UNIT TWO, DAY 4
10.29.14
OPENER
• Complete the “Student Led Conference Reflection
Sheet”
• Use the grade report provided
• If you suspect there are errors on your grade report,
highlight the assignment/assessment and I will look into it
before conferences
• For the absences/tardies section: instead of numbers,
indicate whether or not you think absences have affected
your grade
• Staple reflection and grade report together (reflection on
top) and turn in (on projector cart)
• You have 12 minutes
AGENDA
• Electronics in class
• Origins of Life: more evidence
• Readings
• Short Video (10 minutes)
• Mini-Lecture: Heredity First vs. Metabolism First
• Putting it all together
• What are the hypotheses and evidence?
• Homework
READING
• Groups of three: each group member takes ONE of
the three articles in the packet
• Read: 7 minutes
• Text Mark:
• Highlight/underline EVIDENCE or HYPOTHESIS
• Margin note: connection
• SHARE:
• Add information to graphic organizer/notes
VIDEO
• About RNA SYNTHESIS
• Hypothesis: RNA World
• Take notes:
• What evidence is presented in the video supporting this
hypothesis?
VIDEO #2
R N A WO R L D
HEREDITY FIRST HYPOTHESIS
• Life was proceeded by a self-replicating RNA
molecule
• Why RNA?
• Catalytic capability (like proteins)
• Storage capability (like DNA)
• SO—RNA can catalyze the chemical reactions used
to make more RNA and Proteins
• Additional evidence supporting this idea:
• Experiments showing generation of RNA nucleotides
• Protein assembly in ribosomes catalyzed by RNA
• MANY important tasks in cell involve RNA
AND, THE BEST PART
• RNA, unlike DNA, has multiple 3D shapes
• Catalytic activity of RNA depends on shape (like proteins)
• Where variation is present, natural selection can act
on that variation:
• Environment selecting for RNAs that can reproduce
themselves more efficiency
• Instability of RNA an advantage: more mutations,
more chance for favorable shapes
• Why the switch to DNA and proteins?
• Stability
• Variability
“METABOLISM FIRST” HYPOTHESIS
• Metabolism: chemical reactions to break down or
make molecules
• Coupled reactions:
• Reaction #1 releases energy (spontaneous, might require
catalyst)
• Reaction #2 used energy to build another molecule (not
spontaneous without energy input)
• Photosynthesis and Cellular Respiration both involve
coupled reactions
• Metabolism precursor of complex organic
molecules (DNA, proteins, etc.)
METABOLISM FIRST, CONT.
• Evidence/Argument
• Deep sea vents provided conditions, material and energy
for development of these reactions
• “Cell-like spaces”
• The simplest metabolic pathways can happen OUTSIDE of
organisms, given the right conditions
• Highly unlikely that complex, self-replicating molecules
could be assembled without source of energy (coupled
reaction)
BIG PICTURE
•
•
•
•
Tables 1 and 2: Small Organic Molecules
Tables 3 and 4: Macromolecules
Tables 5 and 6: Cells or Protocells
Table 7: Self-Replicating Molecules
• Discuss hypotheses/evidence
• Resources: text, class video notes, notes, articles,
graphic organizer, website videos
• Record on chart paper: hypotheses and evidence
supporting hypotheses
HW
• #1 Read the final article in the packet
• Take notes (evidence and hypotheses)
• #2 COMPLETE graphic organizer
• #3 Write a description of how life might have
originated that:
• Discusses each of the four stages described in your book
(organic molecules, macromolecules, protocells, selfreplicating molecules)
• Describes the hypotheses and evidence that address each
stage