Origin of Life

1. In layman’s terms: where life came from and how it lived on a tiny ball of water and rock. Origin of Life

2. Bacteria Archae- bacteria Protista Plantae Fungi Animalia 0 Cenozoic Colonization of land by animals Mesozoic Paleozoic 500 Appearance of animals and land plants First multicellular organisms 1000 PROTEROZOIC Oldest definite fossils of eukaryotes 1500 2000 Appearance of oxygen in atmosphere PRECAMBRIAN Millions of years ago Oldest definite fossils of prokaryotes 2500 3000 ARCHEAN 3500 Molten-hot surface of earth becomes cooler 4000 4500 Formation of earth Evolutionary histories have a lot of clear evidence, while the formation of life doesn’t. ???

3. Hypotheses of Life’s Origins • Divine Origin • Was life created by a supernatural or divine force? • not testable • Extra-terrestrial Origin • Did organic life on Earth come from meteors or the materials in them? • testable • Spontaneous Abiotic Origin • Did conditions allow inorganic matter to become organic? • testable

4. Life formation had 4 stages • Stage 1: Organic molecule synthesis: • Inorganic molecules capture energy and undergo inorganic synthesis into organic molecules Stage • Stage 2: Formation of Polymers: • Small organic molecules meet up and bond into polymers that execute different functions • Stage 3: “Protocells” • Creation of a plasma membrane from lipids to protect inside proteins. • Stage 4: The first self-replicating cell • RNA or DNA exists within the cell and drives protein synthesis and cell division.

5. Two different abiotic synthesis theories Two theories exist to explain abiotic synthesis: • Conditions in the early atmosphere of Earth synthesized inorganic reducing agents into organic molecules. • Underwater volcanic vents let out minerals and compounds that allowed synthesis of organic molecules within those highly pressurized areas. low O2 = organic molecules do not breakdown as quickly

6. Just a Theory… • 1920s: Biochemist Alexander Oparin and geneticist and evolutionary biologist J.B.S. Haldane propose the “Primordial Soup” Hypothesis • States that in early years, Earth didn’t have much oxygen and was composed of water vapor, hydrogen gas, methane, and ammonia. • Reducing agents such as methane and ammonia operate well in anaerobic environments, and drove chemical evolution.

7. Electrodes discharge sparks (lightning simulation) Water vapor Mixture of gases ("primitive atmosphere") Condenser Water Condensed liquid with complex, organic molecules Heated water ("ocean") Atmospheric inorganic molecules become organic • Abiotic synthesis • 1953 Stanley Millerattempts to prove Oparin-Haldane Hypothesis in a lab. • This was tested by in a closed system to simulate Earth’s early atmosphere with a variety of representational parts and factors. • Organic molecules were found within a few days. • Not super credible due to lack of N3 in the atmosphere during this time. CH4 H2 NH3

8. The Truth Is Out There… Extraterrestrial Origins Hypothesis: • Comets and meteorites hit Earth very frequently in Earth’s early history, bringing water. Did they bring anything else? • Organic molecules have been found in particular meteorites. • Scientists such as Chandra Wickramsinghe speculate that organic molecules were seeded on Earth long ago. • 13000 years old Mars meteorite ALH84001 found to contain tiny rods in the shape of bacteria.

9. Iron-Sulfur World Hypothesis 1980s: Biochemist Günter Wächtershäuser • Proposes that Earth’s deep sea vents spew out materials needed for organic molecules. • Carbon Monoxide, ammonia, and hydrogen sulfide are emitted and pass over iron and nickel sulfide materials near the vents. • The iron and nickel catalyze the abiotic elements into organic molecules.

10. Polymers are the ultimate connection between molecules. • Monomers must now find a way to join together without the help of proteins that don’t exist as of yet. • Two theories exist to explain this: • Protein-First Hypothesis • RNA-First Hypothesis

11. Protein-First First proposed by Sidney Fox: • Based on findings that amino acids polymerize abiotically when exposed to dry heat. • Clusters of amino acids washed into rocky shores could be hit by the dry heat of sunlight. • Proteinoids: Small polypeptides with some catalytic properties. • If proteinoids are put into water, they form microspheres that have many cellular properties. • More active enzymes would have selective advantages and thus produce more of themselves.

12. RNA-First Suggested that only RNA was needed to cause the formation of cells • RNA can be a substrate as well as an enzyme. • A huge indicator of this is the virus. Viruses can be composed only of mRNA and a protein coat called a “viroid.”

