Introductory Biology 207
Fall, 1998

Problem Two

Problem Title:    Cubby Cactus and Friends

The Problem:    Cubby Cactus has lived all of his life in the Arizona desert near Tucson. He has a beautiful view of the mountains and the sunsets are quite spectacular. However, his home is very sandy and the temperatures during the daylight hours vary from 60^o F in the winter months to as high as 120^o F during the summer. Nights  can get quite cool though with temperatures as low as 30^o F during the winter. Cubby's desert environment is also extremely dry. The humidity is seldom above 20%, sometimes as low as 7%. The humidity rises somewhat at night when the intense desert sun has set and the temperatures get cooler.

Question?    Is Cubby Cactus a plant? If so, does he still need to photosynthesize even though he lives in such extreme conditions? Why?

Question?    What special obstacles to photosynthesis are caused by this environment?

Because of these obstacles, Cubby and his fellow cacti have had to undergo several adaptaions as they evolved into desert dwellers.

Question?    How does Cubby fix carbon-dioxide?

Question?    How does this differ from how Patty Petunia, who lives in New York City, fixes carbon-dioxide?

    Cubby has another friend, Maizey the corn plant, who grows on the Nebraska plains. She has similar problems to Cubby's during the hot summer months. However, her environment is not so extreme as is Cubby's. Maizey's solution to the problem is quite different from Cubby's.

Question?    What is special about how Maizey's leaves are structured that solves the problem for her?

Question?    How does Maizey fix carbon-dioxide?

Question?    Why don't human beings have these problems? Or do they?