What characterizes algae?

Algae are a diverse group of photosynthetic organisms that can exist in both single-celled and multi-celled forms. One of their key characteristics is that they do not possess true conducting tissues, which distinguishes them from higher plants. Instead, algae rely on diffusion to transport nutrients and photosynthetic products within their cells. This ability to exist in various cellular forms, ranging from unicellular species like diatoms to multicellular species like seaweeds, showcases their adaptability and ecological range.

Additionally, while algae can sometimes be harmful when they bloom excessively, they are not always detrimental to aquatic ecosystems. In fact, they play a crucial role in these environments as primary producers, forming the base of the food web. Algae are also found in a variety of habitats, not limited to freshwater but also in marine environments and moist terrestrial areas.

This underscores the importance of recognizing the versatility of algae in both structure and ecological role, making the response indicating their ability to exist in single-celled or multi-celled forms without true conducting tissues correct.