BIO 10 Lecture 2

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BIO 10 Lecture 2

• THE UNIVERSE AND ITS CHEMISTRY WHAT IS LIFE?

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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

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• 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

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A PERIODIC TABLE OF THE ELEMENTS

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• 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)

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• 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

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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.
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• 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

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• 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

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• 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
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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

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In the Nebular Hypothesis, a cloud of gas and
dust collapsed by gravity begins to spin faster
because of the conservation of angular momentum
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The collapsing, spinning nebula begins to flatten
into a rotating pancake
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As the nebula collapses further, local regions
begin to contract gravitationally on their own
because of instabilities in the collapsing,
rotating cloud
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• The Moon formed as a result of an early
  catastrophic collision between Earth and another
  planetoid, which also created the tilt in Earths
  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

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• 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

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Earths 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
• Earths 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

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What is Life?

• What is Life?
• In-class Exercise
• How is life distinguished from non-life? How do
  we know that something is ALIVE?

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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

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• 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

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• 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

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• BUDDHA and the man with 84 problems
• Dr. Seuss and trying to get to Solla Sollew
  (where there arent any problems, or else just a
  few )

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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?