Final answer:
Adopted siblings, fraternal twins, and identical twins can be placed in order from least to most biologically similar.
Step-by-step explanation:
In terms of biological similarity, the order from least to most similar would be:
- Adopted siblings
- Fraternal twins
- Identical twins
Adopted siblings share no genetic material, while fraternal twins share about 50% of their genetic material. However, identical twins are genetically identical because they come from the same fertilized egg. They share 100% of their genetic material, making them the most biologically similar.