Download Moss: Non-Vascular Plants

Biology 11
Transition onto Land
Advantages of living in the water included…
1. Prevents drying out.
2. Gives structural support (less affected by gravity)
3. Provides nutrients and gas exchange by
diffusion.
4. Helps to disperse spores and the meeting of
gametes.
Question to think about: Why bother move onto
land?
Plant Kingdom Distribution
Cone-bearing Plants
760 species
Flowering Plants
Ferns & relatives
11,000 species
Mosses & relatives
15,600 species
235,000 species
Plant Phylogeny
Cone-bearing plants
(Gymnosperms)
Flowering plants
(Angiosperms)
Ferns & relatives
(Seedless vascular plants)
Flowers: seeds
enclosed in fruit
Mosses & relatives
(“Bryophytes)
Seeds
Water-conducting
(vascular) tissue
Green algae
ancestor
General Plant Life Cycle
Sporophyte is the
dominant
generation in
higher plants
(diploid stage: 2n)
Gametophyte is the
dominant
generation in lower
plants
(haploid stage: n)
2 Major Groups of Plants
Nonvascular
- Lack vascular tissue which transport H2O and nutrients
- include mosses, liverworts, and hornworts
Vascular
- possess water/nutrient transporting system (xylem-water and
phloem-nutrients from photosynthesis)
- include ferns, conifers, and flowering plants
Non Vascular Plants
•
•
•
•
Primitive land plants
Are photosynthetic
Cell wall made of cellulose
Lack vascular tissue( i.e. missing “xylem” and
“phloem” )
• Do NOT have true leaves, stems and roots
• Require water for fertilization (adapted for wet
habitats)
• Asexual and sexual reproduction
• Alternation of generations
• Gametophyte generation is dominant (mainly
exist as a haploid individual)
Mosses: Phylum Bryophyta
Mosses
• Live only in wet habitats
– Don’t have vascular tissue to transport water.
Water moves by osmosis from one cell to the
next.
• Remain small.
– Water can only diffuse short distances to cells.
• Don’t have true roots to transport water.
Structure
• Sporophyte (diploid) generation
grows out of the gametophyte,
and is a skinny stalk with a
capsule full of spores at the top.
• Gametophyte (haploid)
generation is the common green
fuzzy moss.
– Carries out photosynthesis
• Rhizoids are root-like structures
that anchor the moss to the
ground.
Gametophyte Structures
• Structures protect gametes (egg
and sperm) from drying out
• Antheridium- produces
flagellated sperm cells
• Archegonium- produces eggs
• Sperm require water to swim to
egg in archegonium… involves
dew or rain droplets
• When water is present, fertilization can occur
if sperm swims to egg
• Diploid zygote forms and eventually
germinates and grows into diploid sporophyte
• Sporophyte cannot live
independently… Grows out of
the gametophyte
• Gametophyte is photosynthetic
and supplies water and nutrients
to the sporophyte that grows
out of it
Sporophyte Structure
• Contains seta or stalk raises
spores for dispersal (by wind or
water)
• Capsule contains haploid spores
that will be released under ideal
conditions
• Calyptra covers and protects
the capsule
• If spores disperse and land in ideal area,
spores germinate and a protonema grows
• Protonema are thread like filaments that will
develop into gametophyte
Life Cycle Overview
• Starting with the gametophyte, draw the life
cycle of a typical moss
1) Haploid Gametophyte contains archegonium
and antheridium (produces haploid eggs and
sperm cells through mitosis)
2) When water present, sperm cell swims to
fertilize egg cell in archegonium.
3) Diploid zygote forms and develops into
sporophyte… grows out of the archegonium of
the gametophyte
4) Mature sporophyte produces haploid spores
through meiosis
5) Spores disperse, form protonema, and
develop into mature gametophyte
• Why do bryophytes require an
environment that is moist?
– For fertilization
– To transport water from cell to cell (have no
vascular tissue)