The Evolution of Plants: a Major Problems for Darwinism — Bergman Papers

Total Page:16

File Type:pdf, Size:1020Kb

The Evolution of Plants: a Major Problems for Darwinism — Bergman Papers Papers pollen must penetrate in order to fertilize the seed.22 The evolution of Angiosperms, in turn, are divided into monocotyledons (plants with seeds that have one cotyledon such as grains, grasses, and certain flowers, including orchids and lilies), plants: and dicotyledons (plants with seeds with two cotyledons, which includes most angiosperms). Went concludes that a major problem botanists have used a seemingly insignificant character— viz., the number of seedling leaves (cotyledons)—to classify the estimated 250,000 types of flowering plants. for Darwinism Categorizing the 300 different groups of flowering plants Jerry Bergman into families is enormously difficult because the ‘ … individual species are so numerous that they A major problem for Neo-Darwinism is the complete have never yet been listed in any one book, or even lack of evidence for plant evolution in the fossil re- in one series of books. Such a listing would have cord. As a whole, the fossil evidence of prehistoric to describe about a quarter million known plants; to plants is actually very good, yet no convincing tran- compile it, all the taxonomic botanists in the world sitional forms have been discovered in the abundant would have to work together for years and years, plant fossil record. This fact has been recognized and the finished product would have perhaps half a million pages, enough to cover a whole wall in a by both creationists and evolutionists as providing 23 strong evidence for abrupt appearance theory. If library.’ The basic groups for which Darwinists must macroevolution were true, some evidence of plant 24 evolution should exist in the abundant plant fossil demonstrate the existence of transitional forms include: record. Instead, what is found are many examples of modern plants, variations of modern plants, or Kingdom Protoctista extinct plants that require still more transitional Subkingdom: Phycobionta - Algae forms. Division: Chrysophyta - Golden-brown Algae Division: Pyrrophyta - Dinoflagellates Division: Euglenophyta - Euglenoids Division: Chlorophyta - Green Algae Division: Phaeophyta - Brown Algae The lack of support in the fossil record for plant evolution Division: Rhodophyta - Red Algae has long been a concern of evolutionists.1 Furthermore, this Kingdom Fungi and Lichens fact has long been recognized by creationists.2–15 Even Division: Zygomycota - Coenocytic True Fungi Charles Darwin acknowledged that the apparent sudden Division: Eumycota - Noncoenocytic True Fungi appearance of plants in the fossil record was a major Class: Basidomycetes - Club Fungi problem for his theory.16–18 And the problem remains today, Class: Deuteromycetes - Imperfect Fungi so much so that in texts dealing with plant evolution, the Plant Kingdom topic of fossil non-support is conspicuous by its absence.19 Division: Hepaticophyta - Liverworts Many reference texts and leading authors on evolution Division: Anthocerotophyta - Hornworts ignore the issue entirely (e.g. Ridley20). At best, writers Division: Bryophyta - Mosses discussed hypothetical scenarios for which they usually Division: Psilotophyta - Whisk Ferns admitted a lack of evidence. Division: Lycophyta - Club Mosses and Quillworts Today, an estimated 375,000 species of living plants Division: Sphenophyta - Horsetails and Scouring are known to exist. For years plants were divided into Rushes Thallophyta, primarily sea plants (plus mosses and ferns); Division: Pterophyta - Ferns and land-dwelling plants called spermatophytes. The former Division: Pinophyta was considered ‘primitive’, and the latter ‘advanced’.21 Class: Pinatae - The Conifers The Thallophyta included all non-seed-producing plants, Division: Magnoliophyta - Flowering Plants while the Spermatophyta included all seed-producing Division: Monocots plants (sperma = seed, phyta = plant). Recent research Class: Poaceae - Grasses has stirred many to abandon this long held Darwinistic Class: Liliaceae - Lily Family scheme. Most seed-producing plants are also flowering Class: Orchidaceae - Orchid Family plants. Spermatophytes are divided into gymnosperms Division: Dicots (naked seed plants such as evergreens that use pine cones Class: Ranunculaceae - Buttercup Family as seeds) and angiosperms (angion = vessel)—plants whose