Macroevolution 1

Question 1

What is a fossil

Answer 1

direct evidence of organisms that lived in the past, remains or traces of once living organisms

Question 2

what is a Lagerstatten

Answer 2

fossil site with exceptional fossil preservation

Question 3

what was the Burgess Shale

Answer 3

• famous Lagerstatten from the Cambrian and has yielded many of the organisms that contribute to our understanding of the Cambrian explosion
• formed when an avalanche of fine mud carried animals into deep water
• animals buried in sediments free of oxygen -> remarkable preservation

Question 4

what is absolute dating

Answer 4

• can determine the number of years that have elapsed since an event occurred or the specific time when that event occurred
• can determine how much time has passed since rocks formed by measuring the radioactive decay of isotopes or the effects of radiation on the crystal structure of minerals

Question 5

what is relative dating

Answer 5

puts geologic events in chronological order without requiring that a specific numerical age be assigned to each event. used to describe the sequence of events

Question 6

what is the geologic time scale

Answer 6

representation of time based on the rock record of earth

Question 7

what is superstition

Answer 7

youngest layers on top, oldest layers on bottom

Question 8

what is lateral continuity

Answer 8

layers continue laterally over distances

Question 9

what is original horizontality

Answer 9

layers are first deposited horizontally and then may deform later

Question 10

what is cross-cutting

Answer 10

geological layers or intrusions that cut across other layers are always younger

Question 11

what is an index fossil

Answer 11

• fossil species that are used to distinguish one layer from another
• common, easily identified, found across a large area
• primate fossils often rare -> usually not good index fossils
• pigs + rodents more typically used bc they’re more common, widely distributed, evolve relatively rapidly

Question 12

what is carbon dating

Answer 12

• only useful for measuring things that were formed in the relatively recent geologic past
• organic material such as bones, wood, charcoal, shells
• radioactive decay of 14C in organic matter after removal from biosphere

Question 13

what is uranium-lead dating

Answer 13

• radioactive decay of uranium to lead via two separate decay chains
• 10,000-billion of years
• material dated: unranium-bearing minerals

Question 14

what is potassium-argon dating

Answer 14

• radioactive decay of 40K in rocks and minerals
• 1,000-billion of years
• material dated: potassium-bearing minerals and glasses

Question 15

what is radiometric dating

Answer 15

uses the half-life of isotopes to calculate the ages of rock layers based on the amount of daughter or parent isotope

Question 16

what percent of the parent isotope is present in 0 half lives

Answer 16

100%

Question 17

what percent of the parent isotope is present in 1 half life

Answer 17

50%

Question 18

what percent of the parent isotope is present in 2 half lives

Answer 18

25%

Question 19

what percent of the parent isotope is present in 3 half lives

Answer 19

12.5%

Question 20

what is the method for using radiometric dating

Answer 20

1. measure ratio of isotopes
2. convert to # to half lives
3. multiply by time for a half life