Convergent evolution is illustrated by

Options

A. Dogfish and whale
B. Rat and dog
C. Bacterium and protozoan
D. Starfish and cuttle fish

Answer

### Step-by-Step Solution:

1. **Understanding Convergent Evolution**:
- Convergent evolution occurs when organisms from different evolutionary backgrounds develop similar traits or adaptations due to similar environmental pressures or ecological niches.

2. **Examples of Convergent Evolution**:
- The question asks for illustrations of convergent evolution. Some classic examples include:
- **Dogfish and Whale**: Despite being from different taxonomic groups (fish vs. mammals), both have streamlined bodies adapted for swimming.
- **Rat and Dog**: Both are mammals but have evolved different features suited to their lifestyles while sharing some functional similarities.
- **Bacterium and Protozoan**: These are unicellular organisms that may exhibit similar functions despite being from vastly different domains of life.
- **Starfish and Cuttlefish**: Although they belong to different phyla, they may have adaptations for similar functions in their respective environments.

3. **Key Characteristics of Convergent Evolution**:
- **Analogous Structures**: These are structures that perform similar functions but have different evolutionary origins. For example, the fins of a fish and the flippers of a whale serve the same purpose (swimming) but evolved independently.
- **Different Ancestors**: The organisms involved in convergent evolution come from different ancestral lines but adapt similarly due to similar environmental challenges.

4. **Conclusion**:
- Convergent evolution illustrates how different organisms can evolve similar traits when exposed to similar environmental pressures, despite having different evolutionary histories.