Which one of the following is a taxonomical aid for identification of plants and animals based on similarities and dissimilarities?

Options

A. Flora
B. Keys
C. Monographs
D. Catalogues

Answer

To solve the question regarding the taxonomical aid for the identification of plants and animals based on similarities and dissimilarities, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for a taxonomical aid that helps in identifying plants and animals based on their similarities and dissimilarities.

2. **Identify the Options**: The options provided are:
- A) Flora
- B) Keys
- C) Monographs
- D) Catalogs

3. **Define Each Option**:
- **Flora**: This refers to a book or a list that describes the plant species of a particular region. It does not specifically aid in identification based on contrasting characteristics.
- **Keys**: These are analytical tools that consist of a series of choices that lead the user to the correct identification of an organism based on its characteristics. They often present contrasting statements (couplets) to guide the identification process.
- **Monographs**: These are detailed written studies on a single taxonomic group, which may include descriptions and classifications but are not primarily used for identification.
- **Catalogs**: These are systematic lists of species or items, but they do not provide the analytical framework necessary for identification.

4. **Evaluate the Options**: Among the options, "keys" stands out as the tool specifically designed for identification based on contrasting characteristics. It uses a systematic approach to lead to the identification of a species.

5. **Select the Correct Answer**: Based on the definitions and evaluations, the correct answer is **B) Keys**.

### Final Answer:
The taxonomical aid for identification of plants and animals based on similarities and dissimilarities is **B) Keys**.