Evidence of Evolution

Overwhelming evidence supports that natural selection has and continues to act on populations of organisms. Natural selection is behind the reasoning driving many current day decisions:

how to treat species that may be endangered
how public health regulations are decided
how we rid ourselves of disease and pests
how we grow food

In the following video we will visit the Galápagos Islands to see a living "laboratory" of natural selection and unearth the latest discoveries in the islands' fossils. While watching the program, listen and look for information that will help us:

describe the evolution of the elephant from its 50-million-year-old ancestors to today's pachyderms.
explain (by studying fossils on Galápagos) what event seems to be the cause of extinctions on the islands.

The video is approximately 20 minutes long. Pause the video when necessary to make notes.

Homologous Image

Pictures are skeleton images of human arm, cat leg, bat wing, porpoise flipper, and a horse leg. Similarities in the stages of embryonic development and body structures help provide evidence to support the theory of evolution. The embryos of a fish, chicken, salamander, and human have tiny gill silts along their throats and a tail during the very early stages of development. Of course, the adult versions of these animals do not look alike. However, the similarities in the early development of these vertebrate embryos indicate that are related and are descendants of a common ancestor. The presence of vestigial structures is another indication that certain organisms evolved from a common ancestor. Organs or body structures which are present in an organism but have no useful purpose are called vestigial structures. In humans, the tailbone at the tip of the spine and wisdom teeth are vestigial structures. They may have had some important use in the past for our ancestors. Many mammals that have tails use them for balance and communication. The tailbone was no longer useful as our ancestors began to walk upright.

3D CT Image of impacted wisdom tooth Have you had your wisdom teeth removed? The pain a person gets when their wisdom teeth come in is due to them emerging through their gum at an irregular or horizontal angle. There is usually not enough room in a person's jaw for wisdom teeth. The removal of the wisdom teeth has no adverse effect on a person's dental health or wellbeing. It is believed that our ancestors had larger jaws that could accommodate the extra teeth. Homologous structures are organs and bones that are similar in different organisms that were inherited from a common ancestor. The similar forelimb bone structure in a dog, dolphin and bird indicates that they are related. The arrangement of the bones in the dolphin's flipper, bird's wings, and the dog's leg suggests that they were inherited from an earlier vertebrate that is closely related to the three types of animals. The different species evolved from a common ancestor.

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