:origin of eukaryotes: : :characteristics: : -membrane-bound nucleus : -mitochondria, chloroplasts, endomembrane system : -cytoskeleton : -9+2 flagella : -multiple chromosomes : -diploid life cycle stages : -mitosis : -meiosis : -sex : :3 trends in the natural selection of prokaryotes: : 1. toward muulticellular forms with cell types for specific functions : 2. complex bacterial communities where each species benefit from activities of others : 3. compartmentalizatio of different functions within single cells : :two evolutionary processes resulting in eukaryotic cells: :autogenous - invaginations and specializations -> nuclear envelope, E, R, Golgi apparatus, other endomembrane components. :endosymbiosis - mitochondria, chloroplasts, and other organelles evolved from prokaryotes living within other prokaryotes. : :endosymbiotic theory - lynn margulis : -chloroplasts descended from cyanobacteria, living in larger cells : -mitochondria descended from prokaryotic aerobic heterotrophs : -may have been parasites or undigested prey : -association progressed from this to mutaualism : -as interdependence increased, integrated into single organism : -extant organisms in endosymbiotic relatinships today :mutualism - a symbiotic relationship whre both organisms involved benefit : :alternation of generations between multicellular haploid forms and multicellular diploid forms : :sporophyte - diploid, produces spores which are reproductive cells :gametophyte - : :the evidence : -appropriate size : -inner membranes and transport systems like prokaryotes : -replicate by splitting like binary fission : -circular dna w/no histones : -contain everything for dna transcriptin/translation :were "created" through evolution : -9+2 flagella, cilia : -mitosis for large genomes : -meiosis for sexual reproduction : :evolutionary adaptions of seweed : habitat is in intertidal zone - waves/winds/tidal rhythms result in active habitat alternately covered by seawater and exposure to sunlight/drying. :structual adaptations: : -thallus plantlike body : -holdfast rootlike : -stipe stemlike to support blades : -blades leaflike large surface for photosynthesis : -air bladders floats to suspend blades near water surface : :biochemical adaptations : -cellulose cell walls contain gel-forming polysaccharides to cushion thalli against wave action and dessication (to dry out) : -red algae have lots of calcium carbonate in the cell walls - reason? : :alternation of generations between multicellular haploid forms and multicellular diploid forms. :sporophyte (actual plant) - diploid, produces spores which are reproductive cells :gametophyte - produces haploid gametes which fuse to form diploid zygote :what does diploid zygote become - : a sporophyte (after going through mitosis) :if sporophyte and gametophte generatins are morphologically different - heteromorphic : ex. laminaria fig. 26.20 p.537 :if they look alike - isomorphic : ex. ulva a green algae : :the sex stuff: :sexual reproductin is stimulated by environmental stress from shortage of jnutrients, dying of pond, etc. :isogamy - fusion of haploid gametes that are morphologically indistinguishable. the diploid zygote formed secretes a protective resistant coat. four haploids are produced when dormancy is broken. ex. chlamydomonas : :anisogamy - male/female gametes differ in size or morphology :oogamy - a type of anisogamy where flagellated sperm fertilize nonmotile egg : :plants :characteristics - adaptatins to land: : -cuticle - prevents desiccation but also gas exchange : -stomata- allows gas exchange by diffusion from surrounding air to interior of leaf : -chloroplasts in photosynthetic cells (pigments?), cell walls with cellulose, carbohydrate stored as starch in chloroplasts and other plastids. :embryophyte condition - gametes protecyted in gametangia. egg is fertilized in female gametangium where zygote develops into embryo. : :male=antheridia :female=archegonia : :life cycles: all plants have alternate generatins that are heteromorphic, with the diploid sporophyte being larger and more noticeable - except in mosses it is smaller. : :the evolutionary trend in these life cyckles is :*toward reduction of the haploid generation and dominance of the diploid :*replacement of flagellated sperm by pollen. why?? adaptation to life on land : :in plants, division replaces phyllum : :12 divisions :non vascularplants: bryophyta, hapatophyta, anthecerophyta divisions :terrestrial, multicellular, retain reproductive features of those found in aquatic algae. includes mosses liverworts, or hornworts. : :1. bryophytes - first step from water to land. problems faced: :a. desiccation - skin covering had to be waterproof or moist :b. support - on land, gravity to deal with :c. little water to provide sperm and egg easy passage :d. water minerals and carbon dioxide had to be absorbed and wastes removed :e. :bryophyte characteristics - flagellated sperm, no roots, no stems, no leaves :a. rhizoids - rootlike cells for anchorage, water/mineral absorption :b. central cylinder - stemlike cell layers act as central support and place fr food storage. :c. leaf scales - flattened ribbonlike array of photosynthetic cells :d. cutin - moisture barrier over the epidermis :e. archegonia - egg cells surrounded by layer of sterile cells :all bryophytes have dominant haploid form. mosses are representative non-vascular plants; grow in moist, shady places, absorb moisture above ground structures, less than 20 cm in height. : :vascular plants: tracheophytes :conducting tissue, called xylem and phloem, solved the problem of getting water from soil to photosynthetic tissue. all vascular plants have true roots, stems, and leaves. nine main divisios. : :xylem: provides water and ion transport from root to leaves. composed of cells called tracheids, vessel elements, fibers and wood parenchyma. :phloem: carries products of photosynthesis to non-photosynthetic cells. composedof many types of cells; sieve cells, sieve tube members, albuminous cells, companion cells, parenchyma, and fibers. : :seedless plants: whisk fern, club mosses, horse tails : :gymnosperms - naked seed : -lack enclosed chamber : -four divisions : -coniferophyta : -most large and evergreen : -pines, firs, spruce, yews, junipers, cedars : -includes some tallest and oldest : -Adaptations : -thick cuticle : -leaves are pine needles : -stomata are found in pits : -reduces water loss : -life history - pine : -male gametophyte is pollen -no antheridium : -female gametophyte - archegonium develops inside ovule : -heterosporous - male and female gametophytes develop from different spores :