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Chapter 25: Seedless Plants - Coggle Diagram
Chapter 25: Seedless Plants
Algal history
Chlorophytes, Charophytes (Green Algae) and Plants share
Cellulose cell walls
Chloroplasts with same pigments (chlorophyll a & b)
Storage molecule is starch
Multicelluarity
Moving to land
Advantages
more CO2, light, and minerals
more resources and less competition
No "herbivores"
Disadvantages
Desiccation, or drying out, is a constant danger for an organism exposed to air and leads to dehydration
Both gametes and zygotes must be protected from desiccation
Plants need to develop structural support in a medium that does not give the same lift as water
The male gametes must reach the female gametes using new strategies, because swimming is no longer possible
Derived Characteristics of Plants
Alternation of Generations
Haplontic refers to life cycle in which there is a dominant haploid stage.
Diplontic refers to a life cycle in which diploid is a dominant stage (humans are diplontic).
Most plants exhibit alternation of generations
Gametophyte – haploid
Sporophyte – diploid
Gametophyte generation is dominant in lower plants
As plants evolved, gametophyte generation got smaller, sporophyte generation became more dominant
2n and n multicellular forms
Different from charophyte life cycle where only multicellular is haploid and zygote does meiosis to produce only 4 diverse offspring
Walled haploid spores
Sporopollenin made within multicellular sporangium protects dispersal through air
Multicellular gametangia
Produces gametes
Protecting sperm within antheridium
Egg protected within archegonium
fertilization here forms zygote
Sporophyte embryos grow protected within female gametophyte
Apical meristem tissue in roots and shoots
Continuously dividing cells
Roots and shoots grow toward resources
Waxy cuticle to resist desiccation
pores allow CO2/O2 exchange
controllable stomata in most plants
Mycorrhizae
mutualism with fungi; helps water & mineral absorption
dates back to first land plants (before true roots)!
Secondary metabolites (not essential for metabolism/growth)
Chemicals that deter, repel, or poison competitors, herbivores, and parasites (ex. caffeine, latex rubber)
Groups
First to exist out of water
Bryophytes
Characteristics
non-woody, small, ground-covering plants that require water for reproduction
Rhizoids instead of true roots for attatchment
Haploid gametophyte is dominant (longest lasting/largest)
Makes eggs and flagellated sperm
most small, low growing, in moist areas
diploid sporophyte dependent on gametophyte for food and water
grows within archegonium of gametophyte
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3 Phyla
Marchantiophyta (Liverworts)
most have elevated gametophytes that resemble miniature trees (Marchantia)
Reduced or very small sporophytes; some thalloid and others leafy
Anthocerotophyta (Hornworts)
Common name refers to horn-like long tapered shape of sporophyte
Good colonizers of moist soils
Symbiotic relationship with nitrogen-fixing cyanobacteria
Bryophyta (Mosses)
The most numerous of the non-vascular plants
Inhabit extreme environments as mountain tops, tundra, and deserts
Sporophyte grows up from female gametophyte to gain elevation for spore dispersal
Ecological Importance
“pioneer” species in nutrient-poor soils
moss are major primary producers in cold or high- altitude regions
Sphagnum “peat moss” bogs: important wetlands, also harvested for fuel
some peatlands have preserved corpses for thousands of years
Life cycle
germinating spore becomes a protonema
protonema begins to differentiate into a bud
Seedless Vascular Plants
Characteristics
Branched sporophytes that are independent of gametophyte for nutrition
Microphylls
Small, spine-shaped leaves supported by a single strand of vascular tissue
Only lycophytes
Megaphylls
Leaves with a highly branches vascular system
Greater photosynthetic productivity than microphylls
Almost all vascular plants have them except Lycophytes
Sporophylls
Leaves modified to bear sporangia
Fern sporophylls look like normal leaves but have sori that generate spores on underside
Lycophyte sporophylls modified into a cone-like structure called a strobilus
Homosporous Spore Production
Sporangium on sporophyll
single type of spore
typically a bisexual gametophyte
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Most seedless vascular plants
Heterosporous
All seed plants and few seedless vascular plants
Megasporangium of megasporophyll
megaspore
female gametophyte
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Microsporangium on microsporophyll
microspore
male gametophyte
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Diploid sporophyte dominates life cycle
Transport in Xylem and Phloem (vascular system)
Xylem: cells specialized to move water and minerals
Phloem: cells specialized to move sugars, amino acids, other organic products
Evolution of true roots
Evolution of true leaves
Groups
Lycophytes
Club mosses
homosporous
Quillworts
heterosporous
Spike Mosses
heterosporous
All small and living in tropical and temperate climates
Monilophytes
Horsetails (
Equisetum
)
jointed stems with tiny leaves
Strobili
Homosporous
Photosynthesis occurs in stem
Ferns
most widespread & diverse Monilophytes
homosporous
large megaphylls
sori on underside of sporophylls
mostly in understory or as epiphytes
grows on surface of a plant
Whisk Ferns (
Psilotum
)
dichotomous branching
no true leaves or roots
Homosporous
Photosynthesis occurs in stem
Importance
Disappearance of mosses
Biological indicator of environmental pollution
Ferns
promotes weathering of rocks
accelerates topsoil formation
used as food
Peat moss (
Sphagnum
)
Used as fuel (renewable resource)
Soil conditioner
Extinct SVPs
Coal
Energy source