THEORIES OF THE ORIGINS OF LIFE CH.3 PPT

UNIVERSE, SOLAR SYSTEM, AND EARTH Common accepted theory is that the universe existed as an infinite singularity (concentrated single point of infinite mass) containing all matter, and therefore, energy in the universe. ~ Ga (billion years ago) the singularity exploded outward expanding rapidly, creating our known universe (or a younger more chaotic version of it) Initial universe was very hot, composed mostly of subatomic particles like quarks and so on, after the first million years first hydrogen atoms began to form. The first two elements were hydrogen and helium, both simple elements that are light gasses in our atmospheric conditions.

UNIVERSE, SOLAR SYSTEM, AND EARTH Uneven distribution of matter combined with the gravitational attractions between molecules began to bring hydrogen and helium atoms together. As matter compounded onto of itself, (constantly increasing in density due to higher gravitational pull with greater masses) eventually it collapsed into itself, this is the process of formation for protostars (precursors to stars) If mass continues to compound, and the protostars density continues to increase, then its warm core will begin to heat up constantly due to contraction until pressure and density ignite the nuclear reactions required for atomic fusion.

UNIVERSE, SOLAR SYSTEM, AND EARTH Nuclear fusion is what creates a star from a protostar, as pressure and density increase and induce the necessary nuclear reactions, hydrogen and helium atoms combine their nuclei to produce nitrogen, which then continues to produce carbon, and onto iron and nickel and all the heavy metals common in the universe. These formation of heaver atoms from lighter ones releases immense amounts of energy, usually in the form of solar radiation or photons. The theorized life cycles of starts explains how elements in the known universe are created (technically were all made of old startdust)

GENERAL LIFE CYCLE OF A STAR Once the star forms and nuclear fusion begins and hydrogen starts to combine into heavier elements the life cycle begins. As hydrogen nuclei form new elements, the actual supply of hydrogen begins to deplete, this process continues for millions of years (length varies depending on factors like size and brightness of a star).

GENERAL LIFE CYCLE OF A STAR Eventually all the hydrogen supply with in a stars core becomes exhausted, the stars core becomes denser and contracts, leaving a “space” of lower density between the new core boundary and where the original one was. At this point, the gravitational forces from the core increase greatly due to increased density, which will cause the start to collapse inward under the gravity of its core. Depending on the type and size of star this can either produce a white dwarf (small dense star), or a super nova (large nuclear explosion resulting from an imploding star).

NEUTRON STARS

DIAGRAM OF A STAR

RESULTS OF A SUPERNOVA As the fusion core collapses, the supernova produces some final fussion of heavier metals as the explosion occurs. Supernova explosions are responsible for the distribution of heavier metals throughout the universe. Remnant structures that forms from a supernova along with heavy metals, are nebula clouds, which could eventually develop into new stars if reaches the appropriate density. Supernovas are responsible for supplying the materials necessary for the formation of solar systems around them.

SUPERNOVA

ORIGIN OF SOLAR SYSTEM Stars are clustered into galaxies, each with thousands of stars. Currently theory hypothesizes that the solar system began with a large cloud of hydrogen and helium called a nebula. The shockwave of a supernova caused the cloud to condense, and that inward acceleration of mass resulted in axial momentum (spinning) of the nebula as a whole.

ORIGIN OF SOLAR SYSTEM As the cloud gets denser, combined with the spinning, caused the cloud to flatten into a disk. At the center, a protostar began to develop (which would become the sun), once it gained enough density and nuclear fusion commenced it basically became our sun. Some of the gas continued to revolve around the sun, as molecules orbited around a center and the system began to gradually cool, matter began to condense into masses that would never reach the density necessary for star formation. These small masses began to collide with one another sometimes forming larger and larger bodies which eventually gravitationally attracted gasses and other light molecules forming primitive planets with early atmospheres.

