Based on cladistics, which of the following best defines a clade?

• A. A group of organisms that share similar physical characteristics
• B. A group of unrelated organisms that have convergent traits
• C. A group consisting of an ancestor and all its descendants
• D. A group of species that occupy the same ecological niche

Answer: (C)

Verified step by step guidance

1. Understand the concept of cladistics: Cladistics is a method of classification based on common ancestry. It groups organisms into clades, which represent evolutionary branches stemming from a common ancestor.
2. Define a clade: A clade is a group consisting of an ancestor and all its descendants. This is a key principle in cladistics, emphasizing shared evolutionary history rather than physical similarities or ecological roles.
3. Eliminate incorrect options: Review the provided options and identify why they do not fit the definition of a clade. For example, physical characteristics can be misleading due to convergent evolution, and ecological niches do not necessarily reflect shared ancestry.
4. Focus on the correct definition: The correct answer is the option that describes a clade as 'a group consisting of an ancestor and all its descendants,' which aligns with the principles of cladistics.
5. Apply this understanding: Use this definition to analyze evolutionary trees or phylogenetic diagrams, ensuring you can identify clades based on shared ancestry rather than superficial traits or ecological roles.