Self-study
In a study of tropical forests it was found that while the species of trees that is most common in a particular forest also reproduces the most, trees of the species that is rarest there tend to survive longer. ████ ███████ █████ ██████████ ██ █████ ███████ ██ █████ ██ ███ ████ ██████ ███ █████ ██ ███ ███████
"Surprising" Phenomenon
Why do trees of the rarest species in tropical forests survive longer than trees of the most common species, which reproduce the most?
Objective
The correct answer will be a hypothesis that explains a key difference between the rarest and most common species of trees in tropical forests. That difference must result in the trees of the rarest species surviving longer, either because of some quality or adaptation that is present among rare tree species, or because of overpopulation among common tree species.
12.
Which one of the following, ██ █████ ████ █████ ██ ███████ ███ █████ ██ ███ ██████ ███████ ████ ██ ███████ ██████ ████ █████ ██ ███ ████ ██████ ████████
a
The species of █████ ████ ██ ████ ██████ ██ █ ██████ ███████ █████ ███████ ██ ██ ████ ██████ ██ ███ █████ ████████
This may help to explain why the common trees reproduce the most, but it doesn’t help to explain why the rarest trees survive longer. If the common trees are “best suited to the local climate,” shouldn’t they survive longer than the rarest trees?
b
Older trees tend ██ █████████ ███ ██████
This doesn’t give us a key difference between the common species and the rarest species. Instead it gives us a similarity: that older trees of any species reproduce the least. We still don’t know why the rarest trees live longer while the common trees reproduce the most.
c
The study tracked ███████████ ████ ███████ ███ ███ ███ █████████ ███ ███ ███████ ██ ███ ████████ ████████
The fact that no new species were introduced doesn’t affect the study’s findings: the most common species reproduces the most, while the rarest species lives longer. We still need a key difference between rare and common species to explain these results.
d
The survival of ███ █████ ██ ███ █████ ███████ ███████ ████████ ███████ ██ ███████ ████ ██████ ████ ████████ ████████████
The positive effect of the rare trees doesn’t explain why they live longer. Presumably, the common trees also have positive effects on the forest. But we still don’t know why trees of the rarest species live longer than those of the most common species.
e
The trees of ███ ██████ ███████ ████ ████ ███████████ ███ ███ █████████ ████ ████ ████ ██ ███ █████ ██ ███ ████ ████████
This highlights a key difference between rare and common species that helps explain the study’s results. Common species face more competition for resources, which limits their lifespan, while trees of rare species, with less competition, tend to survive longer.