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195 Cards in this Set
- Front
- Back
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1. To which phylum do we belong?
What is the defining characteristics of our phylum |
Chordata (Chordates)
Defining feature is notochord: stiffened rod of dense tissue running along the length of the animal |
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2. What defines the vertebrate subphylum of the Chordates?
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A well-defined head with a brain and sensory organs
Also, generally a spinal column made of bone or cartilage |
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3. What are protostomes?
What are deuterostomes? |
Protostomes: the first opening when the blastula indents becomes the mouth (arthropods, mollusks, annelids)
Deuterostomes: the first opening becomes the anus and a new fresh opening forms the mouth |
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4. Are we protosomes or deuterosomes?
What is the closed invertebrates relative outside our phylum? |
We are deuterostomes
Echinoderms: star fish, sea urchins, sand dollars (we share a common ancestry - did not evolve from them) |
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5. What is the name of the geologic period nicknamed "The Age of the Fishes"?
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Devonian in the Palezoic
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6. When did the first vertebrate appear in the fossil record (time period name, approximate age)?
What type of animal was it? |
Early Cambrian (Cambrian explosion)
Approximately 540 million years ago Soft-bodied fish like creature called Haikouichthys |
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7. Are jawed or jawless fishes more successful today in terms of diversity?
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Jawed fishes are (jawless fishes came first though)
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8. What were the first fishes with armor plates like?
Who were the first impressive jawed fishes and what was unique about them? Are any armor plated fish left to menace the sea? |
Had no fins, jaw, bones, and little or no cartilaginous skeleton
Placoderms and they had very heavy armored plating No, placoderms were only around for a short period of time, but they dominated that Devonian period |
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9. Who are the jawed, cartilaginous fishes?
Have they changed much? |
Sharks
Since they first appeared in Devonian, they haven't changed much |
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10. What are ray-finned fishes?
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They have fins supported by thin bones
Bony, jawed fish Fishes we know and love: goldfish, Nemo, Perch, etc |
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11. Based on bone structure and genetics, which group of fishes is most closely related to the terrestrial vertebrates?
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The Osteolepiforms (lobe-finned fish)
Their strong lobe-fin allowed them to push into very shallow water and even onto shore |
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12. What about the fins make the Osteolepiform fishes the clear choice for one of our closest fossil fish ancestors?
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Osteolepiform fins show a series of strong bones leading to many thin fin supports
There are clear homologies with our limb bones: |
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13. What is the homologies with our limb bones
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both front and rear fins have a single upper bone (humerus/femur) and two lower 'arm' bones (radius and ulna/ribula and tibia)
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14. Skeleton of Osteolepiform.
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Osteolepiform
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15. Who are Tiktaalik?
What are it's fish-like and tetrapod-like features? |
Discovered in Late Devonian (latest,greatest fossil)
Fish-like: internal gills, fins, scales, streamlined shape Tetrapod-like: flattened head and body (like alligator), head is attached to neck (can turn head), fin has shoulder blade, 'upper' arm, ELBOW, lower 'arm', & beginning of wrist |
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16. Who are Acanthostega?
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Transitional creature in Late Devonian
FIRST TETRAPODS (creature w/ four legs) |
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17. What were their characteristics?
What did they use their legs for? |
1. Streamlined fishy shape
2. Webbed feet (8 toes) 3. Fin-like tail Legs used for swimming; could not walk on land well (flimsy rib cage flattened on land making it hard to breath) |
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18. Who was the Ichthyostega?
Is it adapted for land? Why? |
More terrestrial creature in Late Devonian
Better adapted for life on land: -thicker leg bones/fewer toes -thick ribs (lungs didn't get squished) |
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19. Did they evolve legs to walk on land or move in (shallow) waters?
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Probably to swim in shallow waters because Ichthyostega had canals in skull that in fish are used to detect pressure changes while swimming
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20. Skeletons of Tiktaalik, Acanthostega, and Ichthyostega.
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Skeletons
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21. What were the early amphibians like?
What did the shape of their body suggest? |
Flat-bodies, relatively large, short, sprawling legs, massive skulls, short neck
Shape of body suggest that it lived like an alligator, prowling in waters in search of prey |
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22. Where early amphibians good runners? Why?
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No, it was tough for them to run
They had a sprawling walk were they alternatively compressed one lung and then the other |
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23. Were the amphibians of the Paleozoic (Carboniferous and Permian) a small boring group or were they divers?
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There was some diversity in amphibian body form
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24. Why is Diadectes interesting, besides being a long dead Pittsburgher?
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1. Transitional creature: reptilian body and amphibian skull
2. World's first vegetarian |
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25. So what were the first tetrapods?
What about the way this group reproduces makes this a logical group to bridge the gap between fully aquatic and fully terrestrial lifestyle? |
Amphibians
Some began laying eggs on land and these we call amniotes (today amniotes includes birds, mammals, and reptiles) |
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26. What is the difference between anapsids, diapsids, and synapsids?
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Anapsid: no holes in skull behind eyes (amphibians/early reptils)
Diapsids: two holes in skull behind eyes Synapsids: one hole in skull behind eyes |
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27. Example of each.
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Skull holes
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28. Which type are we?
