Systematics - Elsevier
ISystematics
1Plant Systematics:An OverviewPLANTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3What Is a Plant? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Plants and the Evolution of Life . . . . . . . . . . . . . . . . . . . . . . . . . . . .Land Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Why Study Plants? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Taxonomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Phylogeny . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Why Study Systematics? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101013133356REVIEW QUESTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15SYSTEMATICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7EXERCISES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16What Is Systematics? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7REFERENCES FOR FURTHER STUDY . . . . . . . . . . . . . . . 16This book is about a fascinating field of biology called plantsystematics. The purpose of this chapter is to introduce thebasics: what a plant is, what systematics is, and the reasonsfor studying plant systematics.defined by the common (but independently evolved) characteristicof photosynthesis. However, delimiting organismal groups basedon evolutionary history has gained almost universal acceptance.This latter type of classification directly reflects the patterns of thatevolutionary history and can be used to explicitly test evolutionaryhypotheses (discussed later; see Chapter 2).An understanding of what plants are requires an explanationof the evolution of life in general.PLANTSWHAT IS A PLANT?This question can be answered in either of two conceptualways. One way, the traditional way, is to define groups oforganisms such as plants by the characteristics they possess.Thus, historically, “plants” included those organisms that possess photosynthesis, cell walls, spores, and a more or less sedentary behavior. This traditional grouping of plants containeda variety of microscopic organisms, all of the “algae,” andthe more familiar plants that live on land. A second way toanswer the question “What is a plant?” is to evaluate theevolutionary history of life and to use that history to delimitthe groups of life. We now know from repeated research studiesthat some of the photosynthetic organisms evolved independently of one another and are not closely related.Thus, the meaning or definition of the word plant can beambiguous and can vary from person to person. Some still liketo treat plants as a “polyphyletic” assemblage (see later discussion),PLANTS AND THE EVOLUTION OF LIFELife is currently classified as three major groups (sometimescalled domains) of organisms: Archaea (also called Archaebacteria), Bacteria (also called Eubacteria), and Eukarya oreukaryotes (also spelled eucaryotes). The evolutionary relationships of these groups are summarized in the simplified evolutionary tree or cladogram of Figure 1.1. The Archaea andBacteria consist of small, mostly unicellular organisms thatpossess circular DNA, replicate by fission, and lack membranebound organelles. The two groups differ from one anotherin the chemical structure of certain cellular components.Eukaryotes are unicellular or multicellular organisms thatpossess linear DNA (organized as histone-bound chromosomes), replicate by mitotic and often meiotic division, andpossess membrane-bound organelles such as nuclei, cytoskeletalstructures, and (in almost all) mitochondria (Figure 1.1).3 2010 Elsevier Inc. All rights reserved.doi: 10.1016/B978-0-12-374380-0.00001-5
4CHAPTER 1plant systematics: An iaOpisthokontsFungiChlorobionta/Viridiplantae (Green yta (Browns)GlaucophytaOomycota(water opiles(Heterokonta)Rhodophyta (Red Algae)Eukarya (Eukaryotes) red chloroplast green oroplast originPrimaryEndosymbiosisMitochondria (by endosymbiosis)Cytoskeletal/contractile elements (actin, myosin, tubulin)Other membrane-bound organelles (endoplasm. retic., golgi, lysosomes)Mitosis ( meiosis in sexually reproducing organisms)Nucleus (membrane bound), enclosing chromosomesDNA linear, bound to histones endosymbiotic origin of mitochondrionand chloroplast from ancestral BacteriumFigure 1.1 Simplified cladogram (evolutionary tree) of life (modified from Kim and Graham 2008, Moreira et al. 2007, and Yoon et al.2008), illustrating eukaryotic apomorphies (the relative order of which is unknown) and the hypothesis of a single origin of mitochondria andchloroplasts via endosymbiosis (arrows). Note modification of chloroplast structure in the red and green plants, and subsequent secondaryendosymbiosis in numerous other lineages (indicated by *). Eukaryotic groups with photosynthetic members are in bold.Some of the unicellular bacteria (including, e.g., theCyanobacteria, or blue-greens) carry on photosynthesis, abiochemical system in which light energy is used to synthesizehigh-energy compounds from simpler starting compounds,carbon dioxide and water. These photosynthetic bacteria havea system of internal membranes called thylakoids, withinwhich are embedded photosynthetic pigments, compoundsthat convert light energy to chemical energy. Of the severalgroups of eukaryotes that are photosynthetic, all have specialized photosynthetic organelles called chloroplasts, whichresemble photosynthetic bacteria in having pigment-containingthylakoid membranes.How did chloroplasts evolve? It is now largely accepted thatchloroplasts of eukaryotes originated by the engulfment of anancestral photosynthetic bacterium (probably a cyanobacterium)by an ancestral eukaryotic cell, such that the photosyntheticbacterium continued to live and ultimately multiply inside theeukaryotic cell (Figures 1.1, 1.2). (Mitochondria also evolvedby this process, from an ancestral, nonphotosynthetic bacterium;see Figure 1.1.) The evidence for this is the fact that chloroplasts,
