Ch 29 - Plant Diversity

I. CHARACTERISTICS OF MEMBERS OF THE PLANT KINGDOM

A. There are about 330,000 species in this kingdom. Members of this kingdom are

      referred to as “Land Plants.” The earliest fossils of plants date back 400 million 

      years. 

B. Plants are Eukaryotic and Multicellular.

C. Plant cells are covered by a thick, protective Cell Wall that is composed of the

      complex polysaccharide cellulose.

D. Most plants are Autotrophic (can produce their own sugar by photosynthesis).

1. In photosynthesis, plants can capture sunlight energy to generate 

    the glucose required for metabolism.

2. Plants can store extra supplies of glucose as starch (a polysaccharide).

E. Plants contain several photosynthetic pigments:

1. Chlorophylls a and b are found in all plants. These are the primary 

    photosynthetic pigments. Chlorophyll is green in color.

2. Many plants contain accessory pigments known as carotenoids. These 

    pigments are yellow to orange in color. 

3. Some plants contain phycocyanin (blue pigment) and phycoerythrin (red

      pigment).

F. Green algae are most likely the initial ancestors for land plants. This is based on

      the presence of similar pigments, the ability to store glucose as starch, and the

      the presence of a cell wall composed of cellulose.

1. Land Plants had to develop special tissues to obtain water so they could 

    survive on land. Land plants developed roots which can take up water and

    nutrients from the soil. They also have xylem (for water transport) and 

    phloem (for organic nutrient movement) to conduct materials throughout

    the plant itself.

II. PLANT DIVERSITY

A. 10 Major Phyla of Land Plants-for convenience, some of these groups are often 

      combined based on similar characteristics.

1. Phylum Hepatophyta (Liverworts)-6500 species.

2. Phylum Anthocerophyta (Hornworts)-100 species.

3. Phylum Bryophyta (Mosses)-12,000 species. 

a. The above three groups are often linked together and are known as

      Bryophytes (mosses and their allies).

4. Phylum Lycopodiophyta (Lycophytes)-1000 species.

5. Phylum Pteridophyta (Ferns)-12,000 species.

a. These two groups are referred to collectively as Pteridophytes

    (Ferns and their relatives).

6. Phylum Cycadophyta (Cycads)-300 species.

7. Phylum Ginkgophyta (Ginkgo)-1 species.

8. Phylum Gnetophyta (Gnetophytes)-300 species.

9. Phylum Coniferophyta (Conifers)-500 species.

a. The Cycads, Ginkgoes, Gnetophytes and Conifers are collectively

    referred to as Gymnosperms (“Naked Seed” Plants).

10. Phylum Anthophyta (Flowering Plants)-300,000+ species.

a. These are known as Angiosperms.

III. BRYOPHYTES-Liverworts, Hornworts and Mosses.

A. Characteristics

1. These are nonvascular plants-they do not contain the conducting tissues 

    xylem and phloem. Water and nutrients are typically absorbed from the 

    plant’s surroundings. Due to this, Bryophytes tend to be small plants.

2. They live in moist or wet environments.

3. Bryophytes do not contain roots. Instead, they are held in place by 

    rhizoids.

4. They reproduce sexually.

a. They produce flagellated sperm that swim through water to fertilize

    an egg. Obviously, they are tied to water for reproduction to occur. 

b. They typically produce spores in their life cycle.

c. Bryophytes produce structures known as gametophytes and 

    sporophytes in their life cycle.

IV. PTERIDOPHYTES-Ferns and their allies.

A. Characteristics

1. These contain the conducting tissues xylem (conducts water/minerals)

    and phloem (conducts nutrients). These are referred to as vascular tissues.

2. Pteridophytes contain true roots and stems. Conducting tissues allow for 

    this advancement. Also, Pteridophytes can be large due to the presence of

    conducting tissues. Most species have a Rhizome-a special underground 

    stem that is modified to store nutrients and to help the plant survive harsh

    conditions.

3. Pteridophytes reproduce sexually. They produce a gametophyte and 

    sporophyte in their life cycles. Pteridophytes produce motile sperm that

    swim to fertilize the eggs; therefore, these plants require water for 

    fertilization to occur. 

V. GYMNOSPERMS-Cycads, Ginkgoes, Gnetophytes and Conifers.

A. The term Gymnosperm literally means “Naked Seeds.” Gymnosperms produce 

      seeds that are NOT enclosed within a protective vessel.

B. The Conifers are the largest group of Gymnosperms. This group includes the 

      pines, spruce, cedars, and fir trees.

1. The Conifers include the following species:

a. The Bristlecone Pine-the oldest living plants.

b. The Giant Sequoia-the biggest living plant.

c. The Coastal Redwood-the tallest living plant.

C. Characteristics of the Gymnosperms

1. These contain xylem and phloem; however, these tissues are more 

    advanced in Gymnosperms compared to similar structures in 

    Pteridophytes.

2. Gymnosperms do not produce flowers or fruits.

3. Many species thrive in colder climates.

D. Life Cycle of Gymnosperms-is referred to as Alternation of Generations, 

      meaning that they produce a dominant diploid sporophyte stage (the mature 

      plant) and a reduced haploid gametophyte stage (the pollen grain and ovule).

1. Gymnosperms do not require water for external reproduction.

2. Pollen grains are produced in male pinecones and are wind dispersed. These

    contain cells that will develop into sperm. These are blown by the wind and 

    land on female pinecones that contain ovules.

a. A pollen tube delivers the sperm to the ovule which produces a naked

    seed. 

b. Gymnosperm Seed Structure:

1) Seed Coat-thin layer of soft tissue that surrounds the seed.

2) Embryo-the fertilized egg.

3) Stored food

c. Once the seeds are mature, they are released and are dispersed by the

      wind.

VI. ANGIOSPERMS-Phylum Anthophyta. These are “Flowering Plants.”

A. Characteristics

1. These produce flowers, fruits, seeds, and advanced vascular tissues.

2. This group includes a variety of plants, vines and trees.

3. Life Cycle of an Angiosperm-Alternation of Generations

B. Flower Structure and Reproduction in Angiosperms:

1. Stamens-contain an anther (which produces pollen) that sits on a stalk

    known as a filament.

2. Carpels-contain a flat surface known as a stigma that sits atop a tube 

    referred to as a style. The ovary sits at the base of the style.

3. Pollen settles on stigma and sperm are delivered down the style to the ovules

    encased within the ovary. Angiosperms do not depend on water for 

    fertilization to occur. 

a. This produces a seed.

b. Double Fertilization-unique to Angiosperms. In this process, one 

    sperm fertilizes the egg to form the embryo while another sperm 

    combines with two polar nuclei to produce endosperm.

4. Angiosperm Seed Structure

a. Seed Coat

b. Embryo-the developing plant within the seed. The embryo contains a

    radicle (primary root), a hypocotyl (stem), and one or two cotyledons 

    seed leaves).

c. Endosperm-tissue rich in nutrients that provides nutrition for the 

    growing embryo during germination.

d. Seeds are enclosed in a fruit for protection. Fruits also assist in seed

    dispersal. Dispersal can occur via several mechanisms.

5. Fruit Types

a. Fleshy Fruits-grapes are an example.

b. Aggregate Fruits-strawberries are an example.

c. Multiple Fruits-pineapples are examples.

d. Legumes with dry pods-peas are an example.

e. Fruit with husk-coconut is an example.

f.  Dry, winged fruit-produced by Maple trees.

6. Flowers function by attracting pollinators. Typically, this is achieved by color

    of the flower.