Question

3) Multiple mammal species coexisted with dinosaurs starting ~200 million years ago. However, most of the mammal clades that are extant today originated around 65 million years ago, following the Cretaceous-Paleogene extinction event. (38 pts)

a. For each of the following statements, determine if it is most likely TRUE or FALSE.

The likely primary cause of the Cretaceous-Paleogene extinction event was an asteroid impacting the earth leading to rapid changes in climate.      T     F

The diversification of mammals would likely have occurred in the same way even if the non-avian dinosaurs had not gone extinct.      T     F

Speciation rates in mammals were likely the same before and after the Cretaceous-Paleogene extinction event because speciation takes such a long time to occur.    T     F

b. One mammal clade that underwent an adaptive radiation during this time is the Mustelidae, which consists of carnivores such as weasels, mink, otters, etc. This is a diverse clade consisting of ~60 species that are different sizes, use different habitats (aquatic, grasslands, forests,etc.) and feed on a wide array of different prey items. Give a definition of an adaptive radiation and use the concept of ecological niches to explain why the Mustelidae radiation occurred.

c. There are two similar extant mink species that are part of the Mustelidae clade, the American mink and the European mink. In several areas of the European mink’s range American mink have invaded (sometimes after being released from mink farms by animal rights activists) and now compete with the European mink. Imagine you hypothesize that character displacement has occurred in the populations that are now in sympatry. Make a prediction for the degree of phenotypic differences you expect if you compare these two mink species where they occur in sympatry versus if you compare the two species that occur in allopatry. Justify your answer by fully explaining the reasons for your prediction.

Answer 1

A. The statement is exactly TRUE

extinction is caused by the impact of a huge asteroid 10 to 15 km (6 to 9 mi) wide, 66 million years ago, which devastate the global environment,

The satement is false

Mammals get shaped a greater variety of forms in the first few million years after the dinosaurs went extinct.

The answer is true that Speciation rates in mammals were likely the same before and after the Cretaceous-Paleogene extinction event because speciation takes such a long time to occur.

B. Adaptive radiation is the appearance of other species from one common ancestral species that have spread to various regions or environments. The different characteristics among the species correspond to the adaptive necessities of the ecological niches each one occupies, to different environmental pressures.Extant mustelids display extensive ecomorphological diversity, with different lineages having evolved into an array of adaptive zones, from fossorial badgers to semi-aquatic otters. Mustelids are also widely distributed, with multiple genera found on different continents. As with other groups that have undergone adaptive radiation.

Last part i am not familiar.

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