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The Origin and Evolution of Life. The Nature of Life Life –During last 4 by adapted to many environments and physico-chemical conditions –Most organisms.

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Presentation on theme: "The Origin and Evolution of Life. The Nature of Life Life –During last 4 by adapted to many environments and physico-chemical conditions –Most organisms."— Presentation transcript:

1 The Origin and Evolution of Life

2 The Nature of Life Life –During last 4 by adapted to many environments and physico-chemical conditions –Most organisms live at 1 atm and 0-40 o C; Some Bacteria can live up to 1400 atm or -18 to 104 o C –Unicellular Organisms vs Non Living Molecules (Amino acids, RNA (ribonucleic acid) reproduction growth via nutrients and energy responds to outside stimuli Share same genetic code chemical uniformity –C, O, H, N, P >> nucleic acids, proteins, carbohydrates, fats

3 The Nature of Life Prokaryote vs. Eukaryote –small (1-10 um) vs large (10-100um) –No nucleus vs Nucleus –DNA in nucleoid vs Membrane bounded nucleus containing chromosomes made of DNA, RNA –Cell division direct (binary fission) vs mitosis and miosis –Rare multicellular forms vs Multicellular organism with extensive development of tissues

4 Building Blocks: Pattern shared by all life All Life: DNA => RNA => Protein DNA architect plans for building (instructions to build proteins in the ribosome) transcribes information into RNA (Blueprint) RNA messenger translates blueprint into proteins in the ribosomes Genes code for specific proteins (enzymes) Enzymes are proteins that control all chemical reactions Order of nitrogenous bases (read in groups of 3) {A, T, C, G} determines the type of proteins made Each group of 3 codes for a specific amino acid

5 DNA: Our Genetic Code Spiral double helix of sugars and phosphate linked together by nitrogenous bases such as Thymine, Cytosine, Adenine and Guanine. A Gene is a portion of the DNA molecule that includes approximately 1500 base pairs and a Chromosome contains many genes

6 The Origin of Life 19th Century Ideas –life created supernaturally cannot be proven scientifically –continually being formed by spontaneous generation of nonliving matter untenable by numerous experiments 20th Century –life generated spontaneously and evolved through different steps

7 The Origin of Life Origin of life is NOT an event Origin of life is a continuous process Stages –inorganic production of key simple organic molecules –production of more complex molecules that can synthesize more of the same molecule –development of a genetic code of self-replicating molecules (RNA,DNA,proteins) –production of the first cell by separation of these codes from the outer world by a membrane Ocean environment by 4.0 by- fossils evident at 3.8by

8 The Origin of Life Many complex organic molecules must have formed before an organism produced The process of life took many steps over the first 600 my Probability theory would dictate that at least one random event would have produced a result This process cannot occur on Earth today because the simple organism would be destroyed by oxidation or predation

9 Steps in the Origin of Life Aerobic vs. Anaerobic –oxygen poisons living cells so early life was anaerobic Lack of free Oxygen >> No Ozone layer –UV radiation kills cells so life had to originate at depth –Water depths of 10m or more Models –non-oxidizing secondary atmosphere rich in the constituent chemicals for life--H 2 O, CO 2, N –Energy in the form of UV radiation & Hot springs

10 Steps in Origin of Life Before the first cell>>Chemical Evolution –production of significant molecules necessary for life Phosphoric acid crucial to cell chemistry>> phosphoric acid can bond molecules and promote long chain molecule formation Amino acids formed first since they do not form if oxygen present –probably formed on clay surfaces since they are attractive and absorptive, also protection from UV Larger Molecules –amino acids are linked together by dehydration synthesis (water loss), clays have potential to absorb water, thus amino acids could be linked on clay surfaces

11 Experimental Studies A. I. Oparin- 1930s –Produced sugars and fatty acids from the constituents of an early atmosphere Urey and Miller –Production of cyanide, formaldehyde and 4 different amino acids from water vapor, methane, hydrogen and ammonia and electrical sparks Subsequent Experiments –Production of 18 of the 20 known amino acids and extremely simple forms of DNA from gases rich in water vapor, CO 2, and nitrogen and UV radiation –S.W. Fox (1959) produced protein-like (protenoids) chains from a mixture of 18 amino acids at 70 o C in the presence of phosphoric acid

