Biology 200B 1st Edition Lecture 24Chapter 31 Green Algae and PlantsI. Ecosystem servicesII. Green algaeIII. Shared traits IV. Challenges with terrestrial habitatsV. Life cyclesChapter 31 (continued)VI. BrophytesVII. Seedless vascular plantsVIII. Seed plantsIX. Specialized gametophytes Chapter 31 Continued Bryophytes - >20,000 species known- 3 groupso liverworts, hornworts, mosses- not monophyletic Taxonomic terminology - Bryophyte – informal name for all nonvascular plants - Phylum Bryophyta – mosses- Phylum Hepaticophyta – liverworts- Phylum Anthocerotophyta – hornwortsNonvascular plants – some have very simple, unspecialized, conducting cells - no true xylem, phloem 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.Mosses:- Mostly moist, shady places with low pH- Leafy gametophytes - Have spirally-arranged leaves- Usually appear radially symmetric Liverworts and HornwortsBryophytes have dominant gametophyte (green plant most easily seen in nature) generation Sporophyte is very small capsule that produces spores – usually ephemeral Seedless vascular plant life cycle- All have dominant sporophyte- Gametophytes – tiny plants on soil surface or undergroundSeed plants - 2 important variations of alternation of generations1. Homospory – came first (moss/fern)2. Heterospory – evolved independently in several vascular plant lineages (different spores)- Megaspores – female gametophytes (eggs)- Microspores – male gametophytes (sperm)- These gametophytes are microscopic and never leave the spore wall (endosporic) All seed plants are heterosporous(some lycophytes, some ferns)Seed plants still have spores, they just aren’t dispersed Seed plants still follow basic alternation of generations life cycleHeterosporous life cycle was critical to evolutionSeparate male and female gametophytes became tiny and specialized for different jobsSpecialized female gametophyte- Never leaves sporophyte parent- Ovule: novel structure in seed plants o Several layers: fleshy megasporangium, reduced female gametophyte inside megaspore, specialized enclosing tissues called integuments - Following fertilization ovule matures into seedSpecialized male gametophyte- Pollen - Also endosporic- Only a few cells - Produces 2 sperm/sperm nuclei - Carried by wind or
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