Need help ASAP

1.) List a few reasons why a beaver is an example of a keystone species.

2.) In architecture, a keystone is the
stone at the center of an arch that holds the arch together. How does this
definition relate to a keystone species?

18. which statement about cancer is true?

Which number represents a basic ph, 4 or 9? numerical answers expected! answer for blank 1: i'll give

Ascientist is designing an investigation to study the impact of invasive bird populations on local, native bird populations at backyard bird feeders. what population is most likely to be a control group for the investigation? amount of food number of bird feeders invasive bird populations local backyard birdfeeders without food