PLANT EVOLUTION AND CLASSIFICATION

Almost all organisms on Earth depend on the Photosynthetic ability of Plants.  Plants Capture and Store the Energy from Sunlight in various compounds (Autotrophs or Producers).  Other organisms can also this Energy when they consume the Plants (Heterotrophs or Consumers). THE ENERGY MOST ORGANISMS NEED COMES DIRECTLY OR INDIRECTLY FROM PLANTS.  Plants produce the Oxygen you Breath, the Food you eat, and even the Paper used to print this material.  Plants are also a source of many Medicines that help to keep you Healthy.  Without Plants, life as you know it would not exist.

OVERVIEW OF PLANTS

Plants dominate the land and many bodies of water.  Plants exhibit tremendous diversity.  Some plants are less than 1 mm in width, and some plants grow more than 100 m (328 ft) in height.  The 12 Phyla, or Divisions, of Kingdom Plantae include more than 270,000 species.  Some plants complete their life cycles in a few weeks, while others may live 5,000 years.

OBJECTIVES:  Compare and contrast green algae and plants.  Name three adaptations plants have made to life on land.  Compare vascular plants with nonvascular plants.  Define and describe alternation of generations.

1. There are more than 270,000 Different Plant Species, and New Plant Species continue to be discovered in the Tropical Rain Forest.

2. Among the species of plants, there is amazing diversity of Shapes and Sizes (Physical Characteristics).

3. Plants do all share some Characteristics:

    A.  All plants are Photosynthetic.

    B.  All Plants are Multicellular.

    C.  All Plants are Eukaryotic Organisms.

    D.  All Plants can reproduce Sexually.

ADAPTING TO LAND

1. The movement to land of Plants required them to make several Adaptations to survive this new and strange environment. Land Plants had to develop new structures to replace the Advantages provided by an Aquatic Environment.  The first Plants had to be able to survive scarcity of water AND THE CHANGES OF Climate.

2. Water was vital to the first Land Plants.  The earliest plants needed water to supply Nutrients, for Photosynthesis and for Fertilization.

3. On Land (A Terrestrial Environment) Water may be scarce, most usable liquid water exists only in the soil and the amount of water in the soil depends on the amount of Rain or Snow and depth of the Water Table.

4. The Temperature or Climate on Land is more unpredictable and harsher than in the Water.   Air Temperature Changes more rapidly than Water.  Higher Air Temperature on land means Greater Water Loss by evaporation (Transpiration).

PREVENTING WATER LOSS

1. The move from water to land offered some organisms distinct Advantages, including more exposure to Sunlight for Photosynthesis, Increased Carbon Dioxide Levels, and a Greater Supply of Inorganic Nutrients.

2. However, the land environment also presented challenges.  Plants on land are susceptible to Drying out through Evaporation.

3. One Early Adaptation to life on land is the CUTICLE (KYOO-tih-kul), enabled plants to conserve Water by slowing Evaporation from the plants body.

4. THE CUTICLE IS A WAXY, WATERPROOF LAYER THAT COATS THE PARTS OF A PLANT EXPOSED TO AIR.

5.  Cuticle protects the plant by keeping Water In, but it also keeps Carbon Dioxide Out.  Plants that had small openings in their surface, called STOMATA, were able to survive.  Stomata allow the exchange of Carbon Dioxide and Oxygen.
 
 
REPRODUCTION BY SPORES AND SEEDS

1. The Earliest Land Plants needed Water for Reproduction, because sperm had to swim through water to fertilize an egg.  These first plants probably lived in moist areas where water is plentiful, and probably had Mycorrhizae fungi associated with their roots, to help get nutrients.

2. Successful land plants also developed Structures, such as Spores and Seeds, that helped Protect Reproductive Cells from Drying Out.

3. A SPORE contains a Haploid Reproductive Cell surrounded by a hard outer wall.  Spores allowed for the Widespread Dispersal of plant species.

4. Eventually, Most Plants developed SEEDS.  A SEED is an Embryo surrounded by a Protective Coat.  Some Seeds also contain ENDOSPERM, a Tissue that provides Nourishment for the developing Embryo.

5. Seeds are more effective at Dispersal than Spores Are.

TRANSPORTING MATERIALS THROUGHOUT THE PLANT.

