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Canada (161,773)
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BIO205H5 (48)
Chapter 9

Chapter 9.docx

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Christoph Richter

Chapter 9 Properties of populations  Population: a group of individuals of the same species that habitat in a given area at a time  Natural selection acts upon individual  Population evolves  Population properties  Density: # of individuals per unit area  Age structure: proportion of individuals in various age classes  Dispersion: spacing of individuals relative to each other  Dynamics: change in # over time as a result of death, birth, and movement 9.1 types of individuals  Individuals are either unitary or modular  Humans are unitary organisms  Unitary organisms- organisms that grows from birth to adult as single integrated unit, often with determinate development  most organisms that are unitary are determinate  fish is indeterminate and grows throughout their life span  modular organisms- organism that exhibit indeterminate growth involving repeated units, such as plants blanches or shoots  most plants and fungi are modular  Series of repeated units are added to the region of active growth, meristem.  Have wide range of final size  Genet – genetically distinct, free living organism that arise from a fertilized egg.  Ramet- a module that is produced asexually by a genet and is capable of independent existence. o May or may not remain physically attached to their parent genet o Can flower, produce its on ramet and produce seeds o All ramets are genetically identical to their parent genet  Modular population consists of sexually produced genet and asexually produced ramet 9.2 distribution and range  Distribution of population describes its spatial location and the area in which all its members live  Geographic range- total area over which the species occurs  Distribution is influenced by presence of suitable abiotic conditions  Geographic barriers  Within a population, individual only occupy locations that meet their resource needs  Individuals are not distributed equally  Most populations exists as sub populations ( each occupying the suitable patch)  Local subpopulations- occupying local habitat patch  Collective of subpopulation is called metapopulation 9.3 population size  Populations differ in abundance and density  Abundance reflects two factors 1. The area over which the population occurs 2. Population density- # of individuals per unit area  Crude density(varies widely)- simply the # of individuals per unit area  Ecological density- # of individuals per unit of suitable habitat. This measure is rarely used by ecologists cause not all area is homogeneous and not all the area are suitable habitat 9.4 spatial dispersion  Individuals may be spaced randomly, uniformly or in clumps  Spatial dispersion- the position of individual relative to each other  Random dispersion- individual’s position is independent of other individuals  indicates either absence of biotic factors or the random availability of resources  it’s rare  uniform dispersion- individuals are evenly spaced  reflects negative interactions among individuals  i.e intraspecific competition ( within the same species)  uniform dispersion is common in territorial species and in plants experiencing severe competition for water and nutrients  clumped- individuals occur closer together than expected by chance  most common  reflects positive interactions among individuals  i.e schools or fish  plants that produce asexually often grow in clumps  patchy habitat or abiotic factors may cause clumping 9.5 sampling populations  various methods used to measure abundance  population size is function of density and area occupied  abundance = density x area  census : counting all individuals  used when both abundance and distribution are small  most cases, density is estimated by sampling the population  method used for plants and sessile animals involves sampling units called quadrates  more quadrate for better estimate  the accuracy of density estimates is affected by spatial dispersion or quadrate size  for mobile animals, mark and recapture method is used  mark- recapture-capturing , marking and recapturing  called Lincoln index R: recaptured M: kn
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