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Animal Behavior

Animal Behavior

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Animal Behavior

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  1. 41 Animal Behavior

  2. Chapter 41 Animal Behavior • Key Concepts • 41.1 Behavior Has Proximate and Ultimate Causes • 41.2 Behaviors Can Have Genetic Determinants • 41.3 Developmental Processes Shape Behavior

  3. Chapter 41 Animal Behavior • Key Concepts • 41.4 Physiological Mechanisms Underlie Behavior • 41.5 Individual Behavior Is Shaped by Natural Selection • 41.6 Social Behavior and Social Systems Are Shaped by Natural Selection

  4. Chapter 41 Opening Question How can a single gene be responsible for a complex behavior?

  5. Concept 41.1 Behavior Has Proximate and Ultimate Causes • Four questions in studying animal behavior: • Causation: What is the immediate stimulus for the behavior? • Development: How does behavior change with age and learning—what experiences are necessary for it to be displayed? • Function: How does the behavior affect chances for survival and reproduction? • Evolution: How does the behavior compare with similar behaviors in related species, and how might it have evolved?

  6. Concept 41.1 Behavior Has Proximate and Ultimate Causes • Causation and development refer toproximate causes—genetic, physiological, neurological, and developmental mechanisms. • Function and evolution refer toultimatecauses—evolutionary processes that produced the capacity and tendency to behave in certain ways.

  7. Concept 41.1 Behavior Has Proximate and Ultimate Causes • Two classical schools of animal behavior focused on proximate causes. • Behaviorism—derived from Pavlov’s work on conditioning; neural reflexes could be modified by experience to respond to an unnatural stimulus. • Ethology—study of instinctive behaviors—genetically determined fixed action patterns. These are not learned and resist modification.

  8. Figure 41.1 The Conditioned Reflex (Part 1)

  9. Figure 41.1 The Conditioned Reflex (Part 2)

  10. Concept 41.1 Behavior Has Proximate and Ultimate Causes • Fixed action patterns are usually triggered by simple stimuli such as color, smell, or sound. • The triggers are called releasers. • Example: Gull chicks respond to a red dot on their parents’ bills to initiate pecking behavior to get food.

  11. Figure 41.2 Releasing a Fixed Action Pattern (Part 1)

  12. Figure 41.2 Releasing a Fixed Action Pattern (Part 2)

  13. Concept 41.1 Behavior Has Proximate and Ultimate Causes • Behavioral ecologists study why particular behaviors have evolved in a species. • Environmental conditions may put selective pressures on an animal. • Reproductive fitness can be affected by behaviors, such as choices of nest location, mate, defense of a territory or food source.

  14. Concept 41.2 Behaviors Can Have Genetic Determinants • Breeding experiments can test if behavioral phenotypes are genetically determined. • Honeybees demonstrate hygienic behavior when removing larvae killed by a bacterium. • In backcrosses, nonhygienic behavior is dominant, yet intermediate behavior also occurs—components controlled by separate genes.

  15. Figure 41.3 Genes and Hygienic Behavior (Part 1)

  16. Figure 41.3 Genes and Hygienic Behavior (Part 2)

  17. Concept 41.2 Behaviors Can Have Genetic Determinants • Mutants with altered behaviors allow studies to identify the genes involved. • Male courtship behavior in fruit flies is under control of a single gene, fruitless (fru)—results in male sexual behavior. • The fru product is also a transcription factor for other genes involved in sexual differentiation and behavior. • Alterations in fru lead to a variety of effects on a male’s sexual behavior.

  18. Concept 41.2 Behaviors Can Have Genetic Determinants • Knockout experiments can reveal the roles of specific genes. • Mice have a small olfactory organ adjacent to the nasal passages—the vomeronasal organ. • Male mice engineered to lack a receptor for pheromones could not distinguish between males and females.

  19. Figure 41.4 The Mouse Vomeronasal Organ Identifies Gender (Part 1)

  20. Figure 41.4 The Mouse Vomeronasal Organ Identifies Gender (Part 2)

  21. Concept 41.3 Developmental Processes Shape Behavior • The development and expression of behavior can be controlled by hormones. • In rats, males and females adopt different sexual behaviors: • Females—lordosis, a receptive posture • Males—copulate with receptive females

  22. Concept 41.3 Developmental Processes Shape Behavior • Experiments with neutered rats receiving hormone treatments concluded: • Male sexual behavior requires exposure to testosterone, but female behavior does not require estrogen, in newborns • Testosterone masculinizes the nervous systems of both sexes

  23. Concept 41.3 Developmental Processes Shape Behavior • Exposure to sex steroids as adults is necessary for normal behavior, but only if brains were exposed as newborns • Thus, sex steroids present at birth determine pattern of behavior; steroids present as adults determine when behavior is expressed

  24. Figure 41.5 Hormonal Control of Sexual Behavior (Part 1)

  25. Figure 41.5 Hormonal Control of Sexual Behavior (Part 2)

  26. Concept 41.3 Developmental Processes Shape Behavior • Imprinting—the animal learns a set of stimuli during a critical period, such as recognition of parents and offspring. • Learning of stimuli takes place during a limited time called the critical period, or sensitive period. • Emperor penguins lay eggs far inland in Antarctica. • Imprinting allows males to find their chicks after they have returned from feeding in the ocean.

