Model 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?

Model 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.

Model Answer:

Molecular biology techniques (especially assessing where a gene is expressed in an organism) and breeding techniques can both be used to determine whether a behavior stems primarily from genetics or environment. The example of ADH receptor distribution in prairie and montane voles utilized molecular techniques to determine how genes are involved in vole mating choices. Where ADH receptors are expressed determines whether or not these voles will be monogamous or promiscuous. Similarly, breeding techniques can help determine whether a gene is involved in a certain behavior. 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.

Model Answer:

Habituation and sensitization are both types 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. Sensitization, on the other hand, is when one stimulus alters an organism’s response to a second stimulus. Recall the example of Aplysia being sensitized to siphon stimulation following an electric shock.

Model Answer:

With associative learning, an organism learns that a particular behavior will result in a specific outcome (whether positive or negative). If you own fish, have you ever noticed that when you go to feed your fish they swim up to the top of the tank when the tank lid is lifted? This is an example of associative learning. The fish associate the opening of the tank lid with food, and swimming to the water’s surface results in more food (and quicker access to it). 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. Specific variations on associative learning include classical and operant conditioning.

Model 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).

Model 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 use the term communication.

Model 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.

Model Answer:

Intersexual selection depends on the interaction between members of different sexes. Females pick a male based on certain characteristics, and these traits are selected for in a population because males with these characteristics have greater reproductive success. A prime example of intersexual selection is the intricate plumage of male birds of paradise, which is used to court females directly.

Conversely, intrasexual selection depends of the interactions between members of the same gender in a species. Here, traits are selected for by males (or females) competing with one another for mates. Antlers on bucks, for example, are the result of intrasexual selection; antlers of a certain size and shape make bucks more successful during altercations, conferring greater reproductive success. Thus, this trait is selected for not by direct interactions between bucks and does, but by interactions between male deer.