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Biological Sciences
Kamini Persaud

BIOC54H Chapter 3 Tharsini Sivananthajothy January 28, 2012 Chapter 3: The Development of Behaviour Page 68 – 72, 77 – 88 The Nature or Nurture Fallacy - honey bee example shows that it is a mistake to say that some behavior phenotypes are more genetic than others - worker foraging behavior cannot be purely genetically determined because the behavior is the product of thousands of gene-environemnt interactions - information in the DNA that makes up a gene is expressed only when the gene is in the appropriate environment - DNA is both inherited and environmentally responsive - Environmental signals such as those provided by juvenile hormone and ethyl oleate influence gene activity - When a gene is turned on or off by changes in the environment, changes in protein output can directly or indirectly alter the activity of other genes within affected cells - Gene- environment interactions are responsible for the construction of every trait - Development of every attribute of every living thing requires the information contained in large numbers of genes and expressed in a multitude of gene-environment interactions - Neither genotype nor environment is more important than the other Behavioural Development Requires Both Genes and Environment - contribute that DNA makes can be seen by the development of the ability to learn - learning is a change in an animal’s behavior linked to a particular experience it has had - environment is involved when an animal learns something but genetic influence on development cannot be ignored - imprinting in which a young animal’s early social interactions usually with its parents, lead to its learning such things as what constitutes an appropriate sexual partner - group of graylag goslings imprinted on Lorenz formed a learned attachment to Lorenz and a preference for humans as mates - experience of following a particular individual in earl life altered those regions of male goose’s nervous system responsible for sexual recognition and courtship - imprinting could not have occurred without a prepared brain whose genetically influenced development enabled it to respond to the special kinds of information available from its social environment - different species exhibit different imprinting techniques so must be a genetic contribution to learning - group of Norwegian researchers provided this kind of evidence when they switched broods from blue tit nests into nests of breeding great tits and vice versa - some of the cross fostered birds grew up and survived to court and form pair bonds with members of opposite sex - of the surviving fostered great tits, only 3 of 11 found mates which were blue tit females which had been fostered by great tits - of the surviving blue tits, all 17 found mates and only 3 of these were females that socially mated with cross fostered male great tits - so although some individuals of both speicies became imprinted on another specieis due to foster experience, the degree to which invidiuals imprinted on their foster parents differed between the two species BIOC54H Chapter 3 Tharsini Sivananthajothy January 28, 2012 - none of the cross fostered great tits mated with a member of its own species but most of the blue tits did - also each of the blue tit female that had a great tit as a social partner must have mated with a blue tit male because all had 33 offspring which were blue tits and not hybrids - mis-imprinting occurred in both species but the developmental effect of being reared by members of another species was far greater for great tits than for blue tits - indicates that the hereditary basis of the imprinting mechanism was not the same for both species - birds also possess specialized learning ability to remember where they have hidden food - black capped chickadee is really good at this task - this bird’s spatial memory enables it to relocate large number of seeds that it has hidden - David Sherry provided captive chickadees with a chance to store food in holes drilled in small trees placed in an aviary - After the birds placed seeds in 4 -5 of 72 possible storage sites, it was kept in a holding cage for 24 hours - In this time Sherry removed the seeds and closed each of the 72 sites with Velcro - When the birds were released, they spent much more time inspecting and pulling at the covers of the hoard sites than the sites where they had not stored food - Because sites were empty and covered, there were no olfactory or visual cues provided by stored food to guide the birds in their search – had to rely solely on their memories - In nature, birds only store one food item per hiding spot and never use the same location twice - Can relocate caches as late as 28 days - Clark’s nutcrackers have even better memory – 33, 000 seeds in 5000 caches which are 25 km from site o Digs a hole and then covers cache o Does this work in the fall and relies on store during winter and spring o Experiments like the chickadee show that they remember exactly where they hid their food - In one test, a nutcracker was given a chance to store seeds in a large outdoor aviary and then moved to another cage - Balda mapped location of each cache and removed buried seeds and swept the cage floor removing any signs of cache making - No visual or olfactory cues were available to the bird when it was permitted to go back a week later - Balda mapped locations were bird probed with bill o Memory served well and it dug into 80% of ex-cache sites and only rarely digging in other places - Other experiments show it can remember for 6 months even 9 - When Balda tested his grad students as if they were a food storing bird, they did only half as well as a typical nutcracker when tested a month after making caches - Birds can even remember the size of the seeds – shown by tendency to spread their bills farther apart when probing the earth for large seeds o can only retrieve one seeds at a time so more efficiently by opening beaks just the right distance to grash and pluck a seed of a given size - this ability to remember in birds is related to ability of certain brain mechanisms to change biochemically and structurally in response to the kinds of sensory stimulation associated with food hiding BIOC54H Chapter 3 Tharsini Sivananthajothy January 28, 2012 - changes could not occur without genes needed to construct the learning system and the genes that are responsive to key sensory stimuli relevant to learning task Genetic Differences and Behavioral Differences - to see if a genetic difference underlies why some blackcaps spend the winter in southern Great Britain while others go to Africa, Berthold checked whether winter in Britain birds inherit their parents’ behavior - captured blackcaps in Britain and took them to lab in Germany where birds spent time indoors - in spring, they were released where they bred a crop of youngsters that had never migrated - once the birds were older, Bert put them in special cages that had been electronically wired to record the number of times a bird hopped from one perch to another - data revealed that when fall arrived, birds became restless at night, heightened activity characteristic before migrating - immature parents also became nocturnally restless when places in the same kind of cages in the fall - showed that birds wintering in Britain is not composed of birds that have simply lost their ability to migrate o must be migrants that flew to Britain from somewhere else - where does the British wintering population come from? o Researchers put some birds in cages shaped like funnel
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