Ch. 29 - Chapter 29 Plant Diversity I: How Plants Colonized...

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Chapter 29 Plant Diversity I: How Plants Colonized Land Book Notes Overview 29.1 – Land plants evolved from green algae 29.2 – Land plants possess a set of derived terrestrial adaptation 29.3 – The Life Cycles of mosses and other bryophytes are dominated by the gametophyte stage 29.4 – Ferns and other seedless vascular plants formed the first forests Summary Table Key Terms Overview
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The Greening of Earth o Looking at a lush landscape it is difficult to image the land without any plants or other organism o For more than the first 3 billion years of Earth’s history The terrestrial surface was lifeless ~ 1.2 billion years ago cyanobacteria covered land surface ~ 500 million years ago plants entered terrestrial environments o Since Colonizing land plants have diversified into roughly 290,000 living species Section 29.1 Researchers have identified green algae called charophyceans as the closest relatives of land plants Many characteristics of land plants also appear in a variety of algal clades Morphological and Biochemical Evidence o There are four key traits that land plants share only with charophyceans Rose-shaped complexes for cellulose synthesis Peroxisome enzymes Structure of flagellated sperm Formation of phragmoplast during cytokinesis Genetic Evidence o Comparisons of both nuclear and chloroplast genes point to charophyceans as the closest living relatives of land plants Adaptations Enabling the Move to Land o In charophyceans a layer of a durable polymer called sporopollenin prevents exposed zygotes from drying out o The accumulation of traits that facilitated survival on land may have opened the way to its colonization by plants
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o Many adaptations emerged after land plant diverged from their charophycean relatives Section 29.2 Defining the Plant Kingdom o Systematists are currently debating the boundaries of the plant kingdom
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Ch. 29 - Chapter 29 Plant Diversity I: How Plants Colonized...

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