Scio NSZ Biology flashcards

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

Cell theory

All living organisms are made of one or more cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.

Homeostasis

The maintenance of a stable internal environment in an organism through feedback mechanisms that counteract deviations from a physiological set point.

Enzyme function

Enzymes are protein catalysts that lower the activation energy of reactions, are not consumed, and are sensitive to temperature and pH.

Prokaryote vs eukaryote

Prokaryotes lack a membrane-bound nucleus and organelles; eukaryotes have a nucleus and membrane-bound compartments such as mitochondria and chloroplasts.

Fluid mosaic model

The plasma membrane is a phospholipid bilayer with embedded proteins, cholesterol, and glycoproteins, giving it a fluid, mosaic-like structure.

Osmosis

The diffusion of water across a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Mitochondrion

Organelle that performs aerobic cellular respiration, producing most of the cell's ATP; it contains its own circular DNA and ribosomes.

Mitosis versus meiosis

Mitosis yields two genetically identical diploid cells for growth; meiosis yields four genetically distinct haploid gametes for sexual reproduction.

Golgi apparatus

An organelle that modifies, sorts, and packages proteins and lipids received from the endoplasmic reticulum for transport or secretion.

DNA base pairing

In double-stranded DNA, adenine pairs with thymine via two hydrogen bonds and guanine pairs with cytosine via three hydrogen bonds.

Mendel's law of segregation

The two alleles of a gene separate during gamete formation, so each gamete carries only one allele for each gene.

Monohybrid cross ratio

A cross between two heterozygotes (Aa × Aa) produces a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio in offspring.

Transcription

The synthesis of an mRNA molecule from a DNA template, catalyzed by RNA polymerase, occurring in the nucleus of eukaryotes.

Sex-linked inheritance

Traits carried on sex chromosomes, usually the X chromosome; an affected father passes the allele to all daughters but no sons.

Hardy-Weinberg equation

p² + 2pq + q² = 1 describes genotype frequencies in a non-evolving population, where p and q are allele frequencies.

Heart blood flow

Blood travels right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta.

Alveoli

Thin-walled air sacs in the lungs with a large surface area and rich capillary supply where oxygen and carbon dioxide are exchanged.

Nephron

The functional unit of the kidney; filtration occurs in the glomerulus and reabsorption mainly in the proximal convoluted tubule.

Insulin and glucagon

Pancreatic hormones regulating blood glucose: insulin lowers glucose by promoting cellular uptake, while glucagon raises it by promoting glycogen breakdown.

Neuron depolarization

During a nerve impulse, sodium ions enter the neuron causing depolarization, followed by potassium efflux that repolarizes the membrane.

Photosynthesis equation

6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂, occurring in chloroplasts using light reactions and the Calvin cycle.

Xylem and phloem

Xylem transports water and minerals upward from roots; phloem transports sugars bidirectionally from sources to sinks.

Transpiration

Water loss through stomata that creates tension pulling water upward through the xylem; regulated by guard cells.

Auxin

A plant hormone promoting cell elongation; it accumulates on the shaded side of stems, causing phototropism toward light.

Arthropod characteristics

The most species-rich animal phylum, with a chitin exoskeleton, segmented body, and jointed appendages; includes insects and crustaceans.

Closed vs open circulation

Closed systems keep blood within vessels (vertebrates, annelids); open systems bathe organs directly in hemolymph (arthropods, mollusks).

Nitrogenous waste types

Animals excrete nitrogen waste as ammonia (aquatic), urea (mammals), or uric acid (birds, reptiles) to conserve water.

Carrying capacity

The maximum population size an environment can sustain indefinitely given available resources, denoted K in logistic growth models.

Ten percent rule

Only about 10% of energy at one trophic level is transferred to the next; the rest is lost mainly as heat.

Symbiosis types

Mutualism benefits both species, commensalism benefits one without affecting the other, and parasitism benefits one while harming the host.

Natural selection

Heritable variation combined with differential reproductive success causes traits that improve fitness to increase in frequency over generations.

Homologous structures

Structures in different species sharing common ancestry but possibly different functions, such as the forelimbs of vertebrates.