DIVERSITY OF LIFE I.Origin of Life Hypotheses A. Three Primary Attributes: - Barrier (phospholipid membrane) - Metabolism (reaction pathways) - Genetic System - Barrier (phospholipid membrane) - form spontaneously in aqueous solutions Metabolic Pathways - problem: how can pathways with useless intermediates evolve? ABCDE How do you get from A to E, if B, C, and D are non-functional? Metabolic Pathways - Solution - reverse evolution ABCDE Metabolic Pathways - Solution - reverse evolution E suppose E is a useful molecule, initially available in the env. Metabolic Pathways - Solution - reverse evolution E suppose E is a useful molecule, initially available in the env. As protocells gobble it up, the concentration drops. Metabolic Pathways - Solution - reverse evolution E Anything that can absorb something else (D) and MAKE E is at a selective advantage... D Metabolic Pathways - Solution - reverse evolution E Anything that can absorb something else (D) and MAKE E is at a selective advantage... but over time, D may drop in concentration... D Metabolic Pathways - Solution - reverse evolution E So, anything that can absorb C and then make D and E will be selected for... DC Metabolic Pathways - Solution - reverse evolution ABCDE and so on until a complete pathway evolves. Genetic Systems - conundrum... which came first, DNA or the proteins they encode? DNA RNA (m, r, t) protein Genetic Systems - conundrum... which came first, DNA or the proteins they encode? DNA RNA (m, r, t) protein DNA stores info, but proteins are the metabolic catalysts... Genetic Systems - conundrum... which came first, DNA or the proteins they encode? - Ribozymes info storage AND cataylic ability Genetic Systems - conundrum... which came first, DNA or the proteins they encode? - Ribozymes - Self replicating molecules - three stage hypothesis RNA Stage 1: Self-replicating RNA evolves RNA Stage 1: Self-replicating RNA evolves Stage 2: RNA molecules interact to produce proteins... if these proteins assist replication (enzymes), then THIS RNA will have a selective (replication/reproductive) advantage... chemical selection. m-, r-, and t- RNA PROTEINS (REPLICATION ENZYMES) Stage 3: Mutations create new proteins that read RNA and make DNA; existing replication enzymes replicate the DNA and transcribe RNA. m-, r-, and t- RNA PROTEINS (REPLICATION ENZYMES) DNA Reverse transcriptases Can this happen? Are their organisms that read DNA and make RNA? yes - retroviruses.... Stage 3: Mutations create new proteins that read RNA and make DNA; existing replication enzymes replicate the DNA and transcribe RNA. m-, r-, and t- RNA PROTEINS (REPLICATION ENZYMES) DNA Already have enzymes that can make RNA... Stage 3: Mutations create new proteins that read RNA and make DNA; existing replication enzymes replicate the DNA and transcribe RNA. m-, r-, and t- RNA PROTEINS (REPLICATION ENZYMES) DNA Already have enzymes that can make RNA... Stage 4: Mutations create new proteins that replicate the DNA instead of replicating the RNA... m-, r-, and t- RNA PROTEINS (REPLICATION ENZYMES) DNA This is adaptive because the two-step process is more productive, and DNA is more stable (less prone to mutation). Stage 4: Mutations create new proteins that replicate the DNA instead of replicating the RNA... m-, r-, and t- RNA PROTEINS (REPLICATION ENZYMES) DNA This is adaptive because the two-step process is more productive, and DNA is more stable (less prone to mutation). And that's the system we have today.... DIVERSITY OF LIFE I.Origin of Life Hypotheses II. Early Life - the first cells were probably heterotrophs that simply absorbed nutrients and ATP from the environment. - as these substances became rare, there was strong selection for cells that could manufacture their own energy storage molecules. - the most primitive cells are methanogens, but these are NOT the oldest fossils. II. Early Life - the second type of cells were probably like green-sulphur bacteria, which used H 2 S as an electron donor, in the presence of sunlight, to photosynthesize. II. Early Life - the evolution of oxygenic photosynthesis was MAJOR. It allowed life to exploit more habitats, and it produced a powerful oxidating agent! These stromatolites, which date to > 3 bya are microbial communities. II. Early Life - about bya, the concentration of oxygen began to increase in the ocean and oxidize eroded materials minerals... deposited as 'banded iron formations'. II. Early Life bya - evolution of eukaryotes.... endosymbiosis. II. Early Life Relationships among life forms - deep ancestry and the last "concestor" II. Early Life Woese - r-RNA analyses reveal a deep divide within the bacteria DIVERSITY OF LIFE I.Origin of Life Hypotheses II.Early Life III.Bacteria and Archaea 4.5 bya3.5-8 bya DIVERSITY OF LIFE I.Origin of Life Hypotheses II.Early Life III.Bacteria and Archaea 4.5 bya3.5-8 bya For of lifes history, life was exclusively bacterial. Bacterial producers, consumers, and decomposers. DIVERSITY OF LIFE I.Origin of Life Hypotheses II.Early Life III.Bacteria and Archaea The key thing about bacteria is their metabolic diversity. Although they