North america is currently experiencing an unprecedented and rapid loss of species. what is believed to be the main cause? answer
a. continental drift
b. human activities
c. north america is not experiencing a rapid loss of species
d. natural cycles
e. increased predation by wild carnivores

Which of the following is the best definition of a eukaryota? a. a one-celled organism that does not have a membrane-bound nucleus b. a one-celled organism that does not have a cell wall c. an organism whose cells each contain a membrane-bound nucleus d. an organism whose cells each have a cell wall