Fundamentals of Biology
Lesson 11
Bryophytes, Ferns, Alternation of Generations
I. Bryophytes
A. Mosses, liverworts, hornworts.
B. General Characteristics.
1. No vascular tissue.
2. Therefore no true roots, stems,
leaves.
3. Root-like rhizoids.
4. Height limitation.
5. Need moist environment.
C. Life Cycle.
1. Structure of gametophyte.
2. Male gametophyte
a. Produces
antheridia.
b. Antheridia
produces sperm.
3. Female gametophyte
a. Produces
archegonium.
b.
Archegonium produces egg.
4. Sperm swims to egg and fertilizes.
5. Sporophyte grows on top of female
gametophyte stalk.
6. Sporophyte produces spores.
7. Spore produces protonema.
8. Protonema buds to produce new
gametophytes.
II. Ferns.
A. Tracheophytes: have true roots, leaves, stems, with
vascular tissue.
B. Rhizomes: means of vegetative reproduction.
C. Leaves.
1. Subdivided fronds.
2. Sori on underside.
a. Group of
sporangia.
b. Spore
mother cells in each sporangium.
c. Mother
cell divide by meiosis -> 48 to 64 haploid spores.
III. Fern Life Cycle.
A. Spores.
1. Produced by meiosis in sporangia
under leaves.
2. Haploid.
3. Carried away by wind.
4. Germinates in a moist spot.
B. Gametophyte Generation.
1. Spore grows into a heart-shaped
prothallus - dime-size.
2. Haploid.
3. Rhizoids underneath.
4. Antheridia develop among rhizoids.
5. Archegonia develop at notch.
6. Antheridia produce sperm.
7. Archegonia produce one egg each.
8. Sperm swim toward archegonia.
9. Fertilized egg = zygote.
10. One zygote per prothallus
survives.
C. Sporophyte Generation.
1. Zygote grows into a fern plant.
2. Diploid.
3. Prothallus disintegrates.
4. Mature fern develops sori
(containing sporangia) under leaves.
5. Sporangia produce (haploid)
spores.
IV. Comparative Sizes of Alternate Generations.
Sporophyte Gametophyte
A. Algae
One cell
Few cells to many m
B. Bryophytes
Few mm
Few cm
C. Ferns
1 meter
1 cm
D. Gymnosperms
Up to many m Few mm
& Angiosperms
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