A study on blood sharing among vampire bats has shown that a hungry bat is more likely to receive a blood meal from another unrelated individual if the hungry bat has fed that same individual in the recent past. This observation supports the hypothesis that sharing of blood meals could have evolved by way of…

Which of the following mechanisms would result in lower genetic diversity within a population?

Which of the following was not involved in the evolution of multicellular organisms from single-celled protists?

Prior to European colonization, tens of thousands of whooping cranes lived in North America. By 1938, due to overexploitation and habitat loss, whooping cranes were virtually extinct, with a total population of only 15 individuals. Since then, careful conservation efforts have increased the North American whooping crane population to over 800 today. From a genetic standpoint, as a result of this catastrophe, whooping cranes experienced a “population bottleneck”, which is a severe form of . The current population of whooping cranes should be expected to have , relative to the pre-colonial population.

Following selection, 80% of individuals with the “AA” genotype survive, all “Aa” individuals survive and 40% of “aa” individuals survive. Their respective relative fitnesses are…

Müller’s ratchet is a cost of asexual reproduction and can explain the evolution of sexual reproduction because…

Originally from South America, potatoes became a common food source in Europe during the late 1700s and early 1800s. During the 1840s, however, the European potato crop collapsed due to the rapid spread of potato blight (a fungal pathogen). The loss of this important food source resulted in mass migration and starvation. Most infamously, the potato blight contributed to the Great Famine in Ireland (though other socio-political factors were also to blame). Before the blight, potatoes were typically propagated clonally, by cutting up the tuber (the part you eat) into pieces and using these pieces to grow new, identical plants. Given what you know about the evolution of sex, why did the clonal propagation of the potato make the crop especially susceptible to a devastating pathogen outbreak?

Australian Marsupials have been geographically isolated from Placental mammals for ~50 million years. In that time, many species in both groups have independently evolved the same adaptations via convergent evolution. The analogous adaptations observed in Placental mammals and Marsupials are best explained by…

Some dinosaurs had small, fluffy feathers called “downy” feathers (similar to down feathers in a pillow), but lacked the type of feathers necessary for flight. These dinosaurs are believed to be the ancestors of modern birds, which have several types of feathers that allow them to fly.  How can we explain the evolution of an “intermediate” trait such as downy feather, if they were functionally useless for flight?

Roundworms are able to reproduce sexually or asexually. The graph below shows the results of an experiment that compared sexual reproduction rates in roundworm populations exposed to three different bacteria treatments: roundworm populations that were never exposed to bacteria (dotted black line) roundworm populations that were periodically exposed to bacteria that were allowed to evolve (solid black line) roundworm populations there were periodically exposed to bacteria that were not allowed to evolve (highlighted in red). In Treatment 3, the rate of sexual reproduction increased, but then, after 8 generations, decreased. What is the most likely cause of this decrease in sexual reproduction?