The Origin and Evolution of Life

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 0-40oC; Some Bacteria can live up to 1400 atm or -18 to 104oC • 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--H2O, CO2, 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- 1953 • 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, CO2, and nitrogen and UV radiation • S.W. Fox (1959) produced protein-like (protenoids) chains from a mixture of 18 amino acids at 70oC 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 CO2 and H2 to CH4 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 3.8-3.6 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 18th century • Buffon • Environment involved • Concept of species • Lamarck • “inner want” • Inherited characteristics • Little used structures dissappear

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

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

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. 1975. J. Paleontol. 49(2): 239-283.)

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

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

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

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