Class: Lauraceae - Laurel Family seeds are enclosed in a vessel called the ovary, into which Class: Papaveraceae - Poppy Family 118 TJ 16(2) 2002 The evolution of plants: a major problems for Darwinism — Bergman Papers Class: Brassicaceae - Mustard Family postulated to exist on the early Earth.30 The history of plant Class: Rosaceae - Rose Family life is dominated at all levels by the Class: Fabaceae - Legume Family ‘ … stability of many species over millions of Class: Euphorbiaceae - Spurge Family years. Some blue-green algae appear to be the same Class: Cactaceae - Cactus Family as those that lived over a billion years ago; there are Class: Lamiaceae - Mint Family species of horsetails apparently identical to plants Class: Solanaceae - Nightshade Family living in the great coal swamps of the Carbonifer- Class: Apiaceae - Carrot Family ous some 130 million years ago; and the beautiful, Class: Cucurbitaceae - Pumpkin Family broad-leaved gymnosperm, the ginkgo, has remained Class: Asteraceae - Sunflower Family unchanged since the Cretaceous. In the case of these old species, it appears that the particular environ- The evidence for plant evolution ments to which they are adapted have shrunk in extent and area through time, while the organisms What is the evidence that plants evolved from some have continuously remained in a stable equilibrium simple one celled organism? Harold C. Bold and his co- with their environments.’31 authors at the University of Texas concluded that Because of this lack of evidence, most texts ignore ‘ … after carefully weighing the currently avail- the problems of plant evolution or try to rationalize them. able evidence of comparative morphology, cytol- One argument is to conclude that evidence for evolution is ogy, biochemistry, and fossil record, are at present not found in the fossil record because most plants were so unwilling to amalgamate any two or more of the 19 well adapted that little change was required. For example, divisions in which they have tentatively classified Went noted: the organisms of the plant kingdom. When and ‘The earliest seed plants that have survived to the if additional relevant data become available, such present day are conifers, the members of the pine and amalgamations will undoubtedly be required, but at spruce family. They are so well adapted to life on this time there are no known living or fossil forms earth that in the 300 million years of their existence, that unequivocally link any two of the proposed divi- there has been relatively little evolutionary change sions’ [emphasis added].25 in them. They are among the most successful plants Evidence for the origin of almost all plant divisions in the world. Pine, spruce and fir populate about a and classes listed above is totally lacking, and little third of all existing forest areas. Where the living is evidence exists as to the origin of any land plants, in spite difficult for other plants ... conifers are usually the of an enormously large plant fossil record. Most reference last outpost trees. Among the living higher plants, books on fossils include hundreds of excellent plant fossil the one with the oldest fossil record, the maidenhair examples (see, for example, Pinna26), yet the fossil record tree, or Ginkgo, is related to the conifers.’32 reveals no clear evidence for evolution. We have so many The botany text now used at the college where I teach fossils that we can conclude confidently that plants have includes only a general chapter on evolution, which almost changed little ‘over millions of years’ and that totally ignores plant evolution, as does the remainder of the ‘ … the rootless, seedless plants ... offer fascinat- book. Often it is only speculation that is presented in the ing clues to the structure and nature of ancient and sections on plant evolution, such as the statement that extinct forms. The leafless whisk fern is a direct ‘ … progymnosperms and Paleozoic ferns may descendant of some of the first plants to develop have evolved from the more ancient trimerophytes woody supporting tissue and an internal plumbing … another possibility is that ferns evolved from the system. The liverwort, whose ancestors lived at the progymnosperms … nor is it certain from which same time as those of the whisk fern, failed to evolve group(s) of progymnosperms the gymnosperms such tissue, and as a result never grows more than evolved’ [emphasis mine].33 an inch or two tall.’27 Given