7.12 Origin of Life on Earth Assessment

When was Earth approximately formed?

• 4.6 billion years ago

• 3.5 billion years ago

• 2.5 billion years ago

• 1.5 billion years ago

Answer explanation

Earth was formed approximately 4.6 billion years ago, based on evidence from radiometric dating of the oldest rocks and meteorites. The other options are significantly later in Earth's geological history.

Tags

NGSS.HS-ESS1-6

What evidence suggests that Earth's early atmosphere was different from today's?

• Presence of oxygen-rich minerals

• Absence of oxygen-rich minerals in ancient rocks

• Abundant plant fossils

• High levels of ozone

Answer explanation

The absence of oxygen-rich minerals in ancient rocks indicates that Earth's early atmosphere lacked significant oxygen, contrasting with today's oxygen-rich environment, which is essential for the formation of such minerals.

The RNA World Hypothesis suggests that: A. DNA evolved before RNA B. Proteins were the first genetic material C. RNA served both as genetic material and catalyst D. Cells evolved before genetic material

• DNA evolved before RNA

• Proteins were the first genetic material

• RNA served both as genetic material and catalyst

• Cells evolved before genetic material

Answer explanation

The RNA World Hypothesis posits that RNA was the first molecule to carry genetic information and also function as a catalyst, making it essential for early life forms. Thus, RNA served both roles, confirming option C.

Which experiment demonstrated that organic molecules could form from inorganic compounds?

• Darwin's finch observations

• Miller-Urey experiment

• Pasteur's swan-neck flask

• Mendel's pea plant studies

Answer explanation

The Miller-Urey experiment demonstrated that organic molecules, such as amino acids, could form from inorganic compounds under conditions thought to resemble those of early Earth, supporting theories of abiogenesis.

The earliest fossil evidence of life on Earth dates back approximately:

• 1 billion years ago

• 2 billion years ago

• 3.5 billion years ago

• 4.6 billion years ago

Answer explanation

The earliest fossil evidence of life on Earth, found in stromatolites, dates back approximately 3.5 billion years ago, making this the correct choice among the options provided.

Tags

NGSS.HS-ESS1-6

Primitive Earth's atmosphere was likely composed mainly of:

• Oxygen and nitrogen

• Hydrogen and helium

• Methane, ammonia, and water vapor

• Carbon dioxide and ozone

Answer explanation

Primitive Earth's atmosphere was primarily composed of methane, ammonia, and water vapor, as these gases were abundant in the early environment, unlike oxygen and nitrogen which became prevalent later.

Tags

NGSS.HS-ESS1-6

Where did the first organic molecules likely originate?

• Deep-sea hydrothermal vents

• Mountain peaks

• Desert regions

• Polar ice caps

Answer explanation

The first organic molecules likely originated at deep-sea hydrothermal vents, where extreme conditions and chemical reactions could facilitate the formation of complex organic compounds, unlike the other listed environments.

Tags

NGSS.HS-LS1-6

How did polymers likely form from monomers in primitive Earth?

• Through photosynthesis

• Through condensation reactions

• Through nuclear fusion

• Through cellular respiration

Answer explanation

Polymers likely formed from monomers on primitive Earth through condensation reactions, where monomers combine and release water, creating larger molecules. This process is essential for polymer synthesis.

What conditions made Earth hostile to life initially?

• Excessive plant life

• Too much oxygen

• High temperatures and meteor impacts

• Low temperatures and ice coverage

Answer explanation

Initially, Earth was hostile to life due to high temperatures and frequent meteor impacts, which created an unstable environment. Later, low temperatures and ice coverage also contributed to harsh conditions, making survival difficult.

Tags

NGSS.HS-LS4-5

Which structure is considered a possible site for early organic molecule formation?

• Clay minerals

• Diamond deposits

• Limestone caves

• Granite formations

Answer explanation

Clay minerals are believed to provide a surface for chemical reactions, facilitating the formation of early organic molecules, making them a key site for prebiotic chemistry.

Tags

NGSS.HS-LS1-6