MTLE Life Science (Grades 9-12) key terms

A phospholipid bilayer studded with proteins that surrounds every cell and controls which substances enter or leave, using selective permeability and transport proteins.

Passive movement of particles from high to low concentration; osmosis is the same process applied specifically to water crossing a semipermeable membrane. Neither requires cellular energy input.

Movement of substances against their concentration gradient through membrane proteins, powered by ATP, as in the sodium-potassium pump that maintains ion gradients in nerve cells.

A protein catalyst that speeds a specific biochemical reaction by lowering activation energy; its shape determines substrate specificity and it is not consumed by the reaction.

Loss of a protein's three-dimensional shape, and therefore its function, caused by heat, extreme pH, or heavy metals that disrupt hydrogen bonds and other weak interactions.

The sum of all chemical reactions in a cell, split into catabolic pathways that break molecules down to release energy and anabolic pathways that build molecules using energy.

The oxygen-requiring breakdown of glucose through glycolysis, the Krebs cycle, and the electron transport chain to produce ATP, with carbon dioxide and water as waste products.

The first stage of respiration, occurring in the cytoplasm without oxygen, in which one glucose molecule is split into two pyruvate molecules with a net gain of two ATP.

An anaerobic pathway that regenerates NAD+ so glycolysis can continue, producing lactate in muscle cells or ethanol and carbon dioxide in yeast.

The light-driven process in chloroplasts that converts carbon dioxide and water into glucose and oxygen, coupling light reactions that make ATP and NADPH with the Calvin cycle.

A plant cell organelle containing thylakoid membranes and the pigment chlorophyll, where light energy is captured and converted into chemical energy during photosynthesis.

A double-membraned organelle whose inner membrane hosts the electron transport chain, generating most of a eukaryotic cell's ATP through aerobic respiration.

Nuclear division producing two genetically identical daughter cells, used for growth and repair; it includes prophase, metaphase, anaphase, and telophase followed by cytokinesis.

Two successive nuclear divisions that halve chromosome number and create four genetically varied gametes through crossing over and independent assortment of homologous chromosomes.

The ordered sequence of interphase growth and DNA synthesis followed by mitotic division, tightly regulated at checkpoints so damaged DNA is not copied or passed on.

Semiconservative copying of the double helix, in which helicase unwinds DNA and polymerase builds complementary strands so each new molecule keeps one original strand.

The flow of genetic information from DNA to RNA to protein: transcription makes messenger RNA, and translation at the ribosome assembles amino acids in the order the codons specify.

Transcription copies a gene into mRNA in the nucleus; translation reads mRNA codons at ribosomes, matching each to transfer RNA carrying a specific amino acid.

A sequence of three mRNA bases that specifies one amino acid or a stop signal; the genetic code is nearly universal and redundant, with several codons per amino acid.

A heritable change in DNA sequence, such as substitution, insertion, or deletion; effects range from silent to harmful, and frameshifts usually alter every downstream codon.

Patterns described by Mendel in which alleles segregate and assort independently, producing predictable ratios such as 3:1 from a monohybrid cross of heterozygotes.

A grid used to predict offspring genotype ratios by combining the possible gametes of two parents, given each parent's genotype at the locus in question.

Genotype is an organism's allele combination at a locus; phenotype is the observable trait produced by that genotype interacting with the environment.

Exchange of chromosome segments between homologous partners during prophase I of meiosis, which reshuffles alleles and increases genetic variation in gametes.

The random orientation of homologous chromosome pairs at meiosis I, so alleles of genes on different chromosomes are inherited independently of one another.

Differential survival and reproduction of individuals whose inherited traits suit their environment, causing allele frequencies in a population to shift over generations.

The proportion of a population's gene copies represented by a particular allele; changes in these frequencies across generations define evolutionary change.

A null model in which allele and genotype frequencies stay constant absent mutation, migration, selection, genetic drift, and nonrandom mating; deviations signal evolution.

The formation of new species, usually when gene flow stops between populations; geographic isolation (allopatric) or reproductive isolation in place (sympatric) allows divergence.

An inherited feature that improves fitness in a particular environment, produced by natural selection over generations rather than acquired during an individual's lifetime.

Maintenance of stable internal conditions such as temperature and blood glucose through negative feedback loops that detect deviation and trigger corrective responses.

A regulatory circuit in which a sensor detects a change and an effector counteracts it (negative feedback) or amplifies it (positive feedback, as in childbirth).

Control of water and solute balance across membranes, achieved in kidneys by filtration, reabsorption, and secretion so body fluids stay within tolerable concentration ranges.

A feeding position in a food web, such as producer, primary consumer, or secondary consumer; only about ten percent of energy passes to the next level.

A network of interconnected feeding relationships among organisms in a community, showing how energy and matter move from producers through consumers to decomposers.

A diagram showing energy lost at each trophic level; because most energy is used in metabolism or lost as heat, higher levels support far less biomass.

The maximum population size an environment can sustain indefinitely given available food, water, space, and other limiting resources; growth slows as it is approached.

Any resource or condition, such as nutrients, light, or predation, that restricts population growth or distribution when it is in shortest supply.

Change in population size over time; exponential growth occurs with unlimited resources, while logistic growth levels off at carrying capacity as density-dependent factors intensify.

A close, lasting relationship between species, classified as mutualism (both benefit), commensalism (one benefits), or parasitism (one benefits at the other's expense).

An iterative cycle of observation, hypothesis formation, controlled experimentation, data analysis, and revision, in which hypotheses must be testable and potentially falsifiable.

A testable, falsifiable proposed explanation for an observation, stated so that predictions can be checked against evidence rather than accepted on authority.

Any factor in an experiment that can change; a valid design manipulates one independent variable while holding others constant to isolate its effect.

The comparison group in an experiment that does not receive the treatment, establishing a baseline against which the experimental group's results are measured.

Ongoing, low-stakes checks on student understanding during instruction, used to adjust teaching in real time rather than to assign a final grade.

An evaluation of learning at the end of a unit or course, such as a test or lab practical, used to judge achievement against standards and report results.

Teaching in which students investigate questions, design procedures, and construct explanations from evidence, with the teacher guiding rather than simply presenting facts.

A scoring guide listing criteria and performance levels, giving students transparent expectations and making grading of lab reports and projects more consistent.

Adjusting content, process, or product to meet varied readiness levels, interests, and learning profiles so all students can access the same learning goals.

Practices that prevent injury in science classrooms: goggles and gloves, chemical labeling and storage, eyewash and shower access, and supervised handling of specimens and equipment.

Barriers such as splash goggles, lab coats, and nitrile gloves worn to shield skin, eyes, and clothing from chemicals, heat, and biological material during laboratory work.

A document supplied with each hazardous chemical that lists its hazards, safe handling, storage, spill response, and first-aid measures for teachers and students.