Biology II Chapter 22

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Biology II Chapter 22
2011-10-06 18:36:55
Biology Campbell Descent Modification Darwinian View Life

Chapter 22 of Campbell's Biology Textbook - Descent with Modification - A Darwinian View of Life
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  1. What are the three key observations about life?
    • 1) The striking ways in which organisms are suited for life in their environments
    • 2) The many shared characteristics (unity) of life
    • 3) The rich diversity of life.
  2. What is evolution defined as by Darwin?
    Descent with modification - Proposing that many of Earth's species are descendants of ancestral species that were different from present-day species.

    Also, it may defined as a change in genetic composition of a population from generation to generation.

    It may be looked at as a pattern and as a process.
  3. Evolution may be defined as a pattern and as a process. The pattern of evolutionary change is revealed by data from a range of scientific disciplines, including biology, geology, physics, and chemistry as observations about the natural world.
    The process of evolution consists of the mechanisms that produce the observed pattern of change. These mechanisms represent natural causes of the natural phenomena we observe.
  4. Aristotle viewed species as fixed or unchanging. Why was this?
    Through his observations of nature, Aristotle recognized certain "affinities" among organisms. He concluded that life-forms could be arranged on a ladder, or scale, of increasing complexity, later called the scala naturae. Each form of life, perfect and permanent, had its alloted rung on this ladder.

    It coincided with the Old Testament account of creation where the match of organisms to their environment was assumed to be evidence that the Creator had designed each species for a particular purpose.
  5. (T/F) Linnaeus developed the two-part or binomial system of naming organisms according to genus and species. In contrast to the linear hierarchy of the scala naturae, he adopted a nested classification system - a grouping similar to species into increasingly general categories.

    Linnaeus did not ascribe the resemblances amount species to evolutionary kinship, but rather to the pattern of their creation.

    This classification system would play a role in Darwin's argument for evolution.
  6. What are fossils? Where are they located?
    The remains or trace of organisms from the past.

    Most fossils are found in sedimentary rocks formed from the sand and mud that settle to the bottom of seas, lakes and swamps. New layers of sediment cover older ones and compress them into superimposed layers of rock called strata.

    Erosion may carve through the upper (younger) strata, revealing deeper (older) strata that had been buried.
  7. What is the study of fossils?

    Cuvier noted that the older the stratum, the more dissimilar its fossils were to current life-forms. He also observed that from one layer to the next, some new species appeared while others disappeared.

    He inferred that extinctions must have been a common occurence in the history of life.
  8. Cuvier advocated catastrophism to explain what observations? What is catastrophism?
    Cuvier noted that the older the stratum, the more dissimilar its fossils were to current life-forms. He also observed that from one layer to the next, some new species appeared while others disappeared.

    Catastrophism is the principle that events in the past occured suddenly and were caused by mechanisms different from those operating in the present.

    Cuvier speculated that each boundary between strata represented a catastrophe, such as a flood, that had destroyed many of the species living at that time. He proposed that these periodic catastrophes were usually confined to local regions, which were later repopulated by species immigrating from other areas.

    Cuvier advocated against evolution.
  9. Lyell's prinicple of uniformitarianism includes what factors?
    LLyell's uniformitarianism stated that mechanisms of change are constant over time and proposed that the same geologic processes are operating today as in the past, and at the same rate.
  10. What was Lamarck's hypothesis of evolution?
    SSeveral naturalists suggested that life evolves as environments change. Only one of Darwin's predecessors proposed a mechanism for how life changed over time.

    Lamarck is remembered for incorrect mechanism he proposed to explain how evolution occurs. The hypothesis was based on two priniciples:

    1) use and disuse - the idea that parts of the body that are used extensively become larger and stronger, while those that are not used deteriorate.

    2) inheritance of acquired characteristics - an organism could pass these modifications to its offspring.

    Lamarck also thought that evolution happens because organisms have an innate drive to become more complex.
  11. How did Hutton's and Lyell's ideas influence Drawin's thinking about evolution?
    Hutton and Lyell proposed that events in the past were caused by the same processes operating today. This principle suggested that Earth must be much older than a few thousand years, the age that was widely accepted at that time.

    Hutton and Lyell also thought that geologic change occurs gradually, stimulating Darwin to reason that the slow accumulationg of small changes could ultimately produce the profound changed documented in the fossil record. In this context, the age of Earth was important to Darwin, because unless Earth was very old, he could not invision how there would have been enough time for evolution to occur.
  12. What are adaptation? What are some of the examples of adaptations that Darwin observed on his voyage?
    Adaptations are characteristics of organisms that enhance their survival and reproduction in specific enviconments.

    He assed from his observations that to the environment and the origin of a new species as closely related processes.

