Question

Use the letters a–d to label where on the phylogenetic tree each of the following derived characters appears. (A) flowers (B) embryos (C) seeds (D) vascular tissue.

Short answer

The letters A to D have been shown in the phylogenetic tree below:

Step-by-step solution

Evolution of plants

Plants are the eukaryotic organisms forming the Kingdom Plantae. These organisms originated in aquatic habitats and evolved to colonize the land. The process of evolution was slow and led to the development of 5 diversified plant groups, each having a characteristic feature common to all its members.

Difference in aquatic and terrestrial habitat for plants

The two major differences in terrestrial and land habitat are the availability of water and temperature range.In aquatic habitats, water is abundant, and it can be used for several purposes, including the union of gametes; also, the temperature in the water was not extremely high.

In contrast, the terrestrial habitats posed several challenges to land colonization due to water scarcity and extreme range of temperature.

Phylogeny of plants

As plants evolved from aquatic to terrestrial regions, several adaptations and structural modifications took place. The thallophyte members (such as algae) have a very simple body structure formed of the thallus. The distinguishing character between thallophytes and other plants was the formation of embryos (absent in thallophytes).

Among the embryo-forming plants, the bryophytes lacked vascular tissues, and the rest of the plant groups had these special conducting tissues. The pteridophyte (ferns) was demarked from the other two groups as it could not form seeds.

The two plant groups which had the potential to develop seeds were differentiated based on flower production; angiosperms produced flowers, while gymnosperms did not. The phylogenetic tree is represented below: