Chapter 8 Review

Front

What is the half-life of a radioactive substance?

Back

The time it takes for one half of the radioactive atoms in a sample to decay.

Front

How old is a rock or fossil that contains equal amounts of potassium-40 and argon-40?

Back

1.3 billion years old.

Front

If the half-life of uranium-232 is 70 years, how many half-lives are needed to reduce 10 g to 1.25 g?

Back

3 half-lives.

Front

What is a daughter atom?

Back

A stable atom that results from the decay of a radioactive atom.

Front

What percentage of rubidium-87 atoms will be left after four half-lives?

Back

6.25%.

Front

What are homologous structures?

Back

Features in organisms that share a common ancestor but have different functions.

Front

What are vestigial structures?

Back

Structures that have lost their original function through evolution.

Front

What are analogous structures?

Back

Features in different organisms that serve similar functions but do not share a common ancestor.

Front

What is radioactive decay?

Back

The process by which an unstable atomic nucleus loses energy by emitting radiation.

Front

What is the significance of half-lives in dating rocks and fossils?

Back

Half-lives help determine the age of rocks and fossils by measuring the decay of radioactive isotopes.