Plant Diversity I Chapter 29
Jan 03, 2016
Slide 2 of 18
Evolution
Land plants descended from Chlorophyta Green Algae Specifically Charophyta Plant-like Protists
Generalized Phylogenetic Relationship:
Charophyta Bryophyta Seedless Vascular Plants
Gymnosperms Angiospems
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How do we know?
Charophytes land plants Cellulose production is identical, but unique to these 2
groups Unique peroxisome structure & enzyme production Sperm structure is closely related Similar cell plate production Nuclear and chloroplast genes are closely related
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Movement to land…
Advantages Increased Sunlight
In water it is attenuated and/or refracted Increased availability of CO2
Nutrient rich soil medium
Disadvantages Risk of desiccation Less water available Gravitational force has greater effect
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Plants are…
Suppliers of oxygen to all other terrestrial organisms
Terrestrial producers Serve as food source for animals & fungi
Alternation of generations Diploid and haploid life stages Diploid = sporophyte Haploid = gametophyte
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Alternation of generations
Sporophyte (2n or Haploid) Produces spores (n) by Meiosis
Spores grow into Gametophyte (n) Mitosis
Gametophyte (n) produces gametes (n)
Gametes (n) fuse in fertilization Zygote (2n) is produced Mitosis = Sporophyte (2n)
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Gametangia
Gamete production occurs in specialized organs called gametangia
Male gametangia = antheridia (antheridium) Only male deer (bucks) have antlers
Female gametangia = archegonia (archegonium)
Land plants called embryophytes since zygote develops inside female
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Land Plants (4 groupings)
Bryophyta – non-vascular plants so they are very small in size & live in moist environments
Seedless vascular plants – ferns Still reside in moist, cooler environments Waxy covering protects from desiccation
Gymnosperms (naked seeds) – Confers bear cones
Angiosperms (Covered seeds) – fruits & flowers
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Bryophyta
First land plants – evolved from Chlorophytes
Mosses, liverworts, hornworts (no Hogwarts)
Concerned with water loss since not living in water anymore
2 Adaptations to deal with water retention Waxy cuticle cover Gametes packaged in structures called
gametangia
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Moar Bryophyta!!
Nonvascular plant The lack of vascularity & flagellated sperm =
dependence on water Bryophytes live in damp areas
Spend the majority of their life in the gametophyte (haploid) stage
Rhizoids anchor the gametophyte Long single tubular cells Does not absorb water or nutrients like
roots do
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Only plants with gametophyte as dominant part of life cycle
Sporophytes basically live off the gametophyte, but do photosynthesis
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Questions
What is the phylogenetic progression in plants?
Chlorophyta is in which Kingdom?
What is the male gametangia called?
What is the female gametangia called?
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Seedless Vascular Plants
Xylem & Phloem – Plant vascularity Xylem transports water throughout the plant and takes
minerals from the soil to the photosynthetic areas of plants
Phloem transports sugar and nutrients to the various plant structures
Vascularity developed as plants needed to be tall for photosynthesis, but also needed to uptake water & nutrients from the soil
Common example = ferns
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Seedless Vascular Plants (Page 2)
Vascularity allowed for taller plants
Outcompete other plant types for sunlight
Still need to be in damp environment for sperm to reach egg
Dominant stage is sporophyte
Pterophyta – may be source of carbon that is now coal Proliferated during the Carboniferous period of late
Paleozoic era
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Homo vs. Hetero
Major Seedless plants are ferns Ferns are homosporous
Homosporous means single spore production that gives rise to bisexual gametophytes
Homosporous heterosporous
Heterosporous – 2 spore types Some produce male gametophyte (microspores) Some produce female gametophytes (macrospores)