life on earth kingdom plantae part ii
DESCRIPTION
Life on Earth Kingdom Plantae Part II. Rhyniophyta and Lycopodiophyta. Cooksonia. Introduction. Sporophyte generation (2N) is the photosynthetic, conspicuous generation All members have evolved specialized tissues for water ( XYLEM ) and food ( PHLOEM ) conduction - PowerPoint PPT PresentationTRANSCRIPT
Life on EarthKingdom Plantae
Part II
Rhyniophyta and Lycopodiophyta
Cooksonia
Introduction
• Sporophyte generation (2N) is the photosynthetic, conspicuous generation
• All members have evolved specialized tissues for water (XYLEM) and food (PHLOEM) conduction
• Groups continue to become better adapted to the terrestrial environment
Evolutionary Lines
PLANT KINGDOM
“bryophytes” “vascular
plants”
“green algae”
Evolution of Non-Seed, Vascular Plants
Early Devonian Landscape(about 400 million years ago)
Reconstructed Early Devonian Landscape
Cooksonia
Aglaophyton
Zosterophyllum
early lycophytes
Psilophyton
Phylum: Rhyniophyta• Known from fossils more
than 400 million years old (all extinct today)
• Sporophytes had no roots or leaves
• Sporangia produced only one kind of spore (homosporous)
• Example:– Rhynia (found in chert
beds in England)
Phylum: Lycophyta
• Plants with true roots and microphyllous leaves
• Some species produce compacted sporophylls into a cone or strobilus
• Some genera are homosporous (Lycopodium and Huperzia) others are heterosporous (Selaginella and Isoetes)
Heterospory vs. Homospory
male gametophyte with antheridia
female gametophyte with archegonia
or
HOMOSPOROUS PLANTS
gametophyte generation with archegonia AND
antheridia (monoecious)spores
HETEROSPOROUS PLANTS
megaspores
microspores
dioeciousgametophytes
Lycopodium
• Common in New England and the Great Lakes Region
• Often used for Christmas decorations (evergreen)
• Spores were once used as photographic flash powder
Lycopodium (strobili)
Selaginella• Species are heterosporous with
microsporangia and megasporangia
• Megaspores develop into female gametophytes
• Microspores develop into male gametophytes
• Large group with tropical, temperate and desert species
Selaginella rupestris
Selaginella with strobili
Selaginella striboli
megasporangium
microsporangium
Selaginella strobilus
Selaginella (sporangia)megasporangium microsporangium
Selaginella lepidophylla
Isoetes• Commonly known as
“quillworts”• Each microphyllous leaf is a
sporophyll, either a microsporophyll or a megasporophyll (heterosporous)
• Stem is a fleshy “corm”• Often grow at the margins of
ponds and lakes
Isoetes
Isoetes microsporangium
Isoetes
Isoetes melanopoda (Nebraska)
Lepidodendron
• Known as the fossil “scale tress”
• Common forest giant of the Carboniferous Period
• Helped to form present day coal deposits
Carboniferous Forest Reconstruction
Lepidodendron
Base of Lepidodendron (Stigmaria)