Which characteristic defines organisms in the kingdom Plantae?

The defining characteristic of organisms in the kingdom Plantae is that they are autotrophic and photosynthetic. This means that they have the ability to produce their own food through the process of photosynthesis, utilizing sunlight, carbon dioxide, and water to create glucose and oxygen. Chlorophyll, the pigment responsible for capturing light energy, is present in green plants and is key to this process.

Organisms in Plantae typically have complex multicellular structures and play a crucial role in ecosystems as primary producers, forming the base of the food chain by converting solar energy into chemical energy that is accessible to other organisms.

The relationship to other answer choices becomes clearer when considering that unicellular eukaryotes are more representative of protists or certain bacterial groups, while heterotrophic and mobile organisms are more characteristic of animals and fungi. Prokaryotic organisms with chitin cell walls describe a different group entirely, namely fungi. Thus, the distinct capability of the Plantae kingdom to perform photosynthesis and generate their own organic compounds is what differentiates them from other kingdoms of life.