BIOL 4503 Lecture Notes - Isotopes Of Hydrogen, Introduced Species, Electronic Tagging

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2 Feb 2013
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How Do Ecologists Study Populations?
Population consists of the individuals of a species within a given area
any given time, an individual organism occupies only one spot in space-
particular age and size
members are distributed over space, differ in age and size
age distribution of individuals in a pop’n and the way they are spread over
the environment describe its population structure
population density: number of individuals of a pop’n per unit of area
structure of a pop’n changes continually b/c of demographic events-
births, deaths, immigration, emigration
study of birth death and movement rates that create population dynamics
changes in pop’n structure and density) is known as demography
ecologists determine how many individuals are found in an area and where
they are located
individuals change their locations by migrating or dispersing
investigators need to be able to recognize and track individual animals
field studies of animals pop’ns require tagging or marking individuals in some
way
birds are marked by coloured bands on legs; butterflies coloured spots on
wings; bees-numbered tags on bodies; mammals-tags or dye on fur; plants-
tags on branch or nearby ground
microchips and other forms of electronic tagging are used on organism of all
sizes
molecular markers used to determine movement of individuals over long
distances
one way – analyze the chemical composition of feathers that the birds molt
as they migrate south-can determine where they molted by evaluating
hydrogen isotopes in feathers b/c there is a strong latitudinal gradient in
stable hydrogen isotopes in precipitation
Most individuals molted their feathers close to the breeding ground
POPULATION DENSITIES
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