Chapter 29 - Plant Diversity I - How Plants Colonized Land

Chapter 29 - Plant Diversity I - How Plants Colonized Land...

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Chapter 29 Class Notes – Plant Diversity I: How Plants Colonized Land – Page 1 Max Sauberman AP Biology – Mr. Schilp Chapter 29 Plant Diversity I: How Plants Colonized Land The Greening of Earth: It is difficult to imagine the land without any plants or other organisms. For more than the first three billion years of Earth’s history, the terrestrial surface was lifeless. Since colonizing land, plants have diversified into roughly 290,000 living species. Why plants moved from the water: Plants moved out of the water because there was less predation on land. All living things were in the water. In order not to be eaten, plants needed to make the move to land. Land plants evolved from green algae: Green algae called charophyceans are the closest living relatives of land plants. Many characteristics of land plants also appear in a variety of algal clades, mainly algae. However, land plants share four key traits only with charophyceans. - Rose-shaped complexes for cellulose synthesis - Peroxisome enzymes to break down H 2 O 2 - Structure of flagellated sperm (that move to the egg) - Formation of a phragmoplast (during mitosis; before the cell plate forms) Comparison of both nuclear and chloroplast genes point to charophyceans as the closest living relative to land plants. Adaptations enabling the move to land: In charophyceans, a layer of a durable polymer called sporopollenin prevents exposed zygotes from drying out. The accumulation of traits that facilitated survival on land may have opened the way to its colonization by plants. Adaptations that are especially paramount are those that keep the plants from losing water. Water is necessary for the flagellated sperm to reach the egg in seedless plants. The move to land began in the intertidal zone.
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Chapter 29 Class Notes – Plant Diversity I: How Plants Colonized Land – Page 2 Defining the plant kingdom: Systematists are currently debating the boundaries of the plant kingdom. Some biologists think the plant kingdom should be expanded to include some or all green algae. Until this debate is resolved, we will retain the embryophyte definition of the kingdom Plantae. Derived terrestrial adaptations of land plants: Many adaptations emerged after land plants diverged from their charophyceans relatives. Five key traits appear in nearly all land plants but are absent in the charophyceans. -
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This note was uploaded on 03/17/2011 for the course BIO 101 taught by Professor Sullivan during the Spring '08 term at Harvard.

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Chapter 29 - Plant Diversity I - How Plants Colonized Land...

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