Fossil evidence indicates that the following events occurred in what sequence, from earliest to most recent?

1. Protostomes invade terrestrial environments.

2. Cambrian explosion occurs.

3. Deuterostomes invade terrestrial environments.

4. Vertebrates become top predators in the seas.

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#Question id: 3274

#SCPH06 I Botany

The common edible frog of Europe is a hybrid between two species, Rana lessonae and Rana ridibunda. The hybrids were first described in 1758 and have a wide distribution, from France across central Europe to Russia. Both male and female hybrids exist, but when they mate among themselves, they are rarely successful in producing offspring. What can you infer from this information?

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#Question id: 1694

#SCPH01 Biochemistry

Antigen processing for presentation by MHC class II molecules involves:

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#Question id: 2072

#SCPH05 I Biotechnology

Which of the following structures would decrease the electrochemical gradient across a membrane?

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#Question id: 364

#SCPH28 | Zoology

 A solution contains 0.0000001 (10-7) moles of hydrogen ions [H+] per liter. Which of the following best describes this solution?

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#Question id: 5845

#SCPH06 I Botany

Which of the following statements is false?  In vitro, the strand-exchange reaction: