Botany - Bio 201
Spring 2008
_ Written by: Sue Kloss
Lake Tahoe Community College
Instructor: Ralph Sinibaldi
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Chapter 23 and 22 - Lower Vascular Plants and Bryophytes
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Chapter 22
I. Algae and plants share several chars:
A. Ps pigments (including chlorophyll and carotenoids)
B. starch as storage
C. cellulose in cell walls
D. cell plates in cell division
E.
Land plants evolved around 400 mya (fossil evidence) Plants derived characteristics=
A. cuticle
B. gametangia
C. multicellular embryos
D. diploid phase predominant
II. Division Bryophyta are herbaceous members of Kingdom Plantae, which have a combination of traits between the
algae and vascular plants, aquatic and terrestrial environments
A. Ecologically diverse bryophytes grow on wet, terrestrial sites, aquatic habitats, and into extreme habitat such
as edges of snow banks and near hot springs.
B. this division contains organisms commonly called mosses, liverworts and hornworts
C. Bryophytes are algae-like organisms which lack a vascular system, or lignified cell walls, but have
structures resembling roots, stems, leaves
D. they have cuticle and stomates, and produce wind borne, asexual spores; they produce gametes in a sterile
jacket of cells, and have diploid offspring sheltered and nourished by the parent; their life cycle contains spores
E. Bryophytes are unique among land plants bc. they have a dominant haploid generation in their life cycle
F. Bryophytes are organized into 5 classes
III. Liverworts - Class Hepaticopsida, are the simplest bryophytes
A. Ecologically, they grow in moist, shady habitats where the gametophyte thallus is held in place by rhizoids
B. Some species have leaflike structures called phyllids and stemlike structures called caulids
C. Sporangia (Capsules) are produced and contain elators which spread spores
D. Marchantia requires a moist environment but is better adapted to terrestrial environments than some
bryophytes
IV. Hornworts belong to Class Anthcerotopsida and have the simplest gametophytes of this divisions
V. The Andreaeopsida, Sphagnopsida an bryopsida are the best known members of the Bryophyta; they are larger,
have a wider distribution and more species than liverworts and hornworts
A. Andreaeopsida are dark colored plants growing on rocks in cool climates
B. Sphagnopsida are large and confined to acidic bogs
C. Bryopsida have the widest range and most species diversity
VI. interesting facts
A. WWI, moss grabbed by MASH nurses proved excellent for bandages with antiseptic properties- Spagnum
B. some bryophytes are found only on bones and antlers of dead reindeers, or dung of herbivores or dung of
carnivores (diff’t species); some on large insect wing covers
C. Bryophytes often have mycorrhizal associates, some mycos are at least partially parasitic
D. Peat mosses are ecologically very important, can help in transition of bogs to dry land,
E. in some, form floating mats over water surface to keep conditions acid enough to inhibit growth of bacteria
And fungi. Orgs can be preserved there for hundreds or thousands of years.
VII. Ecology and human uses
A. some bryophytes and lichens are pioneers on bare rock – glaciers, volcanoes, etc. They accumulate organic
And mineral matter and make it usable for other organisms
B. mosses in particular retain moisture, and release it slowly to the soil.
1. reduce flooding and erosion and add humus to soil
C. mosses in dry area are indication that at least some of the time, area has running water
1. some mosses may clog water pipes
2. may be indicators of high calcium, salinity and acidity
D. bryophytes are not generally edible, though a few are grazed along with lichen in arctic areas
E. NA. Used mosses for diapers and underneath splints when setting bones
F. 1 kg (2.2 lbs) of peat moss will take up 25 kg of water – used as soil conditioner
1. live shellfish are shipped in it
G. scotch whiskey is made by drying barley over a peat fire – imparts a smoky flavor
Chapter 23
I. The transition from water to land - Earth is 4.5 byo; within 1 billion years of earth’s formation, microscopic bacteria
lived in seas and pools. An additional 3 billion yrs before land plants evolved. Diversification happened relatively quickly
(50 million years)
A. The movement to land required the evolution of new structures and chemicals; in water, plants bathed in
nutrients and soluble gases; organs are thin and diffusion carries material to all cells. Need no special tissues
for structure or conduction of nutrients
1. On land plants needed special organs to absorb nutrients
2. Land plants needed a conducting system for water
3. Spores of land plants needed protection from drying out
4. Above ground structures needed protection from drying out - chemical sealing keeps water in, but
allows gases to diffuse
B. The majority of land plants have vascular tissue and are called vascular plants
1. Some vascular plants reproduce by seeds (cone bearing and flowering plants)
2. Other vascular plants disperse spores, these are called the seedless vascular plants or lower
vascular plants
3. Lower vascular plants are represented by 4 divisions: Psilophyta (whisk ferns), Lycophyta (Club
mosses), Sphenophyta (scouring rushes), and the Pterophya (ferns)
4. Lower vascular plants, in addition to having vascular tissue, also have stomata, a waxy cuticle and
spores with tough walls
5. Lower vascular plants retain flagellated sperm cells
6. free living gametophytes require water for fertilization
C. Early vascular plant forests date to the Ordovician (430-470 mya) 1. meiospores of characteristic shape with thick cell walls, portions of epidermis, with cuticle, and cells
