About 200 years ago, Jan Baptista van Helmont wanted to know where growing plants get the materials necessary for increases in size. He planted a tree seedling weighing 5 pounds in a barrel filled with 200 pounds of soil and then watered the tree regularly. After five years, the tree weighed 169 pounds, 3 ounces, and the soil weighed 199 pounds, 14 ounces. Because the tree had gained so much
weight and the soil had lost so little, he concluded that the tree had gained all of its additional weight by absorbing the water he had added to the barrel, but of course he was incorrect. What really happened?
What will be an ideal response?
Let's look at the possibilities. The gain in weight of the tree could have been unchanged water simply absorbed through the roots and retained in the plant tissues, but not 168 pounds of it! Furthermore, we know that the water molecules are not going to combine directly with any other molecules in the tree. Of course we now know much more about the reactions of photosynthesis than van Helmont did, so we can conclude that the gain in weight was from the synthesis of carbohydrate (specifically, cellulose) in the chloroplasts of the leaf cells due to the reacting of carbon dioxide from the air and water from the soil.
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European explorers sailing across the Pacific leave several pairs of pigs on a remote island with the intention of visiting again in future years to harvest fresh meat. This would most resemble a case of artificially induced allopatric speciation through:
A. vicariance. B. dispersal.
Which region is largest in a mammalian brain?
A. cerebral cortex B. brain stem C. cerebellum D. hippocampus
As a result of the hormonal and neuroanatomical differences between the male and female brains of zebra finches,
____.
a. only males sing their species songs b. only females sing their species songs c. males sing their species songs at earlier ages than females d. females sing their species songs at earlier ages than males e. females only sing their species songs later in their lives
Which of the following statements about the epicotyl is true?
A. It is the portion of the stem axis that is directly below the cotyledons. B. It forms immediately above the secondary roots of a seedling. C. It takes up most of the volume within a monocot or dicot seed. D. It remains in the ground after a seed has germinated. E. The shoot apical meristem of a seedling is located just above it.