about 375,000 kinds of plants, and an average The plant phyletic tree of ‘only’ 1,000 transitional forms for each one (most likely many more would be necessary), then 375 million Evolutionists have found it more difficult to develop plant transitional forms would be required. Not one clear phyletic trees (compared to animal phyletic trees) for several example has ever been found in the abundant plant fossil reasons. In the past decade alone, at least 15 phyletic trees record. And yet, the ‘only direct evidence’ of evolution of flowering plant lineages have been published.34 One of is ‘provided by the fossil record’.28 The important survey the problems includes the difficulty of developing a natural of the entire fossil record by Donovan and Paul ignored classification scheme which arranges: plants, except to note that phosphatized
Recommended publications
  • Plant Evolution an Introduction to the History of Life
    Plant Evolution An Introduction to the History of Life KARL J. NIKLAS The University of Chicago Press Chicago and London CONTENTS Preface vii Introduction 1 1 Origins and Early Events 29 2 The Invasion of Land and Air 93 3 Population Genetics, Adaptation, and Evolution 153 4 Development and Evolution 217 5 Speciation and Microevolution 271 6 Macroevolution 325 7 The Evolution of Multicellularity 377 8 Biophysics and Evolution 431 9 Ecology and Evolution 483 Glossary 537 Index 547 v Introduction The unpredictable and the predetermined unfold together to make everything the way it is. It’s how nature creates itself, on every scale, the snowflake and the snowstorm. — TOM STOPPARD, Arcadia, Act 1, Scene 4 (1993) Much has been written about evolution from the perspective of the history and biology of animals, but significantly less has been writ- ten about the evolutionary biology of plants. Zoocentricism in the biological literature is understandable to some extent because we are after all animals and not plants and because our self- interest is not entirely egotistical, since no biologist can deny the fact that animals have played significant and important roles as the actors on the stage of evolution come and go. The nearly romantic fascination with di- nosaurs and what caused their extinction is understandable, even though we should be equally fascinated with the monarchs of the Carboniferous, the tree lycopods and calamites, and with what caused their extinction (fig. 0.1). Yet, it must be understood that plants are as fascinating as animals, and that they are just as important to the study of biology in general and to understanding evolutionary theory in particular.
    [Show full text]
  • Construct a Plant Evolution Timeline
    Constructing a Timeline of Plant Evolution Use this photo as a guide to creating an interactive timeline. Refer to Geologic Time Scale charts. A good resource is http://www.ucmp.berkeley.edu/help/timeform.php Use the “Plant Timeline Cards” found at the end of this document. Attach pictures with Velcro to allow for manipulation by students, and to “build” the timeline in increments. Teachers will need to find and print photos for “seed ferns” or omit that step in the timeline. Cut and paste the text below under each picture. Cyanobacteria: Also known as blue- Mosses: These have the first identifiable green algae, these are bacteria transport systems for water (xylem), and (prokaryotes – no nucleus) that can reproduce via spores, which encase sex photosynthesize. cells to prevent desiccation. They still need to live near water. First eukaryotes (cell nucleus): Scientist think that eukaryotes evolved via Hornworts: These developed the cuticle symbiosis, with one bacteria engulfing (waxy coating to prevent water loss) and another, but not digesting it. stomata (openings in the cuticle to allow Chloroplasts were originally for gas exchange.) All land plants except cyanobacteria engulfed by another liverworts have these two features. bacterium. Development of a true vascular system Anabaena: These water organisms allowed for better transport of water evolved from being unicellular to more and provided structural support for the complex, multicellular organisms. Their plant to grow taller. specialized cells help with nitrogen fixation. Club mosses: These were the first plants to have true leaves with veins. They also Stoneworts: Scientists think that developed roots as an anchoring system colonization of land occurred only once, to allow plant to grow taller.
