BIOL-1507EL Lecture Notes - Lecture 3: Gnetophyta, Gymnosperm, Psilotum

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Biology 2 - Day 3
Vascular Plants
Seedless Vascular Plants
-The life cycle is dominant in the sporophyte stage
-1) First adaption - sporophyte generation
-Among existent vascular plants, the sporophyte (2n) generation is the largest and
most complex in the alternation of generations
-However, the gametophyte becomes more reduced, and even more reduced during
the evolution of seed vascular plants
-2) Second adaptation - Xylem and Phloem
-Development of Xylem and Phloem
-These are the conducting tissue of the vascular system
-The functioning xylem cells are actually dead cells, whose walls remained to
function as microscopic water pipes, and the walls of the xylem cells are
generally lignified (they contain lignin) which adds toughness and flexibility
-Xylem functions in support, as well as water transport
-There are 2 types of xylem cells
-Tracheid cells
-Vessel element cells
-Phloem is a living tissue of elongated cells arranged into tubes, that distribute
sugar, amino acids, and other organic nutrients, throughout the plant
-3) Third adaptation - Leaves
-Leaves are organs that inquire the surface area of the
vascular plant, to capture more solar energy for
photosynthesis
-Early vascular plant leaves have a single view
(vascular bundle) known as microphylls, while all
others vascular plant leaves have highly branched
vascular systems (megaphylls)
-Phylum lycophyta
-Lycopodium (club moses, groung pine)
-Selaginella (spike mosses)
-Isoetes (quillworts)
-Lycopodium evolved during the devonian period, and became a major part of the
landscape during the carbonifernous period 340 MYA
-Giant lycopods became extinct
-Small lycopods survived, and there are about 1200 species currently and most
belong to general lycopodium and selaginella
-Phylum pteriophyta
-Ferns
-Equisetam (horsetail)
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Document Summary

The life cycle is dominant in the sporophyte stage. Among existent vascular plants, the sporophyte (2n) generation is the largest and most complex in the alternation of generations. However, the gametophyte becomes more reduced, and even more reduced during the evolution of seed vascular plants. These are the conducting tissue of the vascular system. The functioning xylem cells are actually dead cells, whose walls remained to function as microscopic water pipes, and the walls of the xylem cells are generally ligni ed (they contain lignin) which adds toughness and exibility. Xylem functions in support, as well as water transport. There are 2 types of xylem cells. Phloem is a living tissue of elongated cells arranged into tubes, that distribute sugar, amino acids, and other organic nutrients, throughout the plant. Leaves are organs that inquire the surface area of the vascular plant, to capture more solar energy for photosynthesis.

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