12 The Environment for Life Volcanic Hot Springs Oceanic hydrothermal vent system Deep (below the level of UV penetration) Clays and/or Zeolites as templates Similarity with present day chemosynthetic heterotrophic organisms

13 The First Cells All cells use the same genetic code Archaeobacteria- most primitive –Heterotrophs: obtain energy from surroundings by some chemical reaction –Obtain energy by converting CO 2 and H 2 to CH 4 or by the reduction of sulfur compounds Eubacteria –10 Phyla, including cyanobacteria (Autotrophs: manufacture their own food source) First Cells poorly developed metabolic systems –absorbed nutrients directly –fermentation

14 Life Prokaryota –Appear by –no nucleus –single loop chromosome with all genes –reproduction-binary fission Eukaryota –Single cell appear 2 by –Multicellular appear as trace fossils 1by and as body fossils 700my –Nucleus with 2 pairs of chromosomes (2 copies of all genes) –Asexual and SEXUAL reproduction>> more combinations

15 Endosymbiotic Theory- Evidence the observation that mitochondria and chloroplasts posses their own genetic apparatus

16 Stromatolites: laminated structures composed of layers of cyanobacterial (Prokaryotic photosynthetic bacteria) filaments and sediment Foraminifera: Calcium carbonate secreting unicellular eukaryotic organisms, planktonic and marine

17 Taxonomic Hierarchy Linnean Classification –Kingdom –Phylum (Phyla) –Class –Order –Suborder –Superfamily –Family –Genus (genera) –Species Example –Animalia, Chordata, Mammalia, Primate, Anthropoidea, Hominoidea, Hominidae, Homo sapiens

18 Organic Evolution Challenge to special creation in the 18 th century Buffon –Environment involved –Concept of species Lamarck –“inner want” Inherited characteristics Little used structures dissappear

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20 How Evolution Works Organic Evolution is the change in populations of species with time –between species –within a species –during the lifetime of an individual –at the chromosomal level –at the molecular DNA level Species produce more offspring than can survive to maturity Individual species have different genetic combinations, thus also different anatomical attributes Some individuals better suited to their environments

21 How Evolution Works Organic Variation and Heredity –individuals look like their parents but are not exactly like them –sexual reproduction design to produce many and varied combinations –random mutations in gene replication 1 in 10,000 –mutations due to chemical reactions and radiation Reproductive Potential Natural Selection

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23 (A) mitosis, (B) meiosis, and (C) fertilization.

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25 How Evolution Works Reproductive Potential –potential for rapid expansion of a species in a given geographical area –a species will fill a niche until it reaches a climax Natural Selection (Darwin) –interaction between genetics and environment –“survival of the fittest” (H. Spencer) –certain individuals are better suited (engineered) for the habitat they inhabit

26 Physical Factors Controlling Natural Selection Temperature (land and sea) Water Depth (sea) Altitude (land) Rainfall (land) Humidity (land) Salinity (sea) Light Intensity (land and sea) Substrate (sea and land) Seasonality (land) Tidal Range (sea)

27 Biological Factors: The Trophic Relationship Food web sets limits on the number of species Elements govern the structure –predation –parasitism –competition –symbiosis Pyramid structure –each trophic level must have a lower biomass than the level below it (as much as 90% drop)

28 Modes of Evolution Transformation Speciation Extinction Adaptive Radiation Divergent, Parallel and Convergent Evolution

29 Modes of Evolution: Transformation Gradualism (Darwinian concept) Change of properties (morphological) so that over time it warrants to be called something else Transitional forms This mode occurs in species with a relatively small breeding population Common in vertebrates of small isolated populations that are broad ranging Adaptations to changing environments

30 Gradualism Evolution of the Horse Fossils preserved in consecutive formations exhibit sequential morphologic changes Paleocene: small browsing animal the size of a dog, with 4 toes on the front feet and 3 on the back, low crown and weak enamel on teeth (woodland-leaves) In progressively younger rocks the fossils exhibit larger size, reduction of side toes, increase in height and complexity of teeth (grasslands-grasses w/ silt)