    [Show full text]
  • The Big Bloom—How Flowering Plants Changed the World
    The Big Bloom—How Flowering Plants Changed the World Written by Michael Klesius Republished from the pages of National Geographic magazine -- July 2002 In the summer of 1973 sunflowers appeared in my father's vegetable garden. They seemed to sprout overnight in a few rows he had lent that year to new neighbors from California. Only six years old at the time, I was at first put off by these garish plants. Such strange and vibrant flowers seemed out of place among the respectable beans, peppers, spinach, and other vegetables we had always grown. Gradually, however, the brilliance of the sunflowers won me over. Their fiery halos relieved the green monotone that by late summer ruled the garden. I marveled at birds that clung upside down to the shaggy, gold disks, wings fluttering, looting the seeds. Sunflowers defined flowers for me that summer and changed my view of the world. Flowers have a way of doing that. They began changing the way the world looked almost as soon as they appeared on Earth about 130 million years ago, during the Cretaceous period. That's relatively recent in geologic time: If all Earth's history were compressed into an hour, flowering plants would exist for only the last 90 seconds. But once they took firm root about 100 million years ago, they swiftly diversified in an explosion of varieties that established most of the flowering plant families of the modern world. Today flowering plant species outnumber by twenty to one those of ferns and cone-bearing trees, or conifers, which had thrived for 200 million years before the first bloom appeared.
    [Show full text]
  • Evolution of Land Plants P
    Chapter 4. The evolutionary classification of land plants The evolutionary classification of land plants Land plants evolved from a group of green algae, possibly as early as 500–600 million years ago. Their closest living relatives in the algal realm are a group of freshwater algae known as stoneworts or Charophyta. According to the fossil record, the charophytes' growth form has changed little since the divergence of lineages, so we know that early land plants evolved from a branched, filamentous alga dwelling in shallow fresh water, perhaps at the edge of seasonally-desiccating pools. The biggest challenge that early land plants had to face ca. 500 million years ago was surviving in dry, non-submerged environments. Algae extract nutrients and light from the water that surrounds them. Those few algae that anchor themselves to the bottom of the waterbody do so to prevent being carried away by currents, but do not extract resources from the underlying substrate. Nutrients such as nitrogen and phosphorus, together with CO2 and sunlight, are all taken by the algae from the surrounding waters. Land plants, in contrast, must extract nutrients from the ground and capture CO2 and sunlight from the atmosphere. The first terrestrial plants were very similar to modern mosses and liverworts, in a group called Bryophytes (from Greek bryos=moss, and phyton=plants; hence “moss-like plants”). They possessed little root-like hairs called rhizoids, which collected nutrients from the ground. Like their algal ancestors, they could not withstand prolonged desiccation and restricted their life cycle to shaded, damp habitats, or, in some cases, evolved the ability to completely dry-out, putting their metabolism on hold and reviving when more water arrived, as in the modern “resurrection plants” (Selaginella).
    [Show full text]
  • Gene Genealogies and Population Variation in Plants
    Colloquium Gene genealogies and population variation in plants Barbara A. Schaal* and Kenneth M. Olsen Department of Biology, Washington University, St. Louis, MO 63130 Early in the development of plant evolutionary biology, genetic selection. Morphology, karyotypes, and fitness components are drift, fluctuations in population size, and isolation were identified central traits for understanding evolution and adaptation, but as critical processes that affect the course of evolution in plant they limit which evolutionary processes can be studied. In his species. Attempts to assess these processes in natural populations book, Stebbins discusses such events as fluctuations in popula- became possible only with the development of neutral genetic tion size, random fixation (genetic drift), and isolation as all markers in the 1960s. More recently, the application of historically affecting the process of evolution (see passage quoted above; ref. ordered neutral molecular variation (within the conceptual frame- 1). However, the study of these mechanisms requires markers work of coalescent theory) has allowed a reevaluation of these that are not under selection. microevolutionary processes. Gene genealogies trace the evolu- In the years after the publication of Stebbins’ book, among tionary relationships among haplotypes (alleles) with populations. the first major technical advances in evolutionary biology were Processes such as selection, fluctuation in population size, and the development of protein electrophoresis and the identifi- population substructuring affect the geographical and genealog- cation of allozyme variation in natural populations. Many ical relationships among these alleles. Therefore, examination of allozymes are selectively neutral, and thus, for the first time, these genealogical data can provide insights into the evolutionary evolutionary biologists could attempt to assess the amount of history of a species.
