Tracing Evolutionary History Flashcards
What made the origin of life possible?
Conditions on early Earth - The Earth formed about 4.6 billion years ago
What was most likely in the first atmosphere?
The first atmosphere was probably thick with water vapor and various compounds released by volcanic eruptions, including nitrogen and its oxides, carbon dioxide, methane, ammonia, hydrogen, and hydrogen sulfide
Where does the earliest evidence for life on Earth come from?
It comes from 3.5-billion-year-old fossils of stromatolites, build by the ancient photosynthetic prokaryotes still alive today - these prokaryotes suggest that life first evolved earlier, perhaps as much as 3.9 billion years ago
Where did bacteria come from?
Bacteria evolved ~3.5 billion years ago
Chemical and physical processes on early Earth may have produced very simple cells through a sequence of stages
1. Abiotic synthesis of small organic molecules
2. Joining of these small molecules into polymers
3. Packaging of molecules into “protobionts”
4. Origin of self-replicating molecules
What did Russian chemist A. I. Oparin and British scientist J. B. S. Haldane propose in the 1920s?
They independently proposed that the conditions on early Earth could have generated organic molecules
What id Stanley Millers 1953 experiment show?
It tested the Oparin-Haldane hypothesis and showed that the abiotic synthesis of organic molecules is possible
What organic molecules did Miller identify were common in organisms?
Hydrocarbons (long chains of carbon and hydrogen) and some of the amino acids that make up proteins
What was demonstrated to be possible by the Miller experiments?
Stage 1 abiotic synthesis of organic molecules
Where is another place that organic compounds may have been synthesized?
Instead of forming in the atmosphere, the first organic compounds may have been synthesized near submerged volcanoes and deep-sea vents
Protocells
A collection of organic molecules within a membrane-enclosed compartment
What did laboratory experiments demonstrate about lipids and water?
They demonstrated that small membrane-bounded sacs or vesicles form when lipids are mixed with water
What do vesicles exhibit?
They exhibit simple growth, reproduction, and metabolism
They can absorb organic molecules attached to montmorillonite particles through a selectively permeable bilayer
What is the origin of self-replicating molecules?
Today’s cells transfer genetic information from DNA to RNA to protein assembly. However, RNA molecules can assemble spontaneously from RNA monomers
What happens when RNA is added to a solution containing a supply of RNA monomers?
New RNA molecules complementary to parts of the starting RNA sometimes assemble
Ribozymes
An RNA molecule, can carry out enzyme-like functions, and may have facilitated RNA replication
What was probably the first genetic material?
The first genetic material was probably RNA, not DNA
If a vesicle on early Earth could grow, split, and pass on its RNA to its “daughter” what would its daughter be?
Protocells
What is Deinococcus radiodurans?
An extremophile bacterium- can survive cold, dehydration, vacuum, and acid
Means that life might have arrived on earth in/on meteorites
Sedimentary rocks
Deposited into layers called strata and are the richest source of fossils
What does the fossil record show?
It shows changes in the kinds of organisms on Earth over time
What is the fossil recored biased in favor of?
Existed for a long time, were abundant and widespread, and/or had hard parts such as shells or skeletons
What does the sedimentary strata reveal?
It only reveals relative ages
What can absolute dating be determined by?
It can be determined by radiometric dating
What does a “parent” isotope decay into?
It decays into a “daughter” isotope at a constant rate
Half-life
The time required for half the parent isotope to decay
What is Carbon-14 useful for?
Dating relatively young fossils - up to about 75,000 years old
