CLEP Exam - Biology: Organismal Biology 2023

CLEP Exam - Biology: Organismal Biology Root, stem, leaf, flower, seed, fruit - Refer to Angiosperms picture downloaded in Desktop Roots - organ of plants that provide structure, absorb nutrients and water, and help protect against harmful external environments Stem - A vascular plant organ consisting of an alternating system of nodes and internodes that support the leaves and reproductive structures. Leaf - a flattened structure of a higher plant, typically green and bladelike, that is attached to a stem directly or via a stalk. Leaves are the main organs of photosynthesis and transpiration. Flower - The reproductive structure of an angiosperm Seed - The plant structure that contains a young plant inside a protective covering Fruit - structure in angiosperms that contains one or more matured ovaries A mature ovary of a flower that protects dormant seeds and aids in their dispersal. Water and mineral absorption and transport - - Root hairs absorb this water when they grow into the soil-particle's vicinity and then, molecule by molecule, water diffuses through the root-hair's cell membrane, flows toward the main roots, and then enters a kind of pipeline carrying the water upward to the rest of the plant. - Vascular tissue that move water and nutrients up from the soil into the rest of the plant. Also allows for differentiation of the plant body into stems, roots, and leaves - Plants require many minerals, such as calcuim and magnesium along with phosphates, nitrates and potassium ions. These minerals exist in the soil around the plant. Minerals enter root hairs through active transport, a process which requires energy The minerals are dissolved in water and transported around the plant in the xylem. - Osmotic Pressure Geophytes - general terms that refers to bulbs and other related underground nutrient storing organs Xylem - The vascular tissue through which water and nutrients move in some plants Food translocation and storage - Food manufactured by photosynthesis. Food molecules transferred from source cells to phloem tissue through active transport (energy expended to move molecules across concentration gradient). Once in phloem, sugars build up causing osmosis to occur (water enters phloem to lower sugar concentration). This causes pressure which pushes water-sugar solution through sieve plates that join the cells. This pressure pushes water-sugar to all parts of plant. Alternation of Generations in Ferns - 1) Sporophyte Generation 2) Gametophyte Generation Sporophyte Generation - - Diploid - Fronds (leaves): Sori - each contains many sporangia mounted on stalks - Within each sporangium, spore mother cells undergo *meiosis* producing *4 haploid spores each* Gametophyte Generation - - If spore is blown into a suitable moist location: Germinates into a filament of cells - Grows into a *prothallus* with: ---Rhizois: absorb water and minerals from soil --Archegonia: produce single egg (by mitosis) or --Antheridia: form swimming sperm (by mitosis Fertilization - - if moist - sperm swim to archegonia (single egg) -- usually on another prothallus because of 2 kinds of sex organs do not mature at same time on single prothallus - restores the diploid number from haploid to diploid and begin new sporophyte generation - Embryo sporophyte develops a *foot* that penetrates the tissue of the prothallus and enables the sporo to secure nourishment until it becomes self- sifficient Alternation of Generations in flowering plant - 1) Meiosis 2) Fertilization Must occur alternately if sexual reproduction is to continue Meiosis - - Chromosome number is reduced from diploid to haploid number Fertilization (flowering) - - The nuclei of two gametes fuse, raising the chromosome number from haploid to diploid Growth and development: hormonal control in plants - All plant growth occurs by cell division and cell elongation - Cell division occurs primarily in regions of undifferentiated cells known as *meristems* - Secondary growth is the increase in girth of stems and roots Plants have five classes of hormones - Auxins | Gibberellins | Cytokinins | Abscisic Acid | Ethylene Plant hormones are chemicals that in small amounts promote and influence the growth, development and differentiation of cells and tissues. Hormones are vital to plant growth; effecting processes in plants from flowering to seed development, dormancy, and germination. They regulate which tissues grow upwards and which grow downwards, leaf formation and stem growth, fruit development and ripening, as well as leaf abscission and even plant death. Auxins - Growth hormones in plants that are responsible for phototropisms and apical dominance, the preferential growth of a plant towards the sun Gibberellins - A growth hormone that causes a wide variety of effects. One role is to stimulate growth of stems by promoting cell division. Farmers use it to make fruit grow larger. A class of related plant hormones that stimulate growth in the stem and leaves, trigger the germination of seeds and breaking of bud dormancy, and stimulate fruit development. Cytokinins - plant hormones that increase the rate of cell division and in some plants, slows the aging process of flowers and fruits Antagonistic to auxin, promotes branching in stems Abscisic Acid - during water stress, ___ levels increase which causes the stoma to close to conserve water