Common Ancestors- Module 2.1

I chose to look further into common ancestry, because I feel that it is an important part of evolution that incorporates other aspects such as the fossil record and DNA.  A common misconception is that humans are direct descendants of monkeys. I learned in past classes that homologous structures are directly associated with common ancestors, because the structures were inherited from these ancestors. Homologous structures share anatomical structures between animals.

After reading an article from Khan Academy in which he explains how the branching tree depicts how common ancestors can be traced, I learned that the order of the evolution of specific characteristics can be observed. Over the course of multiple generations, we can find one common ancestor. Homologous structures play a role in connecting species together. These structures share similar morphological features even if they are different in their function.  The article mentions how “it’s unlikely that such similar structures would have evolved independently in each species.” One example includes the bone arrangement in limbs of humans, dogs, birds, and whales. Even though the sizes, shapes, and function may differ, the bones are laid out in the same general pattern.

Homologous structures between different species

    After watching a YouTube video, I was able to find an example explaining common ancestors based on vertebrates. It says that there must have been a common ancestor with vertebrae since backbones can be found in mammals, fish, amphibians, and reptiles. In the section of vertebrates, a sub-section of amniotes (which have amniotic eggs) can be recognized; the embryos in amniotic eggs are enclosed by an amnion, a fluid membrane. Amniotes include mammals and reptiles and would have a common ancestor that is more recent. Amniotes include two smaller sub-sections - mammals and reptiles. Mammals are warm-blooded, have hair, and can produce milk. Reptiles are cold-blooded, have scales, and produce watertight eggs.  As the groups get smaller, the organisms in the groups share more traits as they are more closely related to one another.

 

Monophyletic tree depicting common ancestors and shared traits 

Sources: 

Article- “Evidence for Evolution” by Khan Academy https://www.khanacademy.org/science/biology/her/evolution-and-natural-selection/a/lines-of-evidence-for-evolution

YouTube Video- “Why Evolution is True – Part 3: Common Ancestry by the channel MassComprehension... (“This is a “videobook” adaptation of the bestselling book Why Evolution is True by Biologist Jerry Coyne”.)       https://youtu.be/Ef0sTV_6SKw