    The Galapagos Islands are home to more than a dozen species of closely related finches, some found only on a single island. The most striking differences amount them are their beaks, which are adapted for specific diets.
  13. What is Darwin's idea of natural selection?
    A process in which individuals with certaininherited traits leave more offspring than individuals with other traits. Darwin's idea was centered around how adaptation arise and are central to natural selection.
  14. What are the two main ideas in Darwin's The Origin of Species?
    1) Descent with modification explains life's unity and diversity

    2) Natural selection brings about the match between organisms and their environment.
  15. Who was the naturalist who had sent Darwin a manuscript detailing a hypothesis of natural selection similar to Darwin's?
  16. What is Darwin's Descent with Modification?
    Darwin perceived unity in life, which he attributed to the descent of all organisms from an ancestor that lived in the remote past. He also thought that as the descendants of that ancestral organism lived in various habitats over millions of years, they had accumulated diverse modifications, or adaptations, that fit them to specific ways of life.

    Darwin reasoned that over long periods of time, descent with modification eventually led to the rich diversity of life we see today.

    Darwin viewed the histroy of life as a tree, with multiple branchings from a common trunk out of the tips of the youngest twigs. The tips of the twigs represent the diversity of organisms living in the present. Each fork of the tree represents an ancestor of all the lines of evolution that subsequently branch from that point.

    In some cases, there are no living species that fill the gap between some lineagess and their closest relatives today. In fact, many brnaches of evolution, even some major ones, are dead ones.

    To Darwin, the Linnaean hierarchy reflected the branching history of the tree of life, with organisms at the various levels related through descent from common ancestors.
  17. What is artificial selection?
    An example of artificial selection is selective breeding of domesticated plants and animals. In these cases, humans have modified other species over many generations by selecting and breeding individuals that possess desired traits.

    As a result of artificial selection, crop plants and animal bred as livestock or pets often bear little resemblance to their wild ancestors.
  18. What were the four observations from nature that Darwin made?

    From these observations, he drew the following inferences:

    1) Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given encironment tend to leave more offspring than other individuals.

    2) This unqueal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations.
    1) Members of a population often vary greatly in their traits.

    2) Traits are inherited from parents to offspring.

    3) All species are capable of producing more offspring than their environment can support.

    4) Owing to lack of food or other resources, many of these offspring do not survive.
  19. (T/F) Darwin realized that the capacity to overreproduce was characteristic of all spcies. Of the many eggs laid, young born, and seeds spread, only a tiny fraction complete their development and leave offspring of their own.

    The rest are eaten, starved, diseased, unmated, or unable to tolerate physical conditions of the envionement such as salinity or temperature.
  20. (T/F) Natural selection is a process in which individuals that have certain heritable characteristics survive and reproduce at a higher rate than other individuals.
  21. (T/F) Over time, natural selection can increase the match between organisms and their envionment.
  22. (T/F) If an environment changes, or if individuals move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species in the process.
  23. (T/F) One subtle but important point is that although natural selection occurs through interactions between individual organisms and their environment, individuals do not evolve. Rather, it is the population that evolves over time.
  24. (T/F) Natural selection can amplify or diminish only hertiable traits - traits that are passed from organism to their offspring.
  25. (T/F) Environmental factors vary from place to place and over time. A trait that is favorable in one place or time may be useless-or even detrimental - in other places or times. Natural selection is always operating, but which traits are favored depends on the environmental context.
  26. How does the ceoncept of descent with modification explain both the unity and diversity of life?
    Organisms share characteristics (the unity of life) because they share common ancestors; the great diversity of life occurs because new species have repeatedly formed when descendant organisms gradually adapt to different environments, becoming different from their ancestors.
  27. Describe how overreproduction and heritable variation relate to evolution by natural selection.
    All species have the potential to produce more offspring (overreproduce) than can be supported by the environment. This ensures there will be what Darwin called a "struggle for existence" in which many of the offspring are eaten, starved, diseased, or unable to reproduce for a variety of reasons. Mebers of a population exhibit a range of heritable variation, some of which make it likely that their bearers will leave more offspring than other individuals.

    For example, the bearer may escape predators more effectively or be more tolerant of the physical conditions of the environment. Over time, natural selection imposed by factors such as predators, lack of food or the physical conditions of the environment can increase the propotion of individuals with favorable traits in a population (evolutionary adaptation).
  28. What are the four types of data that document the pattern of evolution and illuminate the processes by which it occurs?
    • 1) Direct observations of evolution
    • 2) The fossil record
    • 3) Homology
    • 4) Biogeography
  29. What are some direct observations of evolutionary change?
    Natural selection is a process of editing, rather than a creative mechanism. A drug does not create resistant pathogens; it selects for resistant individuals that were already presnet in the potionlation.

    Natural selection depends on time and place. It favors those characteristics in a genetically variable population that provide advantage in the current, local encironment. What is beneficial in one situation may be useless or even harmful in another.