ORIGIN OF THE EARTH AND MOON The planets in our system formed through accretion, which is a process by which particles clump together because of gravity. As mass grows through accretion, the more gravity it has, and the more additional mass it attracts. Although its mass did not form into a protostar, it did gain enough density that its core began to compress under its own gravitational weight. This increase in pressure as well as the decrease in volume resulted in an immense increase in temperature, resulting in a molten core.

ORIGIN OF THE EARTH AND MOON Within the core, heavy metals (specifically iron and nickel) differentiated towards the center due to their higher densities, while lighter elements like oxygen and silicone rose towards the surface. This is why the Earth’s solid inner core is composed of an iron-nickel complex Also the reason why the Earth’s crust as well as the surface rocks are primarily composed of silicates (SiO_4) and oxides. This process was called Density Stratification, which formed the major layers of the Earth, each with their own unique density and composition.

EARTHS INTERIOR AND DENSITY STRATIFICATION

FORMATION OF THE MOON Most widely accepted explanation is the Orpheus Theory, which states that a planet sized body (possible another planet about 1/3 the size of earth) struck Earth during its early development and sent some of its mantle material into orbit forming the moon. Moon is mostly composed of a relatively dense rock known as peridotite, which is the major component of earths mantle, also contain specific crystals called ecoglite which are also common to the Earths lower mantle, giving evidence of a common origin. Why did Earth and the Moon form as Spheres?

ORIGIN OF THE ATMOSPHERE AND OCEANS In the beginning, Earth was believed to have had no atmosphere, it was a largely molten liquid and didn’t allow gasses to escape. Eventually it cooled to a temperature where crustal rock could form, and as mantle convection produced plate tectonics it also started volcanic activity Volcanic activity is responsible for massive releases of gasses (mostly co2 and water vapor with some phosphates, sulfate and so on), which come from within the earth and are “dissolved” in the mantel. These gasses were once part of crystals but due to the constant recycling of matter within the earth interior those crystals may break down, releasing gasses which become dissolved in magma and are constantly trying to make their way to the surface.

ORIGINS OF THE ATMOSPHERE AND OCEANS This process, called outgassing, is responsible for the formation of the early atmosphere. In this initial atmospheric phase of earths history, surface temperatures exceeded the normal boiling temperature of water, So even though water vapor existed in the atmosphere, and formed clouds, and even rain. But once the rain reached the surface it immediately boiled So this prevented large bodies of water to form on the Earths surface.

ORIGINS OF THE ATMOSPHERE AND OCEANS After further cooling, Earth’s surface allowed rain to accumulate and the oceans formed as water vapor condensed. Carbon dioxide in the early atmosphere was mostly dissolved in the primitive oceans, so the atmosphere was composed primarily of nitrogen. Although oxygen is essential to almost all life today, data recorded in rocks shows evidence that early life didn’t use oxygen (oxygen entered the atmosphere about 1.5 billion years ago) The appearance of oxygen to the atmosphere is correlated with the increasing biomass and diversity of photosynthetic organisms since as far back as 3.5 Ga (oldest fossils of photosynthetic bacteria) Photosynthesis used up carbon dioxide and released oxygen.

ABIOGENESIS Life on Earth originated in shallow oceans, with supporting evidence being the discovery of marine fossil almost 3.5 Ga. Cyanobacteria (blue-green algae) are aquatic, photosynthetic bacteria. Oldest terrestrial fossils are ~1Ga

ABIOGENESIS In 1953 Stanley Miller and Harold Urey tested a previous hypothesis which stated that molecules necessary for the creation of life were originated from lighting or ultraviolet light in the atmosphere. They tested the hypothesis by discharging electricity within the proposed gasses (water vapor, ammonia, methane, and hydrogen but not oxygen) These experiments produced, among other substances, amino acid (the building block of proteins) Similar experiments produced simple sugars, needed to produce complex carbohydrates.

“PRIMORDIAL SOUP” Biologists proposed that early oceans acted as a primordial soup of simple compounds that are the building blocks of life. Proteins and other complex molecular chains formed when shallow pools evaporated, concentrating the “soup” Driven by solar energy, the first life is believed to have developed from this “soup” due to incredibly complex chemical reactions.

