Which is the most effective way to determine if two species are closely related?

The most effective way to determine if two species are closely related is through the following steps:

1. DNA Sequencing: The most accurate method is to compare the DNA of the two species. The more similar the DNA sequences, the more closely related the species are likely to be. This is because DNA carries the genetic information of all living organisms and changes very slowly over time.

2. Morphological Comparison: This involves comparing the physical characteristics of the two species. If they have many traits in common, they may be closely related. However, this method is not always reliable because similar traits can evolve independently in species that are not closely related.

3. Fossil Record: Fossils can provide evidence of a common ancestor. If two species have a common ancestor, they are related.

4. Biogeography: The geographic distribution of species can provide clues about their evolutionary history. If two species are found in the same area, they may have a common ancestor.

5. Comparative Anatomy: This involves comparing the structures of different organisms to find similarities. If two species have similar structures, they may have a common ancestor.

6. Embryology: This involves comparing the early stages of development in different organisms to find similarities. If two species develop in a similar way, they may have a common ancestor.

Remember, no single method is foolproof. Scientists usually use a combination of these methods to determine the relationships between species.