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Bio1020, Diversity of Life: February 14.docx

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BIOL 1020
Robert Laird

February 14 – Biology (Happy Valentine’s Day!) Plants movement to land Tissue-level changes: • Evolution of land plants from green algae o Algae is aquatic o 3-billion years: no life on land o 1.2-billion years ago: crust of cyanobacteria o 500 million years ago: plants colonize the land (+animals + fungi) o 385 million years ago: formation of the first forests o Land plants  Terrestrial ancestor, even though some are now aquatic  Land plants do not include photosynthetic protists (algae)  Plants supply oxygen and are the ultimate source of most food eaten by land animals  ~290,000 living species  Charophytes the closest relatives of land plants • Plants and many protists: o Multicellular o Eukaryotic o Photosynthetic autotrophs o Cellulose o Chlorophyll a and chlorophyll b • What is the evidence that charophytes are particularly closely related to land plants? o Rings of cellulose-synthesizing proteins  In the plasma membrane  Non-charophyte algae have linear sets of cellulose- synthesizing protein o Peroxisome enzymes  Specialized enzymes in the peroxisome organelles that reduce the negative effects of photorespiration (e.g., loss of organic products) o Structure of flagellated sperm  Not all plants have flagellated sperm, but those that do have sperm that resemble charophytes (mosses have flagellated sperm – those who diverged earliest from the species seems to have flagellated sperm) o Phragmoplast  Group of microtubules between daughter nuclei of a dividing cell  Land plants and some chrophytes only o Charophytes the closest relatives of land plants:  DNA evidence, too  Closest species by this line of evidence: • Chara spp. • Coleochaete spp. • Adaptations enabling the move to land o Challenges faced by land plants compared to ancestors living in water?  Structural support (more prone to falling down), original plants were very small, evolution of wood was important for structure  Moisture o Scarcity of water  Sporopollenin protein • Charophytes: prevents exposed zygotes from drying out • Found plant spore walls  During/since colonizing land, plants have acquired many other water absorption/retention adaptations o What benefits did early plants experience?
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