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A. Individual organisms can change into new species through transitional forms. An example would be an individual fish becoming a new land animal. Therefore, fossils of transitional forms probably exist.
Individual organisms cannot change into different species. The formation of new species involves changes in entire populations of organisms, not just individuals, and may take thousands or millions of years. Try again.
B. All present-day species evolved from preexisting species. There must have been transitional forms with features of both the present-day species and the preexisting species from which they evolved, which could be found in fossils.
Correct! Populations within a species change over time and can give rise to new species. So, Darwin predicted that transitional forms, which have some features of the new species and some features of the ancestral species, would eventually be found in fossils. Select another correct answer. You selected all the correct answers.
C. The fossils of every species that ever existed will eventually be discovered, and it is likely that some transitional fossils will be among them.
Darwin did not expect fossils of every species to be discovered, as it is extremely rare for the remains of most organisms to become fossils. Even when a fossil does form, it may never be found. Try again.
D. Throughout life’s history, the evolution of new, major groups of organisms occurred over long periods of time and in many steps. Therefore, there are probably fossils, like transitional fossils, that show some of these steps.
Correct! Life has been evolving on this planet for at least 3.8 billion years. In that time, there have been several major transitions — for example, the transition from fish to land animals. Most major transitions involved many steps and paths, which are shown by fossils. Select another correct answer. You selected all the correct answers.
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A. wings supported by elongated fourth digits
This characteristic is present in pterosaurs, a group of Mesozoic reptiles, but not in living reptiles or Archaeopteryx. Archaeopteryx had wings with only three digits, and its feathers were attached along its arm and hand bones. Try again.
B. claws on the ends of each digit and a long bony tail
Correct! Both Archaeopteryx and most living reptiles have claws and a long bony tail. Birds, on the other hand, do not have claws on their forelimbs. Their forelimbs are adapted for flight, not grasping, digging, or defense. Living birds also do not have long bony tails. Although some birds may have long tail feathers, these feathers are not supported by bones. Select another correct answer. You selected all the correct answers.
C. the presence of a beak with no teeth
This characteristic is present in living birds, but not in Archaeopteryx or most living reptiles. Archaeopteryx and most living reptiles have jaws with teeth. Try again.
D. large size and the ability to fly
Large size is not a characteristic of all reptiles or of Archaeopteryx. (Archaeopteryx was only about the size of a raven, with a body length of 500 millimeters and weight of about 1 kilogram.) The ability to fly is a characteristic of Archaeopteryx but not of living reptiles. Try again.
A. Fossils of pterosaurs confirmed that these reptiles had hollow bones and wings.
Pterosaurs are reptiles that are closely related to dinosaurs, but they are not dinosaurs themselves. So, discoveries about pterosaurs did not overturn ideas about dinosaurs. Try again.
B. Fossils of the small theropod dinosaur Deinonychus showed that it walked on two legs and had a large sickle-shaped claw used for slashing.
Correct! Deinonychus’ anatomy, including its slashing claw, indicated that it was a fast-moving predator. This discovery showed that not all dinosaurs were large and slow, which helped convince the scientific community that birds had evolved from a certain group of dinosaurs. Select another correct answer. You selected all the correct answers.
C. A fossil of Compsognathus, a turkey-sized dinosaur discovered around the same time as Archaeopteryx, showed that it had features similar to those of Archaeopteryx.
It is true that Compsognathus had features similar to those of Archaeopteryx, which led Thomas Huxley to propose that birds are related to dinosaurs. However, his ideas were questioned and failed to convince the scientific community that birds evolved from dinosaurs. Try again.
D. Fossils of Archaeopteryx, which was about the size of a modern-day raven, showed that it had wings and a jaw with teeth, and that it walked on two feet.
The discovery of Archaeopteryx did suggest a link between dinosaurs and birds. However, this discovery did not change the prevailing view that dinosaurs were large and slow, and it did not immediately convince the scientific community that birds had evolved from dinosaurs. Try again.
A. Some dinosaur species nested and cared for their young in colonies, like birds do.
Correct! In 1978, Horner discovered a dinosaur nesting ground called “Egg Mountain” in Montana. This discovery suggested that some dinosaurs nested in colonies, cared for their young, and repeatedly returned to the same nesting ground — all behaviors associated with birds. Select another correct answer. You selected all the correct answers.
