The Origin and Evolution of Early Life

13-2: The Origin and Evolution of Early Life Study Guide (nl)

So far, we have seen arguments for how simple metabolic pathways can emerge at alkaline vents. But what is needed for this to transition –> life?

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What sorts of environmental factors can cause building blocks to assemble into polymers?

What kind of molecule can both store genetic information (meaning, be a ‘replicator’) and be a catalyst? Do cells use these kinds of molecules today?

The hypothetical time on an early earth in which the first life forms were based on RNA molecules (& not DNA) is known as… …………………………….

The olde fashioned (and I think overly optimistic) version of the RNA World is where….

If you see a text illustration that shows RNA molecules fully ‘self replicating’ itself, or fully replicating other RNA molecules, are you being shown an image that has ever been demonstrated in laboratory experiments?

Why can’t RNA fully replicate an RNA molecule? When RNA is used to make longer RNA, is the mutation rate high or low?

More recent, less ‘extreme’ versions of the RNA world have RNA being helped by what other big molecule?

Summarize the ‘Spiegelmans’ Monster’ experiment. In what way does this show plausible ‘organic evolution’ that parallels natural selection? Be sure to understand the outcome of this experiment. But don’t exaggerate.

Much of the above could be processes that emerged together, in parallel. Of the 3 big molecules (Proteins, RNA, and DNA), which of these likely evolved  last ?

Why do we expect that RNA came before DNA? Why is DNA better at information storage? Why is RNA better (than DNA) at being a catalyst?

What is ‘versatile’ about reverse transcriptase proteins? How could it be a part of the earlier RNA world, and be a harbinger of the ‘DNA world’? That is the world we are in now.

What three sorts of things could communities of the earliest simple life forms do to build the complexity of their metabolic pathways? These kinds of things also occur today, b.t.w.

Building a linear metabolic pathway ‘backwards’ from later steps –> earlier steps is called ……………………………….

Given a linear metabolic pathway, with beginning and final steps in the pathway, be able to tell me which steps would have evolved 1st, and which would have evolved last (more recently), according to this particular view of how pathways evolve.

What is the other way that cells acquire new components to metabolic pathways, or even large portions of pathways all at once?

Are metabolic pathways today seen be be ‘cobbled together’ bits and pieces of other pathways?

An early chemical (and not real ‘fossil’) signs of life in the geological record include an even more skewed 12C / 13C ratio in carbon particles in ancient sedimentary rocks. Compare the isotope ratio in concentrated carbon from non-biological sources (like volcanic vents). How is this ratio different in carbon-rich material made from carbon ‘fixed’ by life?

Worldwide deposits of ancient iron ore called banded iron also represents a chemical signature for life. What is banded iron? These formations indicated the advent of what specific metabolic pathway?

What are stromatolites and how do these figure into the early fossil record of life?

What caused the great oxygenation event? What delayed this event (it would have happened earlier were it not for… (?) The addition of oxygen to atmospheric and oceanic chemistry caused some  crises  for a time. One described here was that …………………………………………………………….

Besides various crises, oxygenation also lead to what extraordinary opportunity? ………………………………………………………………………

Why would it be hard for life to get started on earth now? There are 2 major challenges for abiotic –> biotic evolution on earth today. What are the 2 challenges?

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