Which type are modern reptiles and dinosaurs? |
We are synapsids
Most reptiles are diapsids (includes dinos, lizards, snakes, alligators) |
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29. After amphibians, which group came next in time?
Which was the last of the three main living groups (amphibians, diapsids, synapsids) to emerge? |
Reptiles
Synapsids were the first to rule the Earth Diapsids were last to emerge |
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30. What are the three main groups of synapsids?
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1. Pelycosaurs (first and 70% of all genera by E. Permian)
2. Therapsids (second group) 33. Mammals (last and only surviving group) |
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31. What time period was the "age of the amphibians"?
What time period was the "age of the synapsids"? |
Pennsylvanian
Permian |
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32. Skeletion of representative of oldest major synapsid group.
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Pelycosaurs
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33. Why are pelycosaurs more reptilian?
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Large fins on some suggest that the creatures were essentially cold-blooded and needed morning sun for warmth
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34. The therapsids were next synapsid group. What made them different?
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1. More erect posture (less lizard like)
2. May have started to develop warm-bloodedness (live at higher latitudes - cooler) |
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35. Who was the common therapsid?
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Dicynodont - most abundant herbivore
Fat, compact body w/ short tails designed to slow heat loss |
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36. The cynodonts belong the the therapsid group of synapsids. Why are they important to the history of mammals?
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They were the most mammal-like of the theraspids (rich fossil record goes from reptilian to more mammal)
1. Walked like mammal (legs beneath body) 2. Rib cage closed off by muscular diaphragm 3. Powerful teeth and jaw |
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37. Cynodont structure
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Thrinaxodon
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38. By definition what makes the first mammal fully mammal?
To what time period does this date back to? |
Mammalian jaw bone
Late Triassic this is before the Age of the Dinosaurs (Jurassic and Cretaceous) |
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39. Synapsid skulls from most reptilian to fully mammal.
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Skulls
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40. What in particular about these skulls shows a transition?
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1. Expansion of lower jaw bone (several bones to one large one)
2. Synapsid opening changes (larger and merges w/ eye socket) 3. Teeth more differentiated |
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41. What is the name of one of the oldest, well preserved mammals?
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Megazostrodon
-nocturnal, warm-blooded, small size (mouse like) |
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42. What effect did the end- Permian and late Triassic extinctions have on the evolution of our synapsid ancestors?
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End-Permian: wiped out most vertebrate groups
-most synapsid carnivores died Late-Triassic: wiped out veggie dicynodonts and most cynodonts -mammals emerged thought |
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43. How did these extinctions affect the evolution of the reptiles?
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After End-Permian extinction, ecological nich for carnivores opened
-diapsid (reptile) carnivores diversified Reptile group radiated to fill ecological niches after L. Triassic extinctions |
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44. When was the age of the dinosaurs?
When was the age of the mammals? |
Jurassic and Cretaceous
Cenozoic |
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45. Why do mammals have larger brains?
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Probably being warm blooded and have a high metabolism is a necessary precondition for having a large, expansive brain
-had sharp hearing (needs more processing) -life in trees in complex |
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46. During the dino rule how were mammals?
What role does extinction play? What happened w/in 15 Myr of dino death? |
Small, rodent-size, nocturnal (lost color vision)
Extinction wipes out a dominate group and allows new, minor groups to take over Evolutionary radiation (bodies differentiated!) |
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47. When did the first true primate appear in the fossil record?
How did they look? How do we know is was a primate? |
55 Myr (E. Eocene)
Cross between lemur and squirrel Key features in skull and teeth are exclusively primate and had flat fingernails (not claws) |
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48. What three distinguishing primate characteristics related to our tree-dwelling ancestries are highlighted by females painting their nail bright colors?
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1. Had grasping hands and feet
with FLAT NAILS instead of claws 2. Recovered ability to see color via gene mutations 3. Flattened face and eyes closer together gives depth perception |
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49. Many humans like to throw and catch objects. What key factor related to this activity is directly due to our ancestor's past adaptations?
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Flexible shoulder joints - allowed for swinging from branch to branch
Eyes closer together and flattened face gave depth perception which is handy for catching balls |
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50. Those humans who avoid fertility drugs generally have only one baby, whereas many mammals have liters. How does this relate back to our tree-dwelling ancestors?
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Primates take care of their young for longer periods of time, delay sexual maturity, have two mammary glands
Having only one baby may have been essential to allow adequate instruction in complexity of social tree life |
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51. We may even be intelligent because we were relatively large, tree-dwelling animals. Why?
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A larger brain helps them to cope with the variations of life in trees and with social interactions
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52. What skeletal differences are seen in tree-dwelling versus bipedal primates?
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1. Apes have longer arms, stronger shoulder blades, and shorter legs
2. Neck bone of apes attaches at back of skull (ours at bottom) 3. Apes have larger pelvis (ours is like basket to support guts) 4. Apes have opposable big toe for tree climbing |
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53. What is the age of the oldest primate fossil that is taking the first steps towards human-like characteristics?
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6-7 million years old
Sahelanthropus from Chad |
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54. What characteristics did Sahelanthropus have that were more human like?
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Teeth and flatter (vertical) face are more human-like
*brow ridge and brain size are ape-like |
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55. In what ways did the Australopithicus species mark a transition between ape-like
and human? |
Ape-like:
-shorter -heavy brow ridge (strengthened skull so could eat coarse plant material) Human-like -broad pelvis -support upright walking |
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56. Did this genus climb?
