Period+2+GR+26

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1. Start with the origin of the earth and identify the **time frame, conditions, and evidence** for each of the following steps leading to current life forms on earth.

a. Origin of the earth- 4,6 billion years ago, condensed from a vast cloud of dust, that surrounded the sun, rocks and ice hit earth for 100 mil years, rocks found are 3.8 billion years old, as rocks stopped hitting earth, the water vapor settled as it cooled.

// beal. . . right //

b. Prokaryotes- Dominated life 3.5 to 2.5 billion years ago. Protobionts-->autotrophs--> can use light energy--> hetertrophs--> live on autotrophs.

 //beal. . . right!//

 c. Oxidizing atmosphere- Oxygen began to accumulate 2.7 billion years ago. Photosynthetic bacteria created a reducing or oxidizing atmosphere.

//beal. . . right, but not reducing. the atmosphere changed from a reducing to oxidizing.//

d. Eukaryotic cells - 2.1 billion years ago, maybe a earlier eukaryotic cells traces of molecules like cholestron in rocks, only made by eukaryotic cells may have evolved as oxygen revolution began.

// beal. . . right! //

e. Multicellular life- 1,5 to 1.2 billion years ago. They worked in colonies. Some cells in the colonie specialzed in certain jobs.

// beal. . . where is your evidence? //

2. What was significant about the discovery of the iron oxide bands in the sedimentary layers. **This implies that cynobacteria may have originated as early as 3.5 billion years ago, when microbial mats that left fossilized stromatolites began forming.​**

//beal.//. . what do // cynobacteria produce? //

3. Describe the theory of endosymbiosis.   A prokaryote engulfs smaller aerobic prokaryotes that are heterotrophic and photosynthetic. A symbiotic relationship is formed. The aerobic prokayotes gain protection and the large prokaryote gains free energy. Heterotrophic prokaryotes turn into mitochondria and photosynthetic prokaryote turn into plastid.

 //beal. . . hmmmmmm. . . keep it simple. . . larger prokaryotes engulfed smaller ones as food or because the smaller ones could do something for the larger like make energy. this set the stage for co-evolution between the two prokaryotes where the smaller evolved into today's organelles.//

 4. Why did evolution seem to slow 750 to 570 million years ago?

Due to a severe Ice Age that occured during this time period, evolution seemed to slow up. Organisms were limited in size, diversity, and distribution. In this period of time, the seas were iced over and glaciers covered the entire world from pole to pole. Most life was confined to certain areas sunlight was able to reach the surface waters. This is according to the Snowball Earth hypothesis.

// beal. . . right! //

5. What was special about the Cambrium Explosion?

 At the beginning of the Cambrian Explosion, the already existant phyla suddenly and simultaneously expanded, meaning new species emerged quickly and at the same time. It is said that the Cambrian Explosion "had a long fuse," because there was a long build-up time before all of these new species emerged.

// beal. . . also most of the major phyla of animals appear in the fossil record after this explosion. it was a big leap forward. //

6. Describe a few adaptations essential for the invasion of plants onto land.

500 million years ago plants made adaptions to prevent dehydration; an example of this would be a coating of wax which slows the loss of water to the air.

// beal. . . note the word few. . . which means more than one. //

7. Scientific Hypothesis for the origin of life (briefly elaborate or explain each of these)

 a. The first cells may have originated by chemical evolution on a young Earth  The hypothesis is that life on Earth developed from nonliving materials that turned into aggregates that were capable of self replication and had a metabolism.

 beal. . . good!

 b. Abiotic synthesis of organic monomers is a testable hypothesis  Both A.I. Oparin and J.B.S. Haldane in the 1920’s stated that conditions on early Earth allowed for the synthesis of organic compounds from inorganic ones.

beal. . . good!

<span style="color: #ff6a00; font-family: 'Arial','sans-serif';">c. Laboratory simulations of early-Earth conditions have produced organic polymers <span style="color: #ff6a00; font-family: 'Arial','sans-serif';"> This hypothesis predicts that monomers link to form polymers without enzymes or other cellular equipment. Scientists produced polymers by dripping solutions of monomers into hot sand, clay, or rock.

beal. . . good. . . called dehydration synthesis!

<span style="color: #ff6a00; font-family: 'Arial','sans-serif';">d. RNA may have been the first genetic material <span style="color: #ff6a00; font-family: 'Arial','sans-serif';"> This hypothesis is supported because RNA can also function as enzymes. Scientists can, abiotically, create short polymers of ribonucleotides.

<span style="color: #800000; font-family: Arial,sans-serif;"> beal. . . what else. . . more here! RNA is used for coding and has multiple functions like mRNA, rRNA, tRNA, etc..

<span style="color: #ff6a00; font-family: 'Arial','sans-serif';">e. Protobionts can form by self-assembly <span style="color: #ff6a00; font-family: 'Arial','sans-serif';"> Protobionts can maintain an internal environment that is different form their environment. They also show some properties of life, metabolism, and excitability.

beal. . . good!

