Plant Diversity I

Chapter 29

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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)

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Sporangia-- Site of mieosis

Sporophyte (2n) spores (n)

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Questions

1. As we go from bryophytes to seedless vascular plants, the dominant generation of the life cycle goes from __________ to __________

2. What is the advantage of branched sporophytes?

3. We will see: homosporous (seedless vascular plants) ____________