Chapter41Animalformandfunction[1] - BLY122 Chapter 41...

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Chapter 41 Animal Form & Function 1 BLY122 A. Hunter from C. S. Major Chapter 41 Animal Form & Function I. Form, Function, and Adaptation A. Animals differ in their anatomy (form) and physiology (function) and are adapted for the conditions in which they live. B. Natural selection is the process that produces adaptations. 1. Natural selection occurs when individuals that carry certain alleles leave more offspring than do individuals with different alleles of the same gene. a. The frequency of selected alleles increases from one generation to the next, which results in evolution. b. Evolution also occurs through genetic drift, migration, and mutation. 2. Natural selection is the only process that, over time, increases the ability of the organism to survive and reproduce. C. Trade-Offs 1. Trade-offs, an inescapable compromise between traits, may be the most important type of constraint on adaptation. 2. Trade-offs often involve expenditures of time or energy. a. Example: The amount of time and energy that mothers devote to egg production b. Hypotheses (1) If more eggs are produced, each egg will be smaller and have less nutrient-rich yolk. (2) Larger eggs develop into larger, stronger offspring. (3) Larger offspring survive better than smaller ones. c. Experiment (Sinervo et al.) in which egg size and number were manipulated surgically in side- blotched lizards. (1) Treatment 1: Yolks were removed from young eggs, which resulted in large clutches of small eggs. (2) Treatment 2: All but a few eggs were destroyed, which resulted in small clutches of large eggs. (3) Control females: Their eggs were left alone. d. Results and conclusions (1) As egg size increases, egg number decreases. (2) A female lizard cannot produce large clutches of large eggs. (3) A trade-off occurs between egg size and number. e. Do larger offspring survive better? (1) 1668 hatchling lizards were marked, released, and recaptured a month later. (2) Result: Larger offspring were recaptured more frequently. (3) Conclusion: Offspring size is correlated with offspring success. 3. Organisms cannot be perfectly adapted to all aspects of their environment. a. Desert animals that sweat to cool off are in danger of dehydration. b. Osprey’s beak is highly adapted for tearing meat, not for building nests. 4. All adaptations are compromises, constrained by genetic and historical factors. a. Adaptations are not short-term, reversible responses to environmental fluctuations; those changes are called acclimatizations. b. Adaptations occur due to changes in allele frequencies. II. Tissues, Organs, and Systems: How Does Structure Correlate with Function? A. The function of an anatomical feature often correlates to its size, shape, or composition.
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This note was uploaded on 11/11/2009 for the course BLY 459 taught by Professor Obrien,j during the Spring '08 term at S. Alabama.

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Chapter41Animalformandfunction[1] - BLY122 Chapter 41...

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