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Transcript
Chapter 2 Review Questions Knowledge 1. Primary succession is the process of changing—in successive stages—an environment from an area of bare rock and few species to a complex community. 2. Logging, forest fires, tilling soil, or any other event that removes the vegetation without removing the soil could all cause the process of secondary succession to begin. 3. Secondary succession occurs where soil already exists. It is a much faster process than primary succession. 4. Open populations are affected by the number of births, deaths, immigration, and emigration, while closed populations do not have any immigration or emigration to affect their numbers. In many cases, closed populations are artificial. 5. Carrying capacity is the maximum number of individuals that can be sustained in a given environment for an indefinite period. 6. This graph shows the exponential growth of a population. 7. The carrying capacity of a population is outlined in this graph. 8. a. The ability to fly allows an owl the advantage of being able to see from a great vantage point and attack from the air. b. A sharp beak and talons are good for killing and tearing apart prey. c. Huge eyes allow for good vision even in low light or dark conditions. d. Feathers that muffle the sound of flying make the owl a stealthier hunter. The prey does not even hear the owl approaching for a kill. 9. The three main concepts of Darwin’s theory of natural selection are the following: Organisms usually produce more offspring than can survive. There is variation among individuals in a population. Organisms compete for limited resources. 10. Fitness in biological terms is the ability of an organism to survive and then successfully reproduce. It is not solely a measure of an individual’s strength, speed, or health, although this may influence its fitness. 11. A mutation is a change to the genes. The genes provide instructions to the body and the change in instructions may be harmful—this is demonstrated by cancer. A mutation may provide an advantage, for example, a changed beak shape for the Galapagos finch for a more varied diet. Eye colour for a cat is an example of a neutral mutation. 12. Acceptance of Darwin’s theory is dependent upon acknowledging the evidence preserved in the fossil record that organisms have changed over time. People who are reluctant to accept this evidence have difficulty with Darwin’s theory. 13. Darwin suggested that the variety of finches on the islands all came from a common seedeating finch ancestor. Within the population of offspring there was a variation in many traits, including some finches born with slightly different beaks. This enabled them to eat different types of food that, in turn, provided them with the advantage of less competition for that food source. Those finches best suited to the new food source survived to breed and demonstrated their superior fitness to other members of the population—these finches were able to pass on their adaptation of being able to utilize a new food source to their offspring. Over many generations, several new species of finches developed that were well adapted to eating different foods than their ancestors did. 14. Asexual reproduction does not require a mate for reproduction. Time and energy is saved by simply budding or sending a runner out to create a new plant. Asexual reproduction is fast (as in bacteria). A drawback to asexual reproduction is that there is a lack of variation, which limits natural selection and evolutionary change. Applying Concepts 15. The conditions that allowed the exponential growth of the beavers on Tierra del Fuego include a vast food supply of old-growth forests and no natural predators. 16. Similarities between these two situations would be the exponential growth of both populations after they are introduced by humans to a new habitat where there is a lack of predators and competition. In both cases, the herbivores are causing environmental destruction and are conflicting with the interests of the people who introduced them. 17. A difference between the two situations is the fact that the beavers are aquatic animals and the potential for them to spread further is a risk. The reasons for introduction also differ between the two situations—the beavers were introduced for fur and the rabbits were introduced for food and sport. 18. Note the following polar-bear advantages. Adaptation slightly webbed toes white fur 19. a. b. Reasons for Advantage improves swimming after prey helps polar bear sneak up on its prey by blending in with its surroundings a thick layer of fat and black skin underneath fur thick fat acts as insulation and black skin helps absorb heat female polar bears hibernate in dens with cubs until spring saves on energy required for moving and hunting— can conserve energy and use it for producing milk for young ability to stand up on hind legs allows bear to see prey over snowdrifts or get a better scent of prey covers its black nose when stalking a seal increases its camouflage The conifers preserve their place as the dominant species by keeping their environment most favourable for conifers. Species such as grasses and shrubs are not able to grow as well in a climax forest— this creates stability in the community. The process of succession has ended until the climax community is removed. 20. The disturbed area around the volcano is going through the process of primary succession. The soil has been removed and the graph shows a large number of pioneer species, such as lichens and mosses. 21. Answers will vary somewhat, but the three bar graphs should look similar to these. 22. It would be unlikely for someone to see an equal amount of each type of organism in the sample area. This is because one type of organism creates conditions unsuitable for the growth of another type of organism. The process of succession replaces one dominant community with another. For example, tall coniferous trees would create too much shade for grasses or shrubs to thrive. 23. The graph should look similar to this one. 24. The insect population in terrarium #1 is displaying S-curve growth. The population reaches its carrying capacity and stays there. The insect population in terrarium #2 is displaying Jcurve growth and goes through population explosions and crashes. 25. If both insect populations were placed in the same terrarium, the insects that reproduce exponentially would probably outcompete the slower reproducing insects. The rapidly rising population of the insects that were in terrarium #2 would eat all the food before the other population had a chance to reach its carrying capacity. 26. The sickled cells would have a harder time carrying oxygen because of their shape. Individuals with sickle cell anemia would constantly be short of oxygen. 27. Although the sickle cell anemia mutation makes individuals sick, it provides resistance to malaria. Illness from sickle cell anemia is a better alternative than death from malaria, so the gene persists in the population. 28. The removal of malaria from the population would probably result in a reduction in the number of individuals who carry the sickle cell anemia mutation over time, because carrying the mutation would no longer be an advantage. 29. Darwin would explain the development of the prehensile tail of the New World monkeys as follows. At one time, most New World monkeys had non-prehensile tails, but because of natural variation (mutation) a few had tails that were more flexible. The more flexible tails provided an advantage for moving through the trees, and these individuals were able to find food, mates, and/or escape predators better because of this adaptation. The flexible-tail monkeys were better able to survive to create more offspring, and soon flexible tails were found in much of the population. Over time, more and more flexible tails were selected until a true prehensile tail had developed. 30. Weismann’s experiment did not support Lamarck’s idea of acquired inheritance of characteristics because there was no change to the genes or instructions in the mice to produce shorter tails. Lamarck’s theory was not accepted because there was no evidence to support the theory. 31. It is still important to study Lamarck because he caused people to think about the idea that populations of organisms change over time. This was a revolutionary idea for his time, and he helped pave the way for Darwin’s ideas. Science 20 © 2006, Alberta Education