What is it a transition between ape-like tree climbing and human-like walking and running? |
It was an able tree climber: long fingers and arms in length between apes and humans
It could walk though (not as good as humans) and climb trees (not as good as apes) |
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57. When was Australopithicus alive?
When did our genus, Homo, appear? |
4.2 to 2.3 million years ago
2.4 million years ago |
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58. Was there a huge and sudden jump in brain size going from Australopicthicus to Homo?
What does this suggest? |
Big jump: 450 cm3 to 760 cm3
Suggests we are missing a vast gap...need more skulls between 2.4 and 1.8 million years old |
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59. What was one key thing that the first Homo species used that has been the hallmark of human kind ever since?
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TOOLS!! (and larger brains)
Sharp flakes were chipped off a central stone called a core *suggests early Homo ate a lot more meat than Australopithecus |
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60. How may have climate change forced our ancestors out of trees and onto the ground?
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Major climate (2.6 to 2.4 Myr) change produced glaciers in the artic and a shift from forests to grasslands, esp in E. Africa
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61. So why did Australopithecus disappear?
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Like modern baboons they probably found it tough to be forced out of trees
Like baboons, they probably weren't fast on the ground and were eaten up by predators |
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62. Why did one group survive?
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Happened to be bit smarter (bigger brain?) or leaved in area with few large predators
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63. Why do some think that leaving trees was a good way to allow us to become a more intelligent species?
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Evolved bigger brain because could give birth to babies with larger heads who spend first year rapidly growing their brains
You can set kids down and get other stuff done (some how this relates to above) |
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64. Related to this, why are human babies born with their brains much less mature than other species on the plante?
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Size of babies brain is limited by woman's pelvis
Human babies are essentially born prematurely b/c woman's pelvis cannot pass a fully mature baby brain (BUT brain grows TONS during first year) |
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65. So, what are the conclusions about the origin of life on other Earth-like planets?
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Simple (~prokaryotic) life seems likely
Started quickly on Earth <300 Myr after late bombardment So if rocky planet warm enough to host liquid water and more than 2 Byr probably have primitive life |
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66. What about multicellular life on other planets?
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Multicellular life on old (>4 Byr) Earth-like planets may not be surprising
Need oxygen though which means need oxygen-producing photosynthesis - appeared early on the Earth (may be likely on other E-like planet) |
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67. What about vertebrate-like life on other planets?
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Quite likely in oceans of old (>4 Byr) E-like planets
First bilateral animals appeared along side first multicellular life - vertebrate appeared almost immediately after |
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68. What about terrestrial life on other planets?
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0.2 Byr for life to leave ocean but warm-bloodedness is probably pre-req for intelligent life
Well, all planets get colder moving toward poles so all w/ cold weather provide reason for warm-bloodedness to evolve |
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69. What were the three things that made life possible on Earth?
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1. Plenty of organic compounds
2. Energy to drive the chemistry of life 3. Liquid water at Earth's surface |
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70. Is the supply of organic compounds in the solar system likely to be restricted to just Earth, or were they at least initially probably widespread?
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Chondrite meteorites and comets are packed w/ organic compounds
Same compounds could have been produced inorganically on Earth Supply of raw materials should not be a problem for any planet in our Solar System and probably elsewhere |
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71. What are the two source of
energy that drive life processes on the Earth? |
1. Internal energy: Earth is large enough that its interior is still hot
2. Solar energy: drives circulation of atmo, weather, oceans, photosynthesis |
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72. How does internal energy vary with size of planet?
How does solar energy vary with distance from sun? |
Need to be large enough to have hot interior
All planets orbiting a star get sunlight but amount varies as a function of distance from star |
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73. How do we determine solar energy on other planets?
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Sunlight planet X receives =
(Earth sunlight/distance2) |
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74. Why does liquid water seem like such a critical factor for life as we can conceive it?
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1. Many organic compounds dissolve in water, which allows them to do the cellular
chemistry that drives life 2. Water itself participates in many reactions |
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75. Why not liquid ethane or methane? What key advantages does water have?
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1. Wide stability range means it stays liquid over more extreme seasons
2. It's liquid at relatively high temperature (this affects chemistry by increasing reaction rate) |
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76. Why else is liquid water great?
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1. Polar molecule (useful chemistry)
2. When it freezes, its solid (ice) floats -hard to freeze our ocean b/c sea ice floats on ocean and insulates underlying water (if sea ice sank lakes and oceans could rapidly freeze) |
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77. What signs might we look for on a planet that it has adequate internal energy to fuel hydrothermal systems?
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Evidence for Hydrothermal Activity:
1. Young volcanic landforms 2. Some form of plate tectonic indicating a geologically active surface 3. Hydrothermal activity driven by internal heat leaches Fe,S,and others from rocks bacteria love |
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78. What about what we look for when it comes to a planet getting enough sunlight?
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Look for:
1. Proximity to star 2. Right greenhouse effect |
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89. Why do we tend to cross Mercury off our list of planets that might host (or have hosted) life?
