You have several hives of honeybees, apis mellifera, that you keep in your backyard. some bees uncap and remove dead larvae from cells, while others leave dead larvae in the cells; this difference is genetically determined. after a particularly hot summer in which many bees die from disease, you notice that the only hives remaining are the ones in which bees uncap and remove dead larvae. you have witnessed
a. a population-level change in the frequency of a behavioral trait
b. evolution by natural selection
c. a new species forming
d. a and b

D. A and B

Explanation:

Some Apis mellifera bees genetically inherit the hygienic behaviour to remove the dead and diseased larvae from beehives by uncapping the sealed cells. This activity maintains the overall health of the bee colony by protecting it from unwanted pests and pathogenic diseases. Usually both hygienic and non hygienic bees survive well.

Here, in hot summer many bees had perished due to disease and hot climate. Accumulation of dead larvae in hives of non hygienic bees would have invited more pathogens and created infectious conditions in summer. Hence their hives could not survive. Now the remaining hygienic bees will mate with each other and the offspring will have more chances to be born with the hygienic trait. Hence the frequency of alleles determining this trait will increase in this population. This would also be an example of natural selection as hygienic bees were preferred by the nature over non hygienic ones to survive in hot season.

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explanation:

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an individual’s sex (i.e., whether they are a male or female) is determined by the sex chromosomes. most people have two sex chromosomes, one that is inherited from their mother and one that is inherited from their father. typically, females have two x chromosomes (xx) and males have one x chromosome and one y chromosome (xy). conditions caused by changes (“mutations”) in genes located on the x chromosome are considered x-linked.

x-linked recessive inheritance

most x-linked conditions are recessive. this means that in a person with two x chromosomes (most females), both copies of a gene (i.e., one on each x chromosome) must have a change or mutation whereas in a person with one x chromosome (most males), only one copy of a gene must have a mutation. a female with a mutation in one copy of a gene on the x chromosome is said to be a “carrier” for an x-linked condition. a male with a mutation in a gene on the x chromosome is typically affected with the condition. because females have two copies of the x chromosome and males have only one x chromosome, x-linked recessive diseases are more common among males than females. however, x-linked recessive diseases can occur in both males and females.

for x-linked recessive disorders, an unaffected carrier mother who has a mutation in a gene on the x chromosome can transmit either the x chromosome with this mutation or a “normal” x chromosome to her children. if the father is unaffected, none of her daughters will be affected and all of her daughters will be unaffected—since they will inherit at least one normal x chromosome from their father. however, each daughter will have a 50% chance of being an unaffected carrier like her mother and a 50% chance of both x chromosomes being normal.