AP Intermediate Botany (BIEAP) key terms

A plant body that is not differentiated into true roots, stems, and leaves; algae, fungi, and some bryophyte-like groups show this simple, undivided organisation.

A non-vascular land plant such as a moss or liverwort, with a dominant gametophyte generation and a dependent sporophyte; it needs water for fertilisation.

A vascular plant that reproduces by spores rather than seeds, such as a fern; the sporophyte is dominant and bears sporangia, usually on fronds.

A seed plant whose ovules lie exposed on cone scales rather than enclosed in an ovary, producing naked seeds; cycads, pines, and gnetums are examples.

A flowering plant whose ovules are enclosed within an ovary that matures into fruit; it shows double fertilisation and typically bears flowers with stamens and carpels.

The haploid generation of a plant life cycle that produces gametes by mitosis; in mosses it is the visible plant body, while in flowering plants it is reduced to a few cells.

The diploid generation of a plant life cycle that produces haploid spores by meiosis; in vascular plants and seed plants it is the dominant, familiar plant body.

The regular alternation of a haploid gamete-producing phase and a diploid spore-producing phase in a plant life cycle, with meiosis and fertilisation linking the two phases.

The arrangement of leaves on a stem, such as alternate, opposite, or whorled; it determines light capture and is a standard diagnostic character in morphology.

The arrangement of ovules on the inner wall or central axis of an ovary, as in marginal, parietal, axile, free-central, or basal types; it is used in fruit and flower identification.

The arrangement of sepals or petals in a flower bud before it opens, such as valvate, twisted, imbricate, or vexillary; it is a key floral diagnostic feature.

The arrangement of flowers on a floral axis, either racemose with a continuing main axis or cymose with a terminated main axis; it affects pollination and fruit display.

A strand of conducting tissue containing xylem and phloem, often with cambium and fibres; its arrangement distinguishes monocot and dicot stems and connects roots to leaves.

The complex water-conducting tissue of vascular plants, made of vessels, tracheids, fibres, and parenchyma; it transports water and dissolved minerals upward from roots.

The food-conducting tissue of vascular plants, containing sieve tubes, companion cells, phloem parenchyma, and fibres; it moves sugars from sources to sinks.

Narrow cytoplasmic channels crossing plant cell walls that connect adjacent protoplasts, allowing water, ions, and small molecules to pass between cells.

The continuous network of living protoplasts in a plant tissue joined by plasmodesmata, forming an internal route for water and solute movement between cells.

The non-living continuum of cell walls and intercellular spaces through which water and solutes can move without crossing membranes; it is the main route in roots.

A waterproof band of suberin in the radial and transverse walls of root endodermal cells that forces water and dissolved minerals to cross a membrane before entering the stele.

The tension generated in the xylem when water evaporates from leaf surfaces; cohesion between water molecules transmits this pull up the plant, driving bulk water flow.

The explanation of water ascent in plants: transpiration creates negative pressure in xylem, and cohesion plus adhesion keep the water column continuous from root to leaf.

The pattern in which sugars produced or released by source tissues such as leaves are transported through phloem to sink tissues such as roots, fruits, and growing tips.

The light-driven synthesis of ATP from ADP and phosphate in chloroplast thylakoids, coupled to electron transport through photosystems I and II during photosynthesis.

A protein-pigment complex in thylakoid membranes that absorbs light and transfers excitation energy to a reaction centre; PSII and PSI drive linear electron transport.

The light-independent sequence of reactions in chloroplast stroma in which carbon dioxide is fixed by RuBisCO onto RuBP and reduced to sugar using ATP and NADPH.

Ribulose-1,5-bisphosphate carboxylase/oxygenase, the abundant chloroplast enzyme that fixes carbon dioxide in the Calvin cycle and can also bind oxygen in photorespiration.

A wasteful process in which RuBisCO fixes oxygen instead of carbon dioxide, consuming ATP and releasing carbon dioxide; it is reduced in C4 and CAM plants by concentrating carbon dioxide.

The wreath-like leaf arrangement of C4 plants, with bundle-sheath cells surrounded by mesophyll cells; it separates initial carbon fixation from the Calvin cycle.

The cytoplasmic pathway that splits one glucose molecule into two pyruvate molecules, yielding a small net gain of ATP and NADH without requiring oxygen.

The mitochondrial cycle in which acetyl-CoA is oxidised to carbon dioxide, generating NADH, FADH2, and ATP; it feeds electrons into the respiratory chain.

ATP production in mitochondria driven by a proton gradient built by electron transport along the inner membrane, with oxygen acting as the final electron acceptor.

The unique angiosperm process in which one male gamete fuses with the egg to form a zygote and another fuses with two polar nuclei to form triploid endosperm.

The nutritive tissue formed inside a seed, usually triploid in flowering plants, that supplies the developing embryo with food or is stored for germination.

Asexual reproduction in plants that produces seeds without fertilisation, so offspring are genetically identical to the mother plant; it is useful in fixing hybrid vigour.

The development of fruit without fertilisation of ovules, producing seedless fruits such as banana; it may occur naturally or be induced by growth regulators.

The tendency of genes located close together on the same chromosome to be inherited together rather than assorting independently, producing an excess of parental combinations.

The exchange of corresponding segments between non-sister chromatids of homologous chromosomes during prophase I of meiosis, generating new allele combinations.

A cross of an individual of unknown genotype with a homozygous recessive partner, used to reveal whether the unknown is homozygous or heterozygous by the offspring ratios.

A cluster of genes in prokaryotes transcribed together from one promoter, including structural genes and regulatory sequences; the lac operon is the classic example.

A bacterial enzyme that cuts DNA at a specific recognition sequence, producing fragments with sticky or blunt ends; it is a basic tool of recombinant DNA technology.

A small, circular, extrachromosomal DNA molecule in bacteria that replicates independently and is widely used as a vector to carry foreign genes into host cells.

An in vitro technique that copies a specific DNA segment through repeated cycles of denaturation, primer annealing, and extension by a heat-stable DNA polymerase.

A graphical representation of numbers, biomass, or energy at successive trophic levels; energy pyramids are always upright because energy is lost at each transfer.

The position an organism occupies in a food chain, such as producer, primary consumer, or secondary consumer, determined by how many transfers separate it from the energy source.

The rate at which organic matter is formed in an ecosystem; gross primary productivity is total photosynthesis, while net primary productivity subtracts respiration losses.

The directional, gradual change in species composition of a community over time, from pioneer stages to a relatively stable climax community on a given substrate.

The first organisms to colonise a bare or disturbed habitat, such as lichens on rock; they modify conditions so later successional species can establish.

The relatively stable end stage of ecological succession in which species composition remains broadly balanced with the prevailing climate and soil conditions.

A collection of pressed, dried, labelled plant specimens arranged systematically; herbarium sheets serve as reference material for identification and taxonomic study.

The branch of biology concerned with describing, naming, and classifying organisms according to shared characters and evolutionary relationships, using a hierarchical system of ranks.

The system of naming each species with two Latinised words, a capitalised genus name and a lowercase specific epithet, usually printed in italics.

The permanently preserved specimen to which the scientific name of a new species is formally attached; it acts as the reference for identifying other members of that species.