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1. Virtually no atmosphere
2. Preservation of craters from early bombardment suggests geologically inactive - thus no internal heat 3. Bone dry 4. Sunny side = 425 C 5. Dark side = -150 C |
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90. If Earth were at the position of Venus, its average surface temperature would be tropical. What is Venus' temperature and why is it so hot?
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Surface temperature is 450 C (850 F)
This is because the atmosphere of Venus is very rich in CO2 If Venus had the Earth's atmosphere, its closer position to the sun would give it an ave temp of 95 F |
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91. Is there evidence for potential energy for hydrothermal systems on Venus?
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1. Topographic relief: some geological process made highlands and lowlands
2. No sign of early bombardment preserved on Venus 3. Many volcanoes and relatively fresh appearing lava flows 4. Lack of craters implying an active planet |
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92. Why is life extremely unlikely on Venus?
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1. It's so hot on the surface, many organic compounds cannot survive
2. No liquid water (not even water vapor in atmosphere) |
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93. Since Earth and Venus likely started out as similar planets, why did Venus end up as a hellishly hot hell hole, that's bone dry, with a super dense atmosphere?
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Venus is about 30% closer to the sun than Earth so it gets twice the solar heating that the Earth dose
*Also there was a run away greenhouse effect |
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94. Why did Venus experience a run away greenhouse effect?
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1. Venus' surfaced warmed to point where early oceans gave off a lot of water vapor (this is greenhouse gas)
2. Warmer air holds more water vapor, global warming increases H2O vapor in atmo provoking more global warming 3. Above a certain temp, more warming adds more vapor which increases warming until the ocean boils(runawaygreenhouse) |
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95. If Venus boiled off its oceans, why is the atmosphere bone-dry? Where did all the water go?
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Venus got so hot that water vapor was carried into upper atmosphere (stratosphere) - on Earth is stays in lower atmosphere (troposphere)
The H floated off into space (once free, its light enough to escape gravitational field of Venus) b/c H2O in upper atmosphere is split by UV light from Sun |
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96. What happened to the oxygen left behind?
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It reacted w/ Fe and S in surface rocks also disappearing from the atmosphere
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97. Why does Venus have a thick (dense) atmosphere dominated by CO2?
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The lack of oceans and life on Venus eliminated any way of removing volcanic CO2 from the atmosphere
This makes it VERY HOT! |
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98. How does the mass and average surface temperature of Mars compare to the Earth?
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1. Average surface temperature is -53 C (-63 F)
2. Mars is only 10% the mass of Earth (smaller mass means it is likely to have cooled down a lot faster) |
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99. The atmosphere of Mars is mostly CO2 and dry, like Venus, and yet it is much colder. Why?
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Even though atmosphere is mostly CO2, it's so thin that it doesn't make up for weak solar inputs
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100. Does Mars appear to be geologically dead like Mercury?
What is the evidence? |
1. Topography: crater highlands (old) and smooth lowlands (younger)
2. Appears to have volcanoes BUT they have impact craters (very old and inactive) 3. WAIT! a meteorite from Mars happens to be fairly young volcanic rock suggesting some volcanic activity is still on-going |
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101. What is the evidence for on-going internal heat on Mars?
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A meteorite from Mars happened to be fairly young volcanic rock (< 100 Myr)
So may still have enough internal energy to potentially fuel hydrothermal systems and keep any groundwater present in liquid state |
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102. What is the evidence for flowing water on Mars?
What suggests that most of the water flow was very ancient? |
It is suggested by drainage networks
Small craters suggest ancient water flow and most evidence for flowing water occurs on ancient parts of Mars (started out w/ nice wet climate) |
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103. What suggests that some flow was quite recent?
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There is an 'apron' of sediments burying dunes and dunes are young!
Evidence that waters flowed across surface in last 10s of Myr Also, groundwater from deeper levels may occasionally flow onto the surface as a result of volcanism or spring thaws |
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104. What are potential reserves of atmospheric CO2 on Mars today
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There are water and CO2 ice caps (they grow and disappear w/ Martian seasons)
May be some limestone-type rocks hosting CO2 |
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105. Why are planetary size and the existence of a magnetic field related?
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Because of a small size (like Mars) there is faster cooling
As a result its metallic core no longer circulates and thus the planet (Mars) has not magnetic field |
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106. What importance does the lack of a magnetic field have to the atmospheric history of Mars?
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Billions of years ago Mars' magnetic field died when core solidified
When its magnetic field dropped, the atmosphere was exposed to the sand-blasting effects of the solar winds (our magnetic field shields us from subatomic particles shot by at us by Sun) |
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107. Where did the water go that once flowed across Mars?
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Probably lost like it was on Venus
UV radiation split the H2O and H floated away (oxygen was consumed by reacting w/ Fe in rocks - orange color) |
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108. So what are four possible reasons for why Mars' atmosphere is so thin?
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1. Some of atmo is frozen in water and CO2 ice caps
2. No magnetic field b/c of small size 3. Oxygen was consumed when water was split (no ozone created like we have) 4. Early meteor bombardment blasted much of its atmosphere into space |
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109. What are asteroids?
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1. Blocks of rock and/or metal
moving in orbits between Mars and Jupiter 2. Small and have no atmosphere 3. Very, very cold |
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110. Why are Jupiter and the other gas giants unlikely places for life?
