Ch 2: Methods for Studying Behavior

• Observational Method: involves observing and recording behavior without manipulating the environment or the animal. 
• Experimental Method: involves manipulating an independent variable to examine how this affects a dependent variable.
• Comparative Method: involves examining differences and similarities between species to understand the evolution of behavior. 
• Phylogeny: a diagram showing evolutionary ancestor-descendant relationships among a set of organisms.
• Sister Species: two species that are more closely related to one another than to any other species.
• Parsimony: the simplest explanation of an event or observation is more likely to be correct, all other things are equal.
• Convergent Evolution: distinct ancestry, shared behavior.
• Divergent Evolution: shared ancestry, different behavior.
• Describe a strength and a weakness of the observational approach?

  Strength: it costs less money

  Weakness: you don't have a control
• Natural Selection: the differential survival and reproduction of individuals due to differences in heritable phenotypes.
• Conditions for Natural Selection:

  1. Variation
  2. Differential Reproductive Success
  3. Heritability
• Variation: members of a population differ in characteristics.
• Differential reproductive success depends on that variation, some individuals with particular characteristics have more offspring than others.
• Heritability: parents can pass on characteristics to their offspring.
• How do we Know Variation is Heritable?

  1.Parents Offspring Regression

  2. Selection Experiments
• Parent Offspring Regression: examines the similarity between parents and their offspring. If a trait is heritable, the trait values of offspring should be similar to the trait values of the parents.
• Selection Experiments: individuals are subjected to differential selection of a trait. If this results in a change in average trait value in later generations, the trait is heritable.
• Variability is due to differences in genetic composition and environmental conditions.
• Variability shows up when traits:

  do not affect fitness

  are subjected to certain types of selection

  are influenced by learning
• Adaptation: traits that result from natural selection and confer higher fitness than alternative traits.
• How do we measure Fitness?

  Direct: the number of progeny that go on to reproduce

  Indirect: survivorship, number of maters, body size and growth, etc.
• Eastern screech-owls show great variation in dispersal direction with no coincident differences in reproductive success, indicating fitness is not associated with dispersal's compass direction.
• Honeybee foraging performance increases due to trial and error learning.
• Directional Natural Selection:

  Individuals in a population with an extreme trait value at one end of the spectrum posses the highest fitness.

  Ex: Galapagos medium ground finches with the median beak size have the best chance of survival
• Disruptive Natural Selection:

  Individuals with extreme trait values have the best chance of survival.

  In Spadefoot tadpoles, the detritus and carnivore morphs have the highest chance of survival bc they can feed efficiently.
• Stabilizing Natural Selection:

  Individuals in a population with intermediate trait values have the highest fitness.
• Cooperative Behavior: many social animals help others to survive and reproduce.

  only works when everyone gets involved
• Group Selection: selection operates at the level of the group. Groups that contain too many individuals maximizing individual gain will have lower fitness, than groups that work together.
• Natural Selection Types

  A) Disruptive

  B) Stabilizing

  C) Directional