Estonian Basic-School Biology Exam cheat sheet

Taxonomic hierarchy from broadest to narrowest: domain, kingdom, phylum, class, order, family, genus, species; the species name is written as Genus + species (e.g. Homo sapiens), italicised, with the genus capitalised.

The five-kingdom scheme: Monera (prokaryotes), Protista (single-celled eukaryotes), Fungi, Plantae, Animalia; the three-domain scheme splits prokaryotes into Bacteria and Archaea.

Bacteria: prokaryotic, no membrane-bound nucleus or organelles, cell wall of peptidoglycan, reproduce by binary fission, may be autotrophic or heterotrophic, decomposers or pathogens.

Fungi: eukaryotic, cell walls of chitin, heterotrophic by absorption, body is mycelium of hyphae, reproduce by spores; yeasts are unicellular, moulds and mushrooms form fruiting bodies.

Plants: eukaryotic, multicellular, cell wall of cellulose, photosynthetic with chlorophyll, alternation of gametophyte and sporophyte generations; divided into algae, mosses, ferns, gymnosperms, angiosperms.

Animals: eukaryotic, multicellular, heterotrophic, no cell wall, most have tissues and organs, usually motile at some life stage; invertebrates lack a backbone, vertebrates have one.

Key vertebrate classes: fish (gills, scales, external fertilisation), amphibians (moist skin, metamorphosis), reptiles (dry scaly skin, amniotic eggs), birds (feathers, endothermic), mammals (hair, mammary glands, endothermic).

Identification decision rule: presence of a nucleus distinguishes eukaryotes from prokaryotes; cell wall composition separates plants (cellulose) from fungi (chitin) from bacteria (peptidoglycan); nutrition mode separates autotrophs from heterotrophs.

Prokaryotic cell: no nuclear membrane, circular DNA in the nucleoid, 70S ribosomes, no mitochondria, chloroplasts or endoplasmic reticulum; typical of bacteria and archaea.

Eukaryotic cell organelles: nucleus (DNA, control), mitochondria (aerobic respiration, ATP), chloroplasts (photosynthesis, plants only), ribosomes (protein synthesis), ER (transport and synthesis), Golgi (modification and packaging), lysosomes (digestion), vacuole (storage, turgor).

Plant versus animal cell: plant cells have a cellulose cell wall, large central vacuole and chloroplasts; animal cells have centrioles and no cell wall.

Cell membrane is a phospholipid bilayer with embedded proteins; it is selectively permeable and controls exchange of substances by diffusion, osmosis and active transport.

Levels of organisation: cell → tissue → organ → organ system → organism; a tissue is a group of similar cells with a common function, an organ combines several tissues.

Main tissue types in animals: epithelial (covering), connective (bone, blood, cartilage), muscle (smooth, skeletal, cardiac), nervous (neurons). Plants: meristematic, ground (parenchyma), vascular (xylem, phloem), epidermal.

Diffusion moves substances from high to low concentration without energy; osmosis is diffusion of water across a selectively permeable membrane; active transport moves substances against a gradient and requires ATP.

Cell division: mitosis produces two genetically identical diploid cells for growth and repair; meiosis produces four haploid gametes with recombination and halved chromosome number.

Root functions: anchorage, absorption of water and mineral ions via root hairs, storage; the root tip has a root cap, meristematic zone, elongation zone and maturation zone.

Stem: supports leaves and flowers, conducts water and minerals upward in xylem and sugars in phloem, may store nutrients; dicot stems arrange vascular bundles in a ring, monocots scattered.

Leaf structure: epidermis with stomata and guard cells, palisade mesophyll (main photosynthesis), spongy mesophyll (gas exchange), veins with xylem and phloem; stomata open for CO2 and close to limit water loss.

Photosynthesis equation: 6CO2 + 6H2O + light energy → C6H12O6 + 6O2, occurring in chloroplasts with chlorophyll; light reactions produce ATP and NADPH, the Calvin cycle fixes CO2.

Limiting factors of photosynthesis: light intensity, CO2 concentration and temperature; raising the factor furthest from its optimum increases the rate, other factors held constant.

Mineral nutrition: nitrogen for proteins and chlorophyll, phosphorus for ATP and nucleic acids, potassium for enzyme function and water regulation; deficiency shows as chlorosis or stunted growth.

Transpiration is water loss as vapour through stomata, driven by the water potential gradient; it pulls water up the xylem (transpiration stream) and cools the leaf.

