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Origin and Evolution of Life on Earth

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Questions and Answers

Approximately how old is the Earth?

6.0 billion years
4.5 billion years (correct)
3.7 billion years
5.2 billion years

What does the term 'evolution' refer to?

The process of photosynthesis
The formation of fossils
The origin of the universe
Change over a period of time (correct)

What were the first organisms on Earth believed to be?

Photosynthetic algae
Prokaryotic heterotrophs (correct)
Eukaryotic autotrophs
Multicellular organisms

What source of hydrogen did the earliest photosynthetic autotrophs use to reduce carbon dioxide to sugars?

<p>Hydrogen sulfide (D)</p> Signup and view all the answers

What critical role did the ozone layer play in the evolution of life on Earth?

<p>It allowed organisms to become terrestrial. (C)</p> Signup and view all the answers

Flashcards

Evolution

Change in the characteristics of a species over several generations; relies on natural selection.

First Organisms

Heterotrophic prokaryotes were the first life forms, obtaining energy from organic molecules in the ocean.

Autotrophic Evolution

The rise of autotrophs capable of photosynthesis averted an energy crisis among early life forms.

Photosynthesis Evolution

Early photosynthetic organisms used hydrogen sulfide; later, cyanobacteria used water, releasing oxygen.

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Ozone Layer

Shields the Earth from harmful UV radiation, enabling terrestrial life.