Bio Ecology Lecture 3

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Autecology
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study of ecology of one species
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Synecology
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ecological research which focuses on interactions between different species in communties.
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Population size
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Factors: – Increase: Births, immigration – Decrease: deaths, emigration
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Estimation of abundance
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1. Counting Individuals 2. Quadrats and transects
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1. Counting Individuals
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the simplest form of calculating direct abundance
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2. Quadrats and transects
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quadrats
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– Mark off a particular area (quadrat) and count the number of individuals of a species in that area. – Repeat in another area. – Average the results to estimate the population density of that species within the larger area. – The more quadrats used, the better the estimate.
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transects
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– a line placed across a community of organisms providing information on the distribution of species
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Estimation of abundance (indirect)
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1. tracks and sign 2. associated species
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1. tracks and sign
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ex. poop, footprints * Note that the absolute estimates of population size provide quantitative (numerical) estimates, whereas relative estimates identify populations as relativity larger or smaller than some baseline
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2. special case: associated species
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– correlation between geese number and paragine – paragine kept foxes at bay
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Population number vs. population density
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– Population number: total number of individuals – Population density: total number of individuals/ area or volume
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Mark and recapture method
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a way to estimate populations by capturing, tagging, releasing and recapturing a sample of the original sample. Works for organisms that move. N: total population size m: marked individuals in first sample n: total caught in second sample x: marked individuals in second sample
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Mark and recapture method assumptions
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Assumptions: – animals stay in relative area – circulation- freely mixing into population – no births – no deaths – no immigration – no emigration
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Tracking movement: PIT tags
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– chip to track organisms- goes under skin – Passive integrated transponder
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Tracking movement: Radio collars
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– used for large terrestrial and marine species where home ranges determined and population estimates developed based on area of available habitat
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Population dispersion patterns
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1. Uniform 2. Clumped 3. Random * dispersion pattern is dependent on spatial scale
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Clumped
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– individuals are aggregated in patches – Plants and fungi are often clumped where soil conditions and other environ- mental factors favor germination and growth. ex. Mushrooms: for instance, may be clumped within and on top of a rotting log. Insects and salamanders may be clumped under the same log because of the higher humidity there. Ex. Sea Stars: group together in tide pools, where food is readily available and where they can breed suc- cessfully Ex. Wolf Pack: Forming groups may also increase the effectiveness of predation or defense; for example, a wolf pack is more likely than a single wolf to subdue a moose, and a flock of birds is more likely than a single bird to warn of a potential attack.
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Uniform
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– A uniform, or evenly spaced, pattern of dispersion may result from direct interactions between individuals in the population. – Some plants secrete chemicals that inhibit the germination and growth of nearby individuals that could compete for resources. – Animals often exhibit uniform dispersion as a result of antagonistic social interactions, such as territoriality—the defense of a bounded physical space against encroachment by other individuals – Uniform patterns are rarer than clumped patterns Ex. Birds nesting on small islands, such as these king penguins in the Falkland Islands, near the southern tip of South America, often exhibit uniform spacing, maintained by aggressive interactions between neighbors.
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Random
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– In random dispersion (unpredictable spacing), the position of each individual in a population is independent of other individuals. – This pattern occurs in the absence of strong attractions or repulsions among individuals or where key physical or chemical factors are relatively constant across the study area. – Plants established by windblown seeds, such as dandelions, may be randomly distributed in a fairly uniform habitat. – Random patterns are not as common in nature as one might expect; most populations show at least a tendency toward a clumped distribution. Ex. Many plants, such as these dandelions, grow from windblown seeds that land at random and later germinate.
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Factors in the environment
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1. biotic: interactions with other organisms; internal species factors 2. abiotic: temperature, percipation, water, soil, wind
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allelopathy
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The production of chemicals by plants that inhibit the growth of neighbouring plants
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Territoriality
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1. calls 2. marking
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1. bird calls
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Ex. territoriality in kingfishers
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2. marking
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Ex. Cheetah marking boundary ranges with urine
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Ecology of group living: Advantages
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– increased vigilance – safety in numbers – group defense – finding food – catching prey – thermal advantage – competitive advantage
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Ecology of group living: Disadvantages
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– more conspicuous – competition for food – increased disease – increased cheating
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Principle of allocation
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the principle that if an organism allocates energy to one function, such as growth or reproduction, it reduces the amount of energy available to other functions, such as defense
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Resource Acquisition: Photosynthesis and light intensity
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Resource acquisition: Seed Harvest vs. Seed density
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Life History trade-offs: Reproduction vs. Growth
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Life History trade-offs: Reproduction vs. Survival
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