Introduction to the Plant
Kingdom: Bryophytes
Chapter 22
Mosses in Olympic National Park, WA.
Sphagnum grows out onto the surface of a pond and gradually turns it into a
quaking bog, which really does quake when you walk or jump on it. Eventually it
becomes a bog with no free water.
Peat farmer, digging turf in Ireland.
Tollund Man, found in Denmark, was preserved by the tannic acids of a peat moss bog.
Tollund Man
•
•
•
•
•
•
•
The Tollund Man lived during the late 5th century BC and/or early 4th
century BC, about 2,400 years ago. He was buried in a peat bog on the
Jutland Peninsula in Denmark, a find known as a bog body.
He is remarkable for the fact that his body was so well preserved that
he seemed to have died only recently.
On May 6, 1950, the Højgård brothers from the small village of Tollund
were cutting peat for their tile stove and kitchen range in the
Bjældskovdal peat bog, 10 km west of Silkeborg, Denmark.
Underneath the body was a thin layer of moss. Scientists know that
this moss was formed in Danish peat bogs in the early Iron Age about
the time when Jesus was born. Therefore, the body was suspected to
have been placed in the bog approximately 2,000 years ago during the
early Iron Age.
Subsequent C14 radiocarbon dating of Tollund Man's hair indicated
that he died in approximately 350 BC.
The acid in the peat, along with the lack of oxygen underneath the
surface, had preserved the soft tissues of his body.
Examinations and X-rays showed that the man's head was
undamaged, and his heart, lungs and liver were well preserved.
LEARNING OBJECTIVE 1
•
Discuss some environmental
challenges of living on land
•
Describe how several plant adaptations
meet these challenges
Animation: Evolutionary Tree for
Plants
CLICK
TO PLAY
Colonization of Land
•
Plants required evolution of structural,
physiological, reproductive adaptations
•
Plants produce gametes in multicellular
gametangia that contain a protective layer
of sterile cells
KEY TERMS
•
CUTICLE
•
•
A noncellular, waxy covering over the
epidermis of aerial plant parts that reduces
water loss
STOMA
•
A small pore in the plant epidermis that allows
gas exchange for photosynthesis
Variation in Plants
LEARNING OBJECTIVE 2
•
Name the algal group from which
plants are hypothesized to have
descended
•
Describe supporting evidence
Plant Ancestors 1
•
Plants probably evolved from green algae
•
Similar biochemical characteristics:
•
•
•
pigments (chlorophylls a and b, carotenes,
xanthophylls)
cell-wall components (cellulose)
carbohydrate storage material (starch)
Plant Ancestors 2
•
Similar fundamental processes
•
•
such as cell division
Land plants probably descended from
charophytes (stoneworts)
•
Based on molecular and structural data
Green algae gave rise to bryophytes.
Chara is a green alga that has features similar to the alga that may have been ancestral
to the bryophytes. Its growth habit is plantlike, although this may simply result from
convergent evolution.
Gametangia: Plants and Algae
Developing
gametes
Sterile cell
Multicellular
gametangium
Unicellular
gametangium
Fig. 22-2, p. 431
LEARNING OBJECTIVE 3
•
Explain what is meant by alternation of
generations
•
Diagram a generalized plant life cycle
KEY TERMS
•
ALTERNATION OF GENERATIONS
•
•
A type of life cycle characteristic of plants and
a few algae and fungi
They spend part of their life in a multicellular n
gametophyte generation and part in a
multicellular 2n sporophyte generation
Animation: Haploid to Diploid
Dominance
CLICK
TO PLAY
Plant Life Cycle
Gametophyte
Spore
Sperm
Egg
HAPLOID (n)
GAMETOPHYTE
GENERATION
Fertilization
Meiosis
DIPLOID (2n)
SPOROPHYTE
GENERATION
Zygote
Embryo
Sporophyte
Fig. 22-3, p. 431
Gametophyte
Spore
Sperm
Egg
HAPLOID (n)
GAMETOPHYTE
GENERATION
Meiosis
Fertilization
DIPLOID (2n)
SPOROPHYTE
GENERATION
Zygote
Embryo
Sporophyte
Stepped Art
Fig. 22-3, p. 431
KEY TERMS
•
ANTHERIDIUM
•
•
A multicellular male gametangium that
produces sperm cells
ARCHEGONIUM
•
A multicellular female gametangium that
produces an egg
Plant Gametangia
The Gametophyte Generation
•
Produces haploid gametes by mitosis
•
•
•
Antheridium produces sperm cells
Archegonium produces an egg
Fertilization: Gametes fuse to form a
diploid zygote
KEY TERMS
•
SPORE
•
