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Questions and Answers
What is the primary function of the limbs in Basilosaurus?
What is the significance of the presence of hind limbs in Basilosaurus?
What is the term used to describe organs or parts that have lost their original function but persist in a reduced form?
What does the fossil record of early whales like Pakicetus and Ambulocetus demonstrate?
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What is the primary evidence that supports the idea that Basilosaurus is a transitional form between land-dwelling mammals and fully aquatic whales?
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What is the primary method used to determine the age of fossils and rocks?
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Which group of organisms is thought to have evolved first according to the fossil record?
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What is the significance of transitional characteristics in fossils like Basilosaurus?
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What is the general pattern of appearance of fossils in the geological record?
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What is the main conclusion that can be drawn from the study of fossils and the fossil record?
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Study Notes
Evidences for Evolution
- Classification, fossils, anatomy, chemical/molecular similarities, physiology, embryology, and geographic distribution of organisms are all evidences that support evolution.
Fossil Record
- The age of fossils and rocks is determined using radioactive elements such as carbon, fluorine, and uranium.
- The fossil record reveals that living organisms change gradually and transform from one form to another over millions of years.
- The appearance of fossils occurs according to a regular order, with vertebrates appearing in the following order: jawless fish, amphibians, reptiles, birds, and mammals.
- Non-vascular plants preceded vascular plants in existence.
Fossil Record as Evidence of Evolution
- Fossils provide a record of ancient life and give information about the evolution of living organisms across the eras.
- Fossils provide a complete picture of past life and are conclusive material evidence of evolution.
- The remains and traces of organisms found in sedimentary rocks give an indisputable record of past changes over long periods of time.
- Extinct species have been recorded as having transitional characteristics between the main groups of living organisms, confirming that species are not fixed, but can develop into other species over time.
Basilosaurus: A Fossil Evidence of Evolution
- Basilosaurus is a fossil that supports the theory of evolution, with a mix of features showing it as a transitional form between land-dwelling mammals and fully aquatic whales.
- Basilosaurus lived during the Eocene epoch (around 41.3 to 33.9 million years ago) and had a long, serpentine body with well-developed hind limbs.
- These limbs were likely used for swimming but were not as functional for land movement as those of its ancestors.
Basilosaurus: Transitional Anatomy and Descent with Modification
- Basilosaurus's transitional anatomy shows a mix of features, with a streamlined body for aquatic life and vestigial hind limbs.
- Scientists believe Basilosaurus descended from a group of terrestrial carnivores called Mesonychids, with the presence of hind limbs pointing to this terrestrial ancestry.
- Over time, these limbs became less important as Basilosaurus adapted to a fully aquatic lifestyle, demonstrating a gradual modification of a trait over generations.
Basilosaurus: Fossil Record Progression and Loss of Function
- Fossils of other early whales like Pakicetus and Ambulocetus show an even stronger link to land mammals with well-developed limbs.
- These fossils, along with Basilosaurus, depict a gradual shift in anatomy towards a fully aquatic existence in whales.
- The presence of vestigial hind limbs in Basilosaurus showcases the concept of vestigial structures, which are organs or parts that have lost their original function but persist in a reduced form due to their evolutionary history.
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Description
Explore the various evidences that support the theory of evolution, including classification, fossils, anatomy, and more. Learn how scientists use radioactive elements to determine the age of fossils and rocks.
