Biology 1B Chapter 18
Each of the following observations comes from a different scientific discipline. Which is the best support for Darwin's concept of descent with modification?
Botanists provide evidence that South American temperate plants have more in common with South American tropical plants than temperate plants from Europe.
The selective breeding of plants and animals that possess desired traits is a process called artificial selection. For example, broccoli, cabbage, and kale are all vegetables that have been selected from one species of wild mustard. How is artificial selection both similar to and different from Darwin's conception of natural selection? Does artificial selection provide evidence for evolution by natural selection? Explain.
Both artificial selection and natural selection are the differential reproduction of individual organisms with favored traits. In artificial selection, humans have actively modified plants and animals by selecting and breeding individuals with traits deemed desirable. In natural selection, individuals are selected naturally as its traits deem it more fit for survival and reproduction
Why do scientists consider vestigial structures evidence for evolution?
Vestigial structures may or may not be useful, but have anatomical similarities even in very different organisms, suggesting that different populations of organisms evolved from a common point.
Mosquitoes resistant to the pesticide DDT were first noted in India in 1959. DDT-resistant mosquitoes are now found throughout the world. The graph shows the results of a DDT spray program, in which mosquitoes were considered resistant if they did not die within 1 hour of a 4% DDT dosage. Which scenario best explains the relatively quick increase in DDT resistance among the mosquito population?
A few DDT-resistant mosquitoes were present at the start of DDT application, and natural selection increased their frequency.
How does the scientific meaning of "theory" differ from the common vernacular meaning?
A scientific theory is a thoroughly tested set of explanations for a body of observations of nature, while people often use it to mean a guess or speculation.
Which type of speciation, allopatric or sympatric, is more common? Why?
Allopatric speciation is more common because it prevents gene flow between the species.
What is the key difference between allopatric speciation and sympatric speciation?
Allopatric speciation occurs when population becomes geographically isolated whereas in sympatric speciation, new species forms in the same geographical location as parent species.
Give an example of convergent evolution and explain how it supports the theory of evolution by natural selection.
An example of convergent evolution is the development of the same function, flying, in organisms that do not share a recent common ancestry, such as insects and birds. The fact that wings that allow flight have developed from very different original structures suggests that the process of natural selection can produce similar adaptations in two very different types of organisms who share a similar environment
Genes important in the embryonic development of animals have been relatively well conserved during evolution. This means they are more similar among different species than many other genes. What explains this genetic conservation across animal species?
Changes in the genes that are important to embryonic development have been relatively minor because mutational tweaking in the embryo has magnified consequences in the adult
Prior to 1800 in England, the typical moth of the species Biston betularia (peppered moth) had a light pattern. Dark colored moths were rare. By the late 19th century, the light-colored moths were rare, and the moths with dark patterns were abundant. The cause of this change was hypothesized to be selective predation by birds (J.W. Tutt, 1896). During the industrial revolution, soot and other wastes from industrial processes killed tree lichens and darkened tree trunks. Thus, prior to the pollution of the industrial revolution, dark moths stood out on light-colored trees and were vulnerable to predators. With the rise of pollution, however, the coloring of moths vulnerable to predators changed to light. Commonly used in biology textbooks, the peppered moth is a classic example of evolutionary change in action. The example describes changes in a population's allele frequencies-a small-scale change, evolutionarily speaking. The presence of both light and dark forms within the gene pool is demonstrated by the story, but the peppered moth stays a peppered moth. Which scenario, if it were to occur, would be a model for large-scale evolutionary change?
Conditions change such that the dark form of the moth is favored and the light form is eradicated in the population due to predation. Conditions change again, the dark form is vulnerable, and the dark form is eradicated due to predation.
How do environmental conditions affect the selection of particular adaptations? Cite evidence to support your ideas.
Environmental conditions identify a trait to be favorable or non-favorable. Favorable traits are selected and become more prevalent in a population. For example, an increase in the small bill size of finch population in Galapagos islands due to availability of soft-shelled seeds as a result of changing weather patterns.
Which of the following pieces of evidence illustrates evolution as an ongoing process?
Ethnic Tibetans are unique among humans for having physiological mechanisms that help them live in places with low oxygen levels.
A scientist has been studying a population of penguins in Antarctica for the last 30 years. What kind of evolution should she observe in the population?
Gradual evolution
What pattern in the fossil record would you expect to see to support the model of gradual speciation? How would you expect this pattern to differ from a pattern in the fossil record that supports the model of punctuated equilibrium? Explain.