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1. Nearly all H and He (like Sun)
2. No solid surface (may be core of metal & rock in deep interior) 3. Vigorously circulating atmosphere 4. Basically they are violently windy gas giants (vertical winds make hurricanes weak/pathetic) |
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110. Why could life possibly exist within the atmosphere of Jupiter?
Why could this not be possible? |
The upper atmosphere is cold but it gets warmer as you descend into it as at 100 km, it's warm enough for liquid water
But, the strong vertical winds would carry any life first down into incredibly hot temperatures and then back up to extremely cold ones |
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112. Why are the normal sources of internal energy (heat of accretion, radioactive decay, core crystallization) seen as inadequate sources of energy for life on the 80-odd moons around the gas gaints?
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They are small bodes (2 largest only slightly larger than Mercury) so should have lost all of their original heat of accretion
Small bodies lose their heat faster than it is generated by radioactive elements |
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113. Why is solar energy seen as an inadequate source of energy for life on the 80-odd moons around the gas giants?
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Amount of sunlight reaching moon of Jupiter is 0.04 times that of Earth (too little give any real warmth)
Their small size means small gravity so have essentially no atmosphere w/ which to retain any solar heat |
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114. Are all of the moons of the outer planets dead?
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Io, Europa, and Ganymede are not gray and uniformly cratered like our moon
Lack of craters over their surfaces suggest they are geologically active |
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115. Which is moon is geologically dead?
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Callisto
It is heavily cratered |
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116. What is the source of energy for these geologically active moons?
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Jupiter and its moons formed like a mini-solar system
Consistent change in proportion of high vs low temperature solids making up each moon suggests that they condensed from a mini nebula that formed around Jupiter as it was forming Also, tidal friction (constant flexing back and forth produces a lot of heat) |
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117. Which of the three large geologically active moons of Jupiter is characterized by incredibly active volcanism?
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Io! Surfaced is covered with volcanoes and new/old ones go quick on the time scale of wks
It is the most volcanically active body known |
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118. What is the position of Io relative to the other three with respect to Jupiter?
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Io has a slightly elliptical orbit around Jupiter
When Io is closer, more a ellipsoidal shape. As is moves away, more a spherical shape This creates tidal friction which produces a lot of heat (like kneading Silly Putty back and forth) |
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119. Why is Io an exotic yellow-orange color?
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The yellow, oranges, and reds are sulfur compounds other than SO2
It is the eruptions that provide lots of sulfur to give Io its color *(molten rock passes through sulfur-rich crust) |
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120. Is Io a great place to look for life?
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No there is no water on Io and the extreme levels of volcanic activity make it unlikely that life could have originated or survived
It does reveal possible importance of tidal friction in producing heat needed to sustain life |
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121. Which of the geologically active moons of Jupiter is characterized by an icy surface?
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Europa
Exterior is made of solid water ice cut by many fractures and cracks - many fractures but few craters |
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122. Why do we think Europa is geologically active?
Does lava flow? |
Lack of craters, fracture systems, and broken ice
Europa sees 'eruptions' of liquid waters |
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123. Why is Europa less active than Io?
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It is farther from Jupiter so the gravitational forces are reduces and thus heating from tidal friction is reduced
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124. What is the prospect of life existing on Europa?
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It is believed that beneath a layer of solid ice there is a salty liquid ocean
If tidal heating has warmed up the rocky interior enough it is possible that hot springs support life beneath the cold surface of the moon (life would be bacteria) |
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125. What are the limits to how advanced and abundant this life can be?
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Eukaryotic organisms living near the deep sea vents also depend on oxygen that filters down from the surface (not just chemistry of the vents)
Without oxygen produced by photosynthesis at the surface, only relatively small populations of prokaryotes would survive at hot springs |
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126. Which moon is the largest?
What is the surface like? |
Ganymede - it is covered in ice like Europa
Heavily cratered dark areas & less cratered light areas Large blocks of dark ice have broken up in an icy equivalent to plate tectonics |
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127. Is life possible on Ganymede?
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It experiences weaker tidal forces than Europa, but larger size means that radioactivity may supply significant heat
If liquid ocean exists beneath 150 km of solid ice sparse, primitive life may exist (tough to discover) |
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128. Callisto is undifferentiated. What does this say about the long-term geologic history of Callisto?
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Undifferentiated (no internal layers) indicates that it has never had enough heat to even completely melt ice
May be salty liquid water below surface but source of heat is not tidal friction (must be radioactivity) |
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129. What is unique about Titan?
Which planet does it orbit? |
Only moon to have a substantial atmosphere, it is mostly nitrogen but no oxygen
*surface pressure is 1.5 times the Earth's pressure Orbits Saturn |
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130. Why do we think that liquid something (methane) has flowed across Titan's surface?
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Landscape has pebbles of ice or rock and some have scouring around their bases (flowing wind or water)
Titan is so cold that solid methane could evaporate and perhaps form big drops of slowly falling (low gravity) rain Also there is low crater density and branching drainage networks suggesting methane rain and erosion |
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131. As far as life goes, what might make Titan really interesting to study?
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Evidence for volcanism suggest internal heat and possibly a subsurface ocean of water and ammonia
Prospects for life seem dim, but great place to study pre-biotic organic chemistry |
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132. What is Triton?
