BIOLOGY 103
      Chapter 47:  BEHAVIORAL ECOLOGY

 
most important concept:
Behavioral choices in animals are mostly genetically-controlled instincts.  Sometimes their evolution seems to be a  paradox, because some behaviors apparently decrease an individual's fitness.
TEXTBOOK, the most important parts

Wednesday's lecture

Assignment for Friday

More fun stuff


BIO 103 HOME PAGE

In chapter 22 we learned this:  when a particular allele increases survivorship or  fecundity or immigration of individuals, the frequency of that allele increases in the population's next generation.  In this chapter we emphasize natural selection of genes for behavior, again emphasizing fitness, which biologists define as the ability of an individual to produce more offspring who survive and then reproduce themselves, transmitting these "successful" genes to yet another generation.    Behavioral choices in animals are genetically-controlled instincts.  Instincts evolve; the agents of selection are still whatever environmental forces influence survival, reproduction, and migration.

The beginning of this chapter, however, examines the proximate causes, or mechanisms, of behavior.  It focuses on experiments which show HOW behaviors are affected by genes and environment.  This gives us an opportunity to review genes and the tools for studying genes.  The second part of the chapter emphasizes the WHY questions, the ultimate causes of adaptive behaviors, providing opportunities to review natural selection and to begin our study of ecology.

An additional question intrigues many people:  how much of human behavior has evolved genetically and how much of human behavior is learned from a culture's traditions?

MAIN POINTS FROM THE TEXTBOOK 
for WEDNESDAY (proximate causes)

  1. Proximate Questions vs Ultimate questions, p. 914  (Activity 47.2 Homing Behavior in Digger Wasps to practice).
  2. Behavioral Traits are influenced by genes and environment pp. 915-919
    • forward and reverse genetic research:  the important point is the difference between looking for the genotype which produces the phenotype or showing that the mutant gene causes a phenotype which provides a mechanism for "mutant" behavior
    • Also see Activity 47.1 Proximate Causes of Behavior for the canary case
  3. Neural and Hormonal Control pp. 919-922
    • these are the mechanistic proximate connections between the gene and the behavior.
    • The book leaves out pheromones, mechanisms in which one animal releases a volatile chemical (ok, a smell) which stimulates a response in another member of its species.  Examples of the responses include fleeing from competitors and moving toward potential sexual partners.  Smelling "mean" is not that different from a hair-raising display, and smelling sexy is not all that different from.....
  4. Checklist of Terms.  behavior, proximate causation, ultimate causation, cross-fostering experiments, teen-onset alcoholism, adult-onset alcoholism, radioactive thymidine, conditional strategy, environmental cues, nature/nurture
  5. Preview of Test and exam Questions:

 

TEXTBOOK POINTS FOR FRIDAY (ultimate causes)