In the case of gradual speciation, the fossil record would show many intermediate forms. For the case of punctuated equilibrium, the fossil record would show new forms that persist essentially unchanged through several geological layers, then disappear just as a new form appears
What conclusions can you draw about the relationship between the way in which the present-day theory of evolution developed and the credibility of the theory? Explain your thinking.
It is meaningful that two naturalists working independently from each other offered the same explanation for the same set of phenomena. When two people independently look at the same evidence and come to the same conclusion, this reinforces the credibility of that conclusion
Which of the following explanations is not correct regarding the Cambrian explosion?
Massive glaciation changed the climate of the Earth.
Select one misconception about evolution and explain what you might say to someone to dispel it.
Misconception: Humans are not currently evolving. Correction: The environmental pressures humans face are different than the ones they faced several thousands of years ago, but they are still there, and they are still producing (slowly!) evolutionary change.
Paleontologists have recovered a fossil for an organisms named Archaeopteryx. It has many features in common with reptiles, but, like birds, shows evidence of feathers. For what aspect of evolutionary theory does this piece of evidence suggest support?
Modern species share a common ancestor.
What role do prezygotic and postzygotic barriers play in speciation?
Prezygotic and postzygotic barriers prevent interbreeding of species such that there is no gene flow between them.
Use adaptive radiation to explain the diversification of the finches Darwin observed in the Galapagos.
The finches likely dispersed from one parent species, and natural selection based on different food sources in differing habitats led to adaptive changes, evidenced in the different beak shapes of the different species-each suited to a different food type.
How does adaptive radiation explain the diversification of the Hawaiian honeycreeper?
The honeycreepers dispersed from one founder species, and evolved in response to natural selection based on different food sources in their isolated habitats provided by water. Seed-eating birds evolved thick, short beaks. Nectar-eating birds evolved long, curved beaks, and insect-eating birds evolved sword-like beaks.
The process of mutation, which generates genetic variation, is random. Thus, life has evolved, and continues to evolve, randomly. Which statement is an appropriately evidence-based refinement of the above?
The process of mutation, which generates genetic variation, is random. However, the process of natural selection, which results in adaptations like the fit between a flower and its pollinator, favors variants which are better able to survive and reproduce. Natural selection is not random, so the overall process of evolution is not random, either.
The upper forelimbs of humans and cats have fairly similar structures. In contrast, the upper forelimbs of whales (their flippers) have bones with a different shape and proportion from both cats and humans. Interestingly, genetic data suggests that all three organisms have a common ancestor from about the same point in time. What is a likely explanation for these data?
The whale flipper is an adaptive characteristic unique to its water environment.
Populations of a nocturnal toad live along a long river. On the other side of a band of territory that is about 10 kilometers wide, there are populations of a toad that appear similar. Which of the following data would provide compelling evidence that the two populations represent different species?
There appear to be some hybrid toads between the two populations, but they are few and frail.
What is the basic difference between things that are homologous and things that are analogous?
Things that are analogous result from convergence and things that are homologous result from common ancestry
A friend says: "Natural selection is about the survival of the very fittest in a population. The fittest are those that are strongest, largest, fastest." Would you agree with that statement? Explain. What evidence from scientific disciplines can you offer to support your agreement or your disagreement?
What is meant by "fittest" is not necessarily strong, large, and fast. Fitness, as defined in evolutionary terms, has to do with survival and the reproduction of genetic material. For example, a small but showy male bird may be selected by female birds to reproduce, while a large but less colorful one is not.
Biogeography is the study of biological species as they relate to geographical space and geological time. The fossil record shows that dinosaurs originated about 200 to 250 million years ago. Would you expect the geographic distribution of early dinosaur fossils to be broad (on many continents) or narrow (on one or a few continents)? Explain.
broad because dinosaurs originated before the breakup of Pangaea
A species of walking stick insect, Timema cristinae, which lives in the hills of California, has two color patterns: solid green, and green with a singular white stripe. Scientists studying the insects found that they live on two species of bush. One type of bush has thick green leaves. The other type has thin green leaves. The scientists' research revealed that solid green insects tend to live on bushes whose appearance corresponds with their own: thick green leaves for the insects with solid green bodies and thin green leaves for the insects with the singular white stripe. The scientists hypothesized that camouflage from predators drove the bush-body correspondence. To study their hypothesis, they placed 200 insects on each type of bush. To some bushes they added well-matched insects. To others, they added mismatched insects. After one month, the mismatched populations were half that of the matched populations. Which of the following evolutionary concepts does the walking stick research most clearly illustrate?
natural selection due to predation
