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Berkeley BIOLOGY 1B - Life Cycles Overview & Plant Group Comparisons

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Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 1 Life Cycles Overview & Plant Group Comparisons Bio 1B Fall ’05 Professor: Thomas Carlson Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 2 Life cycle: events that occur during lifespan of organism, from conception to the reproduction of offspring Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 3 Haploid (1n) Haploid cells (1n) contain one copy of each chromosome Haploid phase is a gametophyte Gametophytes produce gametes (reproductive cells) that must fuse into other gametes before growing into new diploid individuals Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 4 Diploid (2n) Contain two copies of each chromosome Diploid phase is a sporophyte Cells in the reproductive structure of the diploid sporophyte undergo meiosis & produce haploid spores Spore is a reproductive cell that grows into a new individual directly through mitotic divisionBio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 5 Dikaryotic (n + n) Cells in fungi with two separate haploid nuclei per cell Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 6 Alternation of Generations (Figs 13.6b, 29.5) Life cycles that involve: multicellular haploid stage (gametophyte) that produces gametes and alternates with multicellular diploid stage (sporophyte) that produces spores Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 7 Alternation of Generations (Figs 13.6b, 29.5, 30.2) Haploid spores are produced by meiosis from diploid sporophyte Spores germinate and divide mitotically to produce a multicellular haploid gametophyte which produces gametes by mitosis Gametes are mature sexual reproductive cells produced by mitosis from haploid gametophyte Syngamy is when two gametes fuse Haploid organism, diploid organism, or both may also reproduce asexually Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 8 Isomorphic alternation of generations the two (haploid & diploid) generations look similar morphologically - example is Ulva (green algae)Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 9 Heteromorphic alternation of generations the two generations differ morphologically with dominant haploid gametophyte phase Bryophytes (liverworts, hornworts, & mosses) - sporophyte is dependent on dominant gametophyte (Fig 30.2) Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 10 Heteromorphic alternation of generations with dominant diploid sporophyte phase: Haploid gametophyte not dependent on sporophyte: - Brown algae kelp (Laminaria) (Fig 28.21) - Pteridophytes (seedless tracheophytes) (Fig 29.14) Very reduced, tiny, short-lived haploid gametophyte dependent on sporophyte: - Gymnosperms (seed tracheophytes) (Fig 30.4, 30.6) - Angiosperms (seed/flower tracheophytes) (Figs 30.10, 30.12) Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 11 Life cycles with Unicellular Phases Do Not Represent Alternation of Generations Dominant Haploid gametophyte unicellular phase with unicellular zygotic diploid phase - unicellular green algae (e.g., Chlamydomonas) Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 12 Life cycles with Dikaryotic Phase Do Not Represent Alternation of Generations Dominant dikaryotic sporophyte multicellular phase with small haploid gametophyte multicellular phase - haploid phase NOT dependent on sporophyte for nutrition - some fungi (Basidiomycota, Ascomycota) (Fig 39.20)Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 13 Comparison: Algae/Bryophytes/ Pteridophytes/Gymnosperm/Angiosperms Life cycles/reproduction: haploid vs. diploid dominant Fertilization strategy: water vs. wind vs. animal Vascular tissue: none vs. tracheids vs. vessels Leaf type: none vs. microphylls vs. megaphylls Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 14 Life cycle/reproduction Haploid dominant bryophytes some green algae vs. Diploid dominant pteridophytes, gymnosperms, angiosperms some brown algae e.g., kelp (Macrocystis & Laminaria) Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 15 Fertilization strategies water: algae, brypophytes, pteridophytes vs. wind: gymnosperms, angiosperms vs. animal: angiosperms Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 16 Leaf type No true leaves algae, bryophytes microphyll = small leaf with one vein some pteridophytes e.g., lycopods megaphyll = multiple veins in leaves, often large leaves fern pteridophytes, gymnosperms & angiospermsBio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 17 Vascular tissue none: algae, bryophytes (except for some mosses with hydroids) vs. tracheids with lignin: pteridophytes, gymnosperms vs. vessels with lignin: some gnetophytes, angiosperms Bio 1B Fall ’05 Lecture Outline Overview of Life Cycles/Comparisons, Professor Thomas Carlson 18 Vascular Cell Types Tracheids: - elongated water-conducting cells with primary cell wall cellulose - may also contain secondary cell walls with deposits of lignin which could develop into wood to make tree growth possible Vessels: - most advanced type of water conducting tissue in plants - only found in gnetophytes and angiosperms - vessel end wall gaps enable efficient water transport Bio 1B Fall ’05 Lecture


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Berkeley BIOLOGY 1B - Life Cycles Overview & Plant Group Comparisons

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