Evolution over time (chapter 25)
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How can biological molecules form?
under conditions postulated to have been present on early earth
What was early earth rich in?
water, molecular nitrogen (oxidized form), carbon dioxide (oxidized form), methane (reduced form), ammonia (reduced form N), and hydrogen sulfide
What do most synthetic reaction that make biological compounds require?
What does this mean?
-early earth may have been reducing. Volcanic eruptions produce reducing agents.
How could have energy originally be supplied to earth?
What was discovered?
- UV light or by lightening (discovered/tested in the late 1950's)
- -discovered number of amino acids synthesized in these conditions
- -some biomolecules needed to produce life may have been caused by these conditions
What do lipids naturally form?
- membranous enclosures
- vesicle formation is promoted by clay that forms from volcanic ash. Vesicles will enclose hydrophilic molecules like RNA.
- lipid vesicles can spontaneously arise (membranes of vesicles hydrophobic)
What are features of abiotically produced vesicles? (on lipid slide)
Self-assembly, reproduction, and absorption of RNA
RNA is likely the first what?
catalytic and first genetic molecule
What can ribozymes catalyze?
- some biological reactions (peptide bond formation, transphosphorylation during splicing)
- RNA can catalyze chemical reactions (RNA and ribosomes can act as catalyst)
In the past what may a ribozyme been capable of?
replicating RNA (kinda like DNA polymerase does now)
Why did DNA eventually win out over RNA as the genetic molecule?
Because it has greater chemical stability (because it lacks the 2'-hydroxyl on the ribose ring)
What may have RNA genetic material found?
Protein enzymes are more efficient than ribozymes
What is fossilization?
Mostly luck, the right organism in the right place at the right time.
How are fossils dated?
- Using Isotopes (unstable isotopes incorporated into organisms or into the rocks that embed the organisms can tell exact time)
- They capture small atoms that are radioactive
How long ago did life form?
1 billion years ago
What is the order that things became into existence?
origin of solar system and earth-> prokaryotes->atmospheric oxygen-> single-celled eukaryotes -> multicellular eukaryotes -> animals-> colonization of land-> paleozoic, mesozoic, and cenozoic era-> and then humans
What flaw does dividing the past into geological eras present?
Not proportional but gives a better idea of the relationship of the evolutionary progression to the geological eras. (eons, eras, periods, and epochs)
What did early prokaryotes generate? and how did it affect the oceans?
- Oxygen (O2)
- Oceans became saturated and the oxygen gassed out into the atmosphere (very little oxygen in rocks until prokaryotes came about.
How did eukaryotic organelles likely arise?
- by endosymbiosis (living together inside the cell)
- Once the nuclear envelope was formed, mitochondria and chloroplasts were likely prokaryotic organisms that were engulfed and found a happy home in the cell. the Creation of eukaryotes brought need for a membrane.
How long ago did multicellular organisms arise?
1.5 billion years ago. Based on scant fossils and the use of DNA sequences from current organisms to work back in time
What created many of the animal forms we see today?
The Cambrian explosion (early organisms were grazers, but predators evolved quickly)
What claimed the land during the paleozoic era?
- Plants and animals.
- Plants had to adapt by sprouting roots.
- Animals had to gain feet (prominent animals were insects and arthropods)
Are there lots of oceanic fossil records? How do you get more accurate data from fossils?
- few and far between, it just depends
- Fossil records get better with time. more current era, more accurate data
How much time does the mesozoic and cenozoic era cover?
- 250 million years (we understand more about these eras because they are occurred closer to the present.
- Specifically we understand how our geography has contributed to species evolution
How have geological changes contributed to evolution?
- Enormously! We live on plates of land masses that float around, sometimes fusing into a single mass and sometimes coming apart
- the last supercontinent occurred 250 million years ago (when dinosaurs arose, same species in wyoming and china shows how close they must have been) and was given the name pangea
- geography determined by what we see with fossil records
How many mass extinctions do fossil records show?
- 5 mass extinctions
- Each extinction marked by decrease in the number of identifiable families
- The permian extinction (during paleozoic era) and cretaceous extinction (during mesozoic era) are the best studied
What did the permian mass extinction result from?
massive volcanic eruptions (marks the beginning of dinosaur rule, also marks the start of pangea breakup)
What did the cretaceous mass extinction result from?
an asteroid collision. (marks the end of dinosaur rule (massive meteor hit in yukatan peninsula and expunged major life forms (dinosaurs)
What has occurred after each extinction?
- adaptive radiation
- an increase in the number of species, make sense in that extinction means new opportunities. (mammals of the time could adapt to fill things that dinosaurs once did).
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