Origin of Land Plants Bryophytes and SVP

Origin of Land Plants Bryophytes and SVP - Origin of Land...

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Unformatted text preview: Origin of Land Plants Bryophytes Seedless Vascular Plants Life on land Adaptation to life on land involves changes in size, gas exchange, protection for fragile embryos, protection from desiccation , transportation of water from tissues with access to water to tissues without access . ways for sperm to reach egg, mechanisms of dispersal (getting around)... etc Benefits Direct sunlight unfiltered by water and plankton facilitates photosynthesis Abundance of CO 2 in the atmosphere facilitates photosynthesis Soils are rich in mineral nutrients required for growth and metabolism Initially, there would be few predators (herbivores) or plant pathogens Figure 30-10 Leaf cross section Cuticle is a waxy layer that prevents water loss from stems and leaves. Stomata have pores that allow gas exchange in photosynthetic tissues. Stoma Guard cells Pore Moist photosynthetic cells Cuticle A critical adaptation was cuticle. Cuticle is a waxy, watertight sealant that covers the aboveground parts of the plant and gives them the ability to survive in dry environments. However, the cuticle also keeps necessary CO2 out of the plant. Another critical adaptation was the stoma (plural stomata ). Gas exchange is accomplished through a stoma, which consists of an opening called a pore surrounded by specialized guard cells . The pore opens and closes as the guard cells change shape. Preventing Water Loss: Cuticle and Stomata Figure 30-11 Simple water- conducting cells First vascular tissue Tracheids Vessel elements Ends have gaps in secondary cell wall (inside) Ends have gaps through primary and secondary cell walls Primary wall (with cellulose) Secondary wall (with lignin) Primary wall (with cellulose) Secondary wall (with lignin) Primary wall (with cellulose) Primary wall (with cellulose) Lignin Little structural support. Found in fossils and present- day mosses Some structural support. Found in fossils Increased structural support. Found in all vascular plants Found in gnetophytes and angiosperms Transporting Water: Vascular Tissue and Upright Growth The evolution of vascular tissue allowed early plants to both support erect stems and transport water from roots to aboveground tissues. Vascular tissue most likely evolved in a series of gradual steps that provided an increasing level of structural support, allowing plants to grow more upright. A primary adaptation for upright growth was found in the cell walls of early water-conducting cells. They were strengthened with a molecule called lignin, a structural polymer built from six-carbon rings. Today, the presence of lignin in the cell walls of water-conducting cells is the defining feature of vascular tissues. Key Concepts The green plants include both the green algae and the land plants. Green algae are an important source of oxygen and provide food for aquatic organisms; land plants hold soil and water in place, build soil, moderate extreme temperatures and winds, and provide food for other organisms.food for other organisms....
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Origin of Land Plants Bryophytes and SVP - Origin of Land...

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