Bumper sticker of the day: "When you do a good deed, get a receipt, in case heaven is like the IRS."


Review of Lecture 4: Invasion! Mosses and Ferns


1.Terrestrial plants have major differences from algae: need to prevent desiccation (waxy cuticle on epidermis) and have a way to facilitate gas exchange (stomata).

2.Bryophytes include mosses, liverworts and hornworts. Life cycle is similar for each of these. Gametophyte (haploid) phase is dominant. Sporophyte (diploid) dependent on gametophyte.

3.Moss lifecycle: haploid spores germinate to form protonema; protonema divides to form gametophyte; male gametophyte produces antheridium, which produces motile sperm; female gametophyte produces archegonium, which produces egg; water necessary for sperm to swim to egg; fusion of sperm and egg forms zygote (diploid); zygote divides to form sporophyte, which grows out of female gametophyte tissue.

4.Parts of the moss sporophyte: foot, seta, capsule. Haploid spores formed in capsule.

5. Ferns and fern allies: Psilophyta (whisk ferns), Lycophyta (club mosses), Sphenophyta (horsetails), Pterophyta (ferns).

6.Key innovation = vascular tissue. True leaves and a means to transport water and nutrients to these structures.

7.Life cycle of these organisms similar. Focus on fern life cycle: haploid spores germinate to form gametophyte (prothallus); archegonia form near notch, antheridium toward base; motile sperm swim to egg; zygote divides to form sporophyte (roots, rhizome, leaf blade); back of leaf blades is where sporangia form; haploid spores formed in structures clustered together into sori.

8.Mosses and ferns have ecological and economic importance.


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Last updated April 9, 1997.