What did the 1980 mount saint helens volcanic eruptions teach environmental scientists? a. salvage logging was essential to protecting the area from fire and insect threats b. many of the initial pioneering species actually survived the eruptions c. seeding the slopes was necessary to prevent erosion

The 1980 Mount Saint Helens volcanic eruptions teach environmental scientists that many of the initial pioneering species actually survived the eruptions.

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.

the corpus luteum secretes estrogens and progesterone. the latter hormone causes changes in the uterus that make it more suitable for implantation of the fertilized ovum and the nourishment of the embryo. if the egg is not fertilized, the corpus luteum becomes inactive after 10–14 days, and menstruation occurs.

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