Is it geologically active? |
Neptune's moon
Very cold, but lack of crates suggest surface less than 10-100 million years old (must have internal heat to keep geologically active) |
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133. Why aren't we considering the moons of Jovian (outer) planets orbiting other stars in our search for extraterrestrial life?
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1. If life exists, it would be virtually impossible to detect b/c it will live beneath the ice
2. Such life is certainly going to be primitive |
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134. Why do we think that rocky planets throughout our galaxy will start out more or less the same as the Earth and other inner planets of our Solar System?
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We assume they start with out w/ rocky, oceanic, and atmospheric conditions like the early Earth
Nothing about the elements we've got here seems rare |
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135. How do we figure out what the habitability zone is for our sun?
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Use a global climate computer model to stimulate what happens to global climates as you move the Earth closer to the Sun
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136. Optimistically, how close can be get to the sun before experiencing a runaway greenhouse effect?
Pessimistically how close can we get? Which estimate are climate researchers happier with? |
Go as close as 0.84 AU
Not go closer than 0.95 AU Happier with 0.95 AU limit so we're almost as close as we can get and still be habitable |
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137. Optimistically how far can a habitable planet be from the Sun until it freezes up?
Pessimistically how far? |
1.7 AU
1.4 AU before atmosphere is cold enough for CO2 to rain out reducing greenhouse effect so become a frozen wasteland |
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138. What does evidence for water on Mars suggest about the habitability zone?
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Suggests it should extend to at least beyond 1.5 AU (where Mars is)
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139. How many planets fall within the optimistic limits of the habitability zone?
Where is the habitability zone restricted to? |
Venus, Earth, and Mars
Clearly restricted to inner solar system |
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140. Why does the habitability zone migrate farther from the Sum over time?
Has the Earth always been within the habitability zone |
Over geologic time, the Sun has heated up so as it warms up, the habitability zone moves outward
It has always been withing the conservative estmiate |
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141. When will the Earth leave the conservative limits of the habitability zone?
What about the optimistic limits? |
Leave conservative in 0.6 billion years
Leave optimistic in 3 billion years |
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142. Mars will eventually be within the optimistic habitability zone for a planet w/ Earth's atmospheric composition. Does this mean Mars will be habitable?
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Well we may not have the resources to make the move
Will Mars get a nice climate 1.5 billion years from now? Or will we have destroyed it for short-term profits? |
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143. When will the Sun fry us to a crisp?
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In about 5 Byr the Sun will enter the red giant phase
BUT Earth will probably get too hot ~0.6 Byr from now When averages temps exceed 50C in about 1.3 Byr it is likely only microbes will be left alive |
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144. How will the Sun cause the Earth to convert more of its atmospheric CO2 into solid limestone?
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Increased solar inputs should cause CO2 levels in the atmosphere to decrease
This is b/c solar increase warms planets which causes silicate mineral weathering rates to increase which should increase the rate at which limestone is formed in oceans |
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145. How will this affects the Earth's future?
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As solar inputs increase, planet gradually warms and atmospheric CO2 dramatically decreases over next 0.9 Byr
Low CO2 will stabilize temps a little despite increased solar output but by about 1 Byr from now, solar output will warm planet even w/o much CO2 in atmosphere |
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146. When will photosynthesis get shut down?
How does this affect animals? |
Plants find it hard to survive as CO2 drops (die if below 10 ppm)
Plants and thus animals will die out only 0.8 to 0.9 Byr in the future |
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147. Do these results attempt to get the minimum time we have left on the Earth before it runs out of CO2?
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They estimate the EARLIEST reasonable demise
Earth could well remain habitable for more than 1 Byr |
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148. Why is it so hard to spot exoplanets?
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Stars are bright and planets give off only dim reflected light which is tough to spot against brilliant glare from star
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149. Planets more distant from a star might seem easier to spot, but they reflect very little light, why?
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Less sunlight reaches them so there is less light for them to reflect back
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150. Most exoplanets have been discovered by how they influence their star. What is this influence?
How do we detect it? |
The Doppler Effect
1. As planet orbits star, both orbit a common center of mass that's closer to star 2. Stars w/ planets move around a central spot in response to the gravitational tugs from their planets (star rotates) 3. Search for exoplanets has been search for wobbling stars (compression and decompression of light waves) |
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151. In what three ways are nearly all exoplanets different from those of our solar system?
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1. Most are larger than Saturn
and many are many times larger than Jupiter (gas gaints) 2. Most orbit much closer to their star than does Jupiter, or even Earth or Mercury so they orbit star in few days 3. Most have orbits that are much more eccentric (travel in big eclipses) |
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152. Are these planetary systems necessarily a representative sampling of all possible planetary systems?
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No because:
1. Larger masses force star into larger wobbles, which are easier to detect 2. Rapid rotation around host star also make detection much easier |
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153. Why might the gas giants be so close to the star?
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Star may not have produced early strong winds (T-tauri phase) to clear inner disk of gas and ice
Gas and ice in planetary disk may have slowed down the gas giants in the outer disk causing them to migrate in towards the star |
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154. Why is it important to understand how frequently gas giants migrate in from their outer orbits to near star orbit?
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It's important to understand what is normal, if Jupiter moved into our inner solar system, it would either absorb
or eject habitable terrestrial planets from the solar system |
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155. How may have elliptical orbits formed?
