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Evolution Timeline
The upward emergence of land plants with the evolution…
The upward emergence of land plants with the evolution of vascular tissues changed the face of our planet
Vessel elements
The earliest definitive angiosperm vessels do not appear until the mid-Cretaceous. At maturity these cells are dead and function in water and mineral transport over very long distances from root to shoot.
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Vascularization
Tracheophytes
Synapomorphy:apomorphy shared by two or more tax
Lycophytes- Early Example
Creating towering forests.
By late Devonian and Carboniferous periods, the
Lepidodendrales became dominant, and up to 200 species
Vascular Elements
Ground Tissue
Vascular Tissue
Zylem
Critical to the success of land plants.
No mitotic event but is a result of or a daughter cell because of mitosis.
Tracheids
Phloem
Albuminous Cell
Each sieve tube is controlled by a companion cell that loads and unloads photosynthate into the cells.
Found only in Gymnosperms.
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Sieve Cell
Sieve Plate
Aligned end to end to create sieve tube.
ALIVE and require life to function.
Callose and Callose plugs form and block sieve plates and the flow through sieve tube when there is injury.
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In early land plants, water and minerals are absorbed from the environment through capillary action and at a smaller scale through osmosis, diffusion and facilitated transport.
For food-conducting cells, simple parenchyma specialized into leptoids: transitioning from simple parenchyma to paired albuminous cells with sieve cells and then to sieve tube elements with companion cells.
Hydroids
The progression in water-conducting parenchyma cells started with simple water-conducting cells, more specialized hyrdroids to true tracheids and vessel elements
Mosses
The moss has no true vascular tissue; however, the development towards vasculature has already begun with the evolutionary precursors hydroids and leptoids. Hydroids often form a central strand in the gametophyte stem/sporophyte seta in the mosses.
Sieve Cells and Albuminous Cells
Sieve cells are long, conducting cells in the phloem that do not form sieve tubes. Sieve cells are flanked with albuminous cells in order to aid in transporting organic material. Albuminous cells have long, unspecialized areas with ends that overlap with those of other sieve cells and contain nutrients and store food in order to nourish tissues. They enable the sieve cells to be connected to parenchyma, functional tissue in the organs, which helps to stabilize the tissue and transport nutrients.
Tracheids
True tracheids have been defined as single-celled conduits with lignified and ornamented walls, either banded or pitted (Kenrick and Crane 1997a; Doyle 1998). The main functions of tracheid cells are to transport water and inorganic salts, and to provide structural support for trees.
Tracheids then evolved into the vessel elements and structural fibers that make up angiosperm wood.
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Trait Evolution
Apomorphy: Derived Novel Trait
Synapomorphy:apomorphy shared by two or more taxa,hypothesized to have evolved in their most recent common ancestor;synonymous with homology
Autapomorphy:character newer than
Plesiomorphy:character older than
Homoplasy:trait has gained or lost independently in separate lineages during evolution;convergent evolution leads to species independently sharing a trait that is different from the trait inferred to have been present in their common ancestor
Convergence:independent evolution of a similar trait in two or more taxa.
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