BIO 2, Lecture 2

1
BIO 2, Lecture 2

• WHAT IS LIFE?
• THE UNIVERSE AND ITS CHEMISTRY

2
I. What is Life?
What do all living things have in common?
How do living things differ from non-living th
ings?
3

• Living Things
• Can assimilate and use energy
• Can respond to the environment
• Can maintain a relatively constant internal
  environment
  
• Possess an inherited information base
• Can reproduce
• Are composed of one or more cells
• Are highly organized

-Krogh, Biology A Guide to the Natural World,
2004
4

• Life is a stream of digital information that
  changes over time
  
• Living beings are just temporary hosts (survival
  machines) for the information molecule (DNA)
  

-Richard Dawkins, River Out Of Eden, 1995
5

• Entropy (disorder) in the Universe is always
  increasing (arrow of time)
  
• Life is highly organized
• Living things must direct a stream of negative
  entropy upon themselves to create and maintain
  order
  
• Life borrows energy from the Sun (either directly
  or indirectly)
  
• Overall, however, entropy in the Universe always
  increases
  
• - Erwin Schroedinger, What is Life?, 1944

6
SUNS 10 BILLION YEAR CYCLE
7
(No Transcript)
8

• 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 )

9

• Living Things
• Possess an information molecule
• DNA (held digitally)
• Separate self from other
• Fiercely protect their DNA
• Maintain order and homeostasis for their DNA
• Need energy to fight entropy
• To protect and promote their DNA
• REPRODUCE themselves
• But only as vehicles to pass on the DNA they
  host
  
• EVOLVE by natural selection (of the DNA)
• Because replication of the molecule is
  imperfect
  

10
II. The Universe and its Chemistry
What conditions are necessary for life? How d
id those conditions arise?
11
In order to arise from non-living matter, life
requires ... Space, time, and matter Certain k
ey elements hydrogen, oxygen, and carbon
A stable energy source A relatively stable enviro
nment (home)
12
Space, Time, and Matter
The prevailing scientific theory is that the
Universe began with a huge explosion 13.7
billion years ago (The Big Bang Theory)
Time, space, and matter ALL came into existence
with this event Since then, time and space have
been expanding BUT ... the Universe is not expand
ing into anything! All we can really say is that
space and time are both increasing
13

• 300,000 years after the Big Bang, protons
  captured electrons to form the first simple
  atoms
  
• Hydrogen (H) is the simplest element one proton
  (and usually no neutrons)
  
• Helium (He) is the next simplest 2 protons (and
  usually two neutrons)
  
• A small amount of Lithium (Li) and Beryllium (Be)
  atoms also formed soon after the Big Bang
  
• All elements with higher molecular weights were
  created later, due to nuclear fusion in the cores
  of stars or via supernova explosions of massive
  stars

14
A PERIODIC TABLE OF THE ELEMENTS

15
Key Elements

• 600 million years after the Big Bang, the
  first generation of hydrogen and helium gas
  clouds fell together by gravity to form the first
  stars
• 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)

16
Stars congregated into galaxies containing
hundreds of billions of stars and stretching
hundreds of thousands of light years across
17

• As weve seen, stars are nuclear fusion furnaces
• H is being converted to He in the core
• 4 H ? 1 He, so volume drops with fusion, gravity
  squeezes harder, and pressure increases
  
• As pressure increases, temp increases, levels of
  radiation increase, and star is pushed outward,
  maintaining its size
  
• When all the H is used up, massive stars will
  begin to convert He to C (carbon) and other
  elements that are needed for life
  

18
Small stars The smallest stars only convert
hydrogen into helium. Medium-sized stars Late
in their lives, when the hydrogen becomes
depleted, will begin to convert helium into
carbon and oxygen. Massive stars (greater than
five times the mass of our Sun) 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.
19

• Up to the element iron (Fe), fusion releases
  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 collapse of the core 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 heavier than iron
  and scatters all of the elements into space
  

20
(No Transcript)
21
(No Transcript)
22
A Stable Energy Source
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 The Sun is a medium-sized star
-Has been fusing hydrogen to helium for 5
billion years -Will continue for se
veral more billion years -If our Sun was much la
rger, it would have burned out before live
evolved
23
A Home
In the Nebular Theory for the formation of the
solar system, a slowly rotating cloud of gas and
dust collapsed by gravity and began to spin
faster because of the conservation of angular
momentum
24
The collapsing, spinning nebula began to flatten
into a rotating pancake
25
As the nebula collapsed further, local regions
began to contract gravitationally on their own
because of instabilities in the collapsing,
rotating cloud
26

• The Moon probably 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 (a home for life)
  
• Importance of the magnetic field for holding an
  atmosphere
  
• Water

27
Earths early atmosphere consisted of
Nitrogen and its oxides Water vapor (huge amoun
ts later condensed into oceans
Carbon dioxide and carbon monoxide
Methane Sulfur dioxide Hydrogen sulfide and hydr
ogen cyanide Virtually no oxygen Lots of volca
nic activity Comet and asteroid bombardments un
til about 3.9 billion years ago
28
(No Transcript)