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34 Cards in this Set
- Front
- Back
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Begon, Townsend and harpers definition of ecology (2006) |
the scientific study of the distributions abundance and relations of organisms and their interactions with the environment |
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what are the main effects on population size |
In: immigration, birth Out: emigration, death |
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what are the influences on these rates (abiotic and biotic) |
abiotic: meteorological conditions, seasonal temperature fluctuations, terrain
biotic: interaction with conspecifics and heterospecifics |
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what are individuals? |
individual of a species pass through different life history stages showing variation in condition within each stage |
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details on modular organisms |
genets - gentic individuals modules - shoots/polyps
sometimes better to count modules |
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what is a population |
group of individuals of a species
may be discrete units, may be dispersed and studied at density level
counts impractical, estimates based on extrapolation
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name 4 methods of counting organisms per unit area |
quadrats
capture recapture
removal methods
abundance indices |
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problems with measuring birth and death rates |
birth - may not occur when and where can be counted
death- remains short lived in environment - capture recapture can estimate but confounded with emigration rate |
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two primary factors that vary with age |
fecundity, mortality |
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terms for reproduction in life history |
semelparous - single reproduction period
iteroparous - multiple episodes of reproduction |
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2 types of life table |
cohort: follows individudals through time
static: cross section of population |
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explain a simple annual cohort life table |
seasonal changes drive annual synchrony
every individudal breeds then dies
discrete generations |
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What defines the reproductive value (RV) |
life history can be viewed by contribution to fitness
measures of fitness combine suvivorship and fecundity schedules
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example of reproductive cost (RRV) |
Pseudotsuga menziesii - the higher the number the cones (reproductive) the lower the growth of the annual ring |
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investment in offspring - trade offs between number and what 3 fitness for individuals |
size vs number
survivorship vs number
developmental rate vs number |
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4 life history variables |
growth
differentiation
storage
reproduction |
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What are possible high cost of reproduction scenarios |
intense competition amongst established individuals, high reproduction affects RRV very negativley
small individuals vulnerable to mortality - outgrowing predation risk
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Possible low cost of reproduction scenario |
mortality homogenous
benign habitat
high mortality rates on large individuals (size selective predation |
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offspring size sensitivty scenarios |
size sensitive - reproductive value rises significantly with size, small number of large offspring expected (e.g size increases in guppie offspring when predation focusses on smaller individuals
size insensitive scenario - reproductive value not strongly associated with size |
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What does habitat cost of reproduction affect? |
reproductive allocation
age at maturity
semelparity / iteroparity |
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age at maturity? |
maturity delayed in high cost of reproduction habitats
trade off between juvenile survival and reproductive value at maturity |
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r - K Selection (MacArthur and Wilson) Describe K habitat with high CR, offspring size sensitive |
stable environment
crowded, maximal population
intense adult competition
high juvenile mortality |
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characteristics of K habitat organisms (5 points) |
large deferred reproduction low reproductive allocation few, large offspring most short lived |
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r habitat description with low CR, offspring size insensitive |
unpredictable environment
periods of indiscriminate mortality
mortality highly variable
mortality independent of density and individual condition |
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characteristics of r habitat organisms: |
smaller size earlier maturity high reproductive allocation many smaller offspring survivorship depends on environment |
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how can r - K be an over-simplification |
adult and offspring habitats may not be linked
r - K characteristics may arise from other pressures (e.g size specific predation) |
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Begon, Townsend and Harpers definition of competition |
competition is an interaction between individuals, brought about by shared requirment for a resource, and leading to a reduction in the survivorship, growth and/or reproduction of at least some of the competing individuals |
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intraspecifc competition in cave beetles |
beetle fecundity is correlated with cricket fecundity, beetles eat cricket eggs and reduce cricket density
higher density of beetles reduced the foraging and consumption of eggs in experiment |
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asymmetrical competition? |
one individual may exert a much stronger effect on another individual
strong competitors may contribute disproportionately to the next generation, weak may not contribute at all |
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density dependence in intraspecific competition |
higher densities effect competition
reduces birth rates and increases death rates with increasing density
but other factors produce density dependent effects |
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defining density |
abstract concept that may be defined in different ways
per unit area
in or on habitat patches (e.g parasites on hosts), resource weighted density
problem defining density for sessile, modular organsisms, only compete with neighbours |
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how does intraspecific competition regulate population size? |
as density increases so does competition. the mortality rate rises, and the birth rate lowers reaching a point where maximum density occurs (K). past this point the population reduces in size thefore density falls. |
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Definition for the carrying capacity (K) |
the population size that can be maintained by environmental resources without a tendency for increase or decrease
in practice unpredictable environmental fluctuations lead to variation in k, so density dependent processes acting on birth and death rates tend to maintain population size within a range of values |
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where is K not relevant? |
strongly overcompensating populations : there may be cycles or chaotic variation in population size |