1. The earliest plants were probably SHORT, AND HAD NO TRUE ROOTS, LEAVES, OR STEMS (Non-Vascular Plants).

2. Shortness was an advantage, because short plants did not need much support.  The first land plants did require more support than Algae in Water.

3. Adaptation for Support may have included Specialized Cells and Compounds such as LIGNIN, A HARD COMPOUND THAT STRENGTHENS CELL WALLS, ENABLING CELLS TO SUPPORT ADDITIONAL WEIGHT.

4. Certain species of plants Evolved VASCULAR TISSUE, a type of Tissue that Transport Water and Dissolve Substances from one part of the Plant to another.

5. TWO Types of Specialized Tissue make up Vascular Tissue:

    A. XYLEM - Carries WATER and Inorganic Nutrients in ONE Direction, from the ROOTS to the STEMS and LEAVES.

    B. PHLOEM - Carries ORGANIC COMPOUNDS (Carbohydrates), in ANY DIRECTION, depending on the Plant's Needs.

6. Vascular Tissue also helps SUPPORT the plant, which is an important function for land plants.  Aquatic plants are mainly supported by the water around them.

7. Some plants developed WOODY TISSUE and Grew to great heights, giving them an advantage in Gathering Light.

8. WOODY TISSUE (WOOD) is formed from several layers of Xylem, usually concentrated in the center of the Stem.  Woody Stems are usually Brown and Rigid.

9. Nonwoody plants are usually called HERBACEOUS because they have Soft, Usually Green Stems. Because the Vascular Tissue is not surrounded by Rigid Sclerenchyma Cells, the Stem of Herbaceous Plants are Flexible.

CLASSIFYING PLANTS

1. THE 12 Phyla (Divisions) of Plants can be Divided into TWO Groups based on the presence of Vascular Tissue. 

2. The THREE Phyla of NONVASCULAR PLANTS  DO NOT HAVE True Vascular Tissue nor TRUE Roots, Stems, or Leaves.

3. Most members of the Nine Phyla of VASCULAR PLANTS Have Vascular Tissue and TRUE Roots, Stems, and Leaves.

4. Vascular Plants can be Further Divided into TWO Groups:

    A. SEEDLESS PLANTS - The Phylum of Ferns and Three Phylum made up of plants closely associated with Ferns they are plants that produce spores.

    B. SEED PLANTS - Plants that produce Seeds for Reproduction.

5. SEED PLANTS can also further be broken down into TWO Groups:

    A. GYMNOSPERMS - "Naked Seed", which includes Pine Trees, Produce Seeds that ARE NOT Enclosed in FRUITS.

    B. ANGIOSPERMS - also known as Flowering Plants, Produce Seeds WITHIN a Protective FRUIT.

THE FOSSIL RECORD OF PLANTS

1.  In their Characteristics, Plants are Most Similar to the Algae. (Green Algae)

2.  All Plants share a common Ancestor, Scientists have concluded that Plants evolved from a Multicellular Terrestrial Green Algae that lived more than 430 million yeas ago. No organism lived on land until about 430 million years ago when a layer of Ozone formed.

3.  The ozone protected organisms from the sun's Ultraviolet Radiation.

4.  The conclusion that Plants evolved from Green Algae is supported by many Structural and Biochemical similarities between Plants and Green Algae.

5.  PLANTS AND GREEN ALGAE HAVE THESE CHARACTERISTICS IN COMMON:

    A.  Both have the same photosynthetic pigments, Chlorophyll a and b, in similar Chloroplasts.

    B.  Both have Cell Walls that contain Cellulose.

    C.  Both development of a Cell Plate during Cell Division.

    D.  Both Store Energy as Starch.

4. There are also some important DIFFERENCES between Plants and Green Algae:

    A.  Plants consist of Specialized Cells, While Algae usually have few specialized cells.

    B.  Plants have special structures, such as LEAVES, STEMS AND ROOTS, which Algae lack.

    C. Most plants do not require Water for Fertilization.

    D.  A major difference is that Plants are adapted to life on land, while algae are adapted to life in water.

ALTERNATION OF GENERATION

1. ALL PLANTS have a Life Cycle that involves TWO PHASES.

2. Alternation of Generations means that there ARE TWO PHASES IN THE LIFE CYCLE OF PLANTS:

    A.  THE FIRST PHASE CONSISTS OF A HAPLOID GAMETOPHYTE THAT PRODUCES EGGS AND SPERM.

    B.  THE SECOND PHASE A DIPLOID SPOROPHYTE THAT PRODUCES SPORES.

3. The Two Plant Phases are named for the type of Reproductive Cells they Produce.

4. This type of life cycle, which alternates between the Gametophyte Phase and the Sporophyte Phase, is called ALTERNATION OF GENERATIONS.

