Cooksonia is a genus of very early tracheophyte plants. Unlike modern tracheophytes they only grew to a few centimeters in height. What feature provides the best explanation for their diminutive size?

Question

A.  They completely lacked vascular tissues.
B.  They did not have stomata.
C.  They consisted of only photosynthetic stems, not roots or leaves.
D.  Cooksonia species were not autotrophic.

Clarify Question
What is the key concept addressed by the question?
What type of thinking is required?
 
Gather Content What do you already know about Cooksonia? What other information is related to the question?
 
Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
 
Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

C.  They consisted of only photosynthetic stems, not roots or leaves.

Clarify Question
What is the key concept addressed by the question?
        · The concept addressed by this question is the benefit of the smaller stature of Cooksonia.
What type of thinking is required?
        · You are being asked to take what you already know and use, or apply, it to the features that contribute to the smaller size of Cooksonia.
 
Gather Content What do you already know about Cooksonia? What other information is related to the question?
        · Cooksonia is the first known vascular land plant.
        · Cooksonia is now extinct.
        · Little competition existed for Cooksonia.
        · Roots and leaves were absent from Cooksonia.
 
Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
        · Cooksonia was a tracheophyte, so it did have vascular tissue.
        · Photosynthesis was utilized by Cooksonia, and some members of this genus did have stomata that were likely utilized for gas exchange.
        · Since Cooksonia lacked roots, taller stature would not be possible. Since it lacked leaves, and competition was low, photosynthesis could occur on the stem of Cooksonia.
 
Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        · Answering this question correctly depended on your ability to use Cooksonia in a new situation. If you got an incorrect answer, did you remember that Cooksonia lacked roots and leaves, or that there was little competition for space in the habitat of Cooksonia? Did you have trouble extending the features of Cooksonia to determine the correct answer?