Final answer:
Unicellular, eukaryotic organisms belong to the domain Eukarya and are often classified under the kingdom Protista. This group is diverse and includes organisms that are plant-like, animal-like, or fungi-like, with the distinguishing feature being the presence of a nucleus and other membrane-bound organelles.
Step-by-step explanation:
Unicellular, eukaryotic organisms are incredibly diverse, encompassing species that are plant-like, animal-like, or fungi-like. These organisms are part of the domain Eukarya, which includes all life forms with cells that have a nucleus and other membrane-bound organelles. The correct answer to the question 'First eukaryotic organisms' is d) Protista. The kingdom Protista is a collection of eukaryotic organisms that do not fit neatly into the other kingdoms of Animalia, Fungi, or Plantae. Protists can be unicellular or multicellular but generally do not have highly specialized tissues like those found in plants, animals, and fungi.
It's important to note that the domains Bacteria and Archaea comprise all prokaryotic cells, which do not have a nucleus, while eukaryotic cells make up the domain Eukarya. Prokaryotes encompass single-celled or colonial organisms without membrane-bound nuclei, vastly different from the nucleus-containing cells of the eukaryotes.
The kingdom Protista is known for its amazing diversity, with some members being microscopic and unicellular, while others, like kelps, are large and multicellular. Despite this variability, what unites them is their eukaryotic cell structure, distinguishing them from the prokaryotic cells of Bacteria and Archaea.