5. As an Adaptation of plants, the Alternation of Generations provides for Sexual Reproduction, and Sexually Reproduction ENSURES there will be Genetic Recombination in plants.

6.  In Alternation of Generation,

    A.  The Gametophyte produces Structures that Form Gametes, Egg and Sperm, By Mitosis.

    B.  Once an Egg is Fertilized by a Sperm and produces a ZYGOTE, the Plant Begins the Second Phase of its life Cycle.

    C.  The Zygote divides by Mitosis to Form a Sporophyte Plant.

    D.  The Sporophyte produces Structures that undergo Meiosis to Form Haploid spores.

    E.  These Spores are Released by Most Seedless Plants, but are Retained by Seed Plants.

    F.  The Life Cycle Begins again when the Spores Divide by Mitosis to Form New Gametophytes.

7.  In Nonvascular Plants, the Gametophyte is the DOMINANT Phase.

8. In Vascular Plants the Sporophyte Phase is the DOMINANT Phase.

9. In Seedless Vascular Plants, the Gametophyte is usually a separate small organism quite different from the Sporophyte.

10. In Seed Plants, the Gametophyte is a very small Parasite of the Sporophyte.  The Flower.

NONVASCULAR PLANTS

The Three Phyla of nonvascular plants are collectively called BRYOPHYTES.  Botanist have identified 16,600 species of bryophytes.  They LACK vascular tissue and do not from true roots, stems, and leaves.  These plants usually grow on land near streams and rivers.

OBJECTIVES:  Name three types of plants that make up the bryophytes.  List distinguishing characteristics shared by nonvascular plants.  Compare sporophytes in bryophytes with gametophytes in bryophytes.  Describe the environmental importance of bryophytes.  Name the main ways people use Sphagnum moss.

1. BRYOPHYTES are the Most Primitive type of Plants and All Bryophytes are Nonvascular Seedless Plants.

2.  Bryophytes are SEEDLESS, and they Produce Spores.

3. MOSSES, LIVERWORTS, HORNWORTS, AND OTHER RELATED PLANTS ARE NONVASCULAR SEEDLESS PLANTS.

4. These Plants LACK Vascular Tissue, they are very small Plants, usually 1-2 cm (less than 1 in) in height and are more dependent on Water.

5. They must have liquid water to Reproduce Sexually.  The sperm must swim through water to an egg.  The Asexual Reproduction of Haploid Spores Does Not Require Water.

6. They Do Not Have TRUE ROOTS, LEAVES, OR STEMS, but do have structures that perform similar functions.

7. Instead of Roots, they have long, thin strands of cells called RHIZOIDS that attach the plant to the soil.

8. They also have flat, broad tissues that function somewhat like Leaves.  These tissues contain Chloroplasts, where photosynthesis occurs.

PHYLUM BRYOPHYTA - MOSS

1. Almost every land environment is home to at least one Moss.

2. The thick green carpet of Moss you see on shady forest floors actually consist of Thousands of Tiny Moss Gametophytes.

3. Each Gametophyte is attached to the soil by a root-like structures called RHIZOIDS.  Unlike roots, Rhizoids Do Not have Vascular tissue.  But Rhizoids do function like roots by Anchoring the Moss and by Absorbing Water and Inorganic Nutrients.

4. Moss Gametophytes are usually less than 3 cm tall.  The Moss Sporophyte is attached to and Dependent on the Large Gametophyte. 

5. Gametophytes may be male, female, or contain both male and female Reproductive Parts.

6. Mosses are called Pioneer Plants they are often the First to Inhabit a Barren Area. In areas devastated by fire, volcanic action, or human activity, Pioneering Mosses can help trigger the development of new biological communities.

