1. Plant Diversity I How Plants Colonized Land (The Seedless Plants)
Packet #33
Chapter #29
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2. Introduction
There are more than 290,000 species of plants that inhabit the earth.
How, and why, based on the theory of evolution, did plants venture out of the sea and onto dry land?
Charophyceans
Green algae
Provides some of those answers
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3. Information About Plants
Multicellular
Eukaryotic
Photoautotrophs
Cell walls made of cellulose
Chlorophylls a & b are present in land plants
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4. Diversion of Algae and Land Plants
Embryophytes (plants with embryos) is the traditional scheme and equates with Kingdom Plante
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5. Evidence That Plants Moved to Land
Similarities Between Charophyceans & Land Plants
Evidence That Plants Moved to Land
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6. Morphological & Biochemical Evidence
It is thought that land plants evolved from green algae
Four Key Traits that “suggest” an evolutionary relationship between Charophyceans and Land Plants
Homologous peroxisomes
Both groups contain enzymes that minimize the loss of organic products due to photorespiration
Formation of phragomoplast
Synthesis of cell plates during cell division involves the formation of phragomoplast
Homologous Sperm
Many plants (gymnosperms) have flagellated sperm that match charophycean sperm
Homologous cellulose cell walls
Cell walls of both land plants and charophyceans contain 20-26% cellulose
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7. Genetic Evidence Key nuclear genes Homologous chloroplasts
Ribosomal RNA
Cytoskeleton proteins
In agreement with the biochemical and morphological data
Homologous chloroplasts
Algal plastids, of green algae and algal groups such as euglenoids, are similar to those found in land plants
Chloroplast DNA found in charophyceans, green algae, is most closely related to that found in land plants.
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8. Adaptations Enabling the Move to Land
Charophyceans have a layer of a durable polymer called sporopollenin.
Prevents exposed zygotes from drying out.
May be the precursor to the tough sporopollenin walls that encase plant spores.
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9. “Evolutionary” Adaptations to Terrestrial Living/Derived Traits for Terrestrial Living
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10. Evolutionary Adaptations to Terrestrial Living
There are four main groups of land plants
Bryophytes
Pteridophytes
Gymnosperms
Angiosperms
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11. Adaptations II
The colonization of land by plants required the evolution of many anatomical, physiological and reproductive adaptations
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12. Adaptations III Waxy Cuticle Stomata
Used to protect against water loss
Stomata
Gas exchange needed for photosynthesis
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13. Adaptations IV Plant Life Cycles Alternation of Generation
Part of the life cycle is in a haploid gametophyte generation and part in a diploid sporophyte generation.
The gametophyte plant produces gametes via mitosis
During fertilization the gametes fuse together to form the zygote
The zygote is the first stage of the sporophyte generation.
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14. Adaptations IV
Zygote develops into a multicellular embryo that the gametophyte protects and nourishes
Mature sporophyte plant develops from the embryo
Sporogenous cells (spore mother cells) are produced
Cells undergo meiosis to form spores
The spore is the first stage of the gametophyte generation.
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15. Adaptations V Most plants produce multicellular gametangia
Protective jacket of sterile cells surrounding gametes.
Gametophyte generation (More to come later) all produce their gametes within multicellular structures
Gametangia
Male Gametangium
Antheridium
Many sperm released into the environment when mature
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16. Adaptations V Archegonium
Female Gametangium
Archegonium
Produces a single egg cell and retains the egg within the organism
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17. Adaptations VI Production of Secondary Compounds
Plants produce many unique compounds as byproducts of primary metabolic pathways.
Byproducts help plant defend itself against herbivores
Compounds have bitter tastes, strong odors or toxic effects.
Compounds include terpenes, alkaloids and tannins.
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18. Adaptations VII
Mosses and ferns, although adapted to life on land, have motile sperm cells that require water as a transport medium for fertilization.
Ferns, and vascular plants, that “evolved” at a later time, have xylem, to conduct water, and phloem, to conduct dissolved sugar.
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19. Features That Distinguish Bryophytes From Green Algae and Other Plants
The Bryophytes
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20. Bryophytes Have several adaptations that green algae lack Cuticle
Stomata
Multi cellular gametangia
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21. Bryophytes II Non-vascular plants Lack xylem Lack pholem
Only plants with a dominant gametophyte generation.
