We can also look at the bodies of animals today and find features that are similar to what other animals have, but which no longer seem to function or have different functions. Scientists call these vestigial traits. Some classic examples are non-functioning eyes in blind cave fish, the hip bones on whales, and leg bones buried in the muscles of some snakes.
In our own bodies, we can point to the appendix, wisdom teeth, goosebumps, and many other features. Consider the record of whale evolution that has been preserved in fossils. In just the past few decades, paleontologists have found a remarkable succession of fossils.
The oldest known whales, including Pakicetus from around 49 million years ago, looked like land-dwelling mammals but had ears similar to those of modern whales, suggesting adaptations for hearing under water. The slightly younger Ambulocetus shared these ear traits and had feet that were expanded for swimming.
Similar species like Maiacetus and Rodhocetus appear later on with feet and spines adapted for more specialized swimming modes. By 40 million years ago, whales like Dorudon and Basilosaurus were fully aquatic animals with a powerful tail that moved up and down through the water during swimming rather than side to side as in fish and rudimentary but fully formed hind limbs that could no longer support the body on land.
But there are now thousands of fossil specimens—in the whale lineage alone—that fit into this pattern. These include over 60 different species. And closer to home, there are patterns found among the fossils and artifacts in our own lineage that show a transition from four-footed to upright bipedal walking, increase in brain size, and the use of ever more sophisticated tools.
The theory of evolution predicts patterns of species not just over time in the fossil record, but also in the distribution of species today around Earth—the study of which is called biogeography. The differences between species on islands compared to mainlands provide a compelling example of evolution. Because islands provide isolated habitats where there is little chance of interbreeding with mainland species, evolutionary theory predicts that differences will accumulate and new species will evolve.
Before human migration, the only species on the island must have travelled great distances in rare events. After arriving, they adapted over many generations in isolation from their mainland counterparts and in different conditions.
This promoted their evolution into new species. So today we find in Hawaii many species of birds, insects, and plants that are found nowhere else on Earth, but are distant cousins of mainland forms. Other islands were once connected to continents but have moved away because of plate tectonics.
In the case of Madagascar, the island was originally connected to the massive landmass that would become South America, Africa, and Australia. At that time species were able to freely inhabit it. The degree to which the remains are decayed when covered determines the later details of the fossil.
Fossils usually consist of the portion of the organisms that was partially mineralized during life, such as the bones and teeth of vertebrates or the chitinous or calcareous exoskeletons of invertebrates.
However, other fossils contain traces of skin, feathers or even soft tissues. Fossils may also consist of the marks left behind by the organism while it was alive, such as footprints or feces. These types of fossils are called trace fossils, or ichnofossils, as opposed to body fossils. Past life may also leave some markers that cannot be seen but can be detected in the form of biochemical signals; these are known as chemofossils or biomarkers.
The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous fossil-containing rock formations and sedimentary layers strata is known as the fossil record.
The fossil record was one of the early sources of data underlying the study of evolution and continues to be relevant to the history of life on Earth. You can see the bone structure of past organisms and compare with that of present day. Explanation: By looking at fossils, one is able analyze the physical structures of past organisms, many which have since gone extinct.
Related questions Why is the fossil record an incomplete history of life? How does the fossil record corroborate phylogenetic history? How does the fossil record support the theory of continental drift? Species A is therefore most similar to species B.
Species F and G also share a recent, yet different, common ancestor, which itself shared a common ancestor with species E. All seven species share a common ancestor, probably from the distant past. The information is collected from a variety of sources such as fossil records to DNA sequences.
Evidence of evolution - rock fossils Fossils A fossil is the preserved remains of a dead organism from millions of years ago.
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