Large-scale, worldwide adaptive radiations have occurred in which of the following situations? (A)when there are no available ecological niches (B)after each of the big five mass extinctions (C)after colonization of an isolated island that contains suit-able habitat and few competitor species (D)whenever an evolutionary innovation was needed for or-ganisms to thrive

Video transcript

Welcome back. Here's our next problem. Which of the following events does not happen during adaptive radiation? Well, let's recall from our content videos briefly, what is adaptive radiation? That's the evolutionary process where you have a rapid diversification into new forms from a single common ancestor. So you have from a single ancestor suddenly have this diversification to a multiple of new forms. So let's look at our answers to look for which thing does not happen. So, remembering we're looking for a false answer here. So let's look at choice. A choice A says organisms will diversify due to new available resources while this does happen. This is true because what drives this rapid diversification is opening up of new ecological niches or new resources like food when new things are available, driven to evolve new forms to take advantage of those new opportunities. So choice is not an answer. Since this does happen during adaptive radiation, choice B says there's a decrease in the ecological niche. Well, this does not happen. Um Again, the what drives adaptive radiation is an increase in opportunities increase in ecological niche If there were a decrease in the ecological niche, that would drive the opposite process. Because that narrowed um opportunity would favor probably one form of the other, favoring one species over the other rather than a rapid evolution of new different forms. So, Choice B would be our answer. Since this does not happen during adaptive radiation, but we'll just continue to go on and look at our remaining answers. Choice C says new traits are acquired due to the opening of a new niche. But as we discussed in the previous um discussing the previous choice that does happen, the new niche drives rapid evolution of different forms new traits, so Choice C. Is not the correct answer. And finally, Choice D. From a single ancestor speciation and fanatic adaptation may arise yes. Um In response to these new opportunities, new resources, you have different phenotype arise um which then causes speciation as the different forms become different species. So Choice D. Not a correct answer. So again, we have choice be decreased in the ecological niche as the thing that does not happen in adaptive radiation. See you in the next video.