Wednesday February 1 y Chapter 51 Section 51 1 According to Tinbergen a pioneer in the study of animal behavior understanding any organisms behavior requires answering four questions 1 What stimulus elicits the behavior an what physiological mechanisms mediate the response sponse 2 How does the animals experience during growth and development influence the re 3 How does the behavior aid survival and reproduction 4 What is the behavior s evolutionary history Notice how the first two questions ask about proximate causation How a behav ior occurs or is modified The last two questions ask about ultimate causation why a behavior occurs in the context of natural selection Behavioral ecology is the study of the ecological and evolutionary basis for animal behavior A fixed action pattern hereafter FAP is a type of instinct which means that an ani mal is born with it they don t have to learn FAPs An FAP is an innate behavior trig gered by some sign stimulus that causes the animal to go through the exact same routine every time This routine usually has some purpose but even if it becomes im possible to reach that purpose the animal will still carry on the motions of the FAP Example greylag geese lay eggs in nests If a mother goose spots an egg that has rolled out of the nest she will begin a series of movements with her beak in tended to push the egg back into the nest Here s the thing if you remove the 1 Wednesday February 1 y egg from her before she manages to return it to the nest she will STILL continue the beak motions pushing a now imaginary egg The FAP can be triggered by any egg shaped object placed in the vicinity of the nest Again the goose will continue the motions even past the point where she should have realized that the object was not really an egg Example 2 male stickleback fish recognize other males by their red underbellies If a male sees another male entering his territory he will mount an aggressive re sponse The male will actually begin an aggressive FAP when he encounters ANY object with a red underside even if that object only remotely resemble an other fish The aggressive behavior is highly ritualized and like the goose s egg rolling maneuvers is carried to completion each time Environmental stimuli not only trigger behaviors but also provide cues that animals use to carry out those behaviors example a wide variety of birds fish and other animals use environmental cues such as the temperature to guide migration a regular long distance change in location But how the hell do the animals know where they are migration to if they can t read a map Some animals track their position relative to the sun even though the sun changes position in the sky throughout the day Animals have a circadian clock an internal mechanism that maintains a 24 hour activity rhythm or cycle The circadian clock helps the animals adjust for the changes in sun position throughout the day Example migrating birds orient differently relative to the sun at different times of the day 2 Wednesday February 1 y Nocturnal animals instead use the North Star which has a constant position If the animals use the sun and north star as landmarks what happens if they become in the night sky obscure by clouds Earth s magnetic field helps guide the animals It is known that the heads of mi grating birds and fishes contain bits of magnetite a magnetic iron metal There is also evidence that cells in the pigeons brainstem encode information about mag netic field direction intensity and polarity Magnetoreceptors may be located in the eye beak or maybe the inner ear of the birds fish When a small magnet was placed on the head of a pigeon on an overcast day when the sun was blocked the pigeon was unable to find its way back to its nest This suggests that the pigeon does use some type of magnetic field to orientate itself The circadian clock also plays a major role in the daily activity of all animals The clock is normally synchronized with the light and dark cycles of the environment but can maintain rhythmic activity even under constant environmental conditions such as during hibernation Behavioral rhythms linked to the yearly cycle of seasons are called circannual rhythms Like the circadian clock Circannual rhythms are influenced by the light and darkness in the environment not food availability Example bears hibernate in the winter Not all biological rhythms are linked to the light and dark cycles in the environment Example fiddler crabs are linked to the moon cycles A stimulus transmitted from one organisms to another is called a signal The trans mission and reception of signals between animals is called communication 3 There are four components to animal communication Wednesday February 1 y 1 Visual 2 Chemical 3 Tactile 4 Auditory A stimulus response chain when the response to a stimulus itself stimulates the next behavior Example a male fruit fly detects a female and orients his body toward her To confirm she belongs to his species he uses his olfactory system to detect chemicals she releases into the air chemical communication The male then touches the female with a foreleg this touch is tactile communication and alerts the female of the males presence Next the male plays a song to inform the female he is of the same species which is a form of auditory communication The form of communication that evolves is closely related to an animals lifestyle an environment Example species that have poor eyesight rely on auditory or ol factory communication Animals that communicate through odors or tastes emit chemical substances called pheromones Pheromones are especially common among mammals and insects and often re late to reproductive behavior Pheromones can also serve as alarm signals For example when a catfish is in jured it releases pheromones from its skin into the water that can be detected by nearby fish The physiological mechanisms that mediate responses involves the nervous muscular and skeletal systems Stimuli activate the sensory systems are process in in the central nervous system and result in motor outputs that consti tute behavior 4 Wednesday February 1 y The above answers Tinbergen s first question What stimulus elicits the behavior an what physiological mechanisms mediate the response Section 51 2 Innate behaviors are developmentally fixed They are born with the instinct to per form these behaviors They are not learned through experiences Fixed action pattern a stimulus response chain and pheromone
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