The units, molecules, and diversity of life. The theory of evolution explains and connects unity and diversity

Transcription

1 Last time: The subject of biology Definition of life Fields of life sciences The units, molecules, and diversity of life Today: Overview of life forms The unity in the diversity of life The theory of evolution explains and connects unity and diversity Evolution and engineering: Life versus machines

2 A brief overview of biodiversity Taxonomy is the branch of biology that names and classifies species. It formalizes the hierarchical ordering of organisms. ( 분류를일정하게함 ) Copyright 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

3 The Three Domains of Life The three domains ( 영역 ) of life are: (= Archaebacteria )

4 An extraterrestrial look at life on Earth The lengths of the lines are mathematical estimates of the evolutionary distance There is not much difference between a human and a yeast!

5 Most organisms are microbes = microscopically small Some organisms are multicellular Microbes make up about ½ of the earth s biomass (6x10 30 microbes on earth) Animals make up 1/1000 th of the earth s biomass Each ml of seawater contains 1 million bacteria and 10 million viruses

6 This slide is important please know it well Prokaryotes Eukaryotes

7 The domain Eucarya (= eukaryotes) includes at least four kingdoms Kingdoms: Animalia Fungi Plantae.... Protists (multiple kingdoms). Copyright 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

8 Main features of the eukaryotic kingdoms - Protists Single-celled eukaryotes - Plantae: produce sugars by photosynthesis -Fungi: mostly decomposers -Animalia: gain food by ingestion Protists are very diverse Protists are not fundamentally different from plants, animals, fungi Plants, fungi, and animals may be seen as colonial (multicellular) forms of some of the protists

9 Origin of plants = immobile colonies of photosynthetic protists Origin of fungi = immobile colonies of consumer (decomposing) protists (usually parasitic) Origin of animals = mobile colonies of consumer-type protists The simplest known animals are the sponges. Sponges likely are a colonial version of a type of protists called choanoflagellates.

10 Unity in the Diversity of Life Underlying the diversity of life is a striking unity, especially at the lower levels of structure. Universal genetic language of DNA (was mentioned last time) Similarities in chemical compositions (will be discussed soon) Similarities of key metabolic pathways (will be discussed in a few weeks) Similarities of ultrastructure Example of similar ultrastructure: The universal architecture of eukaryotic cilia (a) Paramecium (A protist) (b) Cells from fallopian tube Cilia on cells of the lung (Animal cell types) (c) Cross section of cilium Copyright 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

11 Evolution: Biology s Unifying Theme What can account for this combination of unity and diversity in life? evolution Fossils document that life has changed dramatically over Earth s history Copyright 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

12 Fossils also show that different species have common ancestors ( tree of life ) Copyright 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

13 The Darwinian View of Life The modern view on evolution: Charles Darwin s book The Origin of Species (1859). Copyright 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

14 Darwin was struck by the diversity of animals on the Galápagos Islands. Different islands have 14 different species of Galápagos finches with beak shapes adapted to suit their different environments. Darwin already knew concepts of geology and understood that the Galapagos islands are young He realized that adaptation to the environment and the origin of new species are related processes. (Today the molecular basis of the different beak shapes is known) Copyright 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

15 Darwin synthesized his theory of evolution from two facts that everybody knew and knows. Fact 1: Overproduction and competition Fact 2: Individual variation ( Descent with modification ) The inescapable conclusion: Unequal reproductive success Darwin called this unequal reproductive success natural selection. The product of natural selection is adaptation. Natural selection is a key mechanism of evolution (additional mechanisms were discovered after Darwin). Copyright 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

16 Darwin also understood artificial selection; this knowledge contributed to his theory Kale Wild mustard Cauliflower Red cabbage Brussel s sprout Broccoli Wolves Copyright 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

17 Natural selection is still going on Example: The development of antibioticresistant bacteria Tuberculosiscausing bacteria Emergence of antibiotic-resistant bacteria does not mean that the drugs created the favorable characteristics. Rather, the environment screened the heritable variations that existed among individuals of a population and favored the ones best suited to present conditions. Copyright 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

18 Alternative explanations for the origin and diversity of species Inheritance of acquired adaptation (Lamarckism ) Example: A father who exercises his muscles produces children with stronger muscles requires a mechanism by which muscle cells instruct sperm cells or eggs No such mechanism has been found J. Lamarck ( ) Other approaches: Full or partial negation of evolution Creationism (newest variant: Intelligent design )

19 How evolution is studied Evolution not recognized Medieval times Anatomy, embryology Ultrastructure Sequencing 1859 Charles Darwin Origin of Species 1894 Ernst Haeckel Recapitulation hypothesis 1966 Lynn Margulis Endosymbiont hypothesis After 1960 many scientists Note: These are the same methods that describe the diversity of life

20 Darwin s publication of The Origin of Species fueled an explosion in biological research. Evolution is one of biology s best demonstrated, most comprehensive, and longest lasting theories. Evolution is the unifying theme of biology. The catholic church also accepts evolution. Nothing in biology makes sense except in the light of evolution. Theodosius Dobzhansky, 1973 Note parallel with human history: Human society cannot be understood without knowing history.