13. Stage 3: Prototypes of Cells • Life typically requires an outer coating or plasma membrane dividing it from external forces. • A protocell would have to have a semi-permeable membrane to help protect the reactions within from forces outside while still letting nutrients enter the cell.

14. Before the old was out and the new was in • First plasma membranes were likely made of fatty acids instead of phospholipids like modern cells. • Fatty acids are much smaller and have only one tail on them. • In water, fatty acids form spheres called micelles that have one layer of fatty acids. If another micelle is encountered, they can fuse to form a double layer called a vesicle.

15. Does this membrane make me look cellular? • Bubbles of fat called liposomes often incorporated surrounding materials into their membrane, possibly causing creation of protein channels. • ATP synthesis is hugely important to modern cellular processes. It would have originally been available freely to protocells, but as they used it up, protocells would be selected for ones who could recycle ADP into ATP.

16. Stage 4: DUPLICATION • The final component needed for the formation of the first cell would be the ability to self-replicate. • According to the RNA-first hypothesis, if RNA mutated and created reverse transcriptase as viruses do, it would form DNA capable of self replicating. • If it was the Protein-first hypothesis, proteins would have synthesized nucleotides from oceanic materials. • Chicken or egg? Likely, both at the same time. Nucleotides are hard to form with no help and proteins have a hard time just randomly synthesizing DNA. If both evolve simultaneously, it would make sense.

17. Earth’s entire history in a nutshell • The Geological Timescale is divided into 4 periods in biology which each contain eras • Precambrian • Paleozoic • Mesozoic • Cenozoic

18. Precambrian: Life’s baby pictures • Longest period: 87% of geological timescale • Prokaryotes likely form ~3.5 BYA. Able to survive in the most grueling environments. • Complex prokaryotes appear similar to cyanobacteria and photosynthesize for energy. • Atmosphere fills with oxygen, making anaerobic prokaryotes unsuitable. However, this oxygen forms O3 and creates the ozone layer to protect against UV radiation. This prevents new life synthesis but protects already existing life.

19. ~2 bya First Eukaryotes • Development of internal membranes • create internal micro-environments • advantage: specialization = increase efficiency • natural selection! nuclear envelope endoplasmicreticulum (ER) plasma membrane infolding of theplasma membrane nucleus DNA cell wall plasma membrane Prokaryotic cell Prokaryotic ancestor of eukaryotic cells Eukaryotic cell

20. 1st Endosymbiosis • Evolution of eukaryotes • origin of mitochondria • engulfed aerobic bacteria, but did not digest them • mutually beneficial relationship • natural selection! internal membrane system aerobic bacterium mitochondrion Endosymbiosis Eukaryotic cell with mitochondrion Ancestral eukaryotic cell

21. Eukaryotic cell with mitochondrion 2nd Endosymbiosis • Evolution of eukaryotes • origin of chloroplasts • engulfed photosynthetic bacteria, but did not digest them • mutually beneficial relationship • natural selection! photosyntheticbacterium chloroplast mitochondrion Endosymbiosis Eukaryotic cell with chloroplast & mitochondrion

22. Lynn Margulis Theory of Endosymbiosis • Evidence • structural • mitochondria & chloroplasts resemble bacterial structure • genetic • mitochondria & chloroplasts have their own circular DNA, like bacteria • functional • mitochondria & chloroplasts move freely within the cell • mitochondria & chloroplasts reproduce independently from the cell

23. Cambrian explosion • Diversification of Animals • within 10–20 million years most of the major phyla of animals appear in fossil record 543 mya

24. Paleozoic Era: Cambrian Period • Lasts about 300 Million years. • Era takes place mainly in the sea at about 542 MYA. Life becomes abundant with multicellular forms. • Animals that exist have exoskeletons which are more easily fossilized than soft Precambrian organisms.

25. Ordovician Period: Life grows a spine At about 500MYA, organisms begin to slowly diversify to live on land. • Plants: Oceanic algae moves into freshwater environments, followed by damp land areas. Nonvascular plants were most common, meaning that they had no roots. Plant height was low. • Animals: Invertebrates managed to move onto land, becoming arthropods such as spiders. Vertebrates also began during the early when jawless then jawed fish appear. • 57% of marine species go extinct following this era, forming a mass extinction event.

26. Silurian Period: Life takes root About 450 MYA, the Silurian period begins as new species diversify. • Plants: Seedless vascular plants make their debut with the ability to transport water and nutrients. • Animals: Jawed fishes appear and begin to dominate the oceans. New adaptations easily allow new species to outcompete old ones, especially after their mass extinction.