Plant reproduction: asexual by runners, tubers, bulbs, cuttings; sexual in angiosperms involves flower parts - sepals, petals, stamens (anther, filament), carpel (stigma, style, ovary) - pollination, fertilisation, fruit and seed formation.

Growth: primary growth from apical meristems lengthens roots and shoots; secondary growth from lateral cambium thickens stems; germination needs water, oxygen and a suitable temperature.

Nutrition modes: filter feeding (bivalves, whales), herbivory, carnivory, omnivory, parasitism; the digestive tract may be a gastrovascular cavity (cnidarians) or a complete tube with mouth and anus.

Digestion sequence in vertebrates: mechanical breakdown in mouth, enzymatic breakdown in stomach (pepsin, acid) and small intestine (amylase, protease, lipase), absorption in small intestine villi, water reabsorption in large intestine.

Respiration: gills extract dissolved oxygen in water; lungs ventilated by pressure changes in amphibians, reptiles, birds and mammals; insects use tracheae with spiracles; fish use countercurrent gill flow.

Circulation: open systems (insects, most molluscs) bathe organs in haemolymph; closed systems keep blood in vessels; fish have a single circuit, birds and mammals a double circuit with four chambers.

Blood components: plasma, red blood cells (haemoglobin, oxygen transport), white blood cells (defence), platelets (clotting); arteries carry blood away from the heart, veins toward it, capillaries exchange substances.

Excretion and osmoregulation: kidneys filter blood into urine, removing nitrogenous waste; freshwater fish excrete dilute urine, marine bony fish drink seawater and excrete concentrated salts.

Reproduction: asexual (budding in Hydra, fragmentation, parthenogenesis) versus sexual; external fertilisation typical of fish and amphibians, internal of reptiles, birds and mammals; development may be oviparous, ovoviviparous or viviparous.

Nervous and hormonal control: neurons transmit electrical impulses, synapses use neurotransmitters; hormones such as insulin, adrenaline and sex hormones act via the blood to regulate body functions.

Digestive system: mouth, oesophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine, rectum; liver produces bile, pancreas secretes enzymes and bicarbonate into the duodenum.

Respiratory system: nose, pharynx, larynx, trachea, bronchi, bronchioles, alveoli; gas exchange by diffusion across the thin alveolar wall into capillaries; the diaphragm and intercostal muscles drive ventilation.

Circulatory system: heart with right atrium, right ventricle, left atrium, left ventricle; pulmonary circuit carries deoxygenated blood to the lungs, systemic circuit delivers oxygenated blood to the body.

Blood pressure and cardiac cycle: systole is contraction, diastole relaxation; normal adult pressure about 120/80 mmHg; the SA node sets the heart rhythm.

Excretory system: kidneys contain nephrons that filter blood, reabsorb water and glucose, and secrete urine to the bladder via ureters and urethra; the skin and lungs also excrete.

Nervous system: central (brain, spinal cord) and peripheral; reflex arc is receptor → sensory neuron → interneuron → motor neuron → effector; the cerebrum handles thought and voluntary action.

Endocrine system: pituitary (master gland), thyroid (thyroxine, metabolism), pancreas (insulin lowers blood glucose, glucagon raises it), adrenal glands (adrenaline), gonads (sex hormones).

Immune system: non-specific defences (skin, mucous membranes, phagocytes) and specific immunity via lymphocytes and antibodies; vaccination exposes the body to antigens to create memory cells.

Homeostasis: negative feedback keeps temperature near 37 °C, blood glucose near 5 mmol/L and pH stable; sweating and vasodilation cool the body, shivering and vasoconstriction warm it.

A gene is a section of DNA coding for a protein or trait; alleles are alternative forms of a gene; genotype is the allele combination, phenotype the observable trait.

Dominant alleles are written with a capital letter and mask recessive alleles in heterozygotes; recessive traits appear only in homozygotes (aa).

Monohybrid cross of Aa × Aa gives a 3:1 phenotypic ratio and 1:2:1 genotypic ratio; a test cross with a recessive homozygote reveals an unknown dominant genotype.

Human chromosomes: 46 in somatic cells, 23 pairs, with one sex chromosome pair (XX female, XY male); gametes are haploid with 23 chromosomes.

Meiosis halves the chromosome number, and crossing over plus independent assortment produce genetic variation in gametes.

Sex-linked traits such as red-green colour blindness and haemophilia are carried on the X chromosome; males (XY) express recessive X-linked alleles more often than females.

