Chapter 45 Summary

Core Concepts Summary

45.1 For any behavior, we can ask what causes it, how it develops, what adaptive function it serves, and how it evolved.

Tinbergen pointed out that questions about animal behavior can be asked at four different levels of analysis, focusing on cause, development, function, and evolution. page 982

The four questions have different answers, and all may be correct explanations of the behavior. page 982

Behavior can be innate (it is carried out in the absence of experience), or learned (it depends on experience). page 982

45.2 Animal behavior is shaped in part by genes acting through the nervous and endocrine systems.

Most behavior is produced by the interaction between genes (nature) and environment (nurture). page 983

A fixed action pattern is a stereotyped sequence of behaviors that, once initiated by a key stimulus, always goes to completion. page 983

Stimuli are recognized by feature detectors, which are specialized sensory receptors of the nervous system. page 984

Hormones can affect behavior through their wide-ranging and often long-term effects on multiple body systems. page 985

The extent to which genes influence a behavior can be determined by crossing closely related species having different behaviors and analyzing the behavior of the offspring. page 986

Most behaviors are influenced by many genes, but a few are strongly influenced by a single gene. page 987

Molecular studies are providing new ways to understand the role of genes in behavior in laboratory animals. page 987

45.3 Learning is a change of behavior as a result of experience.

Non-associative learning is a form of learning that occurs without linking two events. page 990

Habituation, a form of non-associative learning, is the reduction or elimination of a response to a repeated stimulus. page 990

Sensitization, another form of non-associative learning, is the enhancement of a response to a stimulus that is achieved by first presenting a novel stimulus. page 990

Associative learning occurs when an animal links two separate events. page 990

Classical conditioning is a form of associative learning that occurs when two stimuli are paired and a novel association is made between a formerly neutral stimulus and a behavior. page 990

Operant conditioning is a form of associative learning that occurs when a behavior is rewarded or punished, making the behavior more likely or less likely to occur, respectively. page 990

Imitation and imprinting are forms of learning. page 990

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45.4 Orientation, navigation, and biological clocks all require information processing.

Kineses are undirected movements, whereas taxes are directed movements. page 992

Long-distance navigation may require the processing of many external cues, including the position of the sun, Earth’s magnetic field, and information about time. page 993

Biological clocks control some physiological and behavioral aspects of animals. page 993

45.5 Communication involves an interaction between a sender and a receiver.

Communication is an interaction between two individuals, the sender and the receiver, and often involves attempts by the sender to manipulate the behavior of the receiver. page 995

Communication can evolve by the modification of noncommunicative aspects of an animal’s behavior. page 995

Bird song is a rich form of communication that is often learned during a sensitive period. Acquisition of bird song proceeds through distinct stages. page 996

The dance language of honeybees communicates information about the location and direction of a food source. page 997

45.6 Social behavior is shaped by natural selection.

One of the most perplexing behaviors from the standpoint of natural selection is altruism, in which an organism reduces its own fitness by acts that benefit others. page 997

Group selection is the idea that altruistic behaviors can evolve if they benefit the group, not the individual, but this idea is not widely accepted. page 998

Reciprocal altruism requires that individuals interact regularly and remember each other so that they can “pay back” past favors. page 999

Kin selection is the concept that altruistic behaviors can evolve if they benefit close relatives. page 999

Self-Assessment

  1. Choose a behavior described in this chapter and ask the four kinds of question that Tinbergen might have asked about it.

    Self-Assessment 1 Answer

    Recall the example of Aquaspirillum bacteria being attracted to a magnetic pole. What causes (or what is the mechanism that drives) this movement of Aquaspirillum toward a magnetic pole (does it have to do with iron oxide within the bacteria themselves)? Has this bacterial behavior developed as a result of specific genetic or environmental factors (i.e., to what extent is this an innate or learned behavior)? Why would moving toward a magnetic pole convey greater reproductive success to a bacterium? Did this behavior of moving toward a magnetic pole evolve from random bacterial movements, or from some earlier behavioral trait?