didn't radiate much morphologically (spheres, rod, spirals), they DID radiate metabolically. As a group, they are the most metabolically diverse group of organisms. A. Oxygen Demand all eukaryotes require oxygen. II.Bacteria and Archaea The key thing about bacteria is their metabolic diversity. Although they didn't radiate much morphologically (spheres, rod, spirals), they DID radiate metabolically. As a group, they are the most metabolically diverse group of organisms. A. Oxygen Demand all eukaryotes require oxygen. bacteria show greater variability: - obligate anaerobes - die in presence of O2 - aerotolerant - don't die, but don't use O2 - facultative aerobes - can use O2, but don't need it - obligate aerobes - require O2 to live II.Bacteria and Archaea The key thing about bacteria is their metabolic diversity. Although they didn't radiate much morphologically (spheres, rod, spirals), they DID radiate metabolically. As a group, they are the most metabolically diverse group of organisms. A. Oxygen Demand all eukaryotes require oxygen. bacteria show greater variability: - obligate anaerobes - die in presence of O2 - aerotolerant - don't die, but don't use O2 - facultative aerobes - can use O2, but don't need it - obligate aerobes - require O2 to live represents an interesting continuum, perhaps correlating with the presence of O2 in the atmosphere. II.Bacteria and Archaea The key thing about bacteria is their metabolic diversity. Although they didn't radiate much morphologically (spheres, rod, spirals), they DID radiate metabolically. As a group, they are the most metabolically diverse group of organisms. B. Nutritional Categories: II.Bacteria and Archaea The key thing about bacteria is their metabolic diversity. Although they didn't radiate much morphologically (spheres, rod, spirals), they DID radiate metabolically. As a group, they are the most metabolically diverse group of organisms. B. Nutritional Categories: - chemolithotrophs: use inorganics (H2S, etc.) as electron donors for electron transport chains and use energy to fix carbon dioxide. Only done by bacteria. - photoheterotrophs: use light as source of energy, but harvest organics from environment. Only done by bacteria. - photoautotrophs: use light as source of energy, and use this energy to fix carbon dioxide. bacteria and some eukaryotes. - chemoheterotrophs: get energy and carbon from organics they consume. bacteria and some eukaryotes. II.Bacteria and Archaea The key thing about bacteria is their metabolic diversity. Although they didn't radiate much morphologically (spheres, rod, spirals), they DID radiate metabolically. As a group, they are the most metabolically diverse group of organisms. C. Their Ecological Importance II.Bacteria and Archaea The key thing about bacteria is their metabolic diversity. Although they didn't radiate much morphologically (spheres, rod, spirals), they DID radiate metabolically. As a group, they are the most metabolically diverse group of organisms. C. Their Ecological Importance - major photosynthetic contributors (with protists and plants) II.Bacteria and Archaea The key thing about bacteria is their metabolic diversity. Although they didn't radiate much morphologically (spheres, rod, spirals), they DID radiate metabolically. As a group, they are the most metabolically diverse group of organisms. C. Their Ecological Importance - major photosynthetic contributors (with protists and plants) - the only organisms that fix nitrogen into biologically useful forms that can be absorbed by plants. II.Bacteria and Archaea The key thing about bacteria is their metabolic diversity. Although they didn't radiate much morphologically (spheres, rod, spirals), they DID radiate metabolically. As a group, they are the most metabolically diverse group of organisms. C. Their Ecological Importance - major photosynthetic contributors (with protists and plants) - the only organisms that fix nitrogen into biologically useful forms that can be absorbed by plants. - primary decomposers (with fungi) II.Bacteria and Archaea The key thing about bacteria is their metabolic diversity. Although they didn't radiate much morphologically (spheres, rod, spirals), they DID radiate metabolically. As a group, they are the most metabolically diverse group of organisms. C. Their Ecological Importance - major photosynthetic contributors (with protists and plants) - the only organisms that fix nitrogen into biologically useful forms that can be absorbed by plants. - primary decomposers (with fungi) - pathogens II.Bacteria and Archaea The Diversity of Life III. Domain Eukarya Protists are single celled or colonial organisms they are the most primitive eukaryotes, and they probably evolved by endosymbiotic interactions among different types of bacteria The Diversity of Life III. Domain Eukarya From different types of protists evolved different types of multicellular eukaryotes: the fungi, plants, and animals. The Diversity of Life III. Domain Eukarya A. Protist Diversity - green alga Same chlorophyll as plants alternation of generation genetic analysis confirms relatedness The Diversity