Thousands of years ago, the jaws and teeth of jaguars were more varied in size than they are today. During a period of climate change about 11,000 years ago, jaguars faced a shortage of food. There were fewer mammals to eat, so the jaguars had to eat shelled reptiles. The jaguars with the largest jaws and teeth could most easily eat the shelled reptiles.
Which of the following statements best explains why large jaws and teeth are common characteristics in jaguars today?
O A. Jaguars with the smallest jaws and teeth died out completely.
B. Jaguars with the smallest jaws and teeth were not ever able to mate.
O C. Jaguars with the largest jaws and teeth survived and reproduced more successfully than other jaguars.
D. Jaguars with the largest jaws and teeth strengthened them by using them more frequently than other jaguars.

i think the answer would be d

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.