Which of these would most likely contribute to the extinction of a species?
a. an increase in its genetic variability
b. a decrease in the number of its competitors
c. the extinction of species at higher trophic levels
d. the extinction of species at lower trophic levels

Assume that a student is given two different models of bacteria, with one model consisting of big bacteria and the other consisting of small bacteria. how can the student demonstate the theory of endosymbiosis using the models

Environmental differences within ecosystems are generally caused by

The carbon cycle is best defined as a process in which a. carbon changes from inorganic forms to organic forms and back b. carbon is changed into other elements such as oxygen or nitrogen c. carbon is continually created from the sun’s energy by plants d. carbon is consumed and regenerated from other elements such as oxygen and nitrogen