Armenia Biology Unified Exam flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Cell theory

The principle that all living organisms are composed of one or more cells, that the cell is the basic unit of life, and that new cells arise from existing cells.

Prokaryotic cell

A cell lacking a membrane-bound nucleus and membrane-bound organelles, with genetic material in a nucleoid region; includes bacteria and archaea.

Osmosis

The passive movement of water across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Glycolysis

The first stage of cellular respiration, occurring in the cytosol, in which one glucose molecule is split into two pyruvate molecules, yielding a net 2 ATP and 2 NADH.

Krebs cycle

A series of reactions in the mitochondrial matrix that oxidizes acetyl-CoA, producing NADH, FADH2, ATP or GTP, and releasing carbon dioxide.

Enzyme

A protein that acts as a biological catalyst, lowering the activation energy of a reaction without being consumed or changing the reaction's equilibrium.

Mendel's law of segregation

The principle that the two alleles of a gene separate during gamete formation, so each gamete receives only one allele of each pair.

Test cross

A cross between an individual of unknown genotype showing a dominant trait and a homozygous recessive individual, used to reveal the unknown genotype.

Sex-linked trait

A trait controlled by a gene located on a sex chromosome, such as X-linked traits that appear more frequently in males.

Semiconservative replication

The process by which each new DNA molecule consists of one original parent strand and one newly synthesized strand during DNA replication.

Transcription

The synthesis of an RNA molecule from a DNA template, catalyzed by RNA polymerase, producing messenger RNA for protein synthesis.

Codon

A sequence of three nucleotides in mRNA that specifies a particular amino acid or signals a start or stop during translation.

Meiosis

A type of cell division producing four haploid daughter cells from one diploid cell over two divisions, generating genetic variation in gametes.

Crossing over

The exchange of genetic material between homologous chromosomes during prophase I of meiosis, increasing genetic variation in offspring.

Gastrulation

The stage of embryonic development in which the blastula reorganizes into three germ layers: ectoderm, mesoderm, and endoderm.

Ectoderm

The outermost germ layer of an embryo, which develops into the nervous system and the outer layer of skin.

Xylem

The vascular tissue in plants that transports water and dissolved minerals upward from the roots to the rest of the plant body.

Stomata

Small pores on the leaf surface, flanked by guard cells, that regulate gas exchange and water loss through transpiration.

Angiosperms

Flowering plants that reproduce via flowers and bear seeds enclosed within a fruit, including monocots and dicots.

Arthropods

A phylum of invertebrates with segmented bodies, jointed appendages, and a chitinous exoskeleton; the most species-rich animal group.

Closed circulatory system

A circulatory arrangement in which blood remains inside blood vessels and is pumped by a heart, as found in vertebrates and annelids.

Alveoli

Tiny thin-walled air sacs in the lungs where oxygen diffuses into the blood and carbon dioxide diffuses out.

Nephron

The functional filtering unit of the kidney, which removes wastes from blood and reabsorbs water and useful substances to form urine.

Insulin

A hormone produced by the pancreas that lowers blood glucose levels by promoting uptake and storage of glucose by cells.

Natural selection

The process by which heritable traits that increase reproductive success become more common in a population over successive generations.

Homologous structures

Body parts in different species that share a common evolutionary origin, though they may differ in function, such as vertebrate forelimbs.

Hardy-Weinberg principle

The principle that allele and genotype frequencies in a population remain constant across generations when no evolutionary forces act on it.

Trophic level

A feeding position in a food chain, such as producer or primary consumer, through which energy passes with only about 10% transfer efficiency.

Carrying capacity

The maximum population size of a species that a given environment can sustain indefinitely given available resources.

Primary succession

The ecological succession that begins on bare substrate with no pre-existing soil, such as bare rock or a newly formed volcanic island.

Biosphere

The zone of Earth where life exists, encompassing the lower atmosphere, the hydrosphere, and the upper part of the lithosphere.

Eutrophication

The enrichment of a water body with excess nutrients such as nitrogen and phosphorus, causing algal blooms and oxygen depletion.