What do elliptical orbits do habitable planets? |
Collisions or gravitational interactions between Jupiter-sized planets in early planetary formation ejects one
planet from star system and flings other into elliptical orbit Elliptical orbits tend to fling smaller habitable planets out of inner areas of star system |
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156. From what they've seen so far, do planets form only around a few certain kinds of stars or have they formed around all sorts of stars?
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All sorts of stars
-binary star system -three star system -orbit a white dwarf and a pulsar -a red giant whose core has gone to He fusion -orbit even a brown dwarf |
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157. What is the system like that is for the most like ours?
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It has three planets:
1. Twice size of Jupiter 2. Half size of Jupiter 3. Twice size of Earth |
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158. In what way could detecting light reflected from a distant planet potentially be a vital step in obtaining evidence for extraterrestrial life?
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If we have sufficiently powerful telescopes we can look at spectrum of light reflected off a distant planet
Certain atmospheric compounds absorb (do not reflect) certain wavelengths of life. Thus, we can get info about composition of atmosphere |
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159. What good is information about the composition of the atmosphere?
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Need to see absorption related to CO2 (all three terrestrial planets have it)
Absorption related to water (only Earth shows that) Diagnostic sign of life, ozone (comes from photochemical reactions involving oxygen) |
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160. What is one of the principle activities of SETI?
Are we likely to pick up alien TV broadcasts? |
Search for Extraterrestrial Intelligence
They use huge radio telescopes to look for radio broadcasts from distant planets Not unless we have more powerful equipment, zone right in on the planet, or if they send out usually powerful radio transmissions |
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161. There are a hundred billion galaxies out there. Why aren't we spending any time worrying about life in these many galaxies?
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Galaxies outside our own are so distant that they aren't worth considering (too difficult to detect life in other galaxies)
We still have 100 billion or so stars that potentially have planets around them |
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162. What fives things are required to form habitable planets?
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1. Accumulation of heavy elements (heavier than He) through nucleosynthesis
2. Far enough away from other stars to avoid collisions and especially nearby supernovas (give off huge shock waves and intense radiation) 3. Suitable star to orbit 4. Star needs to be old enough to give time for life to have evolved 5. Can't be too old or the gradually warming star may have pushed all of the CO2 into the limestone |
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163. Where is the highest density of stars?
What does the disk contain? What is the halo? |
Highest density of stars is in the central bulge
Disk contains the stars that make up the spiral arms of the galaxy The halo is a nearly invisible cloud of stars above and below the disk (very low density of stars in halo) |
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164. Which parts of a galaxy will first acquire the heavy elements needed to planetary construction?
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Central bulge becomes enriched
first Has highest density of stars, thus producing most supernovas which produce huge clouds enriched in heavier elements |
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165. Which parts take longer?
Which parts are unlikely to get enough to build rocky planets? |
Inner disk comes next in terms of star density and heavy element production, followed by more distant parts of the disk
Halo has such low density of stars that it has low potential for clouds enriched in heavy elements |
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166. Which parts have the highest risk of collision with
other stars? |
Bulge of star - star density high enough to make a collision significantly likely
over 5 Byr of time |
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167. Which parts are have high risk of experiencing radiation from a nearby supernova?
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Both the bulge and inner galactic disk host a significant risk of a nearby supernova sterilizing an otherwise habitable planet
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168. In general, how does the zone of maximum habitability change over time in a galaxy?
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When young, inhospitable b/c of frequent supernovas
Middle-aged, a zone of habitability forms outside the central bulge and innermost disk Older, on going nucleosynthesis allows habitability zone to migrate further out |
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169. Why does the central area become less habitable as a galaxy evolves?
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There is a suggestion that areas too rich in heavy elements make planetary systems that have huge outer planets that migrate inward, destroying inner planets
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170. Which region on graph has too many supernovas?
Which region is too metal poor? Which is too metal rich? |
Central area (galactic center)
Outer reaches where there are too few stars Central area |
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171. Graph of Evolution of Galactic Habitability
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Graph
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172. Why does the graph showing the potential of intelligent life look different from the other graphs?
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If it is typical that it takes 3.5 Byr for I.L. to evolve, then max number of probable life originations leading to I.L. occurred 5 Byr ago
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173. Graph of Intelligent Life.
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Graph
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174. What is the relationship between the size (mass) of a star, its brightness, its longevity, and its relative abundance in the galaxy?
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Larger stars (more massive) have higher luminosity, shorter lifetime and less percent of all stars
Smaller stars have less luminosity, longer lifetime, and are more abundant |
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175. Relative to the Sun, what size stars burn out too quickly for intelligent life (or even any life) to evolve?
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Stars more than 1.5 times the mass of the Sun do not last more than 2 Byr (these are rare ~3% of total stars in galaxy)
The largest stars may not even last long enough for planets to form |
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176. What size live long enough for intelligent life to potentially evolve?
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Small stars live much longer than the Sun and are much more common
K and M-type comprise 90% of all stars in galaxy |
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177. What are the three problems with forming habitable planets around some K and especially M-type stars?
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1. Give off far less heat making habitability zone closer to star and narrower
2. Tend to have frequent violent flare-ups 3. Tiny habitability zone makes a planet in the zone rare |
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178. What do planets orbiting the habitability zone of K and M-type stars experience?
