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 scientists describe life only in the seas and other bodies of water. precambrian time is the most recent time in earth’s history. precambrian time makes up 88 percent of earth’s history. the first birds appeared during the jurassic period. the basic units of the geologic time scale are periods, eras, and centuries. humans appeared during the cenozoic era.

Options (1), (4), (5) and (7)

Explanation:

The geological time scale refers to the sequential arrangement of all the major events, including the appearance of organisms and formation of rocks, right from the time of formation of the earth to the geologically recent time.

This time scale was constructed based on the study of rock layers that were observed on earth as well as from the study of the index fossils. These fossils are geographically widely distributed and were present for a relatively shorter period of time.

The precambrian time refers to the initial time of formation of earth when the earth undergone extensive geological process that led to the formation of the distinct core, mantle and crustal rocks. It includes the eons namely the Hadean, Archean and Proterozoic, ranging from about 4.6 billion years to 540 million years, covering almost 85-90% of the earth's total history.

The birds first appeared in the Jurrasic era when the theropod dinosaurs existed. The modern day birds are evolved from that ancestor.

Cenozoic era refers to the most recent era that ranges from about 65 million years back to the present time. This period is characterized by the evolution of various organisms and also the humans have first appeared during this era.

Thus, the correct answers are mentioned above.

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