$(a)$ "Evolution has occurred in stages." Justify the statement.
$(b)$ Differentiate between eye and eyespots. Which animal possesses eyespots?

(N/A) The statement "Evolution has occurred in stages" is justified because evolutionary processes take place over vast periods of time, leading to the gradual development of complex organs bit-by-bit across generations. For instance, the eye evolved from simple light-sensing structures known as eyespots into the highly complex organs seen in higher animals today. Furthermore, the presence of vestigial organs, such as the nictitating membrane, vermiform appendix, and wisdom teeth, provides evidence that structures have been reduced or modified over time. These changes demonstrate that evolution is a cumulative, step-by-step process.
$(b)$ An eye is a complex sensory organ composed of various tissues capable of forming images and detecting light. In contrast, an eyespot is a simple, dot-like structure primarily used for sensing light intensity and direction. The animal $Planaria$ (a flatworm) possesses eyespots.