    [Show full text]
  • Sow Thistle Chloroplast Genomes: Insights Into the Plastome Evolution and Relationship of Two Weedy Species, Sonchus Asper and Sonchus Oleraceus (Asteraceae)
    G C A T T A C G G C A T genes Article Sow Thistle Chloroplast Genomes: Insights into the Plastome Evolution and Relationship of Two Weedy Species, Sonchus asper and Sonchus oleraceus (Asteraceae) Myong-Suk Cho 1, Jin Hyeong Kim 1 , Chang-Seok Kim 2, José A. Mejías 3 and Seung-Chul Kim 1,* 1 Department of Biological Sciences, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Korea; [email protected] (M.-S.C.); [email protected] (J.H.K.) 2 Highland Agriculture Research Institute, National Institute of Agricultural Sciences, Rural Development Administration (RDA), Gangwon-do 25342, Korea; [email protected] 3 Department of Plant Biology and Ecology, Universidad de Sevilla, 41004 Seville, Spain; [email protected] * Correspondence: [email protected]; Tel.: +82-31-299-4499 Received: 20 September 2019; Accepted: 1 November 2019; Published: 1 November 2019 Abstract: Prickly sow thistle, Sonchus asper (L.) Hill, and common sow thistle, Sonchus oleraceus L., are noxious weeds. Probably originating from the Mediterranean region, they have become widespread species. They share similar morphology and are closely related. However, they differ in their chromosome numbers and the precise relationship between them remains uncertain. Understanding their chloroplast genome structure and evolution is an important initial step toward determining their phylogenetic relationships and analyzing accelerating plant invasion processes on a global scale. We assembled four accessions of chloroplast genomes (two S. asper and two S. oleraceus) by the next generation sequencing approach and conducted comparative genomic analyses. All the chloroplast genomes were highly conserved. Their sizes ranged from 151,808 to 151,849 bp, containing 130 genes including 87 coding genes, 6 rRNA genes, and 37 tRNA genes.
    [Show full text]
  • Evolution of the Life Cycle in Land Plants
    Journal of Systematics and Evolution 50 (3): 171–194 (2012) doi: 10.1111/j.1759-6831.2012.00188.x Review Evolution of the life cycle in land plants ∗ 1Yin-Long QIU 1Alexander B. TAYLOR 2Hilary A. McMANUS 1(Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA) 2(Department of Biological Sciences, Le Moyne College, Syracuse, NY 13214, USA) Abstract All sexually reproducing eukaryotes have a life cycle consisting of a haploid and a diploid phase, marked by meiosis and syngamy (fertilization). Each phase is adapted to certain environmental conditions. In land plants, the recently reconstructed phylogeny indicates that the life cycle has evolved from a condition with a dominant free-living haploid gametophyte to one with a dominant free-living diploid sporophyte. The latter condition allows plants to produce more genotypic diversity by harnessing the diversity-generating power of meiosis and fertilization, and is selectively favored as more solar energy is fixed and fed into the biosystem on earth and the environment becomes more heterogeneous entropically. Liverworts occupy an important position for understanding the origin of the diploid generation in the life cycle of land plants. Hornworts and lycophytes represent critical extant transitional groups in the change from the gametophyte to the sporophyte as the independent free-living generation. Seed plants, with the most elaborate sporophyte and the most reduced gametophyte (except the megagametophyte in many gymnosperms), have the best developed sexual reproduction system that can be matched only by mammals among eukaryotes: an ancient and stable sex determination mechanism (heterospory) that enhances outcrossing, a highly bimodal and skewed distribution of sperm and egg numbers, a male-driven mutation system, female specialization in mutation selection and nourishment of the offspring, and well developed internal fertilization.
