SC.912.L.15.8 Remediation Unit 2

One of the accepted scientific theories describing the origin of life on Earth is known as chemical evolution. According to this theory, which of the following events would need to occur first for life to evolve?

• onset of photosynthesis

• origin of genetic material

• Synthesis of organic molecules

• formation of the plasma membrane

Answer explanation

During chemical evolution, organic molecules were synthesized by individual elements. All living things are made from organic molecules, so the presence of these molecules is required for life to exist

Which types of organisms developed first due to the early environmental conditions on Earth? 

• prokaryotic and aerobic

• prokaryotic and anaerobic

• eukaryotic and aerobic

• eukaryotic and anaerobic

Answer explanation

Prokaryotic organisms are single-celled and would have evolved first. Since atmospheric oxygen was not initially present on Earth, the ability to use anaerobic respiration to produce energy would have been necessary for the first living organisms

The Miller-Urey experiment of 1953 was designed to test the hypothesis that lightning supplied the energy needed to turn atmospheric gases into organic molecules such as amino acids. Which of the following describes why the Miller-Urey theory is widely accepted today?

• Amino acids spontaneously form from molecules in the atmosphere today.

• Organic molecules are present today in extremely high concentrations.

• The process of synthesizing organic molecules from a mixture of gases has been successfully modeled in the laboratory. 

• No other alternative hypotheses have been introduced. 

Answer explanation

The Miller-Urey experiments have been tested many times in the laboratory and organic molecules have continued to be successfully formed from mixtures of gases.

The diagram below shows a proposed theory of the origin of eukaryotic cells, called endosymbiosis.

Which of the following explains why cells that contained mitochondria-like organelles had an evolutionary advantage?

• They were able to photosynthesize

• They had more DNA

• They were able to make more use of available energy

• They were immune to bacterial invasion.

Answer explanation

Mitochondria are the organelles which manufacture ATP from organic molecules.

Life appears from materials that aren't already alive, such as decomposing wood.

• Biogenesis

• spontaneous generation

• Abiogenesis

One model of the origin of life on Earth hypothesizes that organic molecules arose abiotically under the atmospheric conditions of early Earth. Another model hypothesizes that these organic molecules arrived on Earth from space via a meteorite or other source.

Which of the following questions related to the models described above is most scientifically testable?

• Was the synthesis of simple organic molecules on early Earth a stepping stone toward the evolution of complex organic polymers?

• Why do organic molecules exist both on Earth and on meteorites that have come to Earth from space?

• Can organic molecules be generated abiotically under low temperature and high levels of UV radiation, similar to conditions in space?

• Did simple organic molecules form abiotically in the atmosphere of early Earth with the goal of generating life?

Earth formed approximately 4.5 billion years ago. Until roughly 3.9 billion years ago, the conditions of early Earth were too hostile to support sustained life. The earliest strong evidence of life in the fossil record dates to 3.5 billion years ago.

Based on the information above, which of the following describes when life most likely originated on Earth?

• Over 4.5 billion years ago

• Between 4.5 and 3.9 billion years ago

• Between 3.9 and 3.5 billion years ago

• Less than 3.5 billion years ago

In 1953, the scientists Stanley Miller and Harold Urey conducted an experiment that provided support for the hypothesis that molecules important to life could have formed abiotically under Earth’s early conditions. The apparatus used in the experiment is pictured below.

Which biological molecules were generated during the Miller-Urey experiment?

• Only amino acids

• Both amino acids and polypeptides

• Only nucleotides

• Both nucleotides and RNA polymers