neil by HC1111110998

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									Four main groups of Land Plants


    Bryophytes (mosses, etc.)
    Ferns and relatives
    Gymnosperms
    Angiosperms
                 Bryophytes
 There   are three groups of bryophytes
     Mosses 12,000 species
     Liverworts 6,500 species
     Hornworts 100 species
       Bryophyte diversity


Hornworts
100 species




                        Liverworts
                        6,500 species



       Mosses
       12,000 species
Mosses
Mosses -
12,000
species




 Widely distributed, especially in alpine, boreal,
 temperate, and tropical forests

 Able to live in very dry or very cold habitats

 Many can dry out entirely, then rehydrate
Famous mosses:
Sphagnum

Wetland moss -
           “peat moss”


  Boggy regions
  dominated by it known
  as peat bogs or
  peatlands
       Liverworts and hornworts
 Liverworts are even less conspicuous than
  mosses. Some have a lobed appearance.
 They reproduce both sexually and asexually
  from small bundles of cells known as gemmae.

   Hornworts have elongated sporophytes that are
    hornlike in appearance. They are unusual in
    that each photosynthetic cell contains one large
    chloroplast rather than many smaller ones.
                 Bryophytes
 Bryophytes arose at least 400 mya and
 possess two adaptations that allow them
 to survive on land.
     Waxy cuticle reduces water loss
     Gametes are protected and develop within
      gametangia.
               Bryophytes
 Bryophytesdo not have a vascular system
 and so cannot grow very large.

 Theyalso need moisture to reproduce
 because fertilization depends on sperm
 being able to swim through water to reach
 the egg.
 In bryophytes the gametophyte
  (haploid n) is the dominant
  generation and the sporophyte
  (diploid 2n) is dependent on the
  gametophyte.
Bryophytes
Gametophytes only a few
cells thick. No true “leaves”.

Directly absorb water &
minerals.

No lignified vascular tissue.
     Bryophyte gametophyte

Close to the ground.

Anchored by rhizoids.

Long, tubular single cells - not
tissues.
Bryophyte
sporophyte
          3) Capsule




3 parts       2) Stalk



          1) Basal foot
    Bryophyte life cycle
                       meiosis
          sporophyte
                                 spores
2n
                                                n
embryo

                                      gametophyte



         zygote

                            eggs

                                 sperm
  Bryophyte reproduction
 Spores produced in
 capsule (sporangium)




Spores released to germinate into gametophytes.
         Bryophyte reproduction

 Malegametophytes produce sperm and
 female gametophytes produce eggs.

 When  there is sufficient moisture sperm
 swim to the egg and fertilize it. Fertilized
 egg develops into a zygote and ultimately
 into a sporophyte.
  Seedless vascular plants: Ferns
          and fern allies
 First   vascular plants originated about 420
  mya.
 First seed plants came later about 360
  mya.
 Seedless vascular plants dominated the
  planet during the Carboniferous period
  (300-350 mya).
  Seedless vascular plants: Ferns
          and fern allies
 Gianttree ferns, horsetails and lycopods
 were the dominant vegetation of the
 Carboniferous period.

 Theirfossilized remains formed extensive
 coal beds.

 Theywere ultimately superseded by the
 seed plants and far fewer survive today.
       Present day fern allies
 Lycopods:  About 1,000 species. Includes
 tropical epiphytes and northern
 hemisphere low growing club mosses.

           today about 15 species of
 Horsetails:
 Equisetum occur in northern hemisphere
 in damp conditions.
Equisetum   Lycopod
                 Ferns
A very diverse group about 12,000 species
 most abundant in the tropics, but
 distributed worldwide.

 Most are small to moderately large plants,
 but tree ferns are many meters tall.
                        Boston fern
Common ferns


        Staghorn fern

Maidenhair fern




                           Pteris
Fern morphology
Dominant generation: sporophyte
Fern morphology
Body consists of three organs:
• Underground rhizome (stem)
• Adventitious roots
• Fronds (leaves)
Fern morphology
• Underground rhizome (stem)
Fern morphology
• Adventitious roots

  Roots that grow from
  anywhere but the
  primary root.

  Like out of stems.
Fern morphology     “fiddlehead”

• Fronds (leaves)
           Fern life cycle
Independent and       meiosis
dominant sporophyte
                                spores
 2n
                                            n
embryo
                                Free-living gametophyte


         zygote
                           eggs

                                sperm
Fern life cycle
        Fern life cycle - spores
Unit of dispersal = spores
• Produced by sporangia
• Sporangia clustered in sori
  (singular = sorus)
• Usually small button-like
  dots on backs of fronds
Fern life cycle - sori
Fern life cycle - sori
Fern morphology


Free-living gametophyte
• Also called a prothallus        Sporophyte
• Produces sperm and eggs
• Sporophyte starts attached to
  gametophyte. Gametophyte
  dies after sporophyte
  detaches.
        Spores and seeds
 Thespores of ferns are tiny and vast
 numbers are produced. However, their
 prospects of survival are low.

A new evolutionary innovation, the seed,
 arose in the Carboniferous Period. Seeds
 and later fruit proved to be enormously
 successful and seed plants especially
 angiosperms came to dominate the planet.

								
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