<span style="color: #ff6a00; font-family: 'Arial','sans-serif';">f. Natural selection could refine protobionts containing hereditary information <span style="color: #ff6a00; font-family: 'Arial','sans-serif';"> Natural selection favors RNA genes that are kept close to the RNA molecule, making them bond closer together.

beal. . . ah. . . you didn't answer the question. here we have an internal environmnet that can evolve seperately from the outside!

<span style="color: #ff6a00; font-family: 'Arial','sans-serif';">g. Debate about the origin of life abounds <span style="color: #ff6a00; font-family: 'Arial','sans-serif';"> Scientists cannot prove that these chemical processes created life on early Earth because they cannot prove or replicate it. Their findings show how it might have happened. They also debate where life evolved, in shallow water or by deep-sea vent <span style="color: black; font-family: 'Arial','sans-serif';">s.

beal. . . they can replicate some. . . like miller!

8. Describe the hypothesized conditions on earth when life arose. The hypothesized conditions were that earth’s atmosphere started as thick water vapor that eventually cooled and condensed into our oceans. They have linked water with life, therefore this is likely. Also, it is believed that earth had an electron-adding atmosphere, which set up chemical reactions. Volcanoes erupted and released nitrogen, nitrogen oxides, carbon dioxide, methane, ammonia, hydrogen, and hydrogen sulfide. Lastly, the energy sources needed for life could have been UV rays and lightning.

beal. . . good!

9. What did Louis Pasteur demonstrate with his experiment? [] Pasteur demonstrated how life could have started from nutrients and dust particles. This can be defined as spontaneous generation.

beal. . . umm. . . he demonstrated how life COULD NOT HAVE STARTED from nutrients and dust particles!

10. List the four stages for the formation of life. <span style="color: #ff4b00; font-family: Arial,Helvetica,sans-serif; font-size: 11pt;">a. ​ The abiotic synthesis of small organic molecules b. The joining of the small molecules into polymers c. The packaging of the molecules into protobionts droplets with membranes that maintained an internal chemistry differnt from that of thier surroundings <span style="color: #0b0a09; font-family: Arial,Helvetica,sans-serif; font-size: 11pt;">d. <span style="color: #ff4b00; font-family: Arial,Helvetica,sans-serif; font-size: 11pt;">The origin of self-replicating molecules that eventually ade inheritance possible

<span style="color: #800000; font-family: Arial,Helvetica,sans-serif; font-size: 11pt;"> beal. . . good!

<span style="color: #0b0a09; font-family: Arial,Helvetica,sans-serif; font-size: 11pt;"> 11. What metabolic processes would you expect to see in protobionts?

<span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 11pt;"> Protobionts could maintain internal chemistry different from that of its external enviornment. It could also "reproduce."

<span style="color: #800000; font-family: Arial,Helvetica,sans-serif; font-size: 11pt;"> beal. . . good!

<span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 11pt;"> 12. Why is RNA now thought to be the first genetic code?

RNA is autocatalytic, meaning it can cause reactions on its own. Before biotic organisms such as enzymes, RNA could have been used for ribosome catalyzed replication. It is also possible that it could have been used for aligning amino acids in polypeptid synthesis and nucleotides in a primitive form of self-replication. Early protobionts that had RNA with these abilities would have been better at surviving and would have passed down the trait to their offspring, eventually increasing in number through natural selection.

// beal. . . right. //

13. What did Oparin, Haldane, Miller and Urey accomplish? <span style="color: #3a3ab6; font-family: Arial,Helvetica,sans-serif; font-size: 11pt;"> <span style="color: #0000ff; font-family: Arial,Helvetica,sans-serif; font-size: 11pt;"> Oparin and Haldane independently postulated that a strongly reducing atmosphere could create the necessary ingredients for life. Miller and Urey tested this in an apparatus which would simulate the reducing atmosphere of early earth. The experiment yielded amino acids and organic compounds necessary for life. This supported Oparin's and Haldane's hypothesis.

<span style="color: #800000; font-family: Arial,Helvetica,sans-serif; font-size: 11pt;"> beal. . . good!

<span style="color: #0000ff; font-family: Arial,Helvetica,sans-serif; font-size: 11pt;"> 14. What are some of the possible locations for the first life forms? <span style="color: #ff6a00; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">Scientist J. B. S Halden suggested that a possilbe location for the first life forms were the depths of the early oceans. The depth of the early oceans were called the primitive soup from which life arose. Life forms probably formed at the depths of the ocean because there was no possible way for any life form to emerge from the conditions of the earth about four billion years ago with the earth being bombarded with rocks. Volcanoes were said to have sparked the first life forms on earth. When Miller did his experiment he used gases that were probably from when the earth first evovled, he first zapped the gas with an electric spark and after a few weeks the gas turned into brown water. Then later he experimented on the water and found that it had amino acids which are the building blocks of life.

//beal.. . . good. . . but note the word locations which means more than one.//