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34 Cards in this Set

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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

what are the main effects on population size

In: immigration, birth


Out: emigration, death

what are the influences on these rates (abiotic and biotic)

abiotic: meteorological conditions, seasonal temperature fluctuations, terrain



biotic: interaction with conspecifics and heterospecifics

what are individuals?

individual of a species pass through different life history stages showing variation in condition within each stage

details on modular organisms

genets - gentic individuals


modules - shoots/polyps



sometimes better to count modules

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


name 4 methods of counting organisms per unit area

quadrats



capture recapture



removal methods



abundance indices

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

two primary factors that vary with age

fecundity, mortality

terms for reproduction in life history

semelparous - single reproduction period



iteroparous - multiple episodes of reproduction

2 types of life table

cohort: follows individudals through time



static: cross section of population

explain a simple annual cohort life table

seasonal changes drive annual synchrony



every individudal breeds then dies



discrete generations

What defines the reproductive value (RV)

life history can be viewed by contribution to fitness



measures of fitness combine suvivorship and fecundity schedules


example of reproductive cost (RRV)

Pseudotsuga menziesii - the higher the number the cones (reproductive) the lower the growth of the annual ring

investment in offspring - trade offs between number and what 3 fitness for individuals

size vs number



survivorship vs number



developmental rate vs number

4 life history variables

growth



differentiation



storage



reproduction

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


Possible low cost of reproduction scenario

mortality homogenous



benign habitat



high mortality rates on large individuals (size selective predation

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

What does habitat cost of reproduction affect?

reproductive allocation



age at maturity



semelparity / iteroparity

age at maturity?

maturity delayed in high cost of reproduction habitats



trade off between juvenile survival and reproductive value at maturity

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

characteristics of K habitat organisms (5 points)

large


deferred reproduction


low reproductive allocation


few, large offspring


most short lived

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

characteristics of r habitat organisms:

smaller size


earlier maturity


high reproductive allocation


many smaller offspring


survivorship depends on environment

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)

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

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

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

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

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

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.

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

where is K not relevant?

strongly overcompensating populations : there may be cycles or chaotic variation in population size