  27. Concept 41.3 Developmental Processes Shape Behavior • Some behaviors result from both inheritance and learning. • Male songbirds have species-specific songs that must be learned during a limited developmental time frame. • White-crowned sparrows must hear the song when they are nestlings, even though they don’t sing it for a whole year.

  28. Concept 41.3 Developmental Processes Shape Behavior • As males approach maturity, they begin singing and improve as they match their song with the stored memory. • If a bird is deafened before starting to sing, it will not develop species-specific song. • If deafened after singing, he will continue to sing normally—behavior is crystallized. • There are two critical periods for learning— as a nestling and near sexual maturity.

  29. Figure 41.6 Sensitive Periods for Song Learning

  30. Concept 41.3 Developmental Processes Shape Behavior • Males also hear songs of other species while they are nestlings. • Deprivation experiments have shown that young male sparrows do not learn songs of other species. • Brief exposure to their own species song is enough for imprinting.

  31. Concept 41.3 Developmental Processes Shape Behavior • Hormones have an influence on behavior through their influence on development and the physiological state of an animal. • Male and female songbirds both hear and recognize the songs, but only the males sing. • When females were injected with testosterone in the spring, they too learned to sing.

  32. Concept 41.3 Developmental Processes Shape Behavior • In the spring, increased testosterone causes parts of the brain to enlarge. • Individual neurons get larger and grow longer extensions, and number of neurons increases. • Hormones can control behavior by changing brain structure and function.

  33. Concept 41.4 Physiological Mechanisms Underlie Behavior • Biological rhythms coordinate behavior with environmental cycles. • Circadian rhythms are daily cycles of activities. • Length of a cycle is the period—any point on the cycle is a phase of the cycle. • If two rhythms completely match, they are in phase.

  34. Concept 41.4 Physiological Mechanisms Underlie Behavior • If a rhythm is shifted to an earlier or later time it is phase-advanced or phase-delayed. • The period of a circadian rhythm is not exactly 24 hours, so it must be phase-shifted every day. • The rhythm has to be entrained to match the environmental cycle of light and dark.

  35. Concept 41.4 Physiological Mechanisms Underlie Behavior • If an animal is kept in constant conditions, its circadian clock will run according to its natural period—free-running. • The free-running period is under genetic control. • Environmental signals entrain the free-running period to the light-dark cycle.

  36. Figure 41.7 Circadian Rhythms Are Entrained by Environmental Cues

  37. Concept 41.4 Physiological Mechanisms Underlie Behavior • In mammals the master circadian “clock” consists of two clusters of neurons—the suprachiasmatic nuclei (SCN). • If the SCN are destroyed, the animal becomes arrhythmic. • Circadian rhythms were restored experimentally with transplanted SCN tissue—recipients now had the rhythms of the donor tissue.

  38. Concept 41.4 Physiological Mechanisms Underlie Behavior • The molecular mechanism of the circadian clock involves negative feedback loops. • When clock genes are expressed in the SCN, mRNA is translated in the cytoplasm. • The protein products combine into a dimer—it returns to the nucleus, then acts as a transcription factor to stop clock gene expression. • This cycle lasts about a day.

  39. Concept 41.4 Physiological Mechanisms Underlie Behavior • Animals must be able to find their way in their environment. • Piloting involves knowing and remembering the structure of the environment. • Gray whales find their way from Mexico to the Bering Sea by following the coastline as a cue.

  40. Figure 41.8 Piloting

  41. Concept 41.4 Physiological Mechanisms Underlie Behavior • Homing is the ability to return to a specific location from long distances. • Pigeons can fly from remote sites where they have never been before. • They can navigate without visual cues from the environment, detecting the Earth’s magnetic field.

  42. Concept 41.4 Physiological Mechanisms Underlie Behavior • Humans use two systems of navigation: • Distance-direction navigation—requires knowing in what direction and what distance the destination is. • Bicoordinate navigation (true navigation)—requires knowing longitude and latitude of the current position and destination.

  43. Concept 41.4 Physiological Mechanisms Underlie Behavior • Many animals seem to have a compass sense and can use environmental cues to determine direction. • Others appear to have a map sense to determine their position.

  44. Concept 41.4 Physiological Mechanisms Underlie Behavior • Many animals are capable of bicoordinate navigation—a circadian clock may give information about time of day, and sun position may give map coordinates. • Pigeons showed that they orient by means of a time-compensated solar compass.

  45. Figure 41.9 A Time-Compensated Solar Compass

  46. Concept 41.4 Physiological Mechanisms Underlie Behavior • Many animals are active at night, including many migrating birds. • Stars offer two sources of information about direction—moving constellations and a fixed point. • Birds learn to identify the fixed point in the sky.

  47. Figure 41.10 Coming Home (Part 1)

  48. Figure 41.10 Coming Home (Part 2)

  49. Concept 41.4 Physiological Mechanisms Underlie Behavior • When animals interact, they exchange information—systems of information exchange evolve into communication. • Behaviors may be elaborated as signals if both sender and receiver benefit. • A display is favored if it increases the sender’s probability of passing on his genes, and sexual selection occurs.

  50. Concept 41.4 Physiological Mechanisms Underlie Behavior • Animals use multiple modalities to communicate. • Pheromonesare chemical signals between individuals. • Diverse molecular structures mean very specific communication—used for alarms, territory-marking, trail-marking, and to attract mates.