Which of the following types of information is not always useful for identification purposes? Answer a. Presence or absence of anterior/posterior projections b. Number of appendages c. Number of eyes d. Exact size (e.g length)

The answer is **d. Exact size (e.g., length)**.<br /><br />Here's why:<br /><br />* **a. Presence or absence of anterior/posterior projections:** These features can be crucial for distinguishing between different groups of organisms. For example, the presence of antennae is a key characteristic of insects.<br /><br />* **b. Number of appendages:** This is another important characteristic. Spiders have eight legs, insects have six, and crustaceans have a variable number. These differences are significant for identification.<br /><br />* **c. Number of eyes:** The number and arrangement of eyes can be a distinguishing feature. Spiders, for example, can have varying numbers of eyes, which helps in classifying them.<br /><br />* **d. Exact size (e.g., length):** While size can be helpful *in conjunction with other characteristics*, it's not always reliable on its own. Individuals within the same species can vary significantly in size due to age, nutrition, and other factors. Therefore, relying solely on size for identification can be misleading. A young, small individual of one species might be mistaken for a different, smaller species.<br />