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Originally, international law was unaccepting of treaty reservations, rejecting them unless all parties to the treaty accepted the same reservations. However, in the interest of encouraging the largest number of states to join treaties, a more permissive rule regarding reservations has emerged. While some treaties still expressly forbid any reservations, they are now generally permitted to the extent that they are not inconsistent with the goals and purposes of the treaty.

A more permissive rule regarding what emerged to encourage the largest number of states to join treaties?
Answer: reservations
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During mutualistic symbioses, the host cell lacks some of the nutrients, which are provided by the endosymbiont. As a result, the host favors endosymbiont's growth processes within itself by producing some specialized cells. These cells affect the genetic composition of the host in order to regulate the increasing population of the endosymbionts and ensuring that these genetic changes are passed onto the offspring via vertical transmission (heredity).

What does the host make that affect its genes?
Answer: specialized cells
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Ectosymbiosis, also referred to as exosymbiosis, is any symbiotic relationship in which the symbiont lives on the body surface of the host, including the inner surface of the digestive tract or the ducts of exocrine glands. Examples of this include ectoparasites such as lice, commensal ectosymbionts such as the barnacles that attach themselves to the jaw of baleen whales, and mutualist ectosymbionts such as cleaner fish.

Name a parasitic ectosymbiont.
Answer:
lice