unit photosyntheticbacterium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .eukaryotic cell. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .photosyntheticeukaryotic cellDiagrammatic illustration of the origin of chloroplasts by endosymbiosis of ancestral photosynthetic bacterium within ancestral eukaryotic cell.Figure 1.2like bacteria today, (a) have their own single-stranded, circularDNA; (b) have a smaller sized, 70S ribosome; and (c) replicateby fission. These engulfed photosynthetic bacteria providedhigh-energy products to the eukaryotic cell; the “host” eukaryotic cell provided a beneficial environment for the photosyntheticbacteria. The condition of two species living together in closecontact is termed symbiosis, and the process in which symbiosisresults by the engulfment of one cell by another is termed endosymbiosis. Over time, these endosymbiotic, photosyntheticbacteria became transformed structurally and functionally, retaining their own DNA and the ability to replicate, but losingthe ability to live independently of the host cell. In fact, overtime there has been a transfer of some genes from the DNA ofthe chloroplast to the nuclear DNA of the eukaryotic host cell,making the two biochemically interdependent.Although knowledge of eukaryotic relationships is still influx, the most recent data from molecular systematic studiesindicates that this so-called “primary” endosymbiosis of thechloroplast probably occurred one time, a shared evolutionarynovelty of the red algae (Rhodophyta) and green plants (Viridiplantae or Chlorobionta; Figure 1.1). This early chloroplastbecame modified with regard to photosynthetic pigments, thylakoid structure, and storage products into forms characteristicof the red algae and green plants (see Figure 1.1). In addition,several lineages of photosynthetic organisms—including theeuglenoids, dinoflagellates, and brown algae (Phaeophyta),and a few other lineages—may have acquired chloroplastsvia “secondary” endosymbiosis, which occurred by the engulfment of an ancestral chloroplast-containing eukaryote byanother eukaryotic cell (Figure 1.1). The final story is yet tobe elucidated.LAND PLANTSOf the major groups of photosynthetic eukaryotes, the greenplants (Viridiplantae or Chlorobionta) are united primarily bydistinctive characteristics of the green plant chloroplast withrespect to photosynthetic pigments, thylakoid structure, and storage compounds (see Chapter 3 for details). Green plants includeboth the predominately aquatic “green algae” and a group knownas embryophytes (formally, the Embryophyta), usually referredto as the land plants (Figure 1.3). The land plants are unitedby several evolutionary novelties that were adaptations to thetransition from an aquatic environment to living on land. Theseinclude (1) an outer cuticle, which aids in protecting tissues fromdesiccation; (2) specialized gametangia (egg and sperm producing organs) that have an outer, protective layer of sterile cells; and(3) an intercalated diploid phase (sporophyte) in the life cycle,the early, immature component of which is termed the embryo(hence, “embryophytes”; see Chapter 3 for details).Just as the green plants include the land plants, the landplants are inclusive of the vascular plants (Figure 1.3), the latterbeing united by the evolution of an independent sporophyte andxylem and phloem vascular conductive tissue (see Chapter 4).The vascular plants are inclusive of the seed plants (Figure1.3), which are united by the evolution of wood and seeds(see Chapter 5). Finally, seed plants include the angiosperms(Figure 1.3), united by the evolution of the flower, includingcarpels and stamens, and by a number of other specializedfeatures (see Chapters 6–8).For the remainder of this book, the term plant is treated asequivalent to the embryophytes, the land plants. The rationalefor this is partly that land plants make up a so-called monophyletic group, whereas the photosynthetic eukaryotes as awhole are not monophyletic and, as a group, do not accuratelyreflect evolutionary history (see later discussion, Chapter 2).And, practically, it is land plants that most people are talkingabout when they refer to “plants,” including those in the fieldof plant systematics. However, as noted before, the word plantcan be used by some to refer to other groupings; when in doubt,get a precise clarification.
