).

Arthropods: chitinous exoskeleton, jointed limbs, segmented body; insects have three body parts, six legs, and tracheal respiration.

Fish: gill respiration, two-chambered heart, single circulation; amphibians: moist skin and lungs, three-chambered heart, two circulations.

Reptiles: dry scaly skin, three-chambered heart (crocodiles four), eggs on land; birds: feathers, four-chambered heart, warm-blooded, lungs with air sacs.

Mammals: hair, mammary glands, four-chambered heart, diaphragm, live birth (except monotremes).

Digestion in animals proceeds extracellularly in a gut; the circulatory system transports substances; excretion removes metabolic wastes.

Nervous regulation is fast and precise (reflexes); humoral regulation is slower via hormones and acts through body fluids.

Classification ranks: kingdom, phylum, class, order, family, genus, species; the species name is binomial.

Organ system overview: musculoskeletal, digestive, respiratory, circulatory, excretory, nervous, endocrine, and reproductive systems.

Blood: plasma + formed elements - erythrocytes (oxygen transport, haemoglobin), leucocytes (immunity), thrombocytes (clotting).

Human circulation: two circuits; the heart has four chambers; arterial blood leaves the left ventricle via the aorta.

Respiration: gas exchange in alveoli; vital capacity is measured by spirometry; smoking damages cilia and alveolar walls.

Digestion: enzymes act sequentially - saliva (starch), gastric juice (protein), pancreatic and intestinal juice (all nutrients); the liver produces bile.

Hygiene rules: wash hands, keep food covered, follow a daily routine, avoid smoking and alcohol, get sufficient sleep and physical activity.

First aid: bleeding - apply a pressure bandage or tourniquet above the wound; fracture - immobilize the limb; burns - cool with water, do not open blisters; fainting - fresh air and elevate the legs.

Vaccination introduces weakened pathogens to form immunity; a therapeutic serum contains ready-made antibodies.

An ecosystem is a community of organisms plus their abiotic environment; it includes producers, consumers, decomposers, and abiotic factors.

Food chain example: plant → herbivore → predator; energy is lost at each trophic level (about 90%), so chains are short.

Abiotic factors: light, temperature, humidity, soil; biotic factors: predation, competition, symbiosis; anthropogenic factors: human activity.

A population is characterized by size, density, age and sex structure; limiting factors control population growth.

The biosphere is the living envelope of Earth; the boundary is set by the ozone layer above and by high temperature and pressure below.

The water cycle, carbon cycle, and nitrogen cycle link organisms and the environment; plants and cyanobacteria fix carbon and nitrogen.

Human impact: deforestation, pollution, invasive species, and habitat destruction reduce biodiversity and ecosystem stability.

Conservation measures: protected areas (reserves, national parks), the Red Book, waste recycling, and sustainable resource use.

Darwin's theory: hereditary variability provides material; the struggle for existence and natural selection preserve useful traits.

Driving forces of evolution: heredity, variability, struggle for existence, natural selection; the leading force is natural selection.

Evolutionary results: adaptation, speciation, and increasing diversity of life.

Aromorphosis is a major change raising organization level (e.g., lungs, four-chambered heart); idioadaptation is a private adaptation (e.g., beak shape).

The species criterion includes morphological, genetic, physiological, ecological, and geographic criteria; the genetic criterion is universal.

Biogeocenosis is a self-regulating system of interacting populations and the abiotic environment; its stability depends on species diversity.

Ecosystem change (succession) proceeds from pioneer communities to a stable climax community.

Evolutionary evidence: fossil record, homologous and analogous organs, rudiments and atavisms, and embryonic similarities.