Viruses evolve in response to what component of the human immune system listed below?

A scientist might use the “molecular clock” technique to…

There are 500 toads in the population. Within this population, coloration is determined by one gene with two alleles, a brown allele (B) and a yellow allele (b). The brown allele is dominant to the yellow allele. There are 350 toads that are brown. Assume the population is in Hardy-Weinberg equilibrium. Given this information, the frequency of the b allele is approximately and you would expect toads to be heterozygous (Bb).  

This phylogenetic tree depicts the evolutionary relationships of eight major vertebrate classes.  Tiktaalik is an intermediate fossil that represents an early ancestor of all tetrapods. Specifically, Tiktaalik is known for its wrist, a key feature of the tetrapod limb that made it possible for which major evolutionary transition in animals? If you were to add Tiktaalik to this phylogeny, where would the Tiktaalik branch extend from?

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…

CHOOSE THE BEST ANSWERS In a population of cows, a single gene controls hair type. The curly hair allele (H) shows incomplete dominance with the straight hair allele (h). The hair of heterozygous individuals (Hh) is wavy. Another gene controls coat color. The red (R) and white (r) alleles are co-dominant. The coloring of heterozygous individuals (Rr) is called roan . After breeding a wavy, roan bull with several wavy, roan females, you observed the following phenotypic ratio in the offspring: 8 curly, red : 16 wavy, roan :  7 straight, white Part 1: Based on this observed ratio,  are the two genes linked?  Part 2:  If they are linked, how are the two genes’ alleles linked?   

Identical (monozygotic) twins were adopted by different families at birth and were raised in different parts of the country. However, both twins grow up to have perfect pitch. This would suggest what about the shared musical talent of these twins?

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?

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?