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Lecture 6

Lecture 6 - lecture notes plus relevant textbook notes

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University of Toronto Scarborough
Biological Sciences
Marc Cadotte

BIOB50Winter2012 Lecture 6 Chapter 7 Life History Analyses o An organisms life history is a record of event relating to its growth development reproduction and survivalo Timing and nature of life history traits are products of adaptation to the environment in which the organism liveso Life history strategy timing and division of resourcesis there an optimal strategyoptimal refers to adapted in such a way to maximize fitnessNO LIFE HISTORY IS PERFECT all organisms face constraints Life History Diversity o Life history patterns vary within and among specieso Life history strategy of a species is the overall pattern in the timing and nature of life history events averaged across all the individuals in the speciesshaped by how the organism divides its energy and resources between growth reproduction and survivaldistribution is a result of genetic variation environmental differences or a combination of botho Phenotypic plasticity one genotype may produce different phenotypes under different environmental conditionso Example most plants and animals grow at different rates depending on temperature development speeds up as temperature warms and then slows down due to heat stress as the temperature approaches the organisms upper lethal temperature o Example Ponderosa pine treesin cool moist climates trees allocate more resources to leaf production than do trees in desert climatesdesert trees are shorter than those grown in cooler climates but for a given height they have thicker trunks they also have lower photosynthetic rates and consume less CO2 because they have fewer leaves o Phenotypic plasticity may produce a continuous range of growth rates in response to temperature o Phenotypic plasticity of other types may produce discrete types called morphs with a few or no intermediate formso Polyphenism a single genotype produces several distinct morphso Example population of spadefoot toad tadpoles contains two morphs omnivore morph feed on detritus and algae and larger omnivore morphs which feed on fairy shrimp and on other tadpolesdifference in body shapes result from difference in the growth rates of different body partscarnivores have bigger and stronger mouths because of accelerated growth in that areadepending on food they can develop into carnivore and omnivore even later in lifeo Allometry differential growth of body parts that results in a change in shape or proportion with sizecommon mechanism of variation among organismsModes of Reproduction o Organisms have evolved many different modes of reproductiono Asexual reproduction simple cell division binary fissionall prokaryotes and many protists do thiso Some multicellular organisms reproduce both sexually and asexually example coralsafter they are initiated by a sexually produced founding polyp coral colonies grow by asexual reproductiononce colony reaches a certain size and conditions are right the polyps will reproduce sexually producing their own offspring which develop into polyps and etc 1
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