Lecture 14. 1. Challenges of land livinga. Drying out: exposure to airb. Structural support: stand up without support of waterc. Reproduction: new way to transport their gametes without water.2. Adaptations to land dwellinga. Embryophytic: all have some structure to protect and prevent embryo from drying out.b. Cuticle: prevent body themselves from drying out; it is excretion of waxy substance -> traps water inside the plant -> prevent the air get in.c. Stomata: little tiny holes that open to let air in; to get carbon dioxide and close to prevent plant to dry out.d. Pigmentation: block out UV radiation.e. Fungal relationship: get nutrient from the soil through fungi.f. Tracheid cells: allow water and nutrients to spread throughout the body -> Plant becomes bigger.- Xylem: water and minerals from root to the leaves - Phloem: nutrients and sugar from the leaves to the root which cannot photosynthesize.g. Seeds: ultimate protection of embryo.3. Diplontic life cycle- Animal and human life cycle- Only diploid stage is multicellular- Gametes are haploid, but they are always unicellular. Never divide by mitosis.- Only diploid stages undergo meiosis.4. Haplodiplontic life cycle- Both haploid and diploid stages are multicellular.- Haploid multicellular mature gametophyte produce gamete via mitosis.- Spores swim, and so do gametes; incredible adaptation is required for once-aquatic plants.- In moss, the gametophytic stage is dominant and sporophytic stage is extremely short. In later plants, the sporophytic stage is dominant.- Haploid phases are sensitive to deleterious recessive mutation.a. Sporophyte- Meiosis occurs in specialized structures on sporophyte called sporangia. - Inside the sporangia, diploid spore mother cells produce haploid daughter spores, which will give rise to spore cells- Indicates the transition between diploid to haploid generation.b. Gametophyte - Mature haploid organism- Produces gametes by mitosis (Antheridium: sperm, Archegonium: eggs)- Once the gametes are produced, they come together and they fuse:fertilization or syngamy5. “Plants”- refer land plants.- some include green algae.6. Red algae; Rhodophyta- Outgroup of “plants”- multiple pigments (not only red) and vary in size.- Chloroplast formation- Primary endosymbiosis: Cyanobacteria was engulfed in a prokaryotic cell and it was survived within the cell. In this figure, this is an ancestor of green algae, land plants and red algae. - Secondary endosymbiosis: Green algae or red algae, which was derived from the primary endosymbiosis organism, was engulfed in another organism, and the properties of the algae still remained in the organism. This would be a brown algae. - Chlorophyll types- Land plants all arose through the green algae lineage, so are photosynthetic due to primary endosymbiosis. - Chlorophyll derived from original cyanobacteria. Plant group Chlorophyll typeRed algae aBrown algae a,cGreen algae a,bLand plant a,b- a: from primary endosymbiosis- b: from the ancestor- c: from secondary endosymbiosis- a,b -> green color.7. Chlorophytes- the 1st plant-like algae.- Flattened cell form; similar to land plant- It is very diverse group. (unicellular + multicellular)a. Volvox (unicellular)o complex, motile colonial organism.o Forms hollow spheres of 500~6000 individual volvox cells.o Within colony, very few are reproductive: represents early form of multicellularity.o Cells are not connected, loosely associated buy only some of them reproduce for the entire group.b. Green algae (multicellular)o haplodiplontic life cycle8. Stoneworts- Sister taxa of land plants- Filamentous form rather than flattened cell shape- Ex) Chara sp.- Apical growth: common traits in land plant -> These organisms led to land plants.- Form green mats around the edges of water at lake: edge habitat.9. Non-vascular plant (Bryophyte)- They do have vascular structure but not as good: simple diffusion- No tracheid cells- Embryophytic- Gametophyte dominant: spend most of their lives haploids.- Sporophyte dependent on gametophyte for nutrient: Sporophyte grows out of gametophyte.- Require water for sexual reproduction.- Ex) Moss (Liverworts, hrnworts) Egg from the archgonia and sperm from the antheridia fuse during fertilization to make a 2N embryo. Moreover, it only happens in wet environment. Sporophyte is very tiny and short-lived. Not photosynthetic Sporophyte dependent on gametophyte for nutrient: Sporophyte grows out of gametophyte.10.Seedless vascular plants (Trachophytes)- Similar to bryophyte: Embryophytic, Need water for sexual reproduction- Sporophyte dominant (diploid organism): the gametophyte in the tracheophyte is free-living gametophyte, but lacks vasculature, so itdoesn’t get very big. However, the dominant diploid sporophyte get very large. - Tracheid cells are small and tiny.- Ex) Club mosses (Lycophytes)o The earliest vascular plants that has tracheid cells.o Mostly look like regular bryophytic mosses, but larger.o Microphylls: an appendage supplied by a single, unbranched vein. Origin of vascular leaves differentiates them from the other vascular plants.11.Monilophaytes- Sister group of seed plant- Megaphylls: main leaf type seen in complex seed plant- Ex) Horsetails (puzzle plant)o Sporophytes have ribbed jointed photosynthetic stems.o No leaveso Continuous growing- Ex) Ferno Sori: underneath of their leaves, clusters of sporangia, release their spores. o Found in moist environment: the sperm from the gametophytic stage needs water to swim to the egg.o Life cycle: Spores develop into heart-shape structure. Unlike moss, after fertilization, sporophyte grows from gametophyte. When it comes long enough to photosynthesize, gametophyte die. Independent between gametophyte and
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