Biology STAAR Practice Test 2025 - Free State of Texas Assessments of Academic Readiness Practice Questions and Study Guide

Green algae are considered the ancestors of plants due to their similarities in cellular structure, photosynthetic pigments, and reproductive strategies. This group of protists shares both morphological and genetic characteristics with land plants, particularly the chlorophyll a and b pigments that are critical for photosynthesis. Additionally, the chloroplasts in green algae are similar to those in plants, suggesting that they both evolved from a common ancestor that engaged in photosynthesis.

The close evolutionary relationship is further supported by the fact that green algae are part of the same clade, known as Archaeplastida, which includes all land plants. This evidence highlights how these organisms paved the way for the transition of life from water to land, which is a key milestone in the evolution of terrestrial ecosystems.

Other protists listed do not share the same lineage or characteristics with land plants, making green algae the clear ancestors in the evolutionary history of plants.