Why do the herbivores of the Serengeti migrate year after year?

Describe two recent or ongoing space missions.

Astudent reads the following text in a science book: scientific evidence tells us that the cause of earths four seasons is the tilt of earth as it revolves around the sound the student is instructed to illustrate this information in a science book. how will the student illustrate winter in the northern hemisphere? a. earths northern hemisphere will tilt away from the sun. b. earths northern hemisphere will tilt toward the sun. c. earths orbit will be farther away than from the sun d. earths southern hemisphere will tilt away from the sun.

Which of these substances does not protect against invaders in the nonspecific immune response? a. saliva b. mucus c. tears d. urine