Plants first made their way onto land about 475 million years ago. Over the next 50 million years, land plants evolved a number of structures that helped them adapt to a dry, terrestrial environment. These structures include wind-dispersed spores, water-conducting cells called tracheids, and stomates, which are pores on the surface of a plant that allow gas exchange to occur. In addition, the diploid sporophyte began to dominate the plant life cycle over the haploid gametophyte. These adaptations are shown in the character state table. In the table, a 0 represents a lack of the corresponding trait, whereas a 1 represents the presence of the trait. Aglaophyton, Baragwanathia, Cooksonia, and Rhynia are extinct plants known only from fossils. Marchantia is an extant liverwort. Green algae are chosen as the outgroup.
Species | Dominant sporophyte | Spores | Stomates | Tracheids
Green algae | 0 | 0 | 0 | 0
Aglaophyton | 0 | 1 | 1 | 0
Baragwanathia | 1 | 1 | 1 | 1
Cooksonia | 0 | 1 | 1 | 1
Marchantia | 0 | 1 | 0 | 0
Rhynia | 0 | 1 | 1 | 1
Using the character state table, place the plant species into the phylogenetic tree. Assume there are no occurrences of convergent evolution or evolutionary reversal. Green algae has already been placed in the phylogenetic tree.
Answer Bank
Baragwanathia
Marchantia
Aglaophyton
Rhynia
Cooksonia
Phylogenetic trees can be used to assess the timing of evolutionary events. Use the phylogenetic tree you created to identify the order in which traits evolved in the land plants.
dominant sporophyte, tracheids, stomates, spores
tracheids, dominant sporophyte, spores, stomates
dominant sporophyte, spores, stomates, tracheids
spores, stomates, tracheids, dominant sporophyte