Lecture 13 Outline Chapter 30

Lecture 13 Outline Chapter 30 - Bio II - Crampton Lecture...

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Bio II - Crampton 1 Lecture 13: Plant diversity II: Slide 1 Review. Non-vascular versus vascular plants. Slide 2 History of plants: Seed plants have dominated for past 350 My. events: Non-vascular plants appear in Ordovician; Vascular plants appear in Silurian; Seed plants appear in Carboniferous. Slide 3 What is a seed? Sporophyte embryo packed with food and encased in protective coat Slide 4 Derived traits of seed plants. 1. Reduced gametophyte: Evolutionary trend towards reduced gametophyte 1. Gametophytes develop from spores retained within sporangia. 2. Reduced gametophyte dependent on sporophyte (in both gymnosperms and angiosperms) Review Fig. 30.2 Campbell & Reece. Slide 5 Derived traits of seed plants. 2. Heterospory: Heterospory is the rule in seed plants Homosporous (most seedless plants): One kind of spore germinates into a (usually) bisexual gametophyte Heterosporous (All seed plants): Two kinds of spores leading to MALE and FEMALE gametophytes. Female gametophyte: develops from megaspore inside ovules. Male gametophyte: develops from microspores inside pollen grains. Slide 6 Evolutionary advantages of a miniaturized gametophyte stage: Gametophyte small enough to live inside sporophyte:
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Bio II - Crampton 2 1. Gametophyte provided with nutrition 2. Gametophyte protected from environmental stress including desiccation and UV radiation (site of meiosis) 3. No need for sperm + egg to be united by droplets of water … allows colonization of dryer areas 4. MALE gametophyte can be dispersed long distances in a small capsule (a pollen grain). DO NOT CONFUSE UNICELLULAR HAPLOID SPORES WITH MULTICELLULAR DIPLOID MALE GAMETOPHYTE IN POLLEN GRAINS !!! Make sure you understand the difference between these Slide 7 Derived traits of seed plants. 3. Ovules & Seeds Slide 8: SEEDS. Ovule develops into a multicellular, diploid SEED
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Lecture 13 Outline Chapter 30 - Bio II - Crampton Lecture...

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