Question

the paramecium shown below is a single - celled, eukaryotic protist that currently survives and thrives in aquatic environments

based on current theory of how eukaryotic cells evolved, from which organisms did this paramecium, and all other single - celled organisms evolve?
a. another protist
b. single - celled fungi
c. plants
d. bacteria

Explanation:

According to the endosymbiotic theory, eukaryotic cells evolved from prokaryotic cells (bacteria). Prokaryotic cells (such as bacteria) are simpler and are considered the ancestral form. Over time, through symbiotic relationships and other evolutionary processes, more complex eukaryotic cells (including single - celled eukaryotes like paramecium) emerged. Prokaryotes (bacteria) are the more primitive organisms from which eukaryotes evolved. Prokaryotes like bacteria have simpler cell structures (no membrane - bound nucleus, etc.), and eukaryotic cells (including protists) have more complex structures that likely evolved from prokaryotic ancestors.

Answer:

D. bacteria