    [Show full text]
  • Natural Selection and Repeated Patterns of Molecular Evolution
    RESEARCH ARTICLE Natural selection and repeated patterns of molecular evolution following allopatric divergence Yibo Dong1,2†, Shichao Chen3,4,5†, Shifeng Cheng6, Wenbin Zhou1, Qing Ma1, Zhiduan Chen7, Cheng-Xin Fu8, Xin Liu6*, Yun-peng Zhao8*, Pamela S Soltis3*, Gane Ka-Shu Wong6,9,10*, Douglas E Soltis3,4*, Qiu-Yun(Jenny) Xiang1* 1Department of Plant and Microbial Biology, North Carolina State University, Raleigh, United States; 2Plant Biology Division, Noble Research Institute, Ardmore, United States; 3Florida Museum of Natural History, University of Florida, Gainesville, United States; 4Department of Biology, University of Florida, Gainesville, United States; 5School of Life Sciences and Technology, Tongji University, Shanghai, China; 6Beijing Genomics Institute, Shenzhen, China; 7State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China; 8Laboratory of Systematic & Evolutionary Botany and Biodiversity, College of Life Sciences, Zhejiang University, Hangzhou, China; 9Department of Biological Sciences, University of Alberta, Edmonton, Canada; 10Department of Medicine, University of Alberta, Edmonton, Canada *For correspondence: [email protected] (XL); Abstract Although geographic isolation is a leading driver of speciation, the tempo and pattern [email protected] (Y-Z); of divergence at the genomic level remain unclear. We examine genome-wide divergence of [email protected] (PSS); putatively single-copy orthologous genes (POGs) in 20 allopatric species/variety pairs from diverse [email protected] (GK-SW); angiosperm clades, with 16 pairs reflecting the classic eastern Asia-eastern North America floristic [email protected] (DES); disjunction. In each pair, >90% of POGs are under purifying selection, and <10% are under positive [email protected] (Q-Y(J)X) selection.
    [Show full text]
  • Feedbacks and the Coevolution of Plants and Atmospheric CO2 David J
    Feedbacks and the coevolution of plants and atmospheric CO2 David J. Beerling*† and Robert A. Berner‡ *Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, United Kingdom; and ‡Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, CT 06520-8109 Contributed by Robert A. Berner, November 23, 2004 The coupled evolution of land plants, CO2, and climate over the last and arrows with bull’s-eyes indicate inverse responses. For half billion years has maintained atmospheric CO2 concentrations example, an increase in CO2 leads to an increase in global mean within finite limits, indicating the involvement of a complex surface temperature due to the atmospheric greenhouse effect network of geophysiological feedbacks. But insight into this im- (plain arrow i). Conversely, an increase in rock weathering leads portant regulatory network is extremely limited. Here we present to CO2 consumption and a decrease in atmospheric CO2 (bull’s- a systems analysis of the physiological and geochemical processes eyed arrow g). Closed pathways linked together by an even involved, identifying new positive and negative feedbacks be- number of arrows with bull’s-eyes, or by no arrows with bull’s- tween plants and CO2 on geological time scales. Positive feedbacks eyes, represent positive feedback loops (PFLs), and those with an accelerated falling CO2 concentrations during the evolution and odd number of arrows with bull’s-eyes represent negative feed- diversification of terrestrial ecosystems in the Paleozoic and en- back loops (NFLs). hanced rising CO2 concentrations across the Triassic–Jurassic Our systems analysis identifies five important previously boundary during flood basalt eruptions.
    [Show full text]
  • Evolution of Plant Breeding ARTICLE
    Evolution of plant breeding Crop Breeding and Applied Biotechnology 11: 197-206, 2011 Brazilian Society of Plant Breeding. Printed in Brazil ARTICLE Evolution of plant breeding Arnel R. Hallauer1* Received 1 August 2011 Accepted 20 August 2011 ABSTRACT – Plant breeding is considered one of the longest ongoing activities undertaken by humans, who select plants more productive and useful to themselves and the animals for at least 10,000 years ago. The evolution of civilizations paralleled the success of plant breeding, although this has not been recognized by the public. The reason may be lack of understanding of what plant breeding encompasses. The concept of plant breeding evolved, depending on the time it was formulated, but without losing the essence of being art and science of manipulating plants for man. This review discusses the evolution of the concepts and the methods of plant breeding, here divided arbitrarily into selection based on phenotypes, breeding values and genotypes. No matter how big the pool of genetic information in recent years, the phenotype will continues to be important in the present and future. Key words: concepts of plant breeding, phenotypes, breeding values, genotypes. INTRODUCTION that were most productive and useful to provide for the human and animal needs. Plant breeding has to be considered one of the The initial plant efforts were necessary for survival longest, continuous activities conducted by humans. The of the human civilizations because they developed evolution of the human civilizations paralleled the improved cultivars that were more productive, and, in some successes of plant breeding. Although we would consider instances, depended on humans for their survival (e.g.
