Ch. 17 History of Life

Question 1

Did the formation of Earth happen billions or millions of years ago?

Answer 1

Billions (4.6)

Question 2

Did the appearance of the first life on Earth happen bya or mya

Answer 2

Millions

Question 3

Did the Cambrian Explosion happen bya or mya?

Answer 3

Millions

Question 4

Did the time of the dinosaurs happen bya or mya?

Answer 4

Millions

Question 5

How is biology related to geology?

Answer 5

It’s a major source of information about species of the past is from fossils. An organism is most likely to become a fossil if its dead body is deposited in an environment that lacks oxygen. Fossils are present in a layer of rock and geologists can study the rock and determine its age. Therefore, can estimate the age of a fossil.

Question 6

How do we determine the age of a rock layer?

Answer 6

With radioactive isotopes, they decay in a predictable pattern over long periods of time. The time is takes for half of a radioactive isotope to decay is that isotope’s half-life. Each radioisotope has a characteristic half-life. So the ratio of radioactive element to its decay products show how long the radioactive element has existed in the rock.

Question 7

Describe the ratio/relationship between 14C and 12C while an organism is alive and then dead.

Answer 7

The ratio of 14C to 12C is relatively constant in the environment and living organisms. In dead organisms, decaying 14C is no longer replenished, and the ratio of 14C to 12C decreases over time.

Question 8

Name six ways in which the Earth can change.

Answer 8

O2 levels have changed

Sea levels have changed

Climate has changed

Continental drift

Volcanic eruptions can change the entire Earth

Meteorite Impacts can change the entire Earth

Question 9

Name five ways events in Earth’s history can be dated.

Answer 9

Radioactive isotopes (1bya)

Dendrochronology (1000yrs)

Ice Cores (1.5mya)

Paleomagnetic Dating (20mya)

Rock Strata (100mya)