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Strong tidal friction
This causes one side of any planet to always face the sun (one side gets very cold and CO2 would freeze out) |
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179. Stars and habitability zone and tidal locking radius.
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Graph
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180. What percentage of all stars are the right size to be habitable?
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15% of 100 billion stars
So 15 billion stars are habitable saying all G and half of K-class stars are long lasting and warm enough for intelligent life |
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171. Graph of Evolution of Galactic Habitability
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Graph
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172. Why does the graph showing the potential of intelligent life look different from the other graphs?
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If it is typical that it takes 3.5 Byr for I.L. to evolve, then max number of probable life originations leading to I.L. occurred 5 Byr ago
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173. Graph of Intelligent Life.
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Graph
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174. What is the relationship between the size (mass) of a star, its brightness, its longevity, and its relative abundance in the galaxy?
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Larger stars (more massive) have higher luminosity, shorter lifetime and less percent of all stars
Smaller stars have less luminosity, longer lifetime, and are more abundant |
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175. Relative to the Sun, what size stars burn out too quickly for intelligent life (or even any life) to evolve?
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Stars more than 1.5 times the mass of the Sun do not last more than 2 Byr (these are rare ~3% of total stars in galaxy)
The largest stars may not even last long enough for planets to form |
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176. What size live long enough for intelligent life to potentially evolve?
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Small stars live much longer than the Sun and are much more common
K and M-type comprise 90% of all stars in galaxy |
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177. What are the three problems with forming habitable planets around some K and especially M-type stars?
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1. Give off far less heat making habitability zone closer to star and narrower
2. Tend to have frequent violent flare-ups 3. Tiny habitability zone makes a planet in the zone rare |
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178. What do planets orbiting the habitability zone of K and M-type stars experience?
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Strong tidal friction
This causes one side of any planet to always face the sun (one side gets very cold and CO2 would freeze out) |
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179. Stars and habitability zone and tidal locking radius.
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Graph
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180. What percentage of all stars are the right size to be habitable?
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15% of 100 billion stars
So 15 billion stars are habitable saying all G and half of K-class stars are long lasting and warm enough for intelligent life |
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181. Why do binary stars cause yet another problem when it comes to planetary habitability?
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50% of all stars are binary meaning two stars orbit one another
Habitable planets are only possible around binary star systems if they can maintain a long-term stable orbit in a habitable zone Maybe 1/3 to 2/3 of the binary stars potentially host planets in stable orbits w/in the habitable zone |
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182. About how many stars seem to be potentially habitable?
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'Only' 7 to 13 billion (out of 100 billion)
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183. In general what is the Drake equation?
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Estimates the probability of there being other intelligent life forms in our galaxy
N=(Ng x Fhstar x Fpan x Fhplan) x (Flife x Fintel x Ftime) |
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184. What are the parts of the Drake equation?
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N = # of intelligent species in our galaxy
Ng = # of stars in Milky Way Fhstar = fraction of habitable stars Fplan = fraction of habitable stars w/ planets Fhplan = fraction of planetary systems w/ habitable inner rocky planets |
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185. What are the parts of the Drake equation?
|
Flife = fraction of habitable planets w/ life
Fintel = fraction w/ life that have evolved I.L. Ftime = fraction of the lifetime of planet in which, on average, intelligent life lives |
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186. How many Earth-like planets are there?
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3.5 to 7 billion
350 to 700 million 70 to 150 million (still a lot!) |
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187. In terms of the biological terms, how likely is it that life will arise on any given Earth-like planet?
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We don't know how life really started so we can't assign a number between 0 and 100 realistically
Some scientist argue that life is inevitable on Earth-life planet |
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188. What about intelligent life?
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Took 3.5 billion years after life emerged for it to become intelligent
BUT, vertebrates started right along /w most other multicellular life in the Cambrian and it 'only' took 540 Myr after this point for intelligent life to emerge |
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189. How long does intelligent life last?
|
On average, an Earthly species last 1 Myr
Will we last more because we are 'intelligent' or will our animal emotions and breeding instincts win out over our higher more rational intelligence |
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190. What is Sagan's estimate of f(life) x f(intel) x f(time)?
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He says f(life) x f(intel) is 1/300 - thus 1 out of every 300 Earth-like planets would evolve both life and intelligent life
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191. What are the cases with f(time) though?
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Case 1: blow self up in 50 yrs then civilizations are so short lived only one lasts at a time (we're alone today but other existed in past)
Case 2: Last 1 Myr like average species then 3,000 intelligent civilizations are alive right now Case 3: Last longer like 500 Myr, then N could be 3 million civilizations |
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192. What do we need to travel to other planets?
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Space craft that travels at speed near that of the speed of light
Currently we go 1/10,000th the speed of light |
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193. What about rocker fuel?
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Need to load more fuel on rocket to go faster but this adds mass which makes higher speed hard to attain
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194. When will the smallest spacecraft reach the nearest star?
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4,000 years
Nearest star w/ planets is 10 light years away so at current speeds it would take >50,000 years |
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195. What are some alternative rocket fuels?
|
1. Series of small hydrogen bombs could push space craft
2. Master fusion - would get us to 10% the speed of light 3. Matter and anti-matter collisions - 100% efficiency and 90% of the speed of light |