Sporophytes remain permanently attached and nutritionally dependent on the gametophyte.
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22. Phyla of Pryophytes
Bryophytes
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23. Bryophyte Diversity
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24. Phylum Bryophyta The Mosses
Have gametophytes that are green plants that grow from a filamentous protonema.
Green filamentous growth that arises from spore germination in liverworts and mosses and eventually gives rise to a mature gametophyte.
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25. Phylum Bryophyta The Mosses
Gametophyte bears archegonia and/or antheridia at the top of the plant.
During fertilization, sperm cell fuses with an egg cell in the archegonium
Zygote grows into an embryo that develops into a moss sporophyte which is attached to the gametophyte.
Meiosis occurs within the capsule if the sporophyte to produce spores.
Spores are dispersed by wind.
Spore germinates. Grows into a protonema that forms a bud.
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26. Life Cycle of the Mosses
Gametophyte
Sporangium
Life Cycle of the Mosses
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27. Life Cycle of the Mosses
Sporangium
Mature Sporangium
Life Cycle of the Mosses
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28. Life Cycle of the Mosses
Germination
Gametophyte
Life Cycle of the Mosses
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29. Phylum Bryophyta The Mosses
Bryophytes have been distributed around the world from the tropics to the arctic.
They can exist in dry or cold habitats
They can practically desiccate
Rehydrates following rain events.
One wetland moss, Sphagnum, forms extensive deposits of peat.
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30. Phylum Hepaticophyta The Liverworts
Have gametophytes that are flattened, lobelike thalli.
Plant body, not differentiated into roots, stems and leaves, of some algae, fungi and similar simple plantlike organisms.
Others are leafy
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31. Phylum Anthocerotophyta Hornworts
Have thalloid gametophytes
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32. Features That Distinguish Ferns and Other Seedless Vascular Plants From Algae and Bryophytes.
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33. Ferns I Comparison to Bryophytes Ferns have vascular tissue
Ferns have a dominant sporophyte generation.
As in bryophytes, reproduction in ferns depends on water as a transport medium for their motile sperm cells.
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34. Seedless Vascular Plants
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35. Introduction I
Represent the modern groups that formed the forest during the evolutionary time period—The Carboniferous Period.
Organisms left relics, fossils and coals
Seed plants were present during this evolutionary time period but were not dominant.
Became important as the swamps dried up and the global climate cooled.
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36. Introduction II There are four phyla of seedless vascular plants.
Phylum Polypodiophyta
Ferns
Phylum Psilotophyta
Whisk ferns
Phylum Equisetophyta
Horsetail
Phylum Lycophyta
Club Mosses
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37. Phylum Pterophyta Subphylum Polypoiophyta The Ferns
Largest and most diverse group of seedless vascular plants.
More than 12,000 species have been described.
Almost all species are homosporous (details to come)
All have megaphylls.
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38. Phylum Pterophyta Subphylum Polypoiophyta The Ferns
Sprophytes have roots, rhizomes and leaves that are megaphylls.
Leaves, or fronds, bear sporangia in clusters called sori.
Meiosis of sporangia produces haploid spores.
Fern gametophyte, called a prothallus, develops from a haploid spore and bears both archegonia and antheridia.
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39. Keywords Homospory The production of one kind of spore
Bryophytes
Whisk ferns
Horsetails
Most club mosses
Most ferns
Spore gives rise to gametophyte plants that produce both egg and sperm cells.
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40. Keywords II Heterospory Production of two kinds of spores Occurs in
Microspores
Give rise to male gametophytes that produce sperm cells
Megaspores
Give rise to female gametophytes that produce eggs.
Occurs in
Certain club mosses
Certain ferns
ALL SEED PLANTS.
The “evolution” of heterospory was an essential step in the evolution of seeds.
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41. Phylum Pterophyta Subphylum Psilotophyta The Whisk Ferns
Lack true roots and leaves
Consists of dichotomously branching rhizomes
Have erect stems.
Homosporous sporophylls.
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42. Phylum Pterophyta Subphylum Equisetophyta The Horsetails
Sporophytes have roots
Rhizomes
Aerial stems
Hollow and jointed
Leaves that are reduced megaphylls
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43. Phylum Lycophyta The Club Mosses
Consist of roots
Rhizomes
Erect branches
Leaves that are microphylls.
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