DNA structure: a double helix of two strands with sugar-phosphate backbones, bases A-T and G-C paired by hydrogen bonds; the sequence encodes proteins via transcription and translation.

Mutation is a change in DNA sequence; it may be neutral, harmful or beneficial, and is the ultimate source of new alleles; only germ-line mutations are inherited.

Human genetics: ABO blood groups show multiple alleles (IA, IB, i) and codominance; pedigree analysis traces inheritance patterns such as autosomal dominant, autosomal recessive and X-linked.

Natural selection requires heritable variation, competition for limited resources, differential survival and reproduction, and change in allele frequencies over generations.

Adaptation is a heritable feature that increases fitness in a given environment; analogous structures (bird and insect wings) arise by convergence, homologous structures (forelimb bones) by common descent.

Evidence for evolution: fossil record, comparative anatomy, embryology, molecular homology (DNA and protein sequences), biogeography and observed change such as antibiotic resistance.

Speciation occurs when populations become reproductively isolated, for example by geographic barriers (allopatric) or by polyploidy and behavioural isolation (sympatric).

Geological time scale order: Precambrian, Palaeozoic (Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian), Mesozoic (Triassic, Jurassic, Cretaceous), Cenozoic.

Key events: first life about 3.5–4 billion years ago in the oceans, oxygen accumulation from cyanobacteria, colonisation of land by plants and arthropods, age of dinosaurs, extinction of non-avian dinosaurs about 66 million years ago.

Mass extinctions (five major events) remove many species and open ecological niches; the Permian–Triassic event was the largest, and the Cretaceous–Palaeogene event is linked to an asteroid impact.

Theories of evolutionary rate: gradualism assumes slow continuous change, punctuated equilibrium assumes long stasis interrupted by rapid change; both are supported by different parts of the fossil record.

Levels of ecological organisation: organism → population → community → ecosystem → biome → biosphere; a population is individuals of one species in one area, a community is all species present.

Food chain direction shows energy flow from producer to consumer; arrows point to the consumer; decomposers break down dead matter and return nutrients to the soil.

Trophic levels: producers (level 1), primary consumers (2), secondary consumers (3), tertiary consumers (4); typically only about 10 % of energy passes to the next level.

Ecological pyramid types: numbers, biomass and energy; the energy pyramid is always upright because energy is lost as heat at each transfer.

Symbiosis types: mutualism (both benefit, e.g. lichen, mycorrhiza), commensalism (one benefits, other unaffected), parasitism (one benefits, host harmed); competition and predation are also interactions.

Population growth: exponential growth under unlimited resources, logistic growth limited by carrying capacity; factors include birth rate, death rate, immigration and emigration.

Nutrient cycles: carbon cycle (photosynthesis, respiration, combustion, decomposition), nitrogen cycle (fixation, nitrification, assimilation, denitrification), water cycle (evaporation, condensation, precipitation).

Adaptation to environment: morphological (thick fur, water-storing stems), physiological (hibernation, dormancy), behavioural (migration, nocturnal activity).

Human impact: greenhouse gases raise the greenhouse effect and global temperature, sulphur and nitrogen oxides cause acid rain, fertilisers cause eutrophication, habitat loss and invasive species reduce biodiversity; conservation measures include protected areas and sustainable resource use.

Hypothesis is a testable, falsifiable statement; an experiment must include a control group and change only one independent variable at a time.

Variables: independent (manipulated), dependent (measured), controlled (kept constant); a control group receives no treatment or a standard treatment for comparison.

Validity means the experiment measures what it claims; reliability means repeated measurements give consistent results; accuracy is closeness to the true value.

Measurement rules: use SI units (metre, kilogram, second, ampere, kelvin, mole, candela), read instruments to the correct precision, record raw data in a table before calculating means.

Calculate the mean by summing values and dividing by the count; percentage change = (new − old) / old × 100; magnification = image size / actual size.

Graph choice: line graph for continuous variables, bar chart for categories, pie chart for proportions; the independent variable goes on the x-axis, the dependent on the y-axis, and axes are labelled with units.

Drawing conclusions: state whether the hypothesis was supported, cite the data, note anomalies and identify sources of error; do not claim causation from correlation alone.

Working with sources: distinguish primary from secondary sources, check author, date and methodology, and cite sources; a scientific claim should be supported by reproducible evidence.

Safety and ethics: wear goggles and follow teacher instructions with chemicals, heat and sharp tools; living organisms must be treated humanely and fieldwork must not damage habitats.