that resemble tracheids have been found
2. Why did the invasion of land begin in the Ordovician?
a. Berkner and Marshall proposed that movement to land had to wait for enough accumulated
free oxygen in the atmosphere
1. Primeval atmosphere, with little O2, did not shield UV light which can penetrate living
tissue and cause metabolic as well as genetic disruptions; water shields UV
2. Ozone (O3) could shield UV light and would have reached 10% of modern levels
400 mya
b. Other botanists added that phenolic compounds absorb UV light and that any plant
producing these in larger would be at a selective advantage
1. phenols also protect plant from predation by herbivores
2. modern plants use phenols to construct lignin for vascular tissue; lignin important for
vascular tissues, support and structure, and prevent herbivory. Lignin absent from
fossils until invasion of land, 400 mya
3. First undisputed vascular plant in fossils appeared 420 mya = Cooksonia
3. Rapid evolution of plants occurred during the Silurian and Permian periods
a. By the end of the Devonian, vegetation was complex and layered with forests, shrublands
and meadows.
b. Herbaceous plants, shrubs, trees w/ secondary growth, roots, seeds and leaves were
present
4. Fossil fuels began forming during the Carboniferous when lush swamp forests were dominant
a. slight changes in sea level inundated forests and deposited silt
b. buried organic remains were compressed and today form the world coal reserve
II. Division Psilophyta (whisk ferns) are the most primitive vascular plants
A. Division Psilophyta has only a single family (Psilotaceae) and 2 genera (Psilotum and Tmesipteris).
B. Both genera are epiphytes living in tropical and subtropical regions, but in different hemispheres
C. Psilotum is considered the most primitive vascular plant
III. Division Lycophyta is commonly called the Club or Spike mosses. They superficially resemble mosses because of
small size and green microphylls (very small epidermal outgrowth with a single vein - true leaves are megaphylls, with
vascular systems that are netted).
A. Lycophyta are more complex than Psilophyta because they have true stems, true roots and microphylls
1. Lycopodium looks like small pine seedlings
B. Most species are tropical or subtropical; some species extend into temperate, aquatic and arid habitats
IV. Division Sphenophyta has one living genus, Equisetum, w/25 spp. that primarily live in cool moist habitats
A. Equisetum contains silica in stem epidermal cells; pioneers used them to wash pots and pans (hence
name “scouring rushes”)
B. Stems and branches marked with distinct nodes and vertical ridges
C. whorls of branches attached at nodes
V. Division Pterophyta (ferns) contains the second largest and most diverse group of species of vascular plants
A. Ferns grow from underground horizontal perennial stems called rhizomes
1. Roots and fronds arise from rhizome
2. apical meristem initiates all cell divisions
3. vascular tissue arranged in one or more bundles
4. above ground ferns are characterized by a diverse morphology of fronds or macrophylls
Lesson Objectives
1. Briefly (in 2 - 3 sentences and billion year intervals,) describe the history of plant life on earth.
2. List 3 important differences in terrestrial vs. aquatic habitats, and describe the structures that have evolved in
plants to overcome these obstacles.
3. Name the four major groups of plants that exist on earth and describe the major evolutionary adaptation of each
group.
4. Describe 2 hypotheses advanced by scientists account for movement of plants to terrestrial environments about
450 million years ago. (make sure to include UV radiation, Ozone, Phenols/lignins and O2).
5. What traits do mosses share with algae? What true plant traits do they have to distinguish them from algae?
6. Describe the importance to humans and ecosystems of mosses.
7. What traits do ferns and fern allies share with mosses? What traits do they share with gymnosperms and
angiosperms?
8. Where does coal come from and what during what geologic period did it develop?
9. Describe the emphasis in the haploid vs. diploid part of life cycles in algae vs mosses vs. vascular plants (what
are vascular plants?)
10. Name and describe a few characteristics of plants from 2 different Divisions in the Ferns and Fern Allies.