Question

inorganic substances. the first living organisms were likely single-celled, prokaryotic, and anaerobic, meaning they did not require oxygen. as photosynthetic organisms evolved, oxygen began to accumulate in the atmosphere, leading to major changes on earth and allowing more complex life forms to develop.

1. about how long ago did life on earth begin?

a. 1 million years ago
b. 500 million years ago
c. 3.5–4 billion years ago
d. 10 billion years ago

1. what was the early earths atmosphere lacking?

a. carbon dioxide
b. nitrogen
c. oxygen
d. water vapor

1. which type of energy helped drive chemical reactions on early earth?

a. wind
b. lightning
c. sound wave
d. gravity

1. the chemical evolution theory explains how life began from:

a. other planets
b. complex organisms
c. simple inorganic molecules
d. fossils

1. what are amino acids an example of?

a. inorganic gases
b. simple cells
c. organic molecules
d. protocells

1. what was the main purpose of the miller–urey experiment?

a. to create living cells
b. to prove evolution is false
c. to show organic molecules could form naturally
d. to test photosynthesis

Explanation:

1. Scientific evidence (like fossilized microbial mats) dates the first life on Earth to 3.5-4 billion years ago.
2. Early Earth's atmosphere had no free oxygen; oxygen accumulated later from photosynthesis.
3. Lightning is a well-documented energy source that drove early Earth's chemical reactions.
4. Chemical evolution theory states life arose from simple inorganic molecules forming complex organic ones.
5. Amino acids are carbon-based molecules, so they are organic molecules.
6. The Miller-Urey experiment simulated early Earth conditions to show organic molecules could form naturally.

Answer:

1. C. 3.5-4 billion years ago
2. C. Oxygen
3. B. Lightning
4. C. Simple inorganic molecules
5. C. Organic molecules
6. C. To show organic molecules could form naturally