Creatures that share similar structures also share a close common ancestor.
Similar structures between species shows that each of these species also share similar functions of these same parts.
Similar bone structures between these creatures supports Darwin's idea that as species evolve from a common ancestor, modifications will develop.
Whales descended from an ancestor that used hind limbs to walk and swim.
Whales' ancestors have increased their use and function of their hind limbs.
40 million years ago, whales crawled up on land and used these hind limbs to support their weight.
Marsupial species are the same in various geographic locations around the world.
When the common ancestor of these marsupials both inhabited two different locations, over time natural selection led to new species of marsupials.
Natural selection will cause marsupials to evolve into the same species at different locations.
Marsupial evolution on different continents leads to an decrease in diversity.
The ancestors of whale increased its dependence upon these bones
Millions of years ago, the ancestors of whales maintained the function for this structure.
Over time, as the whale evolved in becoming adapted to water, the function for this structure was minimized.
All species have evolved in this area over the last 10 million years.
Natural selection has diversified the fox and dog species in this region over the last 10 million years.
Evolution appears to happen at constant rates.
The arctic fox and the Cape Fox will show more similarities in embryonic development than the cape fox and the raccoon dog.
Dogs and foxes would not share homologous structures.
Dogs would have more homologous structures with the arctic fox than the wolfe species