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Plants

Plants. Chapters 23, 24, and 25. Chapter 23: Plant Diversity and Life Cycles. General Characteristics of Plants: Eukaryotic Multicellular Autotrophic Convert light energy into chemical energy by photosynthesis Takes place in the plant cell’s chloroplasts Range in Size. Origins of Plants.

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Plants

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  1. Plants Chapters 23, 24, and 25

  2. Chapter 23: Plant Diversity and Life Cycles • General Characteristics of Plants: • Eukaryotic • Multicellular • Autotrophic • Convert light energy into chemical energy by photosynthesis • Takes place in the plant cell’s chloroplasts • Range in Size

  3. Origins of Plants • Plants probably evolved from multicellular aquatic green algae that could not survive on land

  4. Before plants could thrive on land, they had to accomplish three things: • Absorb nutrients from their surroundings • Roots were developed • Today, about 80% of all plants species rely on symbiotic relationships with fungi called mycorrhizae

  5. Prevent drying out of their bodies • Plants have a waxy layer called a cuticle that covers the non-woody parts of the plant • Keeps water from flooding the plant tissue and keeps water from evaporating out of the plant • Reproduce without water to transmit sperm • Sperm are enclosed in pollen, a structure that keeps them from drying out • Pollen has the ability to by transported by wind or animals

  6. Plant Reproduction • A life cycle in which a haploid gametophyte alternates with a diploid sporophyte is called alternation of generations. • Gametophyte (haploid, n) stage --- gamete producing stage, sperm and egg • Sporophyte (diploid, 2n) --- spore producing stage, new plant forms by mitosis

  7. Nonvascular Plants • Reproduce by means of spores • Lack true roots, stems, and leaves • Lack vascular tissue • Use osmosis and diffusion to conduct water and nutrients through plant • Ex. Mosses • Usually found in gametophyte form which is the dominant form

  8. Seedless Vascular Plants • Do not produce seeds, reproduce with spores instead • Do contain vascular tissue and have true roots, stems, and leaves • Ex. Ferns • Dominant form is the sporophyte in vascular plants • Fern leaves are called fronds • Clusters of fern spores called sori can be found under the frond

  9. Gymnosperms—seed plants whose seeds do not develop within a fruit; “naked seed” • Ex. Conifers, evergreen • Produce cones to disperse sperm and seeds

  10. Angiosperms—seed plants whose seeds develop enclosed within a fruit; “case seed” • Fruits develop from part of a flower • Ex. Flowering plants

  11. Two types of angiosperms • Monocots—flowering plants whose seeds have one seed leaf or cotyledon • Dicots—flowering plants whose seeds have two seed leaves

  12. Gymnosperm and Angiosperm Reproduction • Sporophyte is the dominant form and the spores develop into female and male gametophytes • Female gametophyte produces eggs (ovule) , male gametophytes produce sperm (pollen) • Pollination occurs when pollen grains from the male reproductive structures of a plant transfers to the female reproductive structures of a plant

  13. Pollen can be dispersed through wind or animals • Pollen grains will develop a pollen tube to transfer sperm into the ovule where the egg is located, this is fertilization • After fertilization, the ovule develops into a seed which contains the embryo, a tough seed coat, and nutritive tissue called endosperm • Seeds may be dispersed by wind, water, animal consumption, etc…

  14. Chapter 25: Plant Processes • Plants require carbon dioxide, sunlight, and water for photosynthesis; oxygen for cellular respiration; and other minerals elements for cell organelles and enzymes • Transpiration drives water from the roots upwards to the rest of the plant • Water is pulled up the plant through cohesion of water molecules • The amount of water that evaporates off of a plant is controlled by the stomata

  15. Plant hormones stimulate or inhibit growth in a plant • A hormone is a chemical that is produced in one part of an organism and transported to another part, where it causes a response • Auxin—causes plants to bend • Gibberellins—stimulate stem elongation, fruit development, and seed germination • Cytokinins—stimulate cell division and slow the aging of plants • Ethylene—promote ripening and loosen fruits for easier harvesting • Abscisic Acid—slows the growth in plants

  16. Tropisms • Hormones can also trigger plants to respond differently called tropisms • A tropism is a response in which a plant grows toward or away from a stimulus • Phototropism—are directional movements in response to light • Thigmotropism—growth that responds to touch • Gravitropism—growth in response to gravity • Photoperiodism­—response to the length of days and nights

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