Download I. The first vascular plants evolve roughly 420 MYA as plants move

Plant Kingdom – Part 1. General Information.
I.
About 500 Million years ago (MYA) plants begin to leave the watery environment for land.
A. Plants are believed to have started around the moist coastal areas.
B. Plant-like protists (algae) are believed to be the ancestors of terrestrial plants.
C. Four major groups (clades) of plants will evolve over millions of years in response to the changing environment.
i. Bryophytes (mosses)
ii. Pteridophytes (ferns and thrushes)
iii. Gymnosperms (Conifers)
iv. Angiosperms (flowering plants)
D. The major evolutionary trends across all four plant clades are as follows:
i. Increased ability to live away from surface water
ii. Decreased dependence on water for fertilization
iii. Increased size of diploid form and decreased size of gametes
iv. Evolution of seeds
v. Evolution of flowers and seeds to increase reproductive success
vi. One could view this sequence of adaptations as a drive towards untapped resources (land, and
sunlight)
II.
The following adaptations will evolve over time in plants to survive on land in a dryer environment.
A. Waxy cuticle on the surface of the leaves. (This helps to avoid dehydrating.)
B. Vascular tissue (This will transport water and nutrients.)
C. A Protective seed (This helps the survival of the embryonic plant during harsh dry times.)
1. An added benefit is dispersal increases. (Seeds can be “moved” into new territory – away from competition.)
D. Flowers and fruit develop. (These structures help moving to new areas or reproducing by using animals.)
III. Unifying traits that support all/most plant common ancestry.
A. The “basic” structure – Root (below ground) and shoot (above ground).
B. Apical meristematic tissue at the tips of roots and shoots. These tissues are areas of growth or elongation.
C. Produce a waxy Cuticle on herbaceous parts. (“herb” means “soft, fleshy”)
D. There are Stomata (openings) on the leaves for gas exchange to occur during photosynthesis.
E. Most plants possess vascular tissue. (Not found in Bryophytes.)(They are only in Tracheophytes.)
1. Xylem (Carries water up the plant towards the leaves.)(These are dead, hollow cells.)(Fig. 35.9)
2. Phloem (Carries sugar water down to feed the plant or store in the roots.) (These are living cells.)
Plant Kingdom – Part 2: Bryophytes. The Mosses.
I.
Bryophytes (Phylum Bryophyta). Evolved roughly 475 million years ago (MYA)
II.
General Characteristics
a. Small, only two tissues (above ground: “green parts” called microphylls; below ground: rhizoids root-like tissue for
anchoring)
b. No vascular tissue: no true roots, stems or leaves
c. Do have waxy cuticle on microphylls.
d. Do have an apical meristem.
e. Do perform photosynthesis.
f. Reproduction is completely dependent on water, therefore they must live in moist, often cool, environments.
III. Environmental Conditions that drove evolution
a. No other terrestrial plants to shade them.
b. Increased access to sunlight (no water to attenuate/block light).
c. Ample water in soil and atmosphere (water, nutrients, waste products all exchanged with environment via
diffusion).
IV. Evolutionary Novelties
a. Very small in size. (Only cellulose in the cell wall…missing Lignin and pectin to reinforce and stiffen cell wall.)
b. Cellulose in cell wall. Gametophyte (haploid) generation is the Dominant generation. This is what you see.
c. Waxy cuticle on microphylls.
d. Release spores into atmosphere for dispersal.
V. Ecological and Economical Importance of Bryophytes
a. They are a major food source (producers) in the Tundra. Think northen Alaska.
b. Peat Moss (A.K.A. Sphagnum) is a fuel source. It is also a CO₂ sink.
c. They can be used as a soil conditioner – as they can hold up 20x its weight in water. (Used by gardeners/farmers.)
Plant Kingdom – Part 3 Pteridophytes. The Ferns and their allies.
I.
The first vascular plants evolve roughly 420 MYA as plants move farther away from water.
II.
General Characteristics
a. Modern ferns are between 6 inches and three feet high
b. Like mosses, gametes depend on water for fertilization (sperm travels to egg through soil, when soil is damp)
c. Usually found near water (Scouring thrush), or in cool, shady areas (most ferns), or growing on other trees (some
ferns near Alabama rivers).
d. Ancient Ferns (during Carboniferous period – 350 MYA) were HUGE…60+feet tall
III. Environmental Conditions that drove evolution
a. Decreased access to water.
b. Increased access to sunlight.
c. Increased nutrient availability in soil (thanks to mosses, and microorganisms “conditioning” the soil.
IV. Evolutionary Novelties
a. Vascular tissue (true xylem and phloem).
b. True leaves (megaphylls).
c. Increased complexity of cell walls and cell-to-cell junctions (cellulose, lignin, and pectin), allows for taller growth.
d. True roots (serve as anchors and for nutrient uptake).
e. Each plant produces thousands of spores, these grow into hermaphroditic leaves which can self fertilize and then
grow into a new fern).