27. Devonian Period: Life Takes Flight Diversifying and dominating of new species starts a new period 420MYA. • Plants: Vascular plants diversify and dominate the land along with the emergence of plants with seeds. • Animals: Invertebrates gain a huge advantage as insects evolve wings and take flight, allowing faster colonization and more consumption. Vertebrate fish become cartilaginous and become ray-finned. This becomes the Age of Fishes. Giant predatory fish with protective armor emerge and sharks enter rivers. Small Lobe-finned fishes live in riverbeds where predators can’t get them. These eventually evolve into amphibians capable of living on land for short times. Mass extinction occurs again for 50% of marine species.

28. Mesozoic Era • After a mass extinction causes the eradication of the death of 50% of marine life, a new era begins. • The Mesozoic era includes the debut of reptiles, mammals, flowering plants, birds, placental mammals, and modern insects. • 3 entire mass extinction events also occur during this time.

29. Carboniferous Period: Life fuels the future • The Carboniferous Era begins around 360MYA. • This time period includes domination of giant forest that will eventually become coal, while ferns, club mosses, and horsetails from previous eras flourish. • Amphibians manage to diversify and this radiation sets up the evolution into reptiles, which also debut. Insects use their wings to undergo evolutionary radiation.

30. Permian Period: Life is Scaled Up • The Permian Period began about 300MYA with the decline of amphibians. • Due to amphibians relying on water to reproduce and others evolving ways to cope by becoming reptiles, a new era begins. • Reptiles manage to diversify and dominate with hard shelled eggs and dry skin. • Gymnosperms diversify through utilization of cones and seeds.

31. Triassic Period: Life Found A Way • The Triassic Period begins roughly 250MYA after an enormous mass extinction of 83% of all land and sea species. • Forests of conifers and cycads manage to dominate by using their vascular systems and large seeds. • Coral retakes the sea and mollusks join the reign. • Both dinosaurs and mammals also appear on land during this period.

32. Jurassic Period: Life REALLY finds a way • Another mass extinction event around 251MYA causes another period to begin. 48% of all species die out. • Flowering plants appear because of the diversification of gymnosperms. • Dinosaurs flourish during this time period while mammals are more covert. • Domination of dinosaurs and the benefit of flight spurs the evolution of the first birds.

33. Cretaceous Period: Kill or be Killed • The Cretaceous Period begins around 150MYA. • Dinosaurs continue to dominate the land as their diversity is maintained. • Mammals and flowers both find ways to diversify by remaining very inconspicuous and using new methods of reproduction effectively. • Sudden huge mass extinction occurs about 65MYA that takes out mostly dinosaurs and reptiles. 50% of all species die out.

34. Cenozoic Era • A new era begins as the extinction of dinosaurs and suppression of mammals causes a new diversity order to emerge. • Mammals, birds, and flowering plants become the main contenders during the two periods that occur: Tertiary and Quaternary.

35. Tertiary Period: Sweet, sweet, radiation. • The Tertiary period begins around 66MYA and includes the Paleocene, Eocene, and Oligocene epochs. • Taking advantage of the last mass extinction, mammals undergo adaptive radiation and diversify rapidly into herbivores, carnivores, insectivores, with the eventual evolution of primates. • Flowering plants continue to diversify, subtropical rainforests thrive, and modern families of flowering plants evolve.

36. Quaternary Period: Freaks of Nature • The Quaternary Period begins about 23MYA including the Miocene, Pliocene, and Pleistocene epochs. • Grasslands expand due to the decline of forests. Herbaceous angiosperms flourish during this period eventually diversify near its end. Multiple glaciation periods occur. • As grasslands become more popular, animals adapt to utilize those more widespread food sources. Megafauna, or enormous mammals, appear but die out very fast. This is hypothesized to be because of the evolution of primates into humans during this period, who spread across the world and hunted most megafauna to extinction.

37. Continental Drift • Shifting of tectonic plates and the formation of Pangaea contributed heavily to evolution. • The breaking apart of the supercontinent isolated species and created different environments that caused the observance of the diversity seen in our epoch, The Holocene.

38. Mass Extinction • At least 5 mass extinction events have managed to occur in the history of life on Earth. • Some occurred because of natural processes but others may have had more intense causes. • Most famously is the one that ended the Cretaceous period, where it is estimated that the impact of a meteor that sent Iridium into the crust and ash into the atmosphere.