B. The bones of dinosaurs are solid but light, like those of birds.
Horner’s discovery did not show that dinosaur bones are solid. In fact, both birds and the dinosaurs thought to be the ancestors of birds have hollow bones, not solid bones. Try again.
C. Many dinosaur species are omnivorous, similar to birds.
Horner’s discovery did not show that many dinosaur species are omnivorous. Try again.
D. Neither birds nor therapod dinosaurs have a wishbone, but other dinosaur species do.
Horner’s discovery did not involve wishbones. Furthermore, both birds and therapod dinosaur species do have a wishbone. The presence of a wishbone is additional evidence supporting the hypothesis that birds descended from dinosaurs. Try again.
A. Birds and theropods have S-shaped necks.
Correct! Theropods and birds walk on two legs, which requires adaptations to other parts of their anatomy, such as an S-shaped neck. Select another correct answer. You selected all the correct answers.
B. Birds and most theropods can fly.
Most theropods probably couldn’t fly. Some modern-day birds, such as penguins and ostriches, also cannot fly. Try again.
C. Birds and many theropods have feathers.
Correct! It was once believed that only birds have feathers. However, reexamination of fossil evidence, as well as new fossil discoveries, revealed that many theropods had feathers too. Select another correct answer. You selected all the correct answers.
D. Birds and theropods have long bony tails.
Theropods have long bony tails, but living birds do not. Although some birds may have long tail feathers, these feathers are not supported by bones. Try again.
A. Feathered birds, which were capable of flight, evolved after the extinction of dinosaurs.
According to the film, feathered birds and dinosaurs coexisted with scaly dinosaurs for tens of millions of years. Try again.
B. Dinosaurs and birds are both endothermic, or warm-blooded.
There is no evidence in the film that dinosaurs were endothermic. In fact, there has been some debate about whether dinosaurs were ectothermic, like living amphibians and reptiles, or endothermic, like birds and mammals. Try again.
C. The evolution of feathers and other characteristics of birds occurred in a simple linear sequence.
As shown in the film, the evolutionary history of birds includes species with different combinations of traits. These traits did not appear in a simple linear sequence. Instead, different combinations of traits appeared in different species at different times. Try again.
D. Out of the many bird species that lived in the past, only toothless birds survived the global mass extinction that occurred 66 million years ago.
Correct! As discussed in the film, a small group of toothless birds survived the mass extinction and evolved into the thousands of bird species seen today. Select another correct answer. You selected all the correct answers.
A. Archaeopteryx had feathers and could probably fly.
Although this statement is true, it does not indicate that feathers had a function other than flight. Try again.
B. Some living birds have feathers but do not fly.
Correct! Some living birds that do not fly, such as penguins and ostriches, use their feathers for other functions, like insulation or communication. This evidence suggests that the first feathers could have been used for other functions too. Select another correct answer. You selected all the correct answers.
C. Bats fly but do not have feathers.
Flight arose independently multiple times in different lineages of organisms. However, flight in bats does not provide insights into the function of feathers. Try again.
D. Feathered theropods were not capable of flight.
Correct! Scientists have found a rich diversity of theropods with various feather structures, many of which lived before the evolution of flight. Since these theropods could not fly, their feathers must have had a function other than flight. Select another correct answer. You selected all the correct answers.
A. Transitional forms provide evidence that species descend with modification from other species.
Correct! Transitional forms support the theory of evolution because they have some traits of the descendant species and some traits of the ancestral species. This suggests that, within a single lineage, some new traits evolved before ancestral traits were lost. For example, Archaeopteryx shows that wings (a trait of modern-day birds) evolved before long bony tails (a trait of nonavian theropods) were lost. Select another correct answer. You selected all the correct answers.
B. DNA from the fossils of transitional forms provides information about how ancient organisms are related.
Most transitional fossils are too old to be a source of DNA. Under most conditions, DNA cannot be preserved as long as fossilized bones. Try again.
C. Transitional forms are evidence that Earth has a long history, spanning billions of years.
Transitional forms are not a major piece of evidence for the long history of life on Earth. Also, just the fact that Earth has a long history does not provide direct support for the theory of evolution. Try again.
D. The fossils of transitional forms allow us to reconstruct a complete history of life on Earth.
Even with transitional fossils, it’s impossible to reconstruct the history of all life on Earth. Most organisms are not fossilized. Even when a fossil does form, it may never be found. Countless fossils have been lost to erosion or tectonic plate movements or are buried too deep to be found by scientists. Try again.