20.3 Review

replicating, or making copies of itself

According to the RNA World hypothesis, which of these tasks was accomplished by early RNA, but is not generally accomplished by the RNA of today's organisms?

No, because the first atmosphere contained very little oxygen.

Could Earth's first atmosphere have supported the lives of humans & other living things of today?

Mitochondria developed from endosymbionts, and then chloroplasts developed from other endosymbionts.

How did eukaryotic cellular organelles evolve?

Some organic molecules, including amino acids, could have been produced from chemical reactions on early Earth.

In the Miller-Urey experiment, electrical sparks were passed through a mixture of gases, including hydrogen, water vapor, methane, & ammonia. These gases were thought to be present in the atmosphere of early Earth. The results showed that the gases reacted to form amino acids, which are the building blocks of proteins. Which conclusion about the origin of life on Earth is MOST STRONGLY supported by this experiment?

The cell took in another ancient prokaryotic cell, which began living inside it.

Lynn Margulis developed the endosymbiont theory to explain the evolution of certain eukaryotic organelles, such as chloroplasts & mitochondria. According to this theory, which of these events occurred to an ancient prokaryotic cell?

an increase in oxygen levels, which led to the extinction of many anaerobic organisms

The first organisms that performed photosynthesis evolved about 2.2 billion years ago. During the next few million years, their actions caused which of these events?