Origins of Complex (Multicellular) Life Flashcards
For Exam 3, May 6th (14 cards)
What are Eukaryotes?
Have a nucleus with genetic material and specialized subunits in their cells (organelles)
What was Earth’s early atmosphere like?
Made of volcanic gases like CO2, nitrogen, and water vapor, with very little free oxygen
From what 3 sources does oxygen come from?
Photosynthesis, Rock Weathering, and Photolysis (a chemical reaction in which a molecule in broken apart by light particles, like when water vapor broke down to form ozone)
What was the Great Oxygenation Event?
A huge increase in the amount of O2 in the atmosphere, leading to a huge extinction of many anaerobic organisms
Important note: they still remained much lower than modern levels for a very long time
What features were present before the GOE?
Presence of rounded, but not rusted, pyrite (which is made of iron and forms in anoxic places)
Iron Band Formations, or red layers of rusted iron that comes from rivers, which indicates little, but some oxygen (too little = no rust but too much = degraded)
What evidence is there for the GOE? In other words, what features were present before that we don’t see now? What features were there?
No more rounded pyrite or iron band formations
We see the formation of gypsum deposits, which need lots of free oxygen to form
Why did oxygen increase in the GOE? What is necessary it to happen?
Organic carbon needs to decrease
The 3 R’s: reduce, remove, release
- Reduce the amount of carbon via photosynthesis (algae)
- Remove the carbon by burying it
- Release more oxygen (also by photosynthesis)
How does rock weathering lead to carbon burial? How does it impact the rise of eukaryotic life?
Weathered sediments are transported via rivers to the ocean, and when deposited, they bury organic material at the bottom of the ocean floor
Nutrients like potassium, phosphorus, and oxygen are carried along with the sediments to the ocean, when they aid in the rise of life
What would a rise in oxygen do to levels of C13 in the rock record?
How did it affect the planet’s climate?
It would increase because this indicates more photosynthesis and planetary cooling (leading to a snowball earth)?
What is runaway albedo and what does it have to do with climate?
Photosynthesis = rising O2 = cooler temps = more ice = more light reflected = cooler tempers = more ice and so on
This effect continues in a runaway fashion until otherwise acted upon
What evidence do we have of extensive glaciation at this time? What exactly is “this time” (what period)?
Striations and conglomerates (little volcanic rocks)
The Proterozoic
So, in summary, why did it take so long for complex life to form?
Extreme temperatures and frequent glaciation makes for an unstable environment that’s difficult for life to form in
When complex life did begin to appear (after glaciation slows), what types of life did we see?
Organisms that require less oxygen than we do, such as sponges
Summarize the order of events (starting with Hadean) thus far (i.e. the end of the Proterozoic and beginning of the Cambrian)
Iron Catastrophe, Atmosphere Formation, Moon Formation, first evidence of prokaryotic and photosynthetic life, GOE, Extensive Glaciation, slowing down albedo effect, first true animal fossils
