One explanation could be the differences in climate (environmental factors). The climate in northern Mexico could support the reproduction of the mosquito species, which is a vector of the dengue virus. Other environmental conditions that influence its endemicity could include living conditions and sanitation. The other possiblity could be that the people in the US have developed immunity for the disease, therefore, are unaffected even when infected by the virus.
Answer:
The correct answer is: positive feedback.
Explanation:
Positive and negative feedback are terms that are used to define the way a system is regulated by its products. For example, when the production of a certain substance <u>inhibits</u> its producer that is called <u>negative feedback</u>. On the other hand, when a substance <u>stimulates</u> its producer to keep secreting said substance, this is called <u>positive feedback</u>.
Estrogen is a hormone of great importance in the female reproductive cycle and is secreted by the follicle cells in response to the presence of FSH (follicle-stimulating hormone), released by the anterior pituitary when stimulated by the GnRH (gonadotropin-releasing hormone).
Estrogen appears at the beginning of the cycle to stimulate the development of the ovarian follicles, and the hormone levels continue to rise as the cycle advances. Up until the 14th day of the cycle, estrogen has a negative feedback on GnRH and FSH, but then it makes an abrupt change to now exert positive feedback on GnRH to stimulate the release of LH (luteinizing hormone), which will be responsible for ovulation.
