Origins of Basic Life Flashcards
For Exam 3, May 6th (19 cards)
What does Drake’s equation mean? What is the consensus of it?
An equation used to estimate how many planets may have life on them
The consensus is that it’s VERY unlikely that we are the only forms of life in the universe
What is the habitability zone? Are we going to stay in it forever? What variables determine it?
The zone around a star where planets may be suitable for life
Based on how hot the star is and how far away from the star you are
This changes as stars progress through their life cycle (they change heat)
What factors might we look at when considering whether a planet is capable of sustaining life?
Plate tectonics (= water), temperature, atmospheric conditions (if it even has one), etc.
Why do we think that Earth has plate tectonics and why do we think its essential to life?
Earth is at a “sweet spot” where its surface temperature and planet radius are balanced in a way that makes plate tectonics possible
Plate Tectonics lower the temperature of the planet via gas release, give us water by releasing steam, and cause mountains to weather (which gives nutrients to the oceans, where life is thought to form)
Where do we think life on Earth may have formed and why?
What are the benefits of living there?
In the ocean, specifically near hydrothermal vents because they’re rich in clay material (which we know promotes organic reactions)
The ocean also contains iron and carbonates, which would counteract the degrading effect of nitrates on amino acids
Overall, we know the benefits of living in the ocean are: less drastic temperature changes, protection from UV radiation, no issues with dehydration, pretty constant food sources, and less extreme effects of gravity
What was the order of events of the Hadean?
The super frickin hot time at the beginning of Earth
1- The Iron Catastrophe (creation of dense core and magnetic field)
2- Atmosphere Formation (degassing by volcanoes releases greenhouse gas, including water vapor)
3- Formation of the Moon (hit by a planetesimal and accreted; now protects us from asteroids)
These events were necessary before the first origins of life could appear
When do we think life started to form?
Its a period of time, not a specific number of years ago
During the Archaean
How can we determine when life began? When photosynthesis began?
Organic chemical signatures
Isotope Data: spike in C13 demonstrates the development of photosynthesis (because the C12 is now being broken down by plants)
What are the requirements for life (i.e. the necessary properties of living systems)?
Metabolism (obtaining + excreting energy), Replication, Carbon-based, and have Cells
Why is life carbon based?
It’s an abundant element (because of nucleosynthesis)
Its versatile or flexible in its bonding with other elements
It can exist in any physical state
Its soluble in water
Why are cells a requirement for life?
Membrane separates the internal from external
Semi-permeable (keeps out toxins but lets in nutrients)
Smallest unit of life that can replicate itself perpetually
What are prokaryotes?
Single celled organisms without a nucleus or membrane bound organelles
How did Miller-Urey attempt to recreate life? What were the results
By recreating what they thought the early atmosphere would look like, then hocking it with “lightning”
They yielded amino acids (the building blocks of proteins), but they also yielded nitrates (which destroy amino acids)
How did Fox-Harada attempt to recreate life? What were the results?
Recreated the Miller-Urey experiment, but under conditions similar to those of a deep-sea hydrothermal vent (i.e. with intense heat and pressure)
They yielded proteinoids, which have similarities to living systems because they act like cell membranes + go through osmotic exchange and division
What is the Theory of Abiogenesis? Is it the same of Evolution?
That life was created from abiotic sources (evidence for this is demonstrated by lab experiments that attempt to create life)
No, evolution explains how life develops and changes over time, but not how it was originally created
What was Panspermia? Is it scientific? Why or why not?
That idea that life started in outer space and was transferred to earth (potentially via meteorites)
It’s not scientific because it cannot be tested
Can science answer the question of WHY life evolved?
On a philosophical level, no
Science is based on testability
Why might life have originated with RNA instead of DNA?
Its more versatile
It can organize and self replicate
Its less susceptible to UV damage (which is helpful in early Earth)
We have evidence of organisms relying on RNA alone (viruses)
What are stromatolites?
Communal masses of prokaryotes like bacteria, very common in the late Archean
