2 The first plants were water plants (algae) Adaptations necessary for life on landThe ability to acquire waterThe ability to conserve waterThe ability to transport waterThe ability to reproduce without water
3 The first land plants…Fossils didn’t tell us much as they had soft bodies, so they didn’t preserve well500 to 600 myaPhylum Bryophyta: Mosses, liverworts and hornwortsPhylum Tracheophyta: Ferns and higher plants
4 Difficult Adaptations to land Requirements for life on land:All cells need a constant supply of water, especially those exposed to dry air like stemsAll plants must prevent water from escaping once it is obtainedFood making parts must have a support system that exposes them to the sunlight
5 Plants must be able to transport water up and food down the stem Exchange water and CO2 without dessicationReproduction in an environment that lacks standing water for the sperm to swim, and to prevent embryo from drying out
6 Have bryophytes adapted? PARTIALLY! They live on land, but still need to remain moist.Tracheophytes continued to evolve
7 Mosses, Liverworts and Hornworts Exhibit alternation of generations between haploid gametophyte and diploid sporophyte stagesGametophyte: dominant in mosses—the stage we SEESporophyte: dependant diploid phase
8 Grow in swamps, near streams in rainforests and in other moist areas Perform photosynthesis (green)Only grow a few cm tall because they don’t have xylem and phloem!Non-vascular
9 Structure of Bryophytes Rhizoids (not roots!) branch into the ground to anchor plantsMature gametophyte stage makes small umbrellas which release eggs and sperm
10 Liverworts: flat green leaves Hornworts: flat green leaves with a sporophyte generation that looks like a tiny french horn
11 Differences from other, more advanced plants—this is what limits Bryophytes Lack vascular tissueWater passes from cell to cell by osmosis…thus mosses are shortLack cuticleLose water very quicklyLack true rootsInefficient absorption and transport of waterRhizoids anchor but do not absorbHave sperm cells with flagella that have to swim to fertilize eggs
12 For these reasons, bryophytes must live in areas that are wet for at least part of the year. They can live in dry areas, but cannot grow while they are dry.
13 Alternation of Generations in mosses Life Cycle: KNOW THIS!Gametophyte stageAntheridium-male reproductive structure; produces sperm cellsArchaegonium-female reproductive structure;produces egg cellsBoth are designed to avoid dessication
14 Alternation of Generations Sporophyte stageA diploid capsule that emerges above moss plant (foot + stalk + capsule)Inside, haploid spores are producedCapsule opens, spores carried awaySpore lands in wet area, grows into PROTENEMA, which grows rhizoids and becomes the moss
15 Summary of Life Cycle Haploid gametophyte is dominant, obvious stage Diploid sporophyte is DEPENDENT, because it requires energy from the gametophyte to occurSome mosses are hermaphrodites, self or cross-fert.Water must be present for sperm to swim and syngamy to occur
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