5. In the evolutionary history of life, identify the most likely order in which the following
entities arose:
a. plasma membrane < RNA < chloroplasts < nucleus
b. nucleus < plasma membrane < RNA < chloroplasts
c. RNA < plasma membrane < nucleus < chloroplasts
d. chloroplasts < RNA < plasma membrane < nucleus

Evolutionary Order of Life’s Key Structures: RNA, Plasma Membrane, Nucleus, Chloroplasts

The correct answer is option c. RNA < plasma membrane < nucleus < chloroplasts, reflecting the established timeline from the RNA World hypothesis to eukaryotic endosymbiosis.​

Option Analysis

Option a (plasma membrane < RNA < chloroplasts < nucleus) fails because RNA predates membranes in chemical evolution theories, and chloroplasts postdate the nucleus in eukaryotes.​
Option b (nucleus < plasma membrane < RNA < chloroplasts) reverses the primordial sequence, as nuclei evolved after prokaryotic membranes and RNA.​
Option d (chloroplasts < RNA < plasma membrane < nucleus) places chloroplasts first, contradicting their late endosymbiotic origin around 1.5-2 billion years ago.​
Only option c aligns with evidence: self-replicating RNA (~4 billion years ago), protocell membranes, prokaryotic-to-eukaryotic nucleus transition (~2 billion years ago), and cyanobacterial chloroplasts.​

Evolutionary Timeline

Life’s origins began with RNA molecules capable of replication and catalysis in the RNA World. Lipid membranes then formed protocells, enclosing RNA for the first cells (prokaryotes). Eukaryotes later acquired nuclei for compartmentalized DNA, followed by chloroplasts via endosymbiosis of cyanobacteria.​