Diversity of Plants
Part I-Mosses and Ferns
Transition from water to land
• Recall Algae like plants conduct
photosynthesis
• However Algae are fully aquatic
• Land plants faced new challenges that algae
did not & as a result had to evolve or change
to live on land to be successful
Challenges
•
•
•
•
1) UV damage
2) Water Loss
3) absorption of water
4) transport of water and food without relying
on osmosis, diffusion, or dialysis (would limit
size)
• 5) reproduction
solutions
• 1) pigments to protect from UV damage—all
photosynthetic organisms due to requirement
for photosynthesis too (capture light so can be
converted to chemical energy/sugar)
2) Cuticles and stomata to prevent water loss &
dehydration
Cuticle
Stomata
3) Water absorption
Rhizoids
Roots—have vascular tissue
4) Transport of water & nutrients
• Xylem (water) and Phloem (food)—type of
vascular tissue.
– Allows ferns, gymnosperms & angiosperms to be
bigger than mosses and algae.
Vascular tissue
5 a) Reproduction & gamete dispersal
• Mosses and ferns have swimming sperm—
requires them to live in v. moist soil since not
submerged in water like algae
• Angiosperm and gymnosperm plants instead
will transports sperm by pollinators (discuss
next week) so less reliance on water
5 b) Reproduction & spore dispersal
• Mosses require water for this haploid spore to
be spread out prior to germination into
gametophyte plant
• Ferns rely on wind
• Next week:
– Gymnosperms & Angiosperms use seeds instead
of spores
FROM SIMPLE TO COMPLEX
• Algae—totally aquatic
• Plants—semi-aquatic
– Nonvascular
• Mosses—water for spores and sperm
• Vascular
– Ferns—don’t need water for spores
– Angiosperm (flowers) and Gymnsperms (pine)
Nonvascular plants—Mosses/Bryophyta
• Land plants
• evolutionary dead end
• gametophyte dominant (most plants are
sporophyte dominant)
• use water for reproduction—dispersal of
gametes (sperm swim)
• and asexual spores (in gemmae cups)
• sporophyte (2n) remains attached to
dominant gametophyte
Sporophyte
Gametophyte
Alternation of generations of plants
What is Alternation of Generation?
Definitions:
Sporophyte = individual with 2 sets of chromosomes
Diploid or 2n; produce N spores by meiosis
Gametophyte = Individual with one set of chromosome
Haploid or 1n; produce gametes by mitosis
Spore = can resist bad times. Made through meiosis
2n ->1n
Gametes = eggs and sperm that unite (fertilization) making a
zygote (2n).
*Spores grow into gametophytes & Zygotes grows into Sporophtyes
• Sporophyte (2N) meiosis spores (n)
• Spores (n) grow into gametophyte plants (n)
by mitosis (since chromosome # the same)
• Gametophytes (n) make gametes (n) by
mitosis
Ferns
• land plants
• vascular—tissues to conduct water and food
• 3 differences from mosses—
–
–
–
–
sporophyte independent
true vascular tissue—xylem & phloem in sporophyte
sporophyte dominant
wind for spore dispersal
• still dependent on water—sperm requires it and
gametophyte lacks vascular tissue
Gametophyte (L) and Sporophyte (R)