6CHAPTER 1plant systematics: An OverviewChlorobionta (Viridiplantae) - green plantsEmbryophytes - land s(incl. HornwortsMosses Green Algae LiverwortsTracheophytes - vascular plantsSpermatophytes - seed plantsMonilophytesFlower, carpels,stamens ( sev.other features)Xylem & phloem vascular tissueIndependent sporophyteCuticle, gametangia, embryo (sporophyte)Green plant chloroplastFigure 1.3 Simplified cladogram (evolutionary tree) of the green plants, illustrating major extant groups and evolutionary events(or “apomorphies,” notated by thick hash marks). *Embryophytes are treated as “plants” in this book.WHY STUDY PLANTS?The tremendous importance of plants cannot be overstated.Without them, we and most other species of animals (as well asmany other groups of organisms) wouldn’t be here. Photosynthesis in plants and the other photosynthetic organisms changedthe earth in two major ways. First, the fixation of carbondioxide and the release of molecular oxygen in photosynthesisdirectly altered the earth’s atmosphere over billions of years.What used to be an atmosphere deficient in oxygen underwenta gradual change. As a critical mass of oxygen accumulatedin the atmosphere, selection for oxygen-dependent respirationoccurred (via oxidative phosphorylation in mitochondria),which may have been a necessary precursor in the evolutionof many multicellular organisms, including all animals. In addition, an oxygen-rich atmosphere permitted the establishmentof an upper atmosphere ozone layer, which shielded life fromexcess UV radiation. This allowed organisms to inhabit moreexposed niches that were previously inaccessible.Second, the compounds that photosynthetic species produce are utilized, directly or indirectly, by nonphotosynthetic,heterotrophic organisms. For virtually all land creaturesand many aquatic ones as well, land plants make up theso-called primary producers in the food chain, the source ofhigh-energy compounds such as carbohydrates, structuralcompounds such as certain amino acids, and other compounds essential to metabolism in some heterotrophs. Thus,most species on land today, including millions of species ofanimals, are absolutely dependent on plants for their survival.As primary producers, plants are the major components ofmany communities and ecosystems. The survival of plants is
unit Iessential to maintaining the health of those ecosystems, thesevere disruption of which could bring about rampant speciesextirpation or extinction and disastrous changes in erosion,water flow, and ultimately climate.To humans, plants are also monumentally important innumerous, direct ways (Figures 1.4, 1.5). Agricultural plants,most of which are flowering plants, are our major source offood. We utilize all plant parts as food products: roots (e.g., sweetpotatoes and carrots; Figure 1.4A,B); stems (e.g., yams, cassava/manioc, potatoes; Figure 1.4C); leaves (e.g., cabbage, celery,lettuce; Figure 1.4D); flowers (e.g., cauliflower and broccoli;Figure 1.4E); and fruits and seeds, including grains such asrice (Figure 1.4F), wheat (Figure 1.4G), corn (Figure 1.4H),rye, barley, and oats, legumes such as beans and peas (Figure1.4I), and a plethora of fruits such as bananas (Figure 1.4J),tomatoes, peppers, pineapples (Figure 1.4K), apples (Figure1.4L), cherries, peaches, melons, kiwis, citrus, olives (Figure1.4M), and others too numerous to mention. Other plantsare used as flavoring agents, such as herbs (Figure 1.5A–D)and spices (Figure 1.5E), as stimulating beverages, such aschocolate, coffee, tea, and cola (Figure 1.5F), or as alcoholicdrinks, such as beer, wine, distilled liquors, and sweet liqueurs.Woody trees of both conifers and flowering plants are usedstructurally for lumber and for pulp products such as paper(Figure 1.5G). Non-woody plants, such as bamboos, palms,and a variety of other species, serve as construction materialsfor a great variety of purposes. Plant fibers are used to makethread for cordage (such as sisal), for sacks (such as jute forburlap), and for textiles (most notably cotton, Figure 1.5H, butalso linen and hemp, Figure 1.5I). Extracts from plants, whichinclude essential oils, latex (for rubber or balata), vegetableoils, pectins, starches, and waxes, have a plethora of uses inindustry, food, perfume, and cosmetics. In many cultures,plants or plant products are used as euphorics or hallucinogenics (whether legally or illegally), such as marijuana (Figure1.5I), opium, cocaine, and a great variety of other species thathave been used by indigenous peoples for centuries. Plants areimportant for their aesthetic beauty, and the cultivation of plantsas ornamentals is an important industry. Finally, plants havegreat medicinal significance, to treat a variety of illnesses orto maintain good health. Plant products are very important inthe pharmaceutical industry; their compounds are extracted,semisynthesized, or used as templates to synthesize new drugs.Many “modern” drugs, from aspirin (originally derived fromthe bark of willow trees) to vincristine and vinblastine (obtained from the Madagascar periwinkle, used to treat childhoodleukemia; Figure 1.5J), are ultimately derived from plants. Inaddition, various plant parts of a great number of species areused whole or are processed as so-called herbal supplements,which have become tremendously popular of late.systematics7The people, methods, and rationale concerned with the plantsciences (defined here as the study of land plants) are as diverseas the uses and importance of plants. Some of the fields in theplant sciences are very practically oriented. Agriculture and horticulture deal with