The black‐footed ferret was listed as endangered in the United States in the late 1960s. In the 1970s, it was thought that the species was extinct. However, a small population was discovered in Wyoming, in 1981. However, this remaining population dwindled to 18 individuals when an outbreak of sylvatic plague and canine distemper affected the black footed ferret. What phenomenon is demonstrated in this case study? A) A population mutation that cause susceptibility to disease. B) A population bottleneck that decreased genetic variation in the ferret population. C) Artificial selection, as humans captively bred only the strongest individuals to survive and reproduce. D) A gene flow from the surviving population to other members of the species that increased genetic variation.

a

explanation:

compost can be added to topsoil as a:

pesticide

atp is used for energy.

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.