Biology Homework Chapter 13: Evolution - Natural Selection
Textbook assignment: Chapter 13: How Populations Evolove, sections 1-11.
- 13.1 The text presents evolution as the central theory of biology, the thread that ties all the other pieces together. Keep this in mind as we study this unit and the next, both of which address the similarities between organisms (based on the common chemical processes and cell functions we have been studying) and the differences that exist between species and between individuals.
- 13.2 Fossil evidence is used to try to establish a sequence of development based on geological interpretation of the age of the rocks containing the fossils. Dating is done by comparing levels of radioactive isotopes (we have to make assumptions about the starting concentrations of the isotopes), and by looking at stratification levels.
- 13.3 Fossils of transitional forms of specific species appear to support the hypothesis that adaptations for new functions occurred.
- 13.4-5 Common structures (homologous structures) with different functions are used to supplement fossils as evidence for evolution. The inheritance of common structures can be traced as well through molecular biology (DNA sequence studies). In some species, homologous structures appear in the embryo but not in adult individuals. These patterns can be used to map how similar different species are. The greater the DNA sequence similarity is, the more recently the species diverged.
- 13.6 Darwin proposed natural selection as a mechanism to explain changes in the distribution of characteristics in individuals of a species over time. In this part of his theory, no new species are created, but the frequency of a given trait in a population shifts over time as those members of a species who lack the form of critical traits that allow them to survive fail to reproduce.
- 13.7 Natural selection occurs in modern populations and can be observed even over short periods of time. One example is the development of resistant strains of insects following widespread use of insecticides.
- 13.8 The only factors that can introduce new traits are mutations in the nucleotide sequences of DNA. "Learned traits" cannot be passed on through any material means. New combinations of traits occur naturally when sexual reproduction includes the mechanism of "crossing-over" during meiosis.
- 13.9 Evolution is not used to explain changes in an individual, but in traits expressed in populations. The only traits that can be considered must be inheritable traits. Over time, the fraction of a population's individuals carrying a particular trait (allele for a given gene) will change in response to environmental factors.
- 13.10 The Hardy-Weinberg equation predicts the percentage of a population with a given trait if NO environmental factors influence it. Changes in the population indicate the level of environmental factors acting on the population. Equilibrium requires calculation of the Hardy-Weinberg equation in large populations with no mutation, random mating, and on external influences.
- 13.11 Public health organizations use the Hardy-Weinberg principles to determine whether non-random changes are occurring in the population.
Read the following weblecture before chat: The theory of evolution
Take notes on any questions you have, and be prepared to discuss the lecture in chat.
Perform the study activity below:
Check out the Evolution in Action game at the PBS Nova site. Click on Launch interactive. Read the Rules and Instructions (available from buttons in the lower right of the game screen).
How does changing the environment (changing the background colors) change the population?
Chat Preparation Activities
- Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
- Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.
- No quiz yet: the Chapter Quiz opens when we finish the chapter.
Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.
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