ЦТ Biology key terms

The type of nuclear division in which one parent nucleus produces two genetically identical daughter nuclei with the same chromosome number, usually followed by cytokinesis and forming the basis of growth and asexual reproduction.

A reduction division in which one diploid nucleus gives rise to four haploid nuclei through two successive divisions, with crossing over and independent assortment generating genetically varied gametes or spores.

The exchange of corresponding segments between non-sister chromatids of homologous chromosomes during prophase I of meiosis, which recombines alleles and increases genetic variation among offspring.

The synthesis of an RNA molecule from a DNA template catalysed by RNA polymerase, producing messenger RNA or other RNA types that carry genetic information out of the nucleus in eukaryotes.

The process in which ribosomes read the sequence of codons on messenger RNA and assemble the corresponding sequence of amino acids into a polypeptide chain with the help of transfer RNA.

The system in which each triplet of nucleotides in messenger RNA specifies one amino acid or a stop signal, and which is nearly universal, degenerate and read without overlapping from a fixed start.

The semi-conservative copying of a DNA molecule in which each strand serves as a template for a new complementary strand, ensuring that daughter cells receive complete and identical genetic information.

One of the alternative forms of the same gene occupying a particular locus on a chromosome, which may be dominant or recessive and determines the variant of a trait an organism expresses.

The complete set of genes or the particular allele combination an organism carries, which interacts with environmental conditions to determine the observable characteristics of that organism.

The observable characteristics of an organism resulting from the interaction between its genotype and environmental factors, including appearance, physiology and behaviour measurable by an observer.

Non-heritable variation in the phenotype caused by environmental influences acting on a fixed genotype, such as differences in body size or leaf colour produced by nutrition, light or temperature.

A heritable change in the nucleotide sequence of DNA, ranging from a single base substitution to chromosomal rearrangements, which may alter gene function and provides raw material for evolution.

The light-dependent synthesis of organic compounds from carbon dioxide and water in chloroplasts, releasing oxygen and storing light energy as chemical energy in sugars and other products.

The synthesis of organic compounds from carbon dioxide using energy released by the oxidation of inorganic substances such as ammonia, hydrogen sulfide or iron compounds, performed by certain bacteria.

The anaerobic first stage of carbohydrate breakdown in the cytoplasm, in which one glucose molecule is converted into two pyruvate molecules with a net gain of ATP and reduced coenzyme.

The oxygen-dependent oxidation of organic molecules, chiefly glucose, in mitochondria, releasing carbon dioxide and water and converting the stored energy into a large yield of ATP.

Adenosine triphosphate, the universal energy carrier of cells, which stores energy in its phosphate bonds and releases it when hydrolysed to ADP and phosphate to drive cellular work.

The green photosynthetic pigment in chloroplasts and cyanobacteria that absorbs mainly red and blue-violet light and converts light energy into the chemical energy used in photosynthesis.

An organelle bounded by a double membrane, containing stacks of thylakoids and a stroma, that carries out photosynthesis and contains its own circular DNA and ribosomes.

A small non-membrane-bound organelle composed of ribosomal RNA and proteins that serves as the site of protein synthesis by translating messenger RNA in both prokaryotic and eukaryotic cells.

A network of membrane-bound channels and sacs in the cytoplasm; the rough form bears ribosomes and synthesises proteins, while the smooth form produces lipids and participates in transport.

A stack of flattened membrane sacs that modifies, sorts and packages proteins and lipids received from the endoplasmic reticulum and forms vesicles and lysosomes for transport and secretion.

A membrane-bound vesicle containing hydrolytic enzymes that digests worn-out organelles, food particles and engulfed material within the cell, functioning in intracellular digestion and recycling.

An organism whose cells lack a membrane-bound nucleus and membrane-bound organelles, having circular DNA in a nucleoid, 70S ribosomes and a cell wall of peptidoglycan in bacteria.

An organism whose cells possess a true nucleus enclosed by a nuclear envelope and contain membrane-bound organelles such as mitochondria, chloroplasts and the endoplasmic reticulum.

A double-membrane organelle with an inner membrane folded into cristae, where the reactions of aerobic respiration and oxidative phosphorylation produce most of the cell's ATP.

An organism able to synthesise its own organic nutrients from inorganic substances using light or chemical energy, forming the producer level of food chains in ecosystems.

An organism that cannot synthesise its own organic food and must obtain energy and carbon by consuming other organisms or their remains, functioning as a consumer or decomposer.

An organism, mainly bacteria and fungi, that breaks down dead organic matter and wastes into simpler inorganic substances, recycling mineral nutrients back into the ecosystem.

A relatively stable community of interacting populations of different species together with the abiotic conditions of a defined area, exchanging matter and energy as a single ecological unit.

A position occupied by a group of organisms in a food chain according to how many energy-transfer steps separate them from the primary producers at the base.

The differential survival and reproduction of individuals whose heritable traits make them better adapted to current conditions, causing favourable allele frequencies to increase over generations.

The relative ability of an organism to survive and leave viable offspring in a given environment, measured as its contribution of genes to the next generation compared with other individuals.

A heritable feature or process that improves an organism's chance of survival and reproduction in its particular environment and that has arisen through natural selection over generations.

The maintenance of a relatively constant internal environment, such as temperature, pH, blood glucose and water balance, by coordinated physiological feedback mechanisms in the living organism.

A control mechanism in which a change in a regulated variable triggers a response that counteracts the initial change, thereby stabilising the variable around a set point.

An acquired response, formed by repeated pairing of a neutral stimulus with an unconditioned stimulus, that is mediated by temporary connections in the cerebral cortex and can fade if unreinforced.

The integrated activity of the cerebral cortex and subcortical structures that underlies conditioned reflexes, learning, memory, speech and complex adaptive behaviour in humans and animals.

The rapid control of organs and systems by nerve impulses travelling along reflex arcs, allowing precise and short-lived responses that coordinate body functions with external changes.

The formation of mature haploid sex cells through mitotic multiplication of precursor cells followed by meiotic division and maturation, producing spermatozoa in males and ova in females.