1. What vitamin do humans mainly get from sunlight?

2. How many teeth does a typical adult human have?

3. Which gas makes up the majority of the Earth’s atmosphere?

4. What is the branch of science that deals with heredity?

5. Which type of photoreceptor cells in the human eye are primarily responsible for color vision?

6. What is responsible for the 'lub-dub' sound of a heartbeat?

7. What is the name of the tiny air sacs in the lungs where gas exchange occurs?

8. Where in the human body is the smallest bone (the stapes) located?

9. Which type of white blood cells are responsible for 'remembering' a pathogen for years or decades?

10. What are the microscopic functional units of the kidney called?

11. How many pairs of 'floating ribs' do humans typically have?

12. Where is the vestibular system, which controls balance and spatial orientation, located?

13. What is the name of the substance that prevents the alveoli from collapsing during exhalation?

14. In which stage of sleep does the brain show activity levels similar to being awake?

15. What is the name of the wave-like muscle contractions that move food through the digestive system?

16. What percentage of human blood is typically composed of plasma?

17. What is the name of the gap between two neurons where chemical signals are transmitted?

18. What is the primary function of red bone marrow in the human body?

19. How thick is the blood-air barrier in the human lungs where gas exchange takes place?

20. What is the name of the fatty insulation that speeds up nerve impulses?