Question

which statements about geologic time are true? check all that apply.
scientists developed the geologic time scale as they studied rock layers and index fossils.
the fossil record helps scientists describe life only in the seas and other bodies of water.
precambrian time is the most recent time in earths history.
precambrian time makes up 88 percent of earths history.
the first birds appeared during the mesozoic era.
the basic units of the geologic time scale are periods, eras, and centuries.
humans appeared during the cenozoic era.

Explanation:

• Scientists developed the geologic time scale by studying rock layers (stratigraphy) and index fossils (which are useful for dating).
• Fossil record helps describe life on land and in water. So the statement about only seas is wrong.
• Precambrian is the earliest time, not the most recent.
• Precambrian makes up about 88% of Earth's history.
• First birds (Archaeopteryx) appeared in Mesozoic Era (Jurassic period).
• Basic units of geologic time scale are eons, eras, periods, epochs (not centuries).
• Humans (Homo sapiens) appeared in Cenozoic era (Quaternary period).

Answer:

• Scientists developed the geologic time scale as they studied rock layers and index fossils.
• Precambrian time makes up 88 percent of Earth’s history.
• The first birds appeared during the Mesozoic Era.
• Humans appeared during the Cenozoic era.