Evolutionary Relationships Learning about the relationship of plants involves the Protista. The protista kingdom is made up of dino­ study of plant fossils (paleobotany), physical character­ flagellates (Pyrrophyta); golden algae, yellow-green istics (anatomy), form (morphology), inheritance algae, and diatoms (Chrysophyta); and other organ­ (genetics), chemical characteristics (physiology and isms. The Protista organisms are eukaryotic and usually plant biochemistry), and plant communities (ecology). one-celled. They often exhibit characteristics of both Carolus Linnaeus (1707-1778) organized a system, plants and animals. Nourishment is obtained by inges­ which has since been expanded, for the classification tion, absorption, or by photosynthesis in plastids (see of plants on the basis of their evolutionary relation­ 3). ships. Some groups of organisms studied by botanists are now not recognized as plants, for example, bacte­ Plantae. Members of the plantae kingdom (plants) are ria, blue-green algae, fungi, and lichens. They are stud­ red algae (Rhodophyta); green algae (Chlorophyta); ied by specialists on bacteria and blue-green algae brown algae (Phaeophyta); stone worts (Charophyta); (microbiologists), fungi (mycologists), and lichens liverworts, horn worts and mosses (Bryophyta); (lichenologists). horsetails and scouring rushes (Equisetophyta); ferns (Polypodiophyta); and plants bearing seeds. Seed-bear­ Whittaker System of Kingdoms ing plants include the gymnosperms (= naked seeds) and the angiosperms (= enclosed seeds). Living gym­ Monera. The monera kingdom consists of bacteria, nosperm groups are cycads (Cycadophyta), Ginkgo blue-greens (Cyanobacteria), and other microorga­ (Ginkgophyta), conifers (Pinophyta) and gnetes (Gne­ nisms such as viruses. In the past, blue-greens were tophyta). The angiosperm group consists of flowering grouped with algae. Now it is known that they are plants (Magnoliophyta). Plant nourishment is obtained more like bacteria. The cells of bacteria and blue­ mainly by photosynthesis. greens do not have organelles; instead, the cell mem­ branes carryon many biological functions. There is no Evolutionary Relationships membrane-bound nucleus; instead, hereditary material (DNA) is contained in fibrils in the central area (see 43). Dashed lines on the chart separate the kingdoms, while This type of cell is called prokaryotic, as opposed to a solid lines show probable evolutionary lines. The living true or eukaryotic cell (see 2). groups shown are those discussed in this book. Living groups that are not discussed are omitted from the Fungi. The fungi kingdom includes slime molds (Myxo­ chart. Shaded groups are extinct. The origin of flow­ my cot a); water molds, downy mildews and white rusts ering plants is not yet known. (For a modified classifi­ (Oomycota); and true fungi. True fungi include chytrids cation system of all living organisms see the Whittaker and allies (Chytridiomycota), black bread mold and and Margulis reference and for an explanation of evo­ allies (Zygomycota), sac fungi (Ascomycota) and club lutionary relationships see the Stebbins reference in the fungi (Basidiomycota). bibliography.) COLOR CODE blue: monera groups tan: fungal groups yellow: protista groups gray: extinct groups (shaded) green: living (extant) plant groups 41 J. Glimm-Lacy et al., Botany Illustrated © Janice Glimm-Lacy and Peter B. Kaufman 1984 Plantae Protista Monera Evolutionary Relationships Geologic Time Scale Time Units and blue-green algae are found. The earliest eukaryotic cells are from rocks about 1,000 million years old. Eras. The largest units of geologic time are known as These fossils are rare, and the early evolutionary his­ eras; each encompasses millions of years. They are tory of non-vascular plants is obscure. In the late Silu­ basically defined by biological events - the appearance rian period, the first vascular plants appear. or disappearance of major groups of organisms. These changes in biology are related to major geologic The groups indicated on the chart are vascular plants, events, but only the biologic changes are seen world­ meaning they had specialized conducting tissues of wide in the fossil record. xylem and phloem. The size of the plant groups reflects their relative abundance in time. Two groups are Periods. Each era is subdivided into periods, and the extinct and are known only from their fossil record. periods are broken down into epochs; again their sep­ arations are most commonly based on fossils. Land plants became abundant during the Devonian period. During the Carboniferous (Mississippian and Fossil Record and Appearance of Vascular Plants Pennsylvanian periods), there were vast forests of trees and swamps preserved now as coal. The Jurassic About 85% of earth's