7. Mosses help prevent soil erosion by covering the soil surface and absorbing water.

8. SPHAGNUM or Peat Moss, is a genus of moss that is a major component of Peat Bogs.

9. Peat moss consists of partially decomposed plant matter.

10. In many Asian and European countries, peat moss is mined and dried for use as a fuel.

11. Sphagnum is widely used to enhance the Water-retaining ability of potting and garden soil, it is also used by florists to pack bulbs and flowers for shipping.

PHYLA HEPATOPHYTA (Liverworts) AND ANTHOCEROPHYTA (Hornworts)

1. Phylum Hepatophyta includes the Liverworts, unusual looking plants that grow in moist, shady areas. 

2. Most Liverworts have Thin Transparent Leaf-like structures arranged along a Stem-like Axis.

3. Some Liverworts have a THALLOID Form, a Flat Body with distinguishable upper and lower surfaces.

4. All Liverworts lie close to the ground, that allows them to absorb water readily.

5. In some species, the Gametophyte is topped by an umbrella-shaped structure (Germmae Cup) that holds the Reproductive Cells.

6. Phylum Anthocerophyta includes the Hornworts. 

7. They grow in moist, shaded areas. They share an unusual characteristic with algae, each cell usually has a single large Chloroplast rather than numerous small ones.

VASCULAR PLANTS

Vascular Plants contain specialized conducting tissue (xylem and phloem) that transport water and dissolved substances from one part of the plant to another.  Vascular plants can grow larger and live in more environments than nonvascular plants.  The strong stems of vascular plants allow the plants to grow tall, enabling them to rise above other plants and receive more sunlight than shorter plants do.

OBJECTIVES:  List two main characteristics of vascular plants.  Distinguish between seedless plants and seed plants.  Distinguish between gymnosperms and angiosperms.  Summarize the adaptive advantages of seeds. Distinguish between monocots and dicots.

SEEDLESS VASCULAR PLANTS

1. Seedless vascular plants dominated the Earth until about 200 million years ago.

2. There are Four Phyla of Seedless Vascular Plants, The First Three are called Fern Allies, and the Last Phylum is the Ferns.

3. Spores are the Mobile Sexual Reproductive Parts of All Seedless Plants.

PHYLUM PSILOTOPHYTA - WHISK FERNS

1. The Phylum Psilotophyta is represented by Whisk Ferns.

2. Whisk Ferns are Not Ferns At All.  They Have NO Roots or Leaves and produce spores on the Ends of Short Branches.  These features Suggest that Whisk Ferns Resemble Early Land Plants.

3. Whisk Ferns are EPIPHYTES, which means the Grow on Other Plants, but they are Not Considered a Parasite.

PHYLUM LYCOPHYTA - CLUB MOSSES

1. The Phylum Lycophyta contains the Club Mosses.  They look like Miniature Pine Trees, and are also called Ground Pines.

2. The cone-like structure, called a STROBILUS, contains Sporangia-Bearing Modified Leaves.

3. Another member of Phylum Lycophyta is a Spike moss called Selaginella lepidophylla, native to the American Southwest, is called the Resurrection Plant, because it turns brown and curls up in a ball during Drought.  When Moistened, the plant uncurls and turns Green again after a few hours.

PHYLUM SPHENOPHYTA - HORSETAILS

1. The Phylum Shenophyta includes Horsetails, or Equisetum. 

2. Horsetails have Jointed Photosynthetic Stems that contain SILICA, with Scale-like Leaves at each Joint.

3. American pioneers used horsetails to scrub pots and pans, they are frequently called Scouring Rushes.

PHYLUM PTEROPHYTA - FERNS

1. Ferns probably originated over 350 million years ago and belong to the Phylum Pterophyta.

2. Some ferns are floating plants that are less than 1 cm across.  Ferns also grow above the Arctic Circle and in Desert Regions.

3. The Largest Living Ferns are Fern Trees, these Ferns can reach 25 m (82 ft) in Height and some have Leaves (FRONDS) 5 m (16 ft) long.

4. Most Ferns have Underground Stems called a RHIZOME.  The fibrous Rhizomes of some Ferns are used for growing Orchids.

5. The Tightly coiled new Leaves of Ferns are called FIDDLEHEADS, the Fiddleheads uncoil and develop into mature Leaves called FRONDS.

