How Were Conditions on the Early Earth of More Than

question 49

Multiple Choice

How were conditions on the early Earth of more than 3 billion years ago different from those on today's Earth?

• A) Only early Earth was intensely bombarded by large space debris.
• B) Only early Earth had an oxidizing atmosphere.
• C) Less ultraviolet radiation penetrated early Earth's atmosphere.
• D) Early Earth's atmosphere had significant quantities of ozone.

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Definitions:

Posttest-Only

A research design where measures are taken only after the experimental manipulation, without a pretest comparison.

Mortality

The loss of subjects who decide to leave an experiment. Mortality is a threat to internal validity when the mortality rate is related to the nature of the experimental manipulation.

Experimental Design

A research design used to test hypotheses and establish cause-effect relationships by manipulating one or more independent variables and observing the effect on dependent variables.

Mortality

The incidence of death within a population; in research, it can also refer to the dropout rate of participants from a study.