Which of these processes returns nitrogen to the atmosphere?
a. respiration
b. denitrification
c. photosynthesis
d. nitrogen fixation

Which of the following statements is true? 1. the mantle of the earth is made of solid nickel and iron. 2. the crust of the earth is made of solid nickel and iron. 3. the inner core is made of solid nickel and iron.

What did not occur in the proterozoic eon a)the oxygen levels increase greatly in the atmosphere,b)the emergence of the eukarya , c)muti cella’s eukaryotic organisms began to diversify,d)anaerobic bacteria kept thriving with more oxygen

Sort the examples by the type of diversity that they exhibit a park has 80 species of trees red, yellow, and orange bell peppers are all members of the same species individuals of the same lizard species have different mating strategies. five different bird species are at a bird feeder. genetic diversity species diversity