1. CRT Study Guide A well-known scientist who built the most powerful microscope of his time was __________________________. His invention was considered a major contribution to science.

2. answer van Leeuwenhoek

3. question Bacteria, which is made of ____________ ___________, are known to be the simplest organisms.

4. answer single cells

5. question Most cells have a ___________. This cell structure is sometimes called the “brain” of the cell because its function (job) is to “control all of the cell’s activities.” It controls how and when the cell grows, develops, and divides.

6. answer nucleus

7. question The __________ ____________ is a cell structure that is common to both plant and animal cells. Its function (job) in both is to “control the movement of substances into and out of the cell.”

8. answer cell membrane

9. question _____________________ is a jelly-like substance found in plant and animal cells. It fills most of the cell and has other cell structures floating in it. It is made up mostly of water.

10. answer cytoplasm

11. question When an organism is made up of many cells and different kinds of cells, each kind of cell has a special______________________. For example, blood cells have a different job than muscle cells. They each have a different job to do, and that keeps us alive and healthy.

12. answer function

13. question There are two cell structures that are found ONLY in plant cells. They are ______ ________ and the ___________________. You will never find these cell structures in animal cells!

14. answer cell wall and chloroplasts

15. question When sunlight passes through a prism, the light ______________________ _________________ called the visible spectrum.

16. answer separates into different colors

17. question When light colors are ______________, we CANNOT see the color.

18. answer absorbed

19. question The “bending of light as it moves from one material to another” is known as ______.

20. answer refraction

21. question Farsighted means a person CAN see far away (distant) objects clearly, but close (nearby) objects look blurry. Glasses with ____________ lenses correct farsighted vision.

22. answer convex

23. question The part of the eye that light passes through to help us see nearby objects is called the ____________.

24. answer lens

25. question On a rainy day, you may observe a ______________ in the sky as light passes through raindrops. This is because raindrops are like tiny prisms in the air.

26. answer rainbow

27. question If you see an object such as a green car, you know that the color green is the color that is reflected…not absorbed. You will not see the colors that are absorbed. Therefore, when you look at grass, you know that __________ is not absorbed.

28. answer green

29. question The function of the _____________ in the human eye is to “control the amount of light that enters the pupil.”

30. answer iris

31. question We know that a ___________ reflects the most light of common household objects. That is why you can see your own image, as well as other images of differing colors, in one.

32. answer mirror

33. question The _________ is the part of the eye that bends light rays.

34. answer cornea

35. question The “bouncing back of light from a surface” is known as ________________.

36. answer reflection

37. question When you see your image in a mirror, ________________ are bouncing back from the surface of the mirror. This is what allows you to see your reflection.

38. answer light rays

39. question A person who can see nearby objects clearly but cannot see distant objects is nearsighted. A nearsighted person’s vision would be corrected by wearing glasses that have ____________ lenses.

40. answer concave

41. question Tilting a mirror in front of your face so that you are changing the angle of the light ray hitting the mirror, prevents you from seeing your own face but instead ___________________.

42. answer another image

43. question Contact lenses are a type of corrective lens for people who “need glasses”. They work to correct vision because they are very similar to the ___________ in the human eye.

44. answer cornea

45. question The reason you SEE colors of objects is that the object is reflecting the light color that you are seeing. It absorbs all the other light colors of the visible spectrum. So, when you notice that an apple is red, you know that it is _____________________________.

46. answer reflecting light