Biology 200B 1st Edition Lecture 23 Chapter 31 Green Algae and PlantsI. Ecosystem servicesII. Green algaeIII. Shared traits IV. Challenges with terrestrial habitatsV. Life cyclesGreen Algae and PlantsEcosystem services:- Produce oxygen- Primary producers- Moderate climate- Build and hold soilResources for humans:- Food- Fuel – biofuel, fossil - Fibers and materials- Pharmaceuticals Humans began domesticating plants ~ 10,000 years ago Agriculture: several independent origins Green Algae:- Mostly freshwater, some marine- Named for bright green pigments - Unicellular, multicellular, and coenocitic- Some are symbiontsTraits shared by green algae and plants- Same photosynthetic pigments- chlorophyll a and b, carotenes These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Same cell wall structure (cellulose), thylakoid structure, sperm structure- DNA sequences - Part of Kingdom Plantae - Charophycean green algae are closest relatives to land plants Life began in the water 3.5 bya- Most of evolutionary history of life has occurred in the water- Invasion of land was only ~ 500-450 myaDistinguishing characteristics of land plants1. Alternation of generations 2. Multicellular embryos dependent on parent plant 3. Sporangia that produce tough cell walled spores Challenges associated with terrestrial habitats:1. Controlling H2O loss while still exchanging gasesa. Some byrophytes have pores (always open); not good in dry environment b. Some plants are desiccation tolerant - Can dry out to 0% free water- Virtually dead (no metabolism)- Can revive rapidly - Earliest plants might have used this - Vascular plants have stomata for gas exchange and cuticle to prevent H2O loss2. Surviving intense sunlight (UV radiation) a. Flavonoids, carotenoids (orange accessory pigments in chloroplasts) take on new role:- Algae have these to help harvest light energy under water- Land plants absorb harmful UV3. Growing upright on landa. Move H2O and sugar rapidly throughout body and holds body upright 4. Reproducing with less/no H2Oa. Adaptation: protect gametes; plants produce gametes in protective structuresb. Adaptation: protect offspring; plants protect and feed embryo c. Adaptation: produce a propagule that be dispersed in dry conditions - Very resistant to harsh temperatures and dry conditions - Sporopollenin – spores of seedless plant, pollen of seed plants; molecular structure not yet known 5. Using animals to disperse pollen/seedsLife Cycle of Plants- Plants have “alternation of generations”- Closest algal relatives do not- Very different from animals- Sporic meiosis - Gametophyte haploid, sporophyte diploid - Ex: Mendell’s pea
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