• SC.912.L.15.8 Describe the scientific explanations of the origin of life on Earth. 

• You need to know the scientific explanations of the origin of life on Earth.

• Students will identify situations or conditions contributing to the origin of life on Earth. 

• Students will assess the reliability of sources of information according to scientific standards. 

• Students will identify the criteria that differentiate science from nonscience and pseudoscience. 

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?

A. onset of photosynthesis 

B. origin of genetic material 

C. Synthesis of organic molecules 

D. formation of the plasma membrane

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

A. prokaryotic and aerobic

B. prokaryotic and anaerobic

C. eukaryotic and aerobic

D. eukaryotic and anaerobic

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?

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

B. Organic molecules are present today in extremely high concentrations.

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

D. No other alternative hypotheses have been introduced. 

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?

A. They were able to photosynthesize

B. They had more DNA

C. They were able to make more use of available energy

D. They were immune to bacterial invasion.

1. Correct answer: C. Synthesis of organic molecules

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.

2. Correct answer: B. prokaryotic and anaerobic

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.

3. Correct answer: C. The process of synthesizing organic molecules from a mixture of gases has been successfully modeled in the laboratory.

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.

4. Correct answer: C. They were able to make more use of available energy

Mitochondria are the organelles which manufacture ATP from organic molecules.