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Are there more Seeded or SeedLESS plants?
Seeded plants
Reproduction by seeds
Vascular
Produce flowers
Seedless plants do NOT produce flowers
What adaptations have plants picked up to live on land?
Challenge: obtaining H2O
Avoid dessication (dehydration)
Overcome gravity
Protection from ultraviolet radiation
Movement and protection of gametes
Benefits:
abundant, unfiltered sunlight
CO2 is more readily available
no natural predators
Early terrestrial plant life did not move far from aquatic environments at first
How do plants avoid desiccation?
Staying close to aquatic environments
tolerance to dry seasons developed over time
colonization of humid habitats (ferns)
FOUR Major adaptations of terrestrial plants
Alternation of generations life cycle
Apical meristem tissue in roots and shoots
Waxy cuticle to prevent dessication
cell walls containing lignin
ALL OF THESE FEATURES ARE MISSING IN MOSS
Why do moss not have any of the 4 major adaptations?
mosses were some of the first organisms that colonized the land
Intermediate species
Mosses
Non-vascular
seedless
flowerless
do not grow true roots or stems
found in wet environments
require water for reproduction
Moss Anatomy
Sporophyte = Multicellular diploid form (the actual plant that you see)
Capsule
Spores
Seta
Gametophyte= Multicellular haploid form, produces gametes by mitosis (Pollen in seed plants)
Leaves
rhizoids
Moss reproduction
Alternation of Generations
All sexually reproducing organisms have both a haploid and diploid phase of their life cycle
Haplontic life cycles: haploid state is dominate
Diplontic life cycles: Diploid state is dominate
Sporangia in seedless plants
Sporangia= Reproductive sac where spores are formed
Homosporous= Produce one type of spore, gametophyte produces both male and female gametes
Non-vascular plants
Heterosporous= Produce two types of spores, develop separately as male and female gametophytes, sporophyte is dominant
Some seedless and all seed plants
Apical meristem in Roots and shoots
lengthen the plant with rapid cell division
UNDIFFERENTIATED CELLS
Give rise to all specialized tissues
Tips of roots and shoots (mitotically active)
Waxy cuticle
Provides protection from water loss (Like chapstick)
Prevents intake of carbon dioxide
Stomata or pores that open and close developed to regulate CO2 intake
Cell walls containing Lignin
As terrestrial plants evolved competition for resources increased
Lignin helped in the ability to grow vertically in competition for sunlight
How do they protect themselves?
Predation is unavoidable
Terrestrial plants evolved both physical and chemical defense mechanisms
Thorns
Poisons
some use fruits to attract animals to help spread seeds
Chemicals
Humans have used chemicals in plants to create poisons and medications for thousands of years
The evolution of Land plants
Ordovician period
Slow colonization of plants onto land
Devonian period
Oldest known vascular plants
Major Divisions of Land plants
Land plants are divided into two main groups:
seeded plants
vascular, reproduce by seeds, produce flowers
Seeded plants include angiosperms and gymnosperms
seedless plants
non-vascular, do not produce flowers
seedless plants include mosses and ferns, which were among the first to colonize land.
Tracheophytes - Vascular plants
90% of Earths vegetation
Have the ability to grow far away from H2O
Due to vascular tissue (xylem and phloem)
Diploid sporophyte phase is dominant
General Sherman Tree
SUPER TALl
What is vascular plant tissue?
tissue responsible for the transport of H2O and nutrients throughout the plant body
Phloem
Xylem
Roots
Xylem
Storage of H2O and nutrients
Long distance transport of H2O and nutrients
Transfer of H2O growth factors
composed of rigid cells that help maintain plant structure
UP-take of these nutrients
Phloem
Transportation of sugars, proteins & other solutes throughout the plant
Transports materials in both directions
Roots
Not Well preserved in the fossil record
appear to have evolved after vascular tissue
Anchor plants
absorb H2O and nutrient from soil
leaves
Increase photosynthetic ability of plants
More chloroplasts employed
increased surface area
leaves evolved more than once
Microphylls
Megaphylls
Sporophylls:
Leaves modified to bear sporangia (Pinecones, ferns)
Modern day seedless plants
Fern
Club moss
horsetails
whisk ferns
Why are seedless plant important?
Recolonization of areas after distaster
Provide food and shelter for organisms
Provide info on the presence of pollution
fix nitrogen in aquatic ecosystems
Used by humans for food, meds and fuel
Dried peat moss burned for heat and fuel
Fossil fuel
Seeded vs. Seedless plants
Seeded plants reproduce by seeds, are vascular, and produce flowers. Seedless plants do not produce flowers and are non-vascular.
key points for NONvascular plants
Have to get water and nutrients by direct contact
limited growth potential due to lack of conductive tissues
need water for reproduction
alternation of generations
Key points for Vascular plants
Have xylem/phloem
Can grow far away from direct water sources
can grow into large plants
roots
leaves