Nelson Text Review Questions   : Chapter 3

 

1. The modern view of evolution is based on scientific evidence which combines both genetic information and the theory of natural selection. It implies a change over time. Earlier beliefs were based on opinion and nonscientific evidence. This earlier view held that living things had been “fixed” since the beginning, and were unchangeable.

 

2. The variety (adaptation) of beak types displayed by the islands’ finch species made the greatest impression on Darwin.

 

3. Survival of the fittest means that individuals with traits best suited for and environment are better able to compete, survive, and reproduce. Adaptation is the basis through which natural selection can occur, with those individuals that are best adapted to particular environments becoming the most successful reproducers. The direction of evolution is determined by the adaptation.

 

 

4. Lamarck offered and explanation for the mechanism of evolution – that species change over time, and that the environment is a factor n that change. He showed that evolution is adaptive and that the diversity of life is the result of adaptation (see pages 91- 93).

 

5. Buffon’s theory indicated that the creation of a species did not occur in a single place at a single time and that a species was not created in a perfect state. Later he wondered if certain species might develop from a common ancestor. Darwin accepted Buffon’s ideas and went on to provide an explanation for the manner in which species change over time.

 

 

6. Structural, physiological, and biochemical are the three types of adaptation.

 

7. The moths adapted a color (pigmentation) change from light-colored to predominantly dark-colored (melanic) forms in response to the environmental changes caused by the industrial fumes of the mid-1800s.

 

Applying the Concepts

 

1. The study of genetics has shown that acquired characteristics cannot be passed on to offspring, so Lamarck’s ideas have been proven incorrect.

 

2. a) Lamarck would have suggested that the zebra wanted to avoid the annoying bite of the tsetse fly and developed the striped to do this.

 

 

1. b) Darwin or Wallace would have suggested that some zebras were striped more than others. Tsetse flies bit those that had few stripes, or had pale stripes. These zebras got the parasite and died, and the striped zebras, which were bitten less frequently, reproduced and passed the stripes to their offspring.

 

1. c) Answers can vary.

 

3. Human activities can affect evolution by isolating populations of organisms in different areas. Small organisms are less likely to cross roads to find a mate, so the road can become an effective barrier. Bridges can bring two isolated populations together, stopping their speciation.

 

4. Lamarck had recognized the impact of environmental factors on the course of evolution. He recognized that the mechanism for evolution was natural selection through adaptation. This became the basis for Darwin’s theory of evolution.

 

 

5. The traditional and widely accepted model for the rate of evolutionary change holds that change occurs slowly or gradually within populations of organisms. The peppered moth case (and others mentioned in the test) demonstrated that certain changes (e.g., coloration in moths) can take place rapidly.

• Some populations (e.g., mosquitoes exposed to insecticides) show wide fluctuations in number, indicating the loss (or gain) of tremendous numbers of individuals, but the species continues (although it may evolve in the process).

 

• The loss of individuals may reduce the gene pool and modify the population, but the species continues.

 

• The life span of individuals is trivial in comparison to the “life span” of species. Hence, specific individuals contribute very little to the survival of the species. On the other hand, if the species does not survive, there will of course be no more individuals.

7. Adaptation to environment is a very complex process and very difficult to study in the natural environment. It is impossible, for example, to devise and experiment to show the effect on a caribou population of another ice age. Adaptation also takes a very long time, and may not be suitable for direct study (e.g., even an adaptation taking hundreds of years would be difficult to study directly). Carefully constructed computer models mimic the response of organisms in the “real world,” and allow scientists to run simulations that show, in minutes, the effects of environmental changes that might take years of real time. They can also vary different aspects of the environment and look at their effects on populations. Supercomputers allow such models to contain far more complexity and to be more realistic. Examples will be various.
8. Answers will vary, and might include some of the following:

 

• Roads can be a barrier to some species, and their construction can subdivide populations. Each smaller population may experience slightly different selection pressures, and it may contain a slightly different gene pool than the original, continuous, population.

 

• Hydroelectric dams cause extensive flooding and disruption of natural populations, creating new sets of selection pressures which can affect the direction and rate of evolution. Some major projects have even been stopped because they would cause the extinction of a specific organism found only in the area that would be disrupted by the dam.

 

• The building of navigable waterways connecting previously unconnected (or poorly connected) bodies of water allows the spread of species beyond previous limits, and alters community composition and selection pressures (e.g., the lamprey entering the Great Lakes).

 

• Pumping of wasted water from ships’ bilges has been implicated in the introduction the zebra mussel to the Great Lakes, introducing a new and fast-growing grazer to the community, with implications both for existing species and for our use of the waterways.

 

9. High reproductive capacity is normally linked with high egg number and short development time (e.g., many species of fish and insects). Where there are many young, there will be many different combinations of parental genes, increasing the chance that there will be some combinations that are better able to withstand a particular selection pressure. Such populations can also respond more rapidly to sudden pressures. (Compare the response of humans, which have a nine-month gestation period and approximately 20 years between generations, with the response of flies, which may have only days between successive generations.)

 

Critical-Thinking Questions

1. Answers will vary. When humans are domesticating animals and plants, they choose traits that they (the humans) want to propagate. They do not allow “nature to take its course.” For example, animals many thousands of miles apart can parent an offspring by artificial insemination; this would not occur naturally.

 

2. answers should recognize that, in the Galapagos, similar populations of organisms invaded a series of islands on which there were different selection pressures. It is almost the type of situation a researcher might set up if she were interested in evolution in natural situations, and if she had hundreds (perhaps thousands) of years to observe the results. Answers should include the idea of isolation one island population from populations on other islands and /or the mainland.

 

3. If a Lamarckian explanation of evolution were to be endorsed, then evolutionary changes in an organism would be interpreted as meeting the needs of the individual organism.

 

4. Answers will vary, but may be evaluated in relation to the literature used to research them.