Evolutionary Microbiology. Chapter 11. Multicellular Eucaryotes Toward Complexity

Transcription

1 Evolutionary Microbiology Chapter 11. Multicellular Eucaryotes Toward Complexity Jong-Soon Choi Chungnam National Univ. GRAST University of Science and Technology Korea Basic Science Institute 225

2 Charles Doolittle Walcott (1850~1927) American Paleontologist (1859) Charles Darwin <Evolution> (1909) Charles Walcott <Trilobites> Cambrian Explosion 540MYa Trilobites ( 삼엽충 ) 5,400 Genus ~60,000 Species - British Columbia, Wifta - China, Chengjian How explain abrupt appearance of trilobites in terms of evolution? (Source: 226

3 (Source: 227

4 5 eyes, tentacle Anomalocaris 60~80cm Opabinia 4cm Horrible predator Ancestor of arthropod ( 절지동물 ) Feeding cyanobacteria Ancestor of annelids ( 환형동물 ) Pikaia 4cm Ancestor of fish < vertebrate Haikouichthys 2.5cm First vertebrate Wiwaxia 6~7cm (Source: 228

5 How does speciation occur? Several hypotheses of the evolution of morphological diversity( 다양성 ), or disparity( 부동성 ) (a) Traditional model (Darwin, 1859) (b) Model of maximum disparity (Gould, 1989) (c) Model of long-term gradually increasing disparity (Fortey, 1996) (d) Model of short-term gradually increasing disparity (B&J, 2000) (Source: 229

6 Phyletic gradualism vs Punctuated Equilibrium Phyletic gradualism : most speciation is slow, uniform and gradual; the steady transformation of a whole species into a new one through a process anagenesis ( 종의進化向上 ) Punctuated equilibrium ( 단속평형 ) : Evolutionary change occurs rapidly with long periods of evolutionary stability to be punctuated by branching evolution (cladogenesis, 分岐進化 ) Stephen J Gould (1941~2002) American Evolutionary Biologist The punctuated equilibrium theory based on geographic speciation (E Mayr), developmental, genetic homeostasis (M Lerner) and his own empirical research (Source: Wikipedia) 230

7 Allopatric Speciation or Geographic speciation Geographic speciation: Speciation that occurs when biological populations of the same species become vicariant ( 대치군 ) or isolated from each other to an extent that prevents or interferes with genetic interchange. The vicariant populations undergo genotypic/phenotypic divergence as (i) different selective pressure, (ii) independently genetic drift, (iii) different mutations in the gene pool Ernst Mayr (1904~2005) German/American Evolutionary Biologist Neo-Darwinian (Source: 231

8 Speciation by Other Factors Geographic speciation : Species occur in different areas, which are often separated by a physical barrier such as a river or mountain range Ecological isolation : Species occur in the same area, but they occupy different habitats and rarely encounter each other Temporal isolation : Species reproduce in different seasons or at different times of the day (Source: 232

9 What is s Species? Species : a distinct kind of animal, plant, fungus, or other organism Where does one species end and another begin? How do we define or recognize the boundary between two species? How should we define species ideally? (Source: 233

10 What is s Species? Aristotle s idea : species = eidos (form) + matter + psyche (anima, spirit) Morphological species : type specimen, considering the same species of morphologically similar individuals Biological species : the largest group of organisms where two hybrids are capable of reproducing fertile offspring using sexual reproduction Phylogenetic and symbiogenetic tree of living organisms, showing the origins of eucaryotes and procaryotes Phylogenetic species : an evolutionarily divergent lineage a lineage that has maintained its hereditary integrity with respect to other lineages through both time and space (16S rrna sequence) (Source: 234

11 On the Origin of Species Charles Darwin (1809~1882) British Explorer and Natural historian One the origin of species by means of natural selection, or the preservation of favored races in the struggle for life (Nov 1859) Populations evolve over the course of generation through a process of natural selection. The diversity of life arose by common descent through a branching pattern of evolution (Source: 235

12 Summary of Darwin s Theory Facts of Darwin s Speculations Every species is fertile enough that if all offspring survived to reproduce the population would grow. Despite periodic fluctuations, populations remain roughly the same size. Resources such as food are limited and are relatively stable over time. In mid-july 1937, Darwin started his notebook on Transmutation of Species and on page 36 wrote I think above his first evolutionary tree Individuals in a population vary significantly from one another. Much of this variation is heritable. (Source: 236

13 Summary of Darwin s Theory Inferences of Darwin s Speculations A struggle for survival ensues. Individuals more suited to the environment are more likely to survive and more likely to reproduce and leave their heritable traits to future generations, which produce the process of Natural Selection. Darwin researched how the skulls of different pigeon breed varied, as shown in his Variation of Plants and Animals Under Domestication of This slowly effected process results in populations changing to adapt to their environments, and ultimately, these variations accumulate over time to form New Species. (Source: 237

14 Properties of Eucaryotes 1. Histone bound to DNA, multiple chromosome, nuclear membrane 2. Cell division by mitosis, spindle fibers, centrosome 3. Respiratory enzymes in mitochondria with bilayer membrane 4. Photosynthetic pigments in chloroplast with bilayer membrane 5. Subcellualr organelles: ER, Golgi, vacuole, etc 6. Ribosome (80S, 60S+40S) Arrangement in microtubule (Source: 240

15 We are what we eat mitochondria Eucaryotic genome B Primitive organism C chronocyte plastid Archaea-like ancestor of nucleus & cytosol A Who engulfed whom? E(eucaryote) = A(archaeon) + B(bacterium) + Contributors of Eucaryotic Genome C(chronocyte) 241

16 Eucaryotic Origin The first eukaryote may have originated from an ancestral prokaryote that had undergone membrane proliferation, compartmentalization of cellular function (into a nucleus, lysosomes, and an endoplasmic reticulum), and the establishment of endosymbiotic relationships with an aerobic prokaryote, and, in some cases, a photosynthetic prokaryote, to form mitochondria and chloroplasts, respectively. (Source: 242

17 Horizontal Gene Transfer Horizontal Gene Transfer (HGT) refers to the transfer of genes between organisms in a manner other than traditional reproduction. HGT (or lateral gene transfer, LGT) contrasts with vertical transfer, the transmission of genes from the parental generation to offspring via sexual or asexual reproduction. HGT is the primary reason for bacterial antibiotic resistance and plays an important role in the evolution of bacteria. HGT mechanisms : transformation, transduction, bacterial conjugation (Source: 243

18 Multicellularity Volvox, multicellular organism? C. elegans (959-cells) Dividing eucaryotic cell : a typical autopoiesis (Source: 244

19 Autopoiesis( 자가보전 ) (Source: Multicellular Regulation - Gene regulation network (Hierarchy) - Apoptosis (Programmed Cell Death) - Totipotency (Stem Cell) - Immortality (Cancer) (i) through their interactions and transformations continuously regenerate and realize the network of processes (relations) (ii) constitute it (the machine) as a concrete unity in space in which they (the components) exist by specifying the topological domain of its realization as such a network 245

20 4BY Microorganisms Evolution : Symbiotic philosophy Creation of biomolecules > cell membranes > primitive cell assembly > prokaryote > oxygen catastrophe > eukaryote > multi-cellular eucaryote (Source: History of Life = Symbiosis! Cooperation is bigger than Competition in long-term. 246