VASCULAR SEED PLANTS

1. The Mobile Sexual Reproductive part of a Seed Plant is the Multicellular Seed.

2. Seeds are an Evolutionary success story.  Plants with Seed have a Greater Chance of Reproductive Success than Seedless Plants.

3. Inside the tough, Protective Outer Coat of a Seed is an Embryo and a Nutrient Supply.

4. When conditions are too hot or cold, or too wet or dry, the Seed Remains Inactive.

5. When conditions favor Growth, the seed sprouts, or GERMINATES, the embryo begins to grow into a young plant, called a SEEDLING.

6. There are TWO main groups of Seed-Bearing Plants based on the Type of SEED THEY PRODUCE: GYMNOSPERMS AND ANGIOSPERMS.  

7. THE FOUR PHYLA OF GYMNOSPERMS PRODUCE NAKED SEEDS.  THEY ARE VASCULAR PLANTS THAT PRODUCE SEEDS LACKING A PROTECTIVE COVERING.

8. The Largest and most familiar division of Gymnosperms are the Conifers.  Conifers include CONE-Bearing Evergreens such as PINE, FIRS, SPRUCES, SEQUOIAS, AND CYPRESSES.

9. A CONE IS A SPECIALIZED REPRODUCTIVE STRUCTURE COMPOSED OF HARD SCALES, THAT PRODUCES SEEDS WITHOUT A FRUIT.  MOST CONIFERS HAVE SIMPLE NEEDLELIKE LEAVES.

10.  The ONE PHLYUM OF ANGIOSPERMS ARE VASCULAR PLANTS THAT PRODUCE SEEDS ENCLOSED AND PROTECTED BY A FRUIT.

11.  ANGIOSPERMS ARE REFERRED TO AS FLOWERING PLANTS.

12.  ALL ANGIOSPERMS PRODUCE FLOWERS AND SEEDS.

13.  THE PROTECTIVE STRUCTURE THAT CONTAINS THE SEED OR SEEDS OF AN ANGIOSPERM IS THE FRUIT.

14. CONES serve the same Function for Gymnosperms that FLOWERS serve for Angiosperms.

PHYLUM CYADOPHYTA - CYCADS

1. Cycads (SIE-KADZ) are Gymnosperms, they flourished during the age of Dinosaurs, only about 100 species survive today.

2. Most are native to the tropics and grow slowly.  Most Cycads have Fern-like, Leathery Leaves at the top of Short, Thick Trunks. 

3. Cycads Plants are either Male or Female, and bear Large Cones.  Cycads are mostly used as ornamental plants.

PHLYUM GINKGOPHYTA - GINKGOES

1. Ginkgoes flourished during the time of dinosaurs. Only One species survives today, Ginkgo biloba, which is native to China. It is called a Living fossil because it resembles Fossil Ginkgoes that are 125 million years old.

2. The Ginkgo Tree has Fan-Shaped Leaves that fall from the tree at the end of each growing season, an unusual characteristic for a Gymnosperm (Evergreens).

3. Trees that lose their leaves at the end of a growing season, like the Ginkgo, are called DECIDUOUS.  Most Gymnosperms are Evergreens and Retain their Leaves Year-round.

4. Ginkgoes are tolerant of Air Pollution, making them good plants for urban settings.  Ginkgo Seeds are plum-shaped, Fleshy Seeds that are often mistakenly called berries or fruit. 

PHYLUM CONIFEROPHYTA - CONIFERS

1. The Conifers are the most common Gymnosperms, and include pine, cedar, redwood, fir, spruce, juniper, cypress, and bald cypress trees.

2. They are an important source of Wood, Paper, Turpentine, Resin, Ornamental Plants, and Christmas Trees.

3. Conifers are Woody Plants, and most have Needle or Scale-like Leaves. 

4. A Conifer usually bears Both Male and Female Cones.  The Small Male Cones typically grow in clusters.  The Male cones release clouds of Pollen, and then the cones fall from the branches.

5. The pollen falls or blows into the Large, Woody Female Cones, where the egg cells are attached to the Scales of Cone.

6. After Pollination, the female cone closes tightly, this protects the developing seeds, which mature after one or two years.