    Predators are a potent force in shaping the adaptation of their food source. The predator is most lilely to feed on prey individuals that are least able to avoid detection, escape, or defend themselves. As a result, such prey individuals are less likely to to reproduce and pass their traits to their offspring than are individuals whose traits help them evade predators.
  30. What is homology?
    As a result of of natural selection, related species can have characteristics with an underlying similarity even though they may have very different functions. These similarities resulting from common ancestry is known as homology.
  31. What are homologous structure? What are vestigial structures?
    Homologous structures: Structures that represent variations on a structural theme that was present in a common ancestor even if they do not have all of the same functions.

    Vestigial structures: Structures that are remnants of features that served important functions in the organism's ancestors but have marginal, if any, importance to an organism.

    ie. Appendages of a human, cat, whale and bat have the same arrangement of bones but have very different functions as these species come from a common ancestor.

    Comparing early stages of development in different animal species reveals additonal anatomical homologies not visible in adult organisms.
  32. What is an evolutonary tree?
    A diagram that reflects evolutionary relationships among groups of organisms.
  33. Distantly related organisms can resmble one another for a different reason known as __________, the independent evolution of similar features in different lineages. This is in contrast to homology.

    The resemblances due to convergent evolution are said to be _________, not homologous.
    Converge evolution; analogous.
  34. What is biogeography? What influences biogeography? What does endemic mean and how does this relate to biogeography?
    BBiogeography is the geographic distribution of species.

    The geographic distribution of organisms is influenced by many factors, including continental drift - the flow movement of Earth's continents over time.

    Islands generally have many species of plants and animals that are endemic (meaning they are found nowhere else in the world). Yet, most island species are closely related to species from the nearest mainland or a neighboring island.
  35. Explain how the following statement is inaccurate: "Anti-HIV drugs have created drug resistance in the virus"
    An environmental factor such as a drug does not create new traits such as drug resistance, but rather selects for traits among those that are already present in the population.
  36. How does evolution account for (a) the similar mammalian forelimbs with different functions and (b) the similar lifestyle of the two distantly related mammals?
    a) Despite their different functions, the forelimbs of different mammals are structurally similar because they all represent modifications of a structure found in the common ancestor.

    b) Convergent evolution: The similarities between the sugar glider and flying squirrel indicate that similar environments selected for similar adaptations despite different ancestry.
  37. Which of the following is not an observation or inference on which natural selection is based?

    a) There is heritable variation among individuals.
    b) Poorly adapted individuals never produce offspring.
    c) Species produce more offspring than the environment can support.
    d) Individuals whose characteristics are best suited to the environment generally leave more offspring than those whose characteristics are less suited.
    e) Only a fraction of the offspring produced by an individual may survive.
  38. The upper forelimbs of humans and bats have fairly similar skeletal structures, whereas the corresponding bones in whales have very different shapes and propotions. However, gentic data suggest that all three kinds of organisms diverged from a common ancestor at about the same time. Which of the following is the most likely explanation for these data?

    a) Humans and bats evolved by natural selection, and whales evolved by Lamarckian mechanisms.
    b) Forelimb evolution was adaptive in people and bats, but not in whales.
    c) Natural selection an aquatic environment resulted in significant changes in what forelimb anatomy.
    d) Gene mutate faster in whales than in humans or bats.
    e) Whales are not properly classified as mammals.
  39. Which of the following observations helped Darwin shape his concept of descent with modification?

    a) Species diversity declines frather from the equator.
    b) Fewer species live on islands than on the nearest continents.
    c) Birds can be found on islands located farther from the mainland than the birds' maximum nonstop flight distance.
    d) South American temperate plants are more similar to the tropical plants of South America than the temperate plants of Europe.
    e) Earthquakes reshape life vy causing mass extinctions.
  40. Within a few weeks of treatment with the drug 3TC, a patient's HIV population consists entirely of 3TC-resistant viruses. How can this best be explained?

    a) HIV can change its surface proteins and resist vaccines.
    b) The patient must have become reinfected with 3TC-resistant viruses.
    c) HIV began making drug-resistant versions of reverse transcriptase in response to the drug.
    d) A few drug-resistant viruses were present at the start of treatment, and natural selection increased their frequency.
    e) The drug cause the HIV RNA to change.
  41. DNA sequences in many human genes are very similar to the sequences of corresponding genes in chipanzees. The most likely explanation for this result is that

    a) Humand and chipanzees share a relatively recent common ancestor
    b) humans evolved from chimpanzees
    c) chimpanzees evolved from humans.
    d) convergent evolution led to the DNA similarities
    e) humans and chipanzees are not closely related.
  42. Which of the following pairs of structures is least likely to represent homology.

    a) the wings of a bat and the arms of a human
    b) the hemoglobin of a baboon and that of a gorilla
    c) the mitochondria of a plant and those of an animal
    d) the wings of a bird and those of an insect
    e) the brain of a cat and that of a dog