31 Fig. 3.15a

32 An example of progressive evolutionary change in a group of Permian ammonoid cephalopods. (From Spinosa,C. Furnish, W. M., and Glenister, B. F J. Paleontol. 49(2): )

33 Modes of Evolution: Punctuated Equilibria 2 species A-B, and C A is a widespread species evolving slowly or not at all B is an isolated small part of species A with a deviant anatomy After extinction event, B is the only survivor and it spreads out over a larger area Unless the small population B is found, then A appears to change abruptly into C

34 Modes of Evolution: Punctuated Equilibria vs Gradualism Morphological change occurs in a sideward direction Time is depicted in a vertical direction The short horizontal side brances of the punctualistic model depict sudden change, whereas the inclined branches of the gradualistic model suggest slow uniform change through time

35 Modes of Evolution: Speciation The splitting of a species into two or more parts as the result of some ecological or geographic barrier or due to migration Barriers can be canyons, mountain ranges, isthmus, deserts, ocean basin

36 Speciation Intercontinental migrations of members of the camel family Camels originate in North America during the Eocene Migration through land bridges Geographic and ecological barriers

37 EXTINCTION The rapid disappearance of a group of organisms As a response to an ecological catastrophe –Climatic Change The extinction of one group releases the resources for another group to thrive Background Rate as a result of random factors: –competition, predation, changes in temp., changes in salinity Mass extinctions >> Catastrophic –asteroid collision, rapid oceanic turn-over; accelerated rates of plate tectonic (volcanism)

38 Adaptive Radiation Organisms rapidly filling new ecological niches increasing both numbers and diversity Typically lasts from 5 to 10 my Major expansion in adaptation of one or more original minor taxa Steps –extinction rate drops –competition is reduced –speciation occurs –species transforms rapidly into different descendants Creation of new ecological niches by plate tectonics

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40 Divergent Evolution: Homologous Structures In 4-limbed vertebrates, the bones of the limbs may vary in size and shape but they are fundamentally similar and in similar relative positions Basically similar structures in dissimilar organisms are referred to as homologous The differences in homologous structures are the result of variations and adaptations to particular environmental conditions, similarities >>common ancestry c:carpal; h:humerous; m:metacarpal; r:radius; u:ulna; 1-5:digits

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42 Parallel Evolution Two related species that evolve similar specializations to the same sort of habitat but independently a) Thoatherium, a Miocene litoptern b) Equus, a modern horse Both shared a common 5 toed hoof mammal ancestor and independently evolved to a one- toed foot for maximum running endurance

43 Convergent Evolution Represented by animals with different ancestry evolving to similar forms and functions in different places or at different times a) Dinogorgon, a saber-toothed therapsid from the Permian of S. America b) Thylacosmilus, a saber-toothed marsupial from the Miocene of Argentina c) Smilodon, a saber-toothed cat from the Pleistocene of N. America

44 Phylogeny The historical development of groups of organisms so as to depict descent from ancestors The depiction is called a phylogenetic tree Branches on the tree are called clades In cladistic phylogeny organisms are analyzed on the basis of characteristics they share in order to determine their ancestor-descendent relationship The shorter the links between groups the closer the relationship Simple cladogram showing the simple primitive trait of a vertebral column

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46 Evolutionary “Laws” Haeckel’s Law Dollo’s Law Cope’s Law Williston’s Law

47 Haeckel’s Law: Ontogeny Recapitulates Phylogeny In its development from embryo to adult, the individual passes through (recapitulates) the evolutionary stages of its ancestors. Thus the human embryo progresses from a single cell thru higher invertebrate stages to resembling a fish, a reptile and finally a mammal

48 Dollo’s Law Structures once lost cannot be regained Difficulty in duplicating the genetic mechanism of the development of a structure

49 Cope’s Law Organisms generally increase in size from their ancestors This is possibly due to –larger organisms have fewer predators and a larger size protects against many smaller predators –food utilization is more efficient –thermal inertia increases, constant body temperature Increase in size >> decrease in population >> decrease in biomass Leads to extinction and increases opportunity for others

50 Williston’s Law Common evolutionary trends occur in related organisms with serially homologous structures Thus structures are reduced in numbers Structures become more differentiated


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