7. The mature seeds are released when the female cone opens.

8. The Redwoods and Giant Sequoia Trees are Conifers that are the Earth's Tallest and most Massive Living Organisms.

9. The Tallest Living Redwood, Sequoia sempervirens, is about 110 m (360 ft) tall, the height of a 30-story building.  The Most Massive Tree is the Giant Sequoia, Sequoiadendron giganteum, estimated to weight 5,600 megagrams (6,200 tons).

PHYLUM GNETOPHYTA - GNETOPHYTES

1. Gnetophytes are an odd group of cone-bearing Gymnosperms that have vascular systems that more closely resemble those of Angiosperms. 

2. Ephedra is a genus of Desert Shrubs with jointed stems, that looks like horsetail.  It is the source of the drug EPHEDRINE, which is used as a decongestant.

3. The Unique Welwitschia mirabilis plant, has a stem that is only a few centimeters tall but can grow to 1 meter in diameter.  Two leaves grow from the stem. A mature leaf may be nearly 1 m wide and 3 m long. 

4. This plant grows in the Namib Desert of Southwest Africa, near the Atlantic Ocean, apparently it gets most of its water from the Dew that condenses from the ocean fog.

PHYLUM ANTHOPHYTA - ANGIOSPERMS

1. The Largest Phylum of Plants, includes over 240, 000 species of Flower Plants OR ANGIOSPERMS.

2. Angiosperms or Flowering Plants, are SEED Plants characterized by the Presence of a FLOWER and FRUIT.

3.  A Fruit is a Ripen Ovary that Surrounds the Seeds of Angiosperms.

4. The OVARY is the Female Reproductive part of the flower that encloses the eggs.

5. Angiosperms grow in many forms and occupy diverse Habitats.

6. Some are HERBACEOUS Plants with Showy Flowers, such as violets and impatiens.  Others, such as Rose Bushes, are SHRUBS. Some Angiosperms are VINES, like grape and ivy plants.  Oak, aspen and birch trees are Flowering Plants that have WOODY STEMS.  GRASSES are also angiosperms, but you must look closely to see their small, highly modified flowers.

7. The World's Largest Flower, which can grow to 1 m in diameter, is produced by Rafflesia - the stinking corpse lily. 

THE EVOLUTION OF ANGIOSPERMS

1. Angiosperms first appeared in the fossil record about 135 million years ago. By about 90 million years ago, Angiosperms begun to outnumber Gymnosperms.

2. Several factors led to this success of Angiosperms:

    A. In many Angiosperms, seeds germinate and produce mature plants, which in turn produce new seeds, all in one growing season. Gymnosperms often take 10 or more years to reach maturity and produce seeds

    B. The Fruits of flowering plants Protect the Seeds and Aid in their Dispersal.

    C. Angiosperms have a more efficient Vascular System, and are more likely to be associated with Mycorrhizae than Gymnosperms are.

    D. Angiosperms also may gain an advantage by using Animal Pollination rather than the less efficient Wind Pollination.  Wind pollination is also used by some Angiosperms, such as grasses and many Deciduous Trees.

    E. Angiosperms are more Diverse than Gymnosperms, so they occupy more NICHES, such as aquatic, epiphytic, and parasitic environments.

MONOCOTS AND DICOTS

1. Angiosperms are divided into TWO CLASSES: MONOCOTYLEDONES (MONOCOTS) AND DICOTYLEDONES (DICOTS), BY COUNTING THE NUMBER OF SEED LEAVES OR COTYLEDONS (KOT-ih-LEE-dunz), IN THE PLANTS EMBRYO.  

2. ANGIOSPERMS WITH ONLY ONE COTYLEDON ARE CALLED MONOCOTS.  A Typical monocot (corn and grasses) has Narrow Leaves with Parallel Veins called PARALLEL VENATION, Flower parts in multiples of three, and vascular tissue in bundles that are scattered throughout the Stem.

3. A DICOT IS AN ANGIOSPERM WHOSE EMBRYO HAS TWO COTYLEDONS.  Dicots (Beans, most trees) usually have broad leaves with branching veins called NET VENATION, flower parts in multiples of four and five and vascular tissue (Bundles) in rings.

4. Neither Gymnosperms nor Angiosperms depend on an external source of water for fertilization. Fertilization occurs after Pollen Grains are transferred from one plant to another by wind or by organisms such as insects.

5. The evolution of the SEED and the Decrease Dependence on Water have made the Gymnosperm and Angiosperm Successful Organisms.