A group of organisms that her single common ancestor and all its dependent are termed as monophylic grouos....
refer to Google you well get perfect ans

**Cladistics: Classification Based on Evolutionary and Genetic Relationships**

**Introduction**

Cladistics is a method of classification that groups organisms based on their evolutionary and genetic relationships. It aims to organize organisms into groups called clades, which consist of an ancestor and all of its descendants. The classification is based on the principle that organisms that share more recent common ancestors are more closely related than those that share more distant common ancestors.

**Principles of Cladistics**

Cladistics is built on several key principles:

1. **Homology:** Cladistics relies on the concept of homology, which refers to similarities in organisms that are inherited from a common ancestor. Homologous traits are used to determine relationships between organisms.

2. **Shared Derived Characters:** Cladistics focuses on shared derived characters, also known as synapomorphies. These are traits that are unique to a particular group of organisms and are not found in their ancestors. Shared derived characters are used to define clades and determine evolutionary relationships.

3. **Outgroup Comparison:** Cladistics uses an outgroup, which is a taxon that is closely related to the group being studied but is not a part of it. By comparing the traits of the outgroup with those of the ingroup (the group being studied), ancestral and derived traits can be identified.

4. **Parsimony:** Cladistics employs the principle of parsimony, which states that the simplest explanation is usually the best. In cladistic analysis, the most parsimonious tree is the one that requires the fewest evolutionary changes to explain the observed data.

**Cladistic Analysis**

Cladistic analysis involves the following steps:

1. **Character Selection:** A set of characters, such as morphological traits or molecular sequences, is selected for analysis. These characters should be informative and show variation among the organisms being studied.

2. **Character Coding:** Each character is coded as either present (1) or absent (0) for each organism. This creates a matrix that represents the presence or absence of characters across the taxa.

3. **Character Analysis:** The matrix is analyzed using computational algorithms to determine the most parsimonious tree that explains the observed data. The tree illustrates the evolutionary relationships between the taxa.

4. **Clade Definition:** Based on the tree, clades are defined, which represent monophyletic groups. A monophyletic group is a group that consists of an ancestor and all of its descendants.

5. **Clade Nomenclature:** Clades are given names based on their relationships and hierarchy. For example, a smaller clade nested within a larger clade is referred to as a subgroup.

**Conclusion**

Cladistics is a powerful method of classification that uses evolutionary and genetic relationships to organize organisms into clades. It relies on homology, shared derived characters, outgroup comparison, and parsimony to determine the most likely evolutionary tree and define monophyletic groups. By studying the patterns of shared traits, cladistics provides insights into the evolutionary history and relationships of organisms.