  1. Nature selects behaviors which improve fitness pp. 922-929.
    • Fitness for rovers and sitters.  What is density?  This example points out the importance of "a specific environment" in selection.  Why would fruit flies have two different alleles for foraging behavior?  Could you design an experiment (and draw frequency distributions to illustrate the results) to cause one of the alleles to become become rare and even extinct in a laboratory population of fruit flies?
    • Notice the new definition for adaptation at the top of p. 923
    • Does hummingbird territorial behavior match optimal foraging theory?  Foraging theory says that a critter should have instincts which make it
      1. maximize its energy benefit (find lots of prey or food)
      2. minimize its risk of dying (like in becoming prey itself and thus having no more fitness)
      3. minimize its costs (like saving enough energy and time to find mates and to manufacture gametes, etc. and not losing its fitness as in passing the genes for this behavior into the gene pool)
        Optimal foraging theory has been tested with many successful experiments, repeatedly showing that most species instinctively do what they ought to do.  In other words, their instincts make them, on average, get the most energy for the lowest cost with the lowest risk of mortality.
    • Social behavior is a paradox, especially in the case of altruism or cooperation involving sacrifice of one's own foraging or sexual opportunities (even more relevant to fitness).  
      Here are two alternative hypotheses to explain the behavior of the second female in figure 47.10a:   
      1. She's a close relative:  it's kin selection, and we could determine their coefficient of relatedness.
      2. She's learned that the mother might return the favor.  Some scientists hypothesize that individual animals in some species instinctively cooperate when they are likely to benefit somehow in the long run, as in reciprocal altruism..  
      • Some scientists believe that true altruism is possible when believe that kin selection evolves in very small populations.  The jury is still out, but you need to be able to explain some examples of cooperative social behavior in animals, like the prairie dog case and other cases which could come up on a test or exam or quiz. 
      • Here's a question which matters, at least at a fine Liberal Arts University like Queens. Do human beings behave in paradoxical patterns?  Do we choose to decrease our own fitness, leaving others to make larger contributions to the gene pool?    
    • Two other categories of behavior are not detailed in the textbook, but will be discussed in class:
      1. Sex again:    This is one of the areas where paradoxes are more obvious.  The classic paradox which Darwin identified is that when females choose to mate with the fanciest peacocks, their sons may be sexy-looking but their flashy sons may also be more attractive to predators and also a little slower in foraging and in migrating and in avoiding predators.  So does the mating advantage outweigh the survival disadvantages?  Most studies say "yes."  Look in your textbook for reasons, but remember that sexual selection is still a big topic of debate among biological scientists.
      2. Immigration or habitat "choice" (how and when should a critter move?  What genes does it need?)  The book doesn't spend much space on this topic except for roving/sitting alleles and hummingbird territory-defending, but you might want to know that there are plenty of research results which show that most species seem to emigrate and immigrate in "logical/optimal" patterns, especially when they have genes for the appropriate "sensors" and movement devices (like feet or aerodynamic gliders, etc.)
  2. Complex behaviors evolve by combining and mutating simpler patterns 926-928
    • Instincts:  What are the differences between innate and learned behavior?  which of the many textbook examples are genetic?  and which are learned through experience and training in the environment ("nurture" even if you teach yourself)?
    • The case of crane courtship behaviors and their phylogenies is a powerful example for how complex behaviors can evolve.  This example is analogous to many other studies where a phylogeny for a complex morphological structure or a complex metabolic pathway can be shown to be similar to the phylogeny based on DNA sequences.  Be prepared to outline the narrative of how the crane courtship most likely evolved.
  3. Summary.
    • Activity 47.2 Homing Behavior in Digger Wasps
    • What insights on human behavior do we learn by studying animal behavior?  Are facial expressions in humans instinctive?  How about body language?  Xenophobia?  Courtship displays in humans?  When animals warn each other or commit infanticide, to what degree is their "choice" instinctive?  Are human being different?
    • Extra credit or Replacement Quiz due Friday.  Type an essay arguing against the conclusions drawn by Daly and Wilson, p. 929.  What is their hypothesis?  Think of at least one alternative hypothesis which could explain the results shown in Figure 1.  
  4. Checklist of Terms ( You should be able to USE all the terms; it is not enough to be able to recognize their definitions):  behavior, proximate causation, ultimate causation, artificial selection experiment, adaptation, flexible behavior, conditional strategy, "decision-making" or animal "choice," selfish behavior, self-sacrificing behavior, infanticide, altruism, Hamilton’s rule, coefficient of relatedness, kin selection, innate behaviors, ancestral behaviors, evolutionary relationships, courtship displays, territorial defense, environmental cues 

  5. QUIZ & TEST & EXAM PREVIEW:

  1. What is "fitness"?
  2. How much of animal behavior is genetic? What types of animal behavior are genetic?
  3. Which phenotypes help prey to survive?
  4. Will prey frequency distributions change? (= Does prey behavior evolve?)
  5. Which instincts help predators to survive?
  6. Will predator gene pool frequency distributions change?
  7. Will predator behavior evolve differently when prey situations change?
  8. Which phenotypes improve fitness in other aspects?


 

Behavioral choices in animals are mostly genetically-controlled instincts.  Sometimes their evolution seems to be a  paradox, because some behaviors apparently decrease an individual's fitness.

 

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