BIO 105 Lecture Notes - Lecture 23: Semelparity And Iteroparity, Exponential Growth
Charlie Kent
Bio 105
Fall 2017
Introduction to Biology
Population Ecology
Population Growth
Recall: exponential growth model
-represents intraspecific/intraspecies competition for resources
-tells us almost exponential growth at low N value
-tells us slow growth at high N value
Life History Traits
-traits that affect an organism’s schedule of reproduction or survival
-age at maturity
-size at maturity
-number of reproductive events in lifetime
-number of offspring
-size of offspring
Number of reproductive events: 2 categories
1. Semelparity:
-‘one shot’ reproduction 1 reproductive event
-many offspring1000’s
e.g. octopus, salmon
2. Iteroparity:
-several reproductive events
-fewer offspring
-increased investment for offspring
e.g. humans, elephants, albatross
2 critical factors for number of reproductive events:
1. Probability that the adult will survive between reproductive events
2. Survival rate of offspring
low survival rate of adult and offspringsemelparity
high survival rate of adult and offspringiteroparity
Tradeoffs in Life History:
Traits tend to be favored at different population densities:
r-selection, k-selection
K-selected traits:
-favored at high N
-constant conditions
Document Summary
Tells us almost exponential growth at low n value. Tells us slow growth at high n value. Traits that affect an organism"s schedule of reproduction or survival. Number of reproductive events: 2 categories: semelparity: Increased investment for offspring e. g. humans, elephants, albatross. 2 critical factors for number of reproductive events: probability that the adult will survive between reproductive events, survival rate of offspring. Low survival rate of adult and offspring semelparity. Traits tend to be favored at different population densities: r-selection, k-selection. Strong/good competitive ability (if they didn"t have, they wouldn"t be there) Large size e. g. mature trees in old-growth forest r-selected traits: 2 major mechanisms: density dependent, density independent. Regulation of population size changes with density per capita birth rate or death rate changes with density (b or d r= b-d) Density independent: (population regulation what limits a population size?) B or d do not change with n.
