Presentation on theme: "BIO 10 Lecture 2 THE UNIVERSE AND ITS CHEMISTRY: WHAT IS LIFE?"— Presentation transcript:
BIO 10 Lecture 2 THE UNIVERSE AND ITS CHEMISTRY: WHAT IS LIFE?
Setting the Stage for Life The prevailing scientific theory for how the Universe came into being (i.e. the theory that explains the most facts and has the best predictive power) is that the Universe began with a Big Bang explosion ~ 13.7 billion years ago. Time, space, and matter came into existence with this event Since an act of creation implies space and time, most scientists do not believe it is even meaningful to talk about a Creator or Creation Event The Universe is not expanding into anything! All we can really say is that space and time are both increasing
~ 300,000 years after the Big Bang, protons captured electrons to form the first hydrogen atoms. Hydrogen (H) is the simplest element; it has only one proton and one electron The Big Bang also created a small amount of Helium (He), Lithium (Li) and Beryllium (Be) All elements with higher molecular weights were created later, in the bellies of massive stars
~600 million years after the Big Bang, the ‘first generation’ of galaxies and stars fell together by gravity Early stars were comprised entirely of H and He (with traces of Li and Be) and had no rocky planets They might have had gaseous planets like our own outer planets (Jupiter, Saturn, Uranus, and Neptune)
Stars are nuclear fusion furnaces –H is being converted to He in the core –4 H → 1 He, so pressure drops with fusion and gravity squeezes harder –As gravity increases, temp increases, levels of radiation increase, and star is pushed outward, maintains size –When all the H is used up, the star will begin to convert He to C (carbon), the most important element for life
Small stars: The smallest stars only convert hydrogen into helium. Medium-sized stars (like our Sun): Late in their lives, when the hydrogen becomes depleted, will begin to convert helium into oxygen and carbon. Massive stars (greater than five times the mass of ourSun): When their hydrogen becomes depleted, high mass stars convert helium atoms into carbon and oxygen, followed by the fusion of carbon and oxygen into neon, sodium, magnesium, sulfur and silicon. Later reactions transform these elements into calcium, iron, nickel, chromium, copper and others.
Up to iron (Fe), fusion creates energy. After iron, fusion requires energy. –When the core of a massive star turns to iron, gravity can no longer be “stopped” –A sudden and massive implosion creates a neutron star or black hole where the core of the star had once been The implosion is accompanied by a massive explosion that fuses elements beyond iron and scatters heavy elements into space
~5 billion years ago, our star, the Sun formed out of a cloud of H and He “contaminated” with the heavier elements produced by the supernova of another star ~ 4.5 billion years ago, The Earth formed from the same spinning disk that formed the Sun. Metals and other heavy elements remained closer to the sun; gaseous planets like Jupiter and Saturn formed farther out
Thus, the solar system, and particularly the inner planets in the solar system, were rich in heavier elements The chemistry of life relies mostly on the following elements: »Hydrogen »Carbon »Oxygen »Nitrogen »Phosphorous Created in supernovas
From Muck to Microbes Formation of the Solar System –The oldest rocks on are just slightly younger than the sun: 4.5 billion years old Nebular Hypothesis: The solar system was born out of a swirling (rotating) cloud of hydrogen and helium, with a smattering of heavier elements –Most of the H and He are found in the sun; rocky planets made of heavier elements (like Earth) are found close to the sun, while gaseous planets (Jupiter, Saturn, Uranus, Neptune) are found further out Earth formed as an accretion of smaller “asteroid- like” bodies
In the Nebular Hypothesis, a cloud of gas and dust collapsed by gravity begins to spin faster because of the conservation of angular momentum
The collapsing, spinning nebula begins to flatten into a rotating pancake
As the nebula collapses further, local regions begin to contract gravitationally on their own because of instabilities in the collapsing, rotating cloud
The Moon formed as a result of an early catastrophic collision between Earth and another planetoid, which also created the tilt in Earth’s axis The heat of early bombardments and impacts kept Earth hot and enabled heavier elements (principally iron) to flow to the core, where they remained molten Over time, the crust of the Earth cooled and became solid
The Nebular Hypothesis is considered to be a good scientific theory because it explains many facts about the solar system –All of the planets revolve around the sun in the same direction –the axes of most planets are at right angles to their plane of orbit –all the planets revolve around the sun in roughly the same plane –All evidence to date suggests that the planets and sun are roughly the same age
Earth’s Early Environment Molecules present on early Earth included nitrogen, water vapor, and carbon dioxide – the same gases currently produced by volcanoes Other minor contributors included methane, ammonia, carbon monoxide, sulfur dioxide, and hydrogen cyanide – NO OXYGEN! Comet impacts may have contributed large amounts of water vapor, helping to form the early oceans Earth’s age can be estimated from levels of radioactive 238U versus 206Pb in rocks, and the age of the Moon can be accurately determined using this method
What is Life? In-class Exercise: –How is life distinguished from non-life? How do we know that something is ALIVE?
Some Definitions for Life Krogh (2004) –Living things: Can assimilate and use energy Can respond to the environment Can maintain a relatively constant internal environment Possesses an inherited information base Can reproduce Are composed of one or more cells Are highly organized
Dawkins (1995) –Living things are the survival machines for a stream of digital information that changes over time –Living beings are just temporary hosts for the information molecule (DNA) and exist for the sole purpose of enabling that molecule to be perpetuated –DNA is ultimately the only thing that survives through time
Schroedinger (1944) –Life directs a stream of negative entropy upon itself to create order from chaos –Entropy (disorder) in the Universe is always increasing –Life works against entropy by borrowing energy from the Sun –In the end, however, entropy always wins
BUDDHA and the man with 84 problems Dr. Seuss and trying to get to Solla Sollew (where there aren’t any problems, or else just a few …)
Short Review of Lecture 2 What is the best current scientific theory for the origin of the Universe? Why does the Big Bang theory make the idea of a "Creator" or "Creation Event" a meaningless thing to discuss? What is space expanding into? What elements were formed in the Big Bang? How were other (heavier) elements (including carbon, the basis for life chemistry) formed? What are the common characteristics shared by all living things but not by non-living things?