V. Ecological and Economical Importance of Ferns
a. Petrified ferns from the Carboniferous are today’s coal seams….provide for 54% of US electricity production and
71% of Alabama’s electricity production
b. Help moderate temperature of forest floor soil.
c. Fern death contributes to organic matter load/litter in forest ecosystems.
Plant Kingdom – Part 4: Gymnosperms. Confiers (Pines and others)
I.
Conifers, the first seed plants, evolve roughly 360 MYA and continue to dominate terrestrial biomes until roughly 250 MYA.
They are still quite present today, but they are not as diverse as their close cousins, the angiosperms.
II.
General Characteristics
a. Reduced size of leaves (also known as needles).
b. Thick, waxy cuticle on the leaves.
c. Shed and replace leaves continually, hence the nickname “ever green”.
d. Large plants with thick, waxy bark .
e. Most Conifers, have cones.
III. Environmental Conditions that drove evolution
a. Cool, dry climate.
b. Decreased availability of water.
c. Ample sunlight, very little shade.
IV. Evolutionary Novelties
a. Fully developed xylem and phloem.
b. “Secondary growth”: the ability to add girth (or width) to the stem in order to support taller growth upward.
c. Small, waxy needles with reduced stomata.
d. Separate male and female cones.
i. Male cones produce microscopic pollen (containing sperm)
ii. Female cones house the microscopic ovum (containing egg/oocyte)
e. Use of wind for pollination. Fertilization completely independent of water.
f. Formation of a seed within the cone.
i. Seeds have a thick “coat” that resists decay
ii. Seeds have food source: oils that can be broken down to feed the embryo during germination
iii. Seeds have a diploid embryo, waiting to germinate when conditions are favorable
V. Ecological and Economical Importance of Conifers
a. The dominant vegetation in Tiaga, Boreal, and subalpine biomes.
b. The dominant vegetation in temperate rainforests.
c. Dominant vegetation in secondary succession in the southeast.
d. Conifers (aka “soft woods”) are lumber for construction, wood chips used to make paper.
e. Waxes and other compounds in leaves contribute to acidity of forest floor. This inhibits growth of
other plants and creates a niche for large browsers to live in forests (deer, elk, rabbits, etc, etc.).
Plant Kingdom – Part 5: Angiosperms. The flowering plants
About 250 MYA Angiosperms begin to evolve due to increased water availability. Angiosperms have continued to evolve and
diversify into the present day. They are the most diverse group of plants on Earth today.
I.
General Characteristics
a. Difficult to describe generalities because they are such a diverse clade.
b. All Angiosperms have…
i. A flower
ii. Reproduce by “double fertilization” (one sperm fertilizes the egg, forming an embryo; the other sperm
fertilizes the food for the developing embryo).
iii. Fruit containing seeds.
iv. Highly developed vascular tissue to transfer water and nutrients throughout plant.
II.
Environmental Conditions that drove evolution
a. Evolution of insects (at first crawling insects, and later winged insects)
i. Insects are both predators and pollinators, hence a coevoltion with plant height and insects’ ability to fly.
b. Increasingly dry conditions in the case grasses and desert succulents.
c. Increasingly wet conditions in the case of tropical plants and trees.
d. The reinvasion of water in the case of aquatic plants like cat tails and “lilly pads” (Nymphea).
III. Evolutionary Novelties
a. All hail the mighty flower! Flowers are a specialized leaf adapted for reproduction.
i. Male parts called stamen contain pollen
ii. Female parts called pistel/carpel contain eggs
iii. Petal colors and arrangement can attract pollinators
iv. Flowers contain nectar, food for the pollinator
v. As pollintators feed on a specific flower, they transfer pollen from one individual flower to another,
increasing the chances of cross-fertilization…this can lead to increased genetic diversity within a flower
population
b. Increased leaf complexity
i. Broad-leafed plants of the sub tropics and tropics.
ii. Decreased leaf size for grasses as well as desert plants
c. In general, increased stomatal density to ensure efficient transfer of water from roots to leaves, and to facilitate
plant cooling.
d. A variety of metabolic adaptations
i. Most plants perform typical photosynthesis and use Calvin Cycle to convert CO 2 to sugar.
ii. Desert plants do CAM photosynthesis. They open stomata at nigh to take up Carbon. They store the
carbon as an organic acid, then make sugar during the day when light is available.
IV. Ecological and Economical Importance of Angiosperms
a. Virtually all our food comes from Angiosperms (3 Angiosperms comprise 80% of global calorie consumption).
b. The source of most pharmaceuticals as well as other industrial important compounds (e.g. rubber).
c. The major source of oxygen and primary productivity in terrestrial biomes.