    [Show full text]
  • Origin and Early Evolution of Chloroplasts
    Paleontological Research, vol. 10, no. 4, pp. 283–297, December 31, 2006 6 by the Palaeontological Society of Japan Origin and early evolution of chloroplasts AKIKO TOMITANI Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Natsushima-cho 2-15, Yokosuka 237-0061, Japan (email: [email protected]) Received July 22, 2006; Revised manuscript accepted September 21, 2006 Abstract. Photosynthetic organisms have played a significant role as primary producers and ultimate sources of the atmospheric oxygen through geologic time. How they have evolved is one of the key ques- tions in the study of the biological and environmental history of the Earth. Modern algal chloroplasts (plas- tids) are greatly diversified in morphology and pigmentation. Because the paleontological record can never be complete, a multidisciplinary approach is essential to reveal the pattern, timing, and mechanism of chlor- oplast evolution. Several independent lines of evidence show that all chloroplasts derived from a single en- dosymbiotic cyanobacterium and spread in different eukaryotic taxa via multiple secondary endosymbioses. With the advent of the genomic era, comparative genomics has been employed to reveal the course of their evolution. Yet, the study of non-model organisms remains important to understand how today’s diverse life has evolved, such as in the case of uniquely pigmented prochlorophytes. Paleontological records may pro- vide constraints on the timing of the primary and secondary endosymbiotic events. Key words: algae, chloroplasts, cyanobacteria, endosymbiosis, evolution, molecular phylogeny, Precam- brian microfossils Introduction spread among different eukaryotic taxa by subsequent endosymbiotic events (Figure 1) (Delwiche and Photosynthesis is a physicochemical process in which Palmer, 1997; Douglas, 1998; McFadden, 2001; Palmer, plants, algae and photosynthetic bacteria use light 2003; Bhattacharya et al., 2003).
    [Show full text]
  • Evolution and Diversity of Green Plant Cell Walls Zoe¨ a Popper
    Available online at www.sciencedirect.com Evolution and diversity of green plant cell walls Zoe¨ A Popper Plant cells are surrounded by a dynamic cell wall that performs biomass for the emerging biofuel industry. Cell walls have many essential biological roles, including regulation of cell been used as a source of fuel for millennia, for example in expansion, the control of tissue cohesion, ion-exchange and the form of wood, derived from dicotyledonous trees, and defence against microbes. Recent evidence shows that the peat, derived from Sphagnum moss. Algae, while being suite of polysaccharides and wall proteins from which the plant among the most efficient photosynthetic organisms and of cell wall is composed shows variation between monophyletic interest for biofuel generation, will not be specifically plant taxa. This is likely to have been generated during the discussed within this review because their greatest poten- evolution of plant groups in response to environmental stress. tial is as a source of oils (localised in the vacuole) for use in Understanding the natural variation and diversity that exists bio-diesel production, rather than cell wall biomass. This between cell walls from different taxa is key to facilitating their review will focus on the natural variation and diversity future exploitation and manipulation, for example by increasing that exists within land plant cell wall composition that is lignocellulosic content or reducing its recalcitrance for use in associated with land plant phylogeny (Table 1). biofuel generation. Address A more comprehensive investigation of diverse land plant Department of Botany, National University of Ireland Galway, Ireland cell walls not only is essential to facilitate wall modifi- cation enabling production of biomass with improved Corresponding author: Popper, Zoe¨ A([email protected]) qualities, for example an increased cellulose concen- tration; but may also suggest the potential of novel crop Current Opinion in Plant Biology 2008, 11:286–292 plants.
    [Show full text]