Chapter 53

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University of Toronto Scarborough
Biological Sciences
Kamini Persaud

Chapter 53 Animal Behaviour Ethology - the study of animal behaviour from an evolutionary perspective - Niko Tinbergen one of the founders of ethology - in order to understand any form of behaviour, several questions need to be asked: (1) how and when individuals perform them using PROXIMATE MECHANISMS such as the neuronal, hormonal, and anatomical mechanisms; (2) the origins and means of acquisition of specific behaviours; (3) why individuals perform them using the ULTIMATE CAUSES of behaviour (the selection pressure that shaped its evolution) - for many individuals, much of their behaviour is unlearned and highly STEREOTYPIC (always exactly the same); this type of behaviour is often SPECIES-SPECIFIC (most individuals of a given species perform the behaviour in the same way) (ex: spiders and their web-spinning ability) Influences of Genes and Environment on Behaviour - an animal may fail to perform even a genetically controlled behaviour if the environmental conditions needed to stimulate it are absent; on the other hand, genes do not encode behaviours, rather, gene products such as enzymes can affect behaviour by setting in motion of series of gene-environment interactions that underlie the development of proximate mechanisms that enable individuals to make certain behavioural responses - experiments can distinguish between genetic and environmental influences on behaviour: Deprivation Experiment investigators rear a young animal so that it is deprived of all experience relevant to the behaviour under study; if it still exhibits the behaviour, it can be assumed that the behaviour can develop without opportunities to learn it ex: the squirrel experiment this experiment showed that heredity underlies the food- storing behaviour of this tree squirrel species but the behaviour was expressed only when the environment provided condition that stimulated the behaviour (the presence of a nut - RELEASER) Genetic Experiments investigators alter the genomes of organisms (1) by comparing individuals that differ in only one or a few genes, (2) by interbreeding closely related species, (3) or by knocking out or inserting specific genes to determine how these manipulations affect their behaviour: 1. Selective Breeding a means of genetic manipulation; has been used extensively to select for both anatomical traits and behaviour (ex: dog breeders, Darwins pigeons) 2. Interbreeding Konrad Lorenz one of the pioneers of ethology ; used interbreeding (or hydridization) of duck species to investigate the hereditary basis of their elaborate courtship delays when Lorenz crossbreed these ducks, the hybrid offspring expressed some elements of each parents courtship display but in different new combinations and some displayed elements that were not in the repertoire of either parent species this study demonstrates that the stereotypic motor patterns of the courtship delays are inherited 3. Gene Knockout Experiments ex: the fosB gene on mice the altered neural connections play a part in motivating the mother to retrieve and care for her pups - genetic control of behaviour is adaptive under many conditions without role models and opportunities for learning, individuals might fail to acquire the appropriate behaviour, or acquire inappropriate behaviour, if genes did not exert strong influences on the development of the behaviour inherited behaviour is also adaptive when mistakes are costly or dangerous inheritance of behaviour patterns used to avoid predators or capture dangerous prey is obviously adaptive even though genetic control of behaviour is adaptive under many conditions, complete stereotypy may not be; the genes that govern development often allow organisms to adjust their forms and behaviour to the particular environment in which they develop - imprinting takes place at a specific point in development
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