ORIGINS OF LIFE More recently scientists have questioned these beliefs. Many theorize that volcanic activity, meteorites, and other influences were to destructive to allow life to develop in shallow surface pools. Also the early atmosphere would not have protected early life from destructive UV radiation, due to the lack of ozone in the atmosphere. Scientists propose that life arose from deep in the ocean, protected by water. Life originated using chemical energy and heat energy from hot mineral springs (hydrothermal vents) on the ocean floor

ORIGINS OF LIFE course-ecology-2/v/crash-course-ecology-01

STROMATOLITES

OXYGEN AND EVOLUTION Heterotrophs: organisms that rely on consumption to obtain chemical energy Autotrophs: organisms that create organic compounds by combining inorganic compounds and an external energy source. (Plants, photosynthetic bacteria ect) Autotrophs are responsible for the rise of oxygen in ATM from 1% to 21%, and they also absorb large amounts of CO2 Oxygen is important to life because it is involved in the RedOx reactions necessary for the efficient use of chemical energy (Cellular Respiration) Availability of oxygen allowed the development of Mitochondria.

EVOLUTION Charles Darwin and the H.M.S Beagle Based on theory of Natural Selection Theory states that over long periods (MY) natural selection and mutations caused the development of all different life forms and their characteristics. Organism became more diverse and complex. (solitary bacteria began to colonize, then bacteria engulfed mitochondria forming modern eukaryote, which then resulted in multicellular life)

OCEAN ZONES AND LIFESTYLES Most basic division based on location is between water column and the bottom Water portion is the pelagic zone ( Greek pelagikos = sea) Bottom is called the benthic zone (Benthos = depths of sea)

LOCATION: THE PELAGIC ZONE The pelagic zone is divided into two horizontal zones: The “Neritic Zone”: the area of water between low tide mark and the end of the continental shelf. The “Oceanic Zone”: open water area beyond continental shelf. Oceanic zone is further divided into vertical regions determined by depth: Epipelagic (epi meaning over or before): m depth, layer that sun penetrates, photic zone. Mesopelagic (mesos meaning middle): m, dysphotic zone has some illumination but cannot support photosynthesis. Bathypelagic (bathos = deep): deep water in open ocean Abyssalpelagic (abyssal = bottomless): even deeper water in ocean trenches Hadalpelagic (Hades = underground adobe of the dead): deepest water in trenches.

BENTHIC ZONE

Divided based on depth as well: Supralittoral zone (latin supra=upper, littus=shore): this is a term used to describe the zone were waves crash. Littoral zone: intertidal zone. Sublittoral: part of littoral zone, ocean bottom close to shore. Outer sublittoral zone: ocean bottom at the end of the continental shelf. Bathyal zone: bottom along continental slope down to deep ocean bottom. Abyssal zone: deep ocean bottom. Hadal zone (>6000m depth): deepest zone.

PLANKTON (greek planktos meaning wanderer) Group of “plants” (phytoplankton) and animals (zooplankton) that exist adrift ocean currents. Very small or microscopic Cant swim against currents.

NEKTON (Greek word meaning swimming) Organisms that swim From small invertebrates to large whales. Most of the seas predators are in this class of organisms, majority are vertebrates such as fish and whales.

BENTHOS Organisms that live on or in the bottom of the ocean. Can move around or be sessile (attached like sea anemones) Neuston (Greek word for neustos = swimming): plankton that float at the surface. Divided into epifauna, epiflora, and infauna.

EPIFAUNA Fauna stems from Faun, class of Roman mythological deities that are part human part animal. Animals, like crabs, which live on the sea floor.

EPIFLORA Flora, Roman goddess of flowers Plants such as seagrasses, that live on the sea floor.

INFAUNA Partially or completely buried under sea floor Some species of clams (like bivalves), sand dollars, tubeworms, and sea pens. Either deposit feeders or suspension feeders: Deposit feeders: feed off detritus (lose organic or inorganic material) drifting down from above. Suspension feeders: filter particles (mostly plankton) suspended in the water.