A reproductive cell that gives rise to individual
offspring in plants, fungi, and certain algae
and protozoa
The Sporophyte Generation
•
First stage is zygote
•
•
Develops into an embryo, protected and
nourished by gametophyte plant
Mature sporophyte plant has spore
mother cells that undergo meiosis to
produce haploid spores
•
First stage in gametophyte generation
LEARNING OBJECTIVE 4
•
Summarize the features that
distinguish bryophytes from other
plants
Bryophytes
•
Small, fairly simple plants
•
Nonvascular
•
Gametophyte is dominant generation
•
grows independently of sporophyte and is
usually perennial
Plant Evolution
Angiosperms
Gymnosperms
Ferns
Club mosses
VASCULAR SEEDLESS VASCULAR SEED
PLANTS
PLANTS
Mosses
Liverworts
Hornworts
NONVASCULAR
BRYOPHYTES
Evolution
of seeds
Evolution of dominant
sporophyte, vascular
tissue
Green
algal
ancestor
Evolution of cuticle, multicellular
gametangia, multicellular embryos
Fig. 22-5, p. 434
LEARNING OBJECTIVE 5
•
Name and briefly describe the three
phyla of bryophytes
Three Phyla of Bryophytes
•
Mosses
•
Liverworts
•
Hornworts
KEY TERMS
•
MOSS
•
A member of a phylum of spore-producing
nonvascular plants in which the dominant n
gametophyte alternates with a 2n sporophyte
that remains attached to the gametophyte
Mosses
•
Leafy moss gametophytes develop from a
protonema
•
A moss sporophyte consists of a capsule,
a seta, and a foot
KEY TERMS
•
PROTONEMA
•
•
In mosses, a filament of n cells that grows
from a spore and develops into leafy moss
gametophytes
CAPSULE
•
Portion of the bryophyte sporophyte in which
spores are produced
Mosses
Mosses
A moss that survives drought. Tortula rurali is a genus of moss that lives in regions
with only occasional rainfall. During dry periods, the plant looks completely dried out
and dead. However, a few minutes after rain, the plants are rehydrated and fully
functional.
Mosses
Capsule
Seta
Foot
Fig. 22-6c, p. 435
Animation: Moss Life Cycle
CLICK
TO PLAY
Alternation of Generation (Moss)
•
http://www.sumanasinc.com/webcontent/a
nisamples/majorsbiology/moss.html
Life Cycle: Mosses
Gametophyte
plants
Buds on
protonema
Antheridia at the tip of
the gametophyte shoot
1
Antheridia
with sperm
cells
Spore
germinates
Spores
released
6
Protonema
Sperm cell
HAPLOID (n)
GAMETOPHYTE
GENERATION
2
Archegonium
with egg
Fertilization
Meiosis
DIPLOID (2n)
SPOROPHYTE
GENERATION
5
Calyptra
Spore
mother cells that
undergo meiosis
Capsule
Zygote
4
Sporophyte
3
Embryo
Gametophyte
plant
Fig. 22-7, p. 437
KEY TERMS
•
LIVERWORT
•
A member of a phylum of spore-producing,
nonvascular, thalloid or leafy plants with a life
cycle similar to that of mosses
KEY TERMS
•
THALLUS
•
•
A body that lacks roots, stems, or leaves
GEMMA
•
A small body of tissue that becomes detached
from a parent liverwort and is capable of
developing into a new organism
Liverworts
Liverworts
Life Cycle: Liverworts
Antheridiophore
Germination of spores
and development of
young gametophyte
5
Spores
released
Archegoniophore
Male
thallus
1
Female
thallus
Antheridia with
sperm cells
Gemmae
cup
Male and female
gametophyte plants
HAPLOID (n)
GAMETOPHYTE
GENERATION
Sperm
cell
Archegonia
with eggs
2
Fertilization
Meiosis
DIPLOID (2n)
SPOROPHYTE
GENERATION
4
Foot
Seta
Zygote
Tissue derived
from archegonium
Capsule
Spore
mother cells that
undergo meiosis
Embryo
3
Sporophyte
Fig. 22-9, p. 439
Liverwort Gametangia and
Sporophyte
Antheridiophore
Gametophyte thallus
Fig. 22-10a, p. 440
Liverwort Gametangia and
Sporophyte
Fig. 22-10b, p. 440
Liverwort Gametangia and
Sporophyte
Foot
Seta
Capsule
Fig. 22-10c, p. 440
KEY TERMS
•
HORNWORT
•
A member of a phylum of spore-producing,
nonvascular thalloid plants with a life cycle
similar to that of mosses
Hornworts
•
Hornwort gametophytes are thalloid; their
sporophytes form hornlike projections out
of the gametophyte thallus
Hornwort
Mature
sporangium
splits open
Spores
Sporophyte
Gametophyte with
embedded archegonia
and antheridia
Fig. 22-11b, p. 441
LEARNING OBJECTIVE 6
•
Describe the ecological significance of
the mosses
Mosses
•
Colonize rock previously colonized by
lichens
•
•
Help form thin soil in which grasses and other
plants can grow
Grow in dense colonies
•
Hold soil in place, help prevent soil erosion
Mosses in Research