geologic time is within the Pre­ period of the Mesozoic era was the "age of cycads" cambrian era. The division that marks the end of Pre­ and was a time when conifers were distributed world­ cambrian time and the beginning of the Paleozoic era, wide. Primitive flowering plants evolved during the about 600 million years ago, is recognized by the Cretaceous, and by the Tertiary period of the Ceno­ worldwide appearance of fossils of invertebrate zoic they dominated the land. Later, grasslands were marine animals. In the Precambrian, in rocks over 3,000 apparent and the landscape has been dominated by million years old, the first fossil organisms of bacteria herbaceous flowering plants ever since. COLOR CODE gray: extinct plant groups green: living (extant) plant groups 42 Flowering Plants ,.----L..-- Seed Ferns ~ I-- --- -- V Cycads i'- -- Seed Plant Gnetes I Ancestors-- ...... 1 -I --- Conifers r-- --- ...... Ginkgophytes ...- Ferns r-- .- Horsetails - .......... Scouring Rushes_"'- .... ---. Clubmosses, Spike mosses, Quillworts r-- _r--- 0 c 00 c c 'c'" :l '" C C 'a' '" ~ '0 '" > 0 '" a. '" c u <l> >- "'0 <l> ';;: c 'c'" '<Ii >- u u '">- ~'" 0 '<Ii '<Ii ~ o 0 '<Ii '"C 'E'" '';::; .~ E "'0 '" > '" c '" '" c '" L. cv ~ <l> <l> ~ '" ~ a. ~ u'" (5 Vi 0 ~ 0.. 0.. ~'" .2, U I- 'E Lr) 0 0 Lr\ o ..0 ~-""'-co N co -- M 8----Lr\ M M N N ,.... era Paleozoic Mesozoic Cenozoic Geologic Time Scale Bacteria Bacteria have existed for billions of years, and with a that derive their energy from the sun are called pho­ wide range of species that have become adapted to all totrophs (= light nourishment). In contrast, those that kinds of environments, they can live almost every­ derive their energy from the chemical environments where on earth. are called chemotrophs (= chemical nourishment). Phototrophs and chemotrophs are further subdivided Bacterial Cell according to whether the electrons they donate for respiration or fermentation come from organic com­ A bacterium is an aquatic micro-organism (1 to 10 pounds or inorganic compounds; thus, the photo­ micrometers in size; 1 micrometer = 0.000039 inch). trophs are classified as either photoorganotrophs or Its prokaryotic cell consists of a protoplast of cyto­ photolithotrophs. Likewise, chemotrophs are classified plasm (a) within a plasma membrane (b). Irregular as either chemoorganotrophs or chemolithotrophs. infoldings of the plasma membrane are called meso­ somes (c), which are involved in many cell functions, Of interest .,. ecosystem: bacteria are the major such as division, nuclear segregation, respiration, and decomposers, breaking down organic materials into secretion. In the cytoplasm are ribosomes (ribonucleo­ simpler substances; nitrogen-fixing: Spirillum lipoferum, protein particles, d), a nucleoid (DNA-bearing struc­ Rhizobium radicicola, and Bacillus radicicola, which ture, e), and some have photosynthetic pigments. Sur­ occur in root nodules of higher plants, convert atmo­ rounding the protoplast of most bacteria is a rigid cell spheric nitrogen into ammonia and amino acids (see wall (g). Some bacteria also have an outer slime layer 12); health: a microflora of bacteria maintains health in or capsule (h). No flagella or up to 30 flagella may be all organisms; industry: manufacture of cheese, vine­ present. Each flagellum (i) is made up of fibers of pro­ gar, butyl alcohol, acetone, antibiotics (streptomycin, tein. The flagella are involved in cell movement. Some aureomycin, chloramphenicol); retting of plant fibers; bacterial types form a resistant endospore (D. The most sewage disposal; research: most biochemistry research common bacterial forms are spherical (coccus), rod­ systems use bacteria; bacteria are used in modern shape (bacillus), and helical (spirillum and vibrio). With genetic engineering; some photosynthetic bacteria can a crystal violet staining procedure (Gram stain), all bac­ convert carbon dioxide to chains of hydrocarbons teria can be divided into two large groups: Gram pos­ (crude oil); human diseases: a very small percentage of itive and Gram negative. the bacteria of the world cause diseases such as scarlet fever, typhoid, diptheria, tuberculosis, botulism, chol­ Cell Wall era, syphilis, gonorrhea, tetanus, anthrax, bubonic plague, leprosy, gangrene, meningitis, tularemia, and The rigid cell wall is characteristic of plant cells (animal some forms of dysentery and pneumonia; plant dis­ cells are bound by a thin membrane). Materials must be eases: wilt disease of potato, cucumber, tomato; citrus dissolved in water in order to pass through the cell canker; fire blight of pear and apple trees, crown rot wall. The bacterial cell wall makes up 20 to 40% of the of cabbage and carrots. cell weight and contains chemical substances found only in bacteria