Unit 7 Lesson 8: Transitional Fossils Flashcards
(15 cards)
By studying the limbs and fossils of different animals, such as a dolphin fin and a human hand what have scienesits noticed
By studying the limbs and fossils of different animals, such as a dolphin fin and a human hand, scientists have noticed that there are similarities in their bone structures. This is evidence that there is a correlation in the bone structures and that the limbs of animals may have evolved from the fins of fish.
The correlation of one variable’s influence on another was found in a specific type of rock that Shubin and his team had looked for in the fossils’ location. This evidence comes from the habitat of the Tiktaalik. The area is currently a dry plain, but when the animal was alive millions of years ago, it was a floodplain.
The bone structure indicates that it may have lived most of its life in the shallow waters and muddy areas of the floodplains near the shore. This protected the Tiktaalik from the larger fish that lived in the deeper waters and allowed it to eat the smaller fish in the shallow waters. The fossils of Tiktaalik indicate that the animal had ribs which were not needed for fish since the water supported its weight. The presence of ribs would allow it to prop itself out of water. The animal did not have a head and shoulders that were connected, which would allow it to move its head independently and raise its head out of the water.
Describe how natural selection leads to species that are adapted to their environment.
There is an increase of the gene that allows individuals to be adapted to their environment each generation. This leads to a population with a widespread expression of the trait that allows the organism to survive in its environment.
An animal that could adapt to living both on land and in water would have a better chance of surviving and reproducing in an area that experienced both flooding and dry periods. The climate during the period may have been a cause of Tiktaalik’s development of limbs that could support its weight on land due to the process of natural selection.
This gave the animal a competitive advantage and is known as the “missing link” between land and aquatic animals.
The discovery of a 375-million-year-old fossil of the animal Tiktaalik in the Canadian Arctic in 2004 helped scientists link land and water animals. What are its features
The Tiktaalik is considered a transitional fossil which has traits common with the first footed animal. The Tiktaalik is classified as a fish with scales and gills but has the head structure of a crocodile. The fins of the Tiktaalik have thin ray bones for paddling like most fish, but also contain sturdy interior bones that would have held the weight of the Tiktaalik in shallow water for wading.
Describe the characteristics of the Tiktaalik fossils that have labeled it a transition fossil.
Tiktaalik had many traits of fish but also had traits not associated with fish. It had stronger bones that allowed it to hold its weight in shallow water. There were also bone structures like ribs and a head and shoulders that were not connected that would also allow it to survive in shallow waters.
Describe how habitat correlated to the transition of the Tiktaalik from water to land, suggesting a causal relationship between its adaptations and the environment.
Scientists looked for specific rocks to show that the Tiktaalik was alive when the area was a floodplain, and they discovered that the Tiktaalik had lived in shallow water and mud plains. The Tiktaalik were animals that were adapted to and could survive in an area with dry periods and flooding, and thus they could reproduce and pass their genetics along.
Explain the difference between correlation and causation.
Correlation describes the relationship between two variables. Causation describes the ability of one variable to influence another.
What is the cause for the Tiktaalik becoming a land animal?
The climate during the period that the Tiktaalik lived could have been the cause of the animal developing limbs that could support its weight on land.
What is the significance of the Tiktaalik the students observed on their tablets?
The Tiktaalik may have been an intermediary organism between animals that lived on water and those that lived on land. Its adaptations also show a clear correlation between the environment, a floodplain, and the anatomical features you would need for survival in this type of environment, suggesting a causal relationship between the two. This supports the theory of evolution by natural selection.
transitional fossil
a fossil that has features of organisms from different parts of the evolutionary tree, which demonstrates an evolutionary relationship between those parts of the evolutionary tree and supports Darwin’s theory of evolution and common ancestry
Archaeopteryx
Archaeopteryx is placed as a transitional form between nonavian dinosaurs and birds. The fossil shows the animal had a long-feathered tail and small teeth, like nonavian dinosaurs. But the animal also had flight feathers and wings, like modern birds. The fossils also showed a fused clavicle bone, which confirmed the relationship between birds and dinosaurs since they are the only two groups with this characteristic.
Pakicetus is another example of a transitional fossil.
This fossil shows the correlation between whales and land animals. The Pakicetus fossils show that whales may have started out as small land mammals. This animal was about the size of a wolf and had a diet of meat and fish. While the Pakicetus has the body of a land animal, its head is shaped like a whale with an ear bone that is unique to whales.
The discovery of Pezosiren portelli connected land and marine sirens such as manatees.
The fossils show that Pezosiren portelli had four legs that were able to walk on land but also the skull, teeth, and thickened ribs like fully aquatic sirens. Its heavy structure suggests the animal spent most of its time in the water.
