General Biology

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General Biology

• Evidence for Evolution

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PART III NOTES EVIDENCE FOR EVOLUTION FOSSILS,
FOSSIL FORMATION AND DATING
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ON THE ORGIN OF SPECIES

• In his book, Darwin argued that organisms had
  been evolving for millions of years.
• This was accepted because it was supported by
  evidence.

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EVIDENCE THAT EVOLUTION HAS OCCURRED

• 1. Fossil record
• Darwin saw fossils as a record of the history of
  life on earth.
• Shows that life on earth has changed over time.
• Ex Fossil record of the whale supports Darwins
  theory that whales evolved from terrestrial
  mammals.

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FOSSIL

• Any evidence left from earlier life forms.

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FOSSIL FORMATION

• 1. Formed in sedimentary rock
• 2. Sediments (particles of clay, sand and silt)
  form by the erosion of existing rock.
• 3. Sediments are transported to lakes and seas
  where they settle. Sometimes the remains of
  organisms are transported too.
• 4. The deposit of additional sediments creates
  enough pressure to compress lower layers into
  sedimentary rock preserving the organisms
  remains.

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FINDING FOSSILS

• Natural processes such as erosion and mountain
  formation can expose deeper rock layers bringing
  fossils to the surface.

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DATING FOSSILS

• 1. Relative Dating fossil age determined by
  comparing its placement to fossils found in other
  rock layers.
• Fossils in deeper layers are older, fossils in
  surface layers are younger.
• Does not provide an absolute age, just whether it
  is older or younger than other fossils.

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DATING FOSSILS

• 2. Radiometric Dating absolute age determined
  by measuring the amount of radioactive decay that
  has taken place.

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• Some atoms are unstable and decay forming a
  different type of atom at a steady rate.
• Rate measured in half-lives (amount of time
  required for half of the parent atoms to decay
  into daughter atoms.)
• Scientists have calculated the half-lives for all
  unstable atoms.
• Comparing the ratio of parent to daughter
  atoms in a rock or fossil sample allows age to be
  determined.

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Ex Unstable Uranium atoms (U) decay into Lead
(Pb) atoms. The half-live is 1 billion years.
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AGE OF EARTH

• 4.6 billion years old
• Determined by the radioactive decay of uranium to
  lead of moon rocks.

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• PART IV NOTES RECORD OF LIFE

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EARLIEST LIFE FORMS

• Appear 3.5 - 3.9 billion years ago
• Anaerobic bacteria (unicellular prokaryotes)

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LATER PROKARYOTES

• Photosynthetic bacteria (release free oxygen to
  create the ozone and build up atmospheric O2).
• Aerobic bacteria (utilize atmospheric oxygen for
  efficient generation of ATP)

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EUKARYOTES

• Appear 1.8 billion years ago
• HOW DID EUKARYOTES EVOLVE?
• Nucleus forms by enfolding of plasma membrane.
• Endosymbiont Theory explains the origin of
  eukaryotic organelles such as mitochondria and
  chloroplasts.

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• Mitochondria evolve from aerobic bacteria
• Chloroplasts evolve from photosynthetic bacteria

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Formation of Nucleus and ER
Prokaryote
Primitive Eukaryote
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Origin of Mitochondria and Chloroplasts
Aerobic bacteria
Animal Cell
Primitive Prokaryote
Photosynthetic Bacteria
Plant Cell
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EVIDENCE FOR ENDOSYMBIOSIS

• Chloroplasts and mitochondria have their own DNA
  (circular like bacterial DNA)
• Chloroplasts and mitochondria have their own
  ribosomes and make their own proteins.
• Chloroplasts and mitochondria grow and reproduce
  independently of the rest of the cell.

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EARLY MULTICELLULAR LIFE

• First multicellular organisms (algae) 1 billion
  years ago
• Advantage larger size easier to obtain food
  and avoid predation by unicellular organisms.

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LATER MULTICELLULAR LIFE

• Invertebrates (arthropods, worms, jellyfish and
  sponges)
• Vertebrates
• Fish Amphibians Reptiles
• All in last 700 million years

BIRDS
MAMMALS
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• HUMANS
• Modern humans emerge 150,000 years ago