BCOR 12 1nd Edition Lecture 12 Outline of Last Lecture I Gram Dyed Bacteria II Metabolic Adaptations of Prokaryotes III Types of Prokaryotes based Metabolic and Nutritional Modes IV The Human Microbiome Outline of Current Lecture I Land Plant Origin II Bryophytes III Obstacles and Rewards for moving to land IV Shared Derived Traits of the Land plants V Key features of Non vascular plants bryophytes VI Alternation of Generations Current Lecture Land plants evolved from a green algae Embryophytes land plants o Some embryophytes live in water but they went back to water after originally being on land Charophytes sister taxa of the embryophytes Embryophytes they protect the embryo o Beneficial evolution Land plants originated 475 MYA Vascular plants originated 420 MYA Extant seed plants originated 305 MYA o The oldest fossil of angiosperms type of seed plant is 125 MYA but using DNA evidence evaluation we can actually determine that they originated 305 MYA Types of bryophytes non vascular plants o Mosses o Liverworts o Hornworts Most dominant plants on Earth seed bearing plants Obstacles and Rewards for making the transition from water to land 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 Obstacles Gravity Plants were used to being weightless in water gravity made them feel how heavy they are Water was necessary for reproduction Desiccation i e drying out Rewards More efficient photosynthesis and CO2 available o Water didn t disperse the light rays and there was plentiful amounts of CO2 o Few competitors since land was inhibited o Abundant nutrients due to few competitors o No predators or pathogens The Green Algae were the species that survived and diversified into many species of land plants Shared Derived Traits of the Land Plants I II III IV V Alternation of generations a life cycle in which there is a multicellular diploid form sporophyte and a multicellular haploid form gametophyte unique to plants this idea is further discussed later in the notes Multicellular depend diploid embryos Walled spores produced by sporangia a part of the sporophyte a Spore haploid reproductive cell produced by the sporophyte by meiosis 2n n Multicellular gametophytes Apical meristems localized regions of cell division at the tips of roots and vegetables Nonvascular plants were the first to conquer land and have a life cycle dominated by gametophytes Key Features of Nonvascular plants bryophytes First plants to move from water to land Dominant gametophyte generation Form ground hugging carpets only a few cell layers thick No true roots leaves or vascular tissues Vascular tissue gives plant support structure and transport water nutrients and sugars around the plant Mosses have sporophytes that take MONTHS to grow Gametophytes support the sporophyte in the nonvascular plants Alternation of Generations Haploid part of plant GAMETOPHYTE Gametophyte produces the gametes through mitosis o Starts out as a spore but germinates and grows via mitosis into a gametophyte Gametes combine in water and fertilize Diploid part of plant SPOROPHYTE Sporophyte produces the spore via meiosis Why is alternation of generations a beneficial adaptation It divides up the labor of reproduction A multicellular gametophyte is specialized for fertilization A multicellular sporophyte is specialized for dispersal of spores on land This idea is unique to land plants REMEMBER Sporophytes spores Gametophytes gametes