Various studies have concluded that song overlapping, the phenomenon where one bird begins a song while another of its species is singing, is a signal of aggression. These studies are based solely on receiver-response tests, which seek to derive conclusions about the intent of a signal based on how others respond to it. However, any response—even no response—can be interpreted as a reaction to perceived aggression. Therefore, _______.

Summary
Studies have concluded that song overlapping is a signal of aggression. These studies are based solely on receiver-response tests, which derive conclusions about behavior based on how others respond to it. Any response, including no response, can be interpreted as a reaction to aggression.

Strongly Supported Conclusions
The studies are inconclusive in showing that song overlapping is a signal of aggression.

A
birds do not respond in a predictable manner to signals of aggression
This is unsupported because we don’t know how birds respond to the signal of aggression based on what the author tells us.
B
receiver-response tests can provide no insight into bird behavior
This is unsupported because even if receiver-response tests could perceive any response as aggression, there may be other ways they could provide insight into bird behavior outside of evaluating the purpose of song overlapping.
C
song overlapping is likely not a signal of aggression
This is unsupported because even though we have reasons to doubt the existing studies conclusion, we cannot go so far as to conclude the opposite. We merely have to acknowledge that the prevailing hypothesis is unsupported.
D
song overlapping has no communicative function
This is unsupported because song overlapping may be used to communicate even if we have reasons to doubt existing studies showing it is a signal of aggression.
E
the conclusion of these studies is unconvincing
This is strongly supported because the studies rely on a method that could show any response to be a signal of aggression. This means we have little reason to believe that song overlapping is uniquely a sign of aggression.

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The prehistoric fish Tiktaalik is the earliest known animal with fingers. Since variations were so great among prehistoric fish species, Tiktaalik would not have stood out as unusual at the time. However, Tiktaalik’s fingers were an important development in animal evolution because it is likely that Tiktaalik is an ancestor to the many land animals with fingers.

Summary
Tiktaalik is a prehistoric fish. Tiktaalik is the earliest known animal with fingers. Tiktaalik would not have stood out as unusual since variations were great among prehistoric fish. Tiktaalik is likely an ancestor to the land animals that have fingers.

Strongly Supported Conclusions
Land animals with fingers today likely trace their ancestry back to a prehistoric fish. Comparing Tiktaalik to other fish at its time would not reveal its evolutionary importance.

A
Tiktaalik likely used its fingers to move on land.
This is unsupported because we don’t know where Tiktaalik lived, and its life may have been confined to the sea.
B
Tiktaalik’s fingers were its only feature to play a significant role in the development of modern land animals.
This is unsupported because the author never reveals if Tiktaalik also had other features that were unique or significant. The discussion is confined to its fingers.
C
Tiktaalik is not the ancestor of any currently surviving fish species.
This is unsupported because Tiktaalik may have had several descendants of fish, either with or without fingers.
D
No fish without fingers would ever be able to move on land.
This is unsupported because there may be other appendages besides fingers that could enable a fish to move on land.
E
The evolutionary significance of Tiktaalik could not be determined just through comparison to fish species of its time.
This is strongly supported because comparing Tiktaalik to other fish wouldn’t yield significant results since many different fish had unique characteristics. The evolutionary significance of Tiktaalik comes from its later land ancestors with fingers.

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https://www.youtube.com/watch?v=ypzWUzP_AOU


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One adaptation that enables an animal species to survive despite predation by other species is effective camouflage. Yet some prey species with few or no other adaptations to counteract predation have endured for a long time with black-and-white coloration that seems unlikely to provide effective camouflage.

"Surprising" Phenomenon
How have some black-and-white prey species survived despite the fact that they have few or no adaptations to counteract predation and their coloration seems unlikely to provide effective camouflage?

Objective
The right answer will describe some factor that has allowed the black-and-white species to endure for a long time, despite their apparent survival shortcomings. This might take the form of explaining how the coloration actually does benefit the species despite what we may think, adding some additional survival information about these species, or showing some weakness in the species’ predators.

A
Most species with black-and-white coloration are more populous than the species that prey upon them.
This doesn’t matter. We expect that predators eat more than one animal throughout their lives, so the prey species being more populous doesn’t explain their survival. This answer also doesn’t say how much more populous the prey are—it could be that there’s only one more of them!
B
No form of camouflage is completely effective against all kinds of predators.
This doesn’t help. The black-and-white species in question seem not to have any camouflage at all, so general information about camouflage effectiveness isn’t relevant or useful.
C
Animals of many predatory species do not perceive color or pattern in the same manner as humans do.
This explains how the black-and-white coloration that humans don’t see as effective camouflage might in fact function as such against predator species. Maybe these predators see the world in black-and-white or perceive patterns that match the prey’s coloration!
D
Conspicuous black-and-white areas help animals of the same species avoid encounters with one another.
This isn’t helpful. We need information about how these black-and-white animals evade predator species in order to survive, not how they avoid one another.
E
Black-and-white coloration is not as great a liability against predators at night as it is during the day.
This doesn’t matter. This answer choice suggests that black-and-white coloration is a liability against predators, even if that liability is less substantial at night!

Extracurricular


70 comments