1 Review In what kind of environments are green
algae found
2 Apply Concepts How is water essential to the life
cycle of a bryophyte
3 Review What function do vascular tissues allow
Infer The size of plants increase dramatically with
the evolution of vascular tissue. How might these
two events be related
CH 22 INTRODUCTION TO PLANTS
22.2 Seedless Plants
Green Algae




“Green algae” are classified with plants
“Algae” applies to any photosynthetic eukaryote
other than a land plant
Found in fresh and salt water
Absorb moisture and nutrients directly from their
surroundings.


Switch back and forth between haploid and diploid
Not always with every generation.
Life Cycle of Chlamydomonas

Haploid and asexual under suitable conditions.
Life Cycle of Chlamydomonas


Unfavorable conditions uses sexual reproduction
Release gametes that fuse into a diploid zygote
(sporophyte) with thick protective wall.


Zygote begins to grow once conditions become
favorable
Divides by meiosis to produce four haploid cells
that swim away, mature, and reproduce asexually.
Bryophytes


Mosses, hornworts, and liverworts
Specialized reproductive organs enclosed by other,
non-reproductive cells.
Mosses and Other Bryophytes


Waxy, protective coating that
makes it possible for them to
resist drying
Rhizoids
 Thin
filaments that anchor them
to the soil
 Absorb water and minerals.
Why Bryophytes Are Small


Do not make lignin, a substance that hardens cell
walls
Do not contain true vascular tissue.
Alternation of Generations

Gametophyte
 Dominant,
recognizable stage
 Carries out most of
the photosynthesis.

Sporophyte
 Dependent
on gametophyte
for water and nutrients.

Sperm swim to egg using flagella
 Needs
water for fertilization.
Gametophyte


Spore sprouts and grows into gametophyte
Forms rhizoids that grow into ground and shoots
that grow into the air.



Gametes are formed in reproductive structures at
the tips of the gametophytes
Archegonia- where eggs are produced
Antheridia- where sperm are produced


Egg and sperm fuse to form zygote
Zygote marks the beginning of the sporophyte
stage.

Sporophyte grows within the gametophyte,
depending on it for water and nutrients.

Sporophyte grows out of the gametophyte and
develops a long stalk ending in a capsule called the
sporangium.


Haploid spores produced in capsule by meiosis
Released when capsule ripens and opens.
Vascular Plants


Contain vascular tissue (xylem and phloem)
Enables vascular plants to move fluids through
their bodies against the force of gravity.

Xylem
 Carries

water and minerals up from the roots
Phloem
 Carries
sugar and carbohydrates from photosynthesis.
Seedless Vascular Plants





Club mosses, horsetails, and ferns
True vascular tissues
Strong roots
Rhizomes
Large leaves called fronds.

Spores produced by the
sporophyte grow into thin,
heart-shaped haploid
gametophytes.


Sperm and eggs are
produced in antheridia
(sperm) and archegonia
(egg)
Fertilization requires
water.



Diploid zygote develops
into a new sporophyte
plant
Dominant stage
Haploid spores develop on
the undersides of the
fronds in sporangia.
Keeping Ferns in Check



Ferns often crowd out tree seedlings blocking
efforts to regrow trees after logging.
To understand the fern better, scientists measured
the number of viable spores per square centimeter
of soil at various distances from existing ferns.
They counted spores in July as the ferns were just
starting to grow and in November after spores had
been released.

Graph the data from the table. Be sure to plot the
data from July on one line and November on a
second. Be sure the graph is fully labeled and
oriented correctly.
1.
2.
3.
Calculate What percentage of the spores after
dispersal are found within 4 meters of the parent
plants
Interpret Graphs Are spore numbers higher
before or after dispersal- Explain
Draw Conclusions Would cutting down nearby
clusters of ferns prevent ferns from invading
patches of the forest that have just been cut for
timber- explain your reasoning based on the data