of Life III. Domain Eukarya A. Protist Diversity - Choanoflagellates The Diversity of Life III. Domain Eukarya B. Kingdom Fungi - Decomposers - Pathogens - Excrete digestive enzymes and absorb the nutrients C. Plants 1. Evolutionary History Green Algal roots Ulva (sea lettuce) C. Plants 1. Evolutionary History 1. Green Algal roots Ulva (sea lettuce) 2. Colonization of Land: Environmental Diffs Aquatic HabitatsTerrestrial Water availableDesiccating Sunlight absorbedSunlight available Nutrients at DepthNutrients available BuoyantLess Supportive Low oxygen, higher CO 2 reverse C. Plants 1. Evolutionary History 2. Diversity 2. Diversity a. Non-Vascular (no true xylem or phloem) Example: Mosses 2. Plant Diversity a. Non-Vascular (no true xylem or phloem) b. Non-seed vascular (club mosses, ferns) 2. Plant Diversity a. Non-Vascular (no true xylem or phloem) b. Non-seed vascular (club mosses, ferns) - dominated swamps 350 mya coal reserves 2. Plant Diversity a. Non-Vascular (no true xylem or phloem) b. Non-seed vascular (club mosses, ferns) - dominated swamps 350 mya coal reserves 2. Plant Diversity a. Non-Vascular (no true xylem or phloem) b. Non-seed vascular (club mosses, ferns) - dominated swamps 350 mya coal reserves c. Vascular Seed Plants a. Gymnosperms naked seed 1. Evolutionary History - dominated during Permian (280 mya) and through Mesozoic, and still dominate in dry env. Today (high latitudes, sandy soils) Gymnosperm Life Cycle 2. Plant Diversity a. Non-Vascular (no true xylem or phloem) b. Non-seed vascular (club mosses, ferns) - dominated swamps 350 mya coal reserves c. Vascular Seed Plants a. Gymnosperms naked seed b. Angiosperms flowering plants all other plants grasses, oaks, maples, lilies, etc. - flower attract pollinators - fruit attract dispersers D. Kingdom Animalia 1. Introduction a. Characteristics: Eukaryotic Multicellular Heterotrophic Lack cell walls. D. Kingdom Animalia 1. Introduction a. Characteristics b. History - first animals in fossil record date to 900 mya largely wormlike soft-bodied organisms D. Kingdom Animalia 1. Introduction a. Characteristics b. History - first animals in fossil record date to 900 mya largely wormlike soft-bodied organisms - in the Cambrian, 550 mya: radiation of predators (Cnidarians) radiation of major phyla organisms with hard parts D. Kingdom Animalia 1. Introduction a. Characteristics b. History c. Diversity - Approximately 1 million described animal species. Of these: 5% have a backbone (vertebrates) ( a subphylum in the phylum Chordata) 85% are Arthropods D. Kingdom Animalia 1. Introduction a. Characteristics b. History c. Diversity d. Evolutionary Trends 1. Body Symmetry asymmetrical radially symmetrical bilaterally symmetrical evolving a head D. Kingdom Animalia A. Introduction 1. Characteristics 2. History 3. Diversity 4. Evolutionary Trends a. Body Symmetry b. Embryological development zygote morula blastula gastrula D. Kingdom Animalia 1. Introduction a. Characteristics b. History c. Diversity d. Evolutionary Trends e. Phylogeny 2. Phylum Porifera: Sponges - asymmetrical - no true tissues, but cell specialization Choanocytes are similar to the free-living protist choanoflagellates 3. Phylum Cnidaria: Radial symmetry Two tissues endo and ectoderm Sac-like gut Diffuse nervous system (no head) Hydra, jellyfish, anemones, coral 4. Bilaterally Symmetrical Animals 1. Protostomes blastopore forms mouth a. Lophotrochozoans - Platyhelminthes - Annelida - Mollusca b. Ecdysozoans - Nematoda - Arthropod Phyla 2. Deuterostomes blastopore forms anus - Echinodermata - Hemichordata - Chordata - cephalochordates - urochordates - vertebrates Lophotrochozoans Phylum Platyhelminthes: Flatworms -Bilateral symmetry -Sac-like gut -Ameobocytes like sponges - planarians, flukes, tapeworms Phylum Annelida segmented worms - bilaterally symmetrical - cephalization (brains) - repeated segments - complete digestive tract one way gut - polychaetes, earthworms, leeches Phylum Mollusca: molluscs - bilaterally symmetrical - segmented body - shell, can be reduced or lost - cephalization correlates with activity - chitons, snails, bivalves, cephalopods Ecdysozoans Phylum Nematoda: round worms - molt cuticle - complete digestive tract - some cephalization with anterior neural ganglion - free living and parasitic - human parasites: trichinosis, filariasis, elephantiasis, Ascariasis (two foot intestinal worms) Arthropod Phyla: - Segmented body, jointed legs - thick exoskeleton -multiplicationspecializationfusion - trilobites (extinct) -Chelicerates (spiders, scorpions, horseshoe crabs, mites, ticks) -Myriapods (millipedes and centipedes) -Crustaceans (crabs, shrimp, lobster) -Insects Deuterostomes Phylum Echinodermata echinoderms - still bilateral - internal skeleton - herbivores and predators Phylum Hemichordata acorn worms - notochrod for support - hollow dorsal nerve tube (spinal cord) Phylum Chordata: chordates - notochord a rigid supporting rod - Hollow dorsal nerve tube - Pharyngeal gill slits - Post-anal tail Urochordates tunicates Cephalochordates lancelets Vertebrates: fish, amphibians, reptiles, birds, mammals