Final answer:
Whisk Ferns, also known as Psilophyta, are the organisms that resemble small, green whisk brooms due to their green branching stems and lack of leaves and roots. They perform photosynthesis through their stems and are closely related to ferns (Pteridophyta), despite their simplified appearance.
Step-by-step explanation:
The organisms that loosely resemble small, green whisk brooms are Whisk Ferns (Psilophyta). Whisk ferns are notable for their green branching stems without leaves and roots; this morphology makes them appear similar to whisk brooms. These plants undergo photosynthesis in their stems and have small yellow sporangia, which are distinctive features of the class Psilotopsida within Phylum Monilophyta. Unlike their appearance would suggest, recent comparative DNA analysis implies that whisk ferns are closely related to other ferns despite the evolutionary reduction (loss) of vascular tissue and roots.Whisk ferns stand out among vascular plants for their simplified structure which may be due to reductive evolution, a process where natural selection reduces structures that are no longer advantageous for survival in a given environment.
This means that while whisk ferns may appear primitive, they are actually a derived group that shares a closer relationship with ferns than with other plant groups such as club mosses or horsetails.The plant group that loosely resembles small, green whisk brooms is the Whisk Ferns (Psilophyta). Whisk ferns have green branching stems with no leaves and produce spherical yellow sporangia. They are classified in the phylum Monilophyta: Class Psilotopsida and are closely related to ferns.