learning objectives 8

Question 1

Define half-life.

Answer 1

A half-life is the amount of time after which half the parent isotope atoms will have decayed into the daughter isotope.

Question 2

What is radiometric dating?

Answer 2

A method to determine the age of fossils using radioactive isotopes.

Question 3

What are isotopes?

Answer 3

Varieties of an element with different numbers of neutrons in the nucleus.

Question 4

Why are radioactive isotopes useful in dating fossils?

Answer 4

Because they decay spontaneously at a constant rate, allowing us to measure the age of a sample.

Question 5

What are parent and daughter isotopes?

Answer 5

A parent isotope is radioactive and decays into a daughter isotope.

Question 6

Provide an example of isotope decay.

Answer 6

14C → 14N and 238U → 206Pb.

Question 7

What is the half-life of 14C?

Answer 7

5730 years.

Question 8

How much of an isotope remains after three half-lives?

Answer 8

1/8 of the original amount.

Question 9

What is carbon dating useful for?

Answer 9

Dating recent organic materials (100-75,000 years old).

Question 10

What is uranium dating useful for?

Answer 10

Dating older rocks.

Question 11

When does the “clock” start for carbon-14 dating?

Answer 11

At death.

Question 12

When does the “clock” start for uranium dating?

Answer 12

When the rock solidifies.

Question 13

What was the Cambrian “explosion”?

Answer 13

The rapid appearance of many animal phyla in the fossil record around 535-525 million years ago.

Question 14

Why did phyla appear in the fossil record during the Cambrian Explosion?

Answer 14

Due to the evolution of hard body parts and larger organisms, which are easier to fossilize.

Question 15

Name some major events during the Paleozoic Era.

Answer 15

• Colonization of land by plants and arthropods.
• Evolution of terrestrial vascular plants.
• Colonization of land by vertebrates.
• Radiation of terrestrial amphibians and bony fish.
• Development of the amniotic egg.

Question 16

How was the carbon cycle disrupted during the Carboniferous period?

Answer 16

The decay of plant materials slowed, leading to the formation of coal and oil, which is now being burned and increasing carbon levels in the atmosphere.

Question 17

What was the Permian extinction?

Answer 17

The biggest mass extinction in the fossil record, caused by massive volcanic activity in Siberia, leading to climate change and ocean acidification.

Question 18

What happened during the Mesozoic Era?
A: - Radiation of dinosaurs.

Answer 18

• Radiation of dinosaurs.
• Emergence of small, nocturnal mammals.
• Replacement of earlier vascular plants with conifers and the emergence of angiosperms.

Question 19

What is continental drift?

Answer 19

The process by which continents formed a giant continent and then separated into today’s continents over time.