BI111 Lecture Notes - Lecture 9: Ordovician, Charales, Marchantiophyta
BI111 – L9
Importance of Land Plants:
Important evolutionary event:
oDramatically influenced both terrestrial, aquatic and atmospheric conditions
oCreated new environmental niches
o3000,000+ living species → 10 phyla
Important to today’s ecological processes:
oCarbon, water, nitrogen etc…
oPrimary producers in terrestrial food web
Domestication and cultivation of plants
490-450 million years of land plants
First evolved in the Ordovician period:
Early to middle ordovician: mild climate with moist atmosphere
Marine and freshwater organism had dramatically changed atmosphere (cyanobacteria use water
as a reducing agent, producing atmospheric oxygen as a byproduct) but carbon dioxide levels
were still 10x greater than today
The Origin of Land Plants: Where, Why and Who?
Why:
oAlgae made the move because there are lots of predators in the ocean
oMore nutrition
oNutrients usually trapped in soil in wet environments
oMore sunlight
Who:
oAncestor was likely a charophyte relative (type of green algae, AKA “Stonewort”)
Multicellular (with cellulose cell walls)
2 forms of chlorophyll (a & b)
Most cells are photoautotrophic
Storage of products of photosynthesis as amylose starch
No specialized transport or support structures: body supported by water, where
nutrients obtained
Phylogeny, Plants, and Plant Body’s
Challenges and Opportunities:
Challenge 1: Dryness
Early plants has no control over water content, were restricted to moist areas
Poikiohydric (poikio=variable; hydric = relating to water)
Like algae, water essential for reproduction (motile gametes)
Selection for Regulation of Water:
Adaption 1: Cuticle:
Present in all bryophytes (mosses, liverworts and hornworts)
Problem: prevents carbon dioxide uptake
Solution: pores
ohow to control water loss?
Adaptation 2: Stomata
Present in mosses and hornworts (not in liverworts)
Document Summary
Important evolutionary event: dramatically influenced both terrestrial, aquatic and atmospheric conditions, created new environmental niches o. Important to today"s ecological processes: carbon, water, nitrogen etc , primary producers in terrestrial food web. Early to middle ordovician: mild climate with moist atmosphere. Marine and freshwater organism had dramatically changed atmosphere (cyanobacteria use water as a reducing agent, producing atmospheric oxygen as a byproduct) but carbon dioxide levels were still 10x greater than today. Why: algae made the move because there are lots of predators in the ocean, more nutrition, nutrients usually trapped in soil in wet environments, more sunlight. Who: ancestor was likely a charophyte relative (type of green algae, aka stonewort ) Storage of products of photosynthesis as amylose starch. No specialized transport or support structures: body supported by water, where nutrients obtained. Early plants has no control over water content, were restricted to moist areas. Like algae, water essential for reproduction (motile gametes)
