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BIO205H5 (17)

This is the note for the WHOLE course compiled into one study review. This was actually an exam reviewer.

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University of Toronto Mississauga
Maria Arts

Properties of Population Population group of organisms of the same species occupying a particular space at a certain time - same species: suggests potential for interbreeding - is a spatial concept which talks about boundaries in space - has structure (density, spacing, various ages), exhibits dynamics (birth, death, immigration, emigration) which make it difficult to study Organisms may be Unitary or Modular Unitary: organism that are an individual unit such as a zygote that grows into a genetically unique organism Modular: organisms that have indefinite growth form such as plants and corals; a genetically unique organism such as a zygote develops into a module and makes similar modules (ex. Root extensions in plants) 9.1 Modular: 2 levels of population structure Genet: genetic individual, an organism that has arisen from a zygote (sexual reproduction) like a flower Ramet: an individual produced asexually, remain attached or grow independently of parents, is a clone of the parents like grass 9.2 Distribution: describes spatial location of population and is based on the presence and absence of individuals Geographic range: area that encompasses ALL individuals of a species Geographic barriers limit the distribution of a population and restrict its ability to colonize areas that are otherwise suitable (ex. mountains, oceans, lakes) The red maple is a wide spread deciduous trees in North America which has a Northern limit: -40deg C Southern limit: gulf coast Western limit: dry conditions Individuals are not distributed evenly throughout the geographic range of a population; some individuals can occupy areas that can meet their requirements like for moss (Tetraphis) moisture is important in areas where moisture is lacking moss cannot grow. Due to local heterogeneity, populations are divided into local (main population) or sub population (dispersed population). 9.3 Abundance: number of individuals in the population -defines its size Abundance is a function of population density (number of individuals per unit area per unit volume) An individuals spatial position relative to another influences population density Three population distribution patterns (pictures in lec are useful in understanding) Random: individuals position is independent of one another usually when there is no limit or competition for resources Uniform: negative interaction among individuals usually they are trying to repel each other Clumped: due to patchy resources or social behaviours when organisms gather due to a water hole or wolves traveling in a pack The spatial distribution of individuals within the population can be described at multiple spatial scales. For example the shrub Euclea in the savannah ecosystems of South Africa are clumped under Acacia trees for canopy cover, but clumps are uniformly spaced 2 approaches on estimating population density 1) Absolute density: number of individuals/area 2) Indices of relative density: area 1 has more organisms than area 2 Measurement of Absolute Density 1) Total counts: counting all organisms in a particular area 2) Sampling Methods: count a small portion of the population and use the sample to estimate the total a) quadrats (subsample) b) capture-recapture 9.4 Population size = density x area In most cases, population density must be estimated by sampling a portion of the population Sampling methods for plants and sessile animals Counting the organisms in a subsample (quadrats) Abundance estimates may be skewed by a clumped spatial distribution Quadrats - Choose quadrats of known size - Count all individuals on these quadrats - extrapolate the average count to the whole area - used a lot in plant ecology Obtaining reliable estimates: 1) the population of each quadrat must be determined accurately and must be able to identify the species by definition 2) The area of each quadrat must be known 3) The quadrats must be representative of the whole area a. you must pick one that has similar distribution with the rest of the area Sampling methods for mobile animals - capture-recapture or mark-recapture methods are used based on trapping, marking, and releasing a known number of marked animals(M) into the population (N) - Some time later, the same population is sampled and the ratio of recaptured (R) to sample (n) individuals in the second sample represents the ratio for the entire population - N/M = n/R N=nM/R - Lincon index or Petersen index of relative population size Capture-Recapture - allows for estimate of density and estimate of birth rate and death rate - technique: capture, mark, release, recapture Assumptions: Closed population No loss of marked individuals Marked and unmarked individuals are captured randomly Marked animals are not overlooked (making sure that marked individuals are not in favour of being captured) N: total population n: second sample size M: marked animals R: marked recaptured animals N/M=n/R N=nM/R So there are 109 trout caught marked and released On the second capture 177 were caught and 57 were marked N/109 = 177/57 N= 109 (177/57) = 338 There were 338 trouts :D Indices of Abundance: The factors you can use to determine the abundance of a population 1) Traps: individuals caught/day/trap 2) Number of fecal pellets 3) Vocalization frequency 4) Pelt records (like bear fur) 5) Catch per unit fishing record 6) Number of: tree nests, pupal cases, snake sheds 7) Number of tracks 8) Roadside counts 9.5 A population usually has an age structure (individuals in different age classes) The proportion of individuals of each group is influenced by reproduction and mortality: affects the rate of population growth - Pre reproductive (infant) - Reproductive (adult) - post reproductive (ancient) The length of time that an individual remains in each stage depends on its life history - short-lived versus long-lived organisms
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