  2. Explain the difference between innate and learned behavior and provide an example of each.

    Self-Assessment 2 Answer

    An innate behavior is one that an organism performs instinctively. For example, when a first-time mother cat gives birth, she instinctively licks her kittens to stimulate breathing. Conversely, a learned behavior is not instinctive, but is shaped by an organism’s experiences over time. An organism learns that a certain behavior can have a positive or negative result; such a behavior is not necessarily “taught” by other members of the species. In keeping with our cat example, a learned behavior could be a cat running to its owner if he or she shakes a bag of treats. The cat learns that the sound of a bag shaking has a positive outcome—a snack.

  3. Explain, with an example, how crosses between closely related species can help us understand the genetic basis of behavior.

    Self-Assessment 3 Answer

    Sometimes there are distinct stereotyped differences in simple behavior between closely related species. By crossing the species and assessing the behavior of hybrids, we can identify the extent of the genetic control of the behavior and, with further crosses, possibly work out how many genes are involved. Consider a case of two behaviors in related species that are entirely learned from the mother: The hybrids in this case will show the behavior of the mother regardless, and we can conclude that the behavior is learned, rather than innate. Recall William Dilger’s experiment of mating two types of lovebirds with different nest-building techniques. These crosses produced lovebirds with an intermediate behavior phenotype, indicating that nest-building is influenced by genes.

  4. Distinguish between associative and non-associative learning and provide an example of each form of learning.

    Self-Assessment 4 Answer

    With associative learning, an organism learns that a particular behavior will result in a specific outcome (whether positive or negative), whereas non-associative involves learning to ignore or be especially sensitive to a particular stimulus. Dog trainers also rely on associative learning. For example, a trainer will reward a dog with a treat or affection when it performs a desired behavior (like sitting or shaking hands). The dog associates a behavior with a reward and will eventually perform that behavior on command. Habituation is a type of non-associative learning. An example of habituation would be squirrels on a college campus. Normally, if you came across a squirrel in the forest, it would flee as you approached. However, campus squirrels are accustomed to people walking past them in close proximity. These squirrels have become “habituated” to high people traffic and will no longer flee as people approach.

  5. Differentiate between a kinesis and a taxis.

    Self-Assessment 5 Answer

    Depending on the stimulus, organisms can undertake different types of movements. An organism can either move toward or away from a stimulus in a directed manner (remember the example of bacteria moving directly toward a magnetic pole). A taxis denotes this kind of directed movement. In contrast, stimuli can also induce undirected movements or kineses, where an organism moves toward or away from a stimulus in a random pattern (remember the example of bacteria making undirected turns to escape high-salinity conditions).

  6. Explain why many biologists would not consider just any transfer of information between a sender and receiver to be a form of communication.

    Self-Assessment 6 Answer

    The term “communication” suggests that two individuals are consciously exchanging information. Recall the example of a vervet monkey serving as a lookout for its family group. When a predator approaches, this lookout (the sender of information) sounds an alarm to the rest of its family (the receivers of information). This is a conscious exchange of information, where the vervet monkey wants its family members to hear the alarm and respond by taking cover or fleeing. However, many exchanges of information in biology aren’t always conscious or intentional; sometimes a sender doesn’t want to communicate a certain piece of information to a receiver, but does so inadvertently. Consider a hunter tracking a deer. The deer leaves tracks in a forest, which signals to the hunter that a deer has passed through the area. Conversely, in certain instances a deer can detect a hunter by his smell. In neither case does the deer or hunter want to provide information about their location to the other party, but they do so unintentionally. This unintentional exchange of information is why many biologists prefer not to apply the term “communication” to this type of exchange.

  7. Describe how an altruistic behavior might evolve by kin selection.

    Self-Assessment 7 Answer

    An altruistic behavior is one of “self-sacrifice”; an organism will perform tasks to help the survival of another member of the species, not necessarily a member of its immediate family. Kin selection may contribute to the evolution and selection of altruistic behaviors. In kin selection, an individual will help assure the survival of genetically similar individuals (either in a hive, a family group, etc.). In helping related individuals survive and reproduce, an individual can assure that more of its genetic material can be passed on to future generations, even without reproducing itself. These genetically similar individuals will also likely carry genes that convey altruistic behaviors, reinforcing this behavior.