Chapter 22

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.  may be indicators of high calcium, salinity and acidity

                       2.  some mosses may clog water pipes

            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

A. The movement to land required the evolution of new structures and chemicals

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

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

2. Ozone could shield UV light; and have reached 10% of modern levels

b. Other botanists argue that phenolic compounds absorb UV light and that any plant producing these 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

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.

A. Lycophyta are more complex than Psilophyta because they have true stems, true roots and microphylls

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 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