21 Examples illustrating the thesis of Dobzhansky Overproduction of sperm. Each human produces typically less than 10 children. Every man produces billions of sperm cells a huge waste. WHY? The sperm cells are not identical! ( descent with modification ) Production of billions of different sperm cells maintains the ability of the species Homo sapiens to adapt (details in the second half of the semester) Junk DNA. Less than 5% of our DNA contains useful genetic information. WHY? The junk DNA is a playground for evolution = provides flexibility for genetic change

22 After Darwin Progress within Darwin s concept New concepts

23 Progress within the Darwinian concept A more detailed picture about Diversity of life Stages of evolution: The key inventions leading to modern life are largely known (steps of chemical evolution, cellular evolution, multicellularity) Timing of evolution Forces driving evolution

24 The time scale of macroevolution as currently known

25 The principal driving force of evolution The ultimate driving force of biological evolution is geological evolution (plate tectonics) However, biological evolution acts back on lithosphere and atmosphere and so influences its own further evolution Example: Oxygen in the atmosphere (20%) results from life processes

26 Conceptual advances made after Darwin Genetic information comes in discrete units (genes) that are packaged in clusters (chromosomes) that can be recombined Cellular and molecular nature of modification : Nature of sex (recombination of chromosomes) Mutations (heritable changes of the genes = changes in the text; example: AGCCTAAC AGGCTAAC) Additional mechanisms of evolution: Cooperation (game theory predicts that cooperation may give an advantage over simple competition) Lateral gene transfer (= the movement of genetic information from one species to another species) refinement of the concept of the Tree of Life The fundamental mechanisms of evolution currently known: Descent with modification (based on genes, chromosomes, and mutations) Selection (based on overproduction and competition) Cooperation (based on game theory) Lateral gene transfer (based on the discovery of mobile genetic elements)

27 Evolution and engineering: Life versus machines Evolution as an engineer: Example - The stepwise invention of mammals T I M E

28 Organisms live in order to live But evolution is stupid and blind: It doesn t have a purpose or goal Organisms don t have a purpose or goal in life except of reproduction (otherwise life would disappear) A machine is a tool that consists of one or more parts, and uses energy to meet a particular goal. (Wikipedia) machines are optimized for a specific, narrow goal, don t have unnecessary parts Therefore, organisms are not just machines. The only goal or purpose of their existence is their existence!

29 Summary The diversity, unity, and evolution of life Life is organized into three domains: bacteria, archaea, and eukarya Millions of species are known to exist. Most life forms are microbial. Multicellular life forms (animals, fungi, plants) are closely positioned on the tree of life. Multicellular life forms are colonial versions of eukaryotic cells that also exist as single cells (protists). Unity: All life forms share the DNA language, principal chemical compositions, metabolic pathways, and some ultrastructural designs. Evolution from a common origin explains both unity and diversity of all known life forms Charles Darwin is credited for developing the successful scientific concept of evolution. According to Darwin, the mechanism of evolution includes overproduction and individual variation, leading to natural selection and adaptation. The main driving force of evolution is a changing environment. Evolution does not stop. Recent conceptual advances in understanding evolution Genetic information comes in discrete units (genes and chromosomes). Individual variation is caused by mutations and by sex (genetic recombination). Newly recognized mechanisms of evolution include cooperation and lateral gene transfer. Evolution versus engineering Evolution may (but does not have to!) lead to remarkable designs that often inspire engineers (bionics). However, evolution is blind and has no purpose (the only purpose of life is to maintain its existence). By contrast, human engineering has a narrow purpose. Therefore it is often possible to make machines that are better than life for a narrow purpose.

30 요약 - 생명의다양성과통일성, 그리고진화 생명체는세개의영역으로조직된다 : 세균, 고세균, 진핵생물. 수백만종들이존재하는것으로알려져있다. 대부분의생명체는미생물이다. 다세포생명체는 ( 동물, 균류, 식물 ) 생물의계통수에서가깝게위치하고있다. 다세포생명체는진핵세포의군체들이며, 진핵세포는또한단세포로서도존재한다 ( 원생생물 ). 통일성 : 모든생명체는 DNA 언어, 기본화학구성성분, 대사경로, 그리고일부초미세구조적설계가공통적이다. 공통기원으로부터진화는알려진모든생명체의통일성과다양성을설명한다. 찰스다윈은진화를성공적인과학적이론으로개발한공로를인정받았다. 다윈에따르면, 진화의기작은과잉생산과자연선택, 적응에따른개체변이를포함한다. 진화를유발하는주된힘은환경의변화이다. 진화는지금도끊임없이계속된다. 진화이해에대한최근개념적진보 유전적정보는별개의단위에저장된다 ( 유전자와염색체 ). 개체간변이는돌연변이와성 ( 유전적재조합 ) 에의해유발된다. 최근에인식된진화의기작은협력과측면유전자전이를포함한다. 진화 Vs 공학 진화는종종공학자에게감명을줄수있는놀라운설계로이끌수도있다 ( 생체공학 ). 그러나, 진화는장님이며, 목적이없다 ( 생명의유일한 목적 은그것의존재를유지하는것이다 ). 대조적으로, 공학자는좁은목적을가지고있다. 결과적으로그것은좁은목적에대해서종종생명보다나은기계를만들수도있다.