improving the yield or disease resistance offood crops or cultivated ornamental plants, e.g., through breeding studies and identifying new cultivars. Forestry is concernedwith the cultivation and harvesting of trees used for lumber andpulp. Pharmacognosy deals with crude natural drugs, often ofplant origin. In contrast to these more practical fields of the plantsciences, the “pure” sciences have as their goal the advancement of scientific knowledge (understanding how nature works)through research, regardless of the practical implications. Butmany aspects of the pure sciences also have important practicalapplications, either directly by applicable discovery or indirectlyby providing the foundation of knowledge used in the morepractical sciences. Among these are plant anatomy, dealingwith cell and tissue structure and development; plant chemistry and physiology, dealing with biochemical and biophysicalprocesses and products; plant molecular biology, dealing withthe structure and function of genetic material; plant ecology,dealing with interactions of plants with their environment; and,of course, plant systematics.Note that a distinction should be made between “botany” and“plant sciences.” Plant sciences is the study of plants, treatedas equivalent to land plants here. Botany is the study of mostorganisms traditionally treated as plants, including virtuallyall eukaryotic photosynthetic organisms (land plants and theseveral groups of “algae”) plus other eukaryotic organismswith cell walls and spores (true fungi and groups that wereformerly treated as fungi, such as the Oomycota and slimemolds). Thus, in this sense, botany is inclusive of but broaderthan the plant sciences. Recognition of both botany and plantsciences as fields of study can be useful, although how thesefields are defined can vary and may require clarification.SYSTEMATICSWHAT IS SYSTEMATICS?Systematics is defined in this book as a science that includesand encompasses traditional taxonomy, the description, identification, nomenclature, and classification of organisms, andthat has as its primary goal the reconstruction of phylogeny, orevolutionary history, of life. This definition of systematics isnot novel, but neither is it universal. Others in the field wouldtreat taxonomy and systematics as separate but overlappingareas; still others argue that historical usage necessitates whatis in essence a reversal of the definitions used here. But words,like organisms, evolve. The use of systematics to describe an
8CHAPTER 1AFJplant systematics: An OverviewBCGDIHKELMFigure 1.4 Examples of economically important plants. A–E. Vegetables. A. Ipomoea batatas, sweet potato (root). B. Daucus carota,carrot (root). C. Solanum tuberosum, potato (stem). D. Lactuca sativa, lettuce (leaves). E. Brassica oleracea, broccoli (flower buds).F–H. Fruits, dry (grains). F. Oryza sativa, rice. G. Triticum aestivum, bread wheat. H. Zea mays, corn. I. Seeds (pulse legumes), from top,clockwise to center: Glycine max, soybean; Lens culinaris, lentil; Phaseolus aureus, mung bean; Ph
systematics. The purpose of this chapter is to introduce the basics: what a plant is, what systematics is, and the reasons for studying plant systematics. PLANTS WHAT IS A PLANT? This question can be answered in either of two conceptual w
systematics. In fact, pre-Darwinian systematics as ahistorical science provides an invaluable resource for understanding what it means that systematics is essentially historical. Systematics is an ideal subject for understanding historical scientific methodology precisely because we
Apr 18, 2013 · systematics, integrating phylogenetic signal from the population up based on DNA and through time based on direct observation rather than inference. Molecular systematics in the 21st century For several years, molecular systematics has been the dominant phylogenetic paradigm [1]. By t
Sep 30, 2021 · Elsevier (35% discount w/ free shipping) – See textbook-specific links below. No promo code required. Contact Elsevier for any concerns via the Elsevier Support Center. F. A. Davis (25% discount w/free shipping) – Use the following link: www.fadavis.com and en
9782294745027 Anatomie de l'appareil locomoteur-Tome 1 Elsevier Masson French Health Sciences Collection 2015 9782294745294 Méga Guide STAGES IFSI Elsevier Masson French Health Sciences Collection 2015 9782294745621 Complications de la chirurgie du rachis Elsevier Masson French Health Sciences Collection 2015 9782294745867 Le burn-out à l'hôpital Elsevier Masson French Health Sciences .
Classification. Also, it is clear that systematics is an old and still very active field not much covered in modern undergraduate textbooks. Paleontology is not part of biology but is essential to Biology Systematics. Sub-division (and aggregation) of the objects studied Extens
systematics-1 Evolution and Biodiversity Laboratory Systematics and Taxonomy by Dana Krempels and Julian Lee Recent estimates of our planet's biological diversity suggest that the species number between 5 and 50 million, or even more. To effective
The Systematics and Biodiversity Science Program supports: 6 research that advances understanding of the diversity, systematics, and evolutionary history of extant or extinct organisms in natural systems projects that addre
The hooks infrastructure is separatede in two parts, the hook dispatcher, and the actual hooks. The dispatcher is in charge of deciding which hooks to run for each event, and gives the final review on the change. The hooks themselves are the ones that actually do checks (or any other action needed) and where the actual login you
