Evolution works by tinkering with what is already there. It is far more likely that an advantageous change to an existing structure can occur than a gross change providing an advantage.
An example would be the transition from fishes to amphibia. Small incremental modifications to fins to provide some of the functionality of walking limbs are far more likely to occur than limbs suddenly sprouting from a body where there was nothing there before, which would be nigh-on impossible.
Yes, homologous structures have common bone and muscle structures suggesting that they came from an common ancestor while analogous structures do not share any similarity in features, suggesting that they derived from two separate origins.
My spidey senses are telling me to tell you to look in your book.
Learning that the flipper of a whale is really just like your upper arm.
Though the forelimb of your cat or dog does not look much like your arms these are homologous structures that are almost identical bone for bone. This shows the common ancestry of all tetrapods and the closer common ancestry of you and your mammal pets.
Homologous structures.
Structures
In biology, homologous structures are defined as structures which serve the same purposes because they evolved from the same source (divergent evolution), the opposite of analogous structures, which serve the same purpose but evolved through convergent evolution. Birds' wings and bats' wings are both homologous and analogous. As wings, the two are analogous, but as forelimbs, the two are homologous.
They don't, Homologous structures, such as the bones in your forearms and the bones in your cat's and dog's forelegs are that similar because you and your pets are mammals and closely related on the evolutionary tree. Before modern genetic showed this to be convincing the study of morphology was showing us pretty much the same thing; homologous structures support evolution.
Homologous structures among animals are similar body parts that suggest a common ancestry. These structures provide evidence for evolution because they indicate that different species share a common evolutionary history and have evolved from a common ancestor.
Yes, homologous structures have common bone and muscle structures suggesting that they came from an common ancestor while analogous structures do not share any similarity in features, suggesting that they derived from two separate origins.
Homologous structures indicate a common ancestor
My spidey senses are telling me to tell you to look in your book.
homologous structures. These structures indicate common ancestry and are evidence for evolution. Examples include the wing of a bird and the flipper of a dolphin.
Learning that the flipper of a whale is really just like your upper arm.
share a common ancestor. These structures are similar in form and function but may have evolved to serve different purposes in different species due to natural selection. The presence of homologous structures supports the theory of evolution.
Homologous structures.
Though the forelimb of your cat or dog does not look much like your arms these are homologous structures that are almost identical bone for bone. This shows the common ancestry of all tetrapods and the closer common ancestry of you and your mammal pets.