ENWC201 Lecture Notes - Lecture 6: Logistic Function, Carrying Capacity, Exponential Growth
16 May 2018
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Lecture 6:
• Irruption
o Snowy owls
o Coming south in unpredictable invasions
o Snowy owls feed there babies lemmings
▪ Population of lemmings is increasing due to increased snow depth
• Population dynamics
o A branch of the life sciences that studies the short term and long term changes in
the size and age composition of population, and the biological and
environmental processes influencing those changes
• Population
o A group of individuals of the same species that inhabit a defined area at a
specific time
• Population terms
o Factors that affect population size
▪ Natality
• Births over time
o =birthrate
• added through reproduction
• usually higher than needed to replace the parents
• factors of natality:
o fertility: physiological capable of producing offspring
o fecundity: potential number of offspring produced by an
individual over time
o production: actual number of offspring produced in a
given time
▪ Mortality
• Deaths over time
o =death rate
• changes throughout the life cycle of an organism
• often high, particularly young individuals
• compensatory mortality
o one mortality factor compensating for another
• additive mortality
o tornado goes through
▪ Sex ratio
• The relative number of males and females
o Out of hundred animals
o Males to females
• Typically, 50/50 when an egg is fertilized
• Following birth ration becomes skewed
• Sex ratio is important to number of offspring produced
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