A recent study examined the daytime and nighttime activity patterns of two populations of tree-dwelling lemurs-the fi...

on November 20, 2019

Can someone please explain?

I chose answer choice E, but that was mainly because I went through all of the answer choices and didn't really feel like any of them explained the difference.

1 Reply

on November 20, 2019

Hello @masonnavarrete,

The stimulus tells us about two forests. The rain forest has tree canopy cover year-round. The deciduous forest doesn't, because its trees lose their leaves in the winter. In the winter, lemurs in both forests increase their nocturnal activity. However, the deciduous forest lemurs have a greater increase in nocturnal activity.

This leads me to ask, "What is the connection between winter canopy cover and nocturnal activity?" Why would less canopy cover cause the deciduous forest lemurs to be especially active at night? Remember, both species increase their activity. We need to explain why the deciduous lemurs increase their activity more.

Take a look at answer choice B. "High-flying" implies that these birds fly above the canopy. In the summer, the two lemur populations face equal danger from these birds, because both forests have tree cover to hide the lemurs. In the winter, what changes? The deciduous forest loses its leaves, making it more dangerous for those lemurs to be active during the day. This would force them to become more nocturnal. The rain forest lemurs do not lose their tree cover, so daytime activity is not so dangerous. This would explain the disparity, making B the correct answer.

When we are given a disparity (in this case the difference between the two populations), we want to look for other differences between the groups. In this question, that was the winter canopy cover. I knew the answer would have something to do with this canopy, which led me to the correct answer.