Chapter 52 Notes

Chapter 52 Notes - Chapter 52 Notes Population Ecology...

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Chapter 52 Notes Population Ecology Dramatic increases in population have caused many problems Population: a group of individuals of the same species that live in the same area at the same time Population ecology: the study of how and why the number of individuals in a population changes over time 52.1 Demography The number of individuals in a population depends on o Birth – any form of reproduction o Death o Immigration: individuals entering from another population o Emigration: individuals leave a population to join another population Demography: the study of factors that determine the size and structure of populations through time Must know the makeup of the population to predict the future of it Generation: the average time between a mother’s first offspring and her daughter’s first offspring Population increases if it has young individuals with high survival rate and reproductive rate, but decreases if it has mainly old individuals, low reproductive rates, and low survival rates Life Tables ***Life table: summarizes the probability that an individual will survive and produce in any given time interval over the course of its lifetime o used by insurance companies and biologists to study demographics of endangered species Lacerta Vivipara: A Case Study L. vivipara in open grassy western Europe, “live birth” ovoviviparous, live young Researchers were interested to see whether populations that live in different environments vary in basic demographic features Marked lizards daily during the 7 months they are active a year, for seven years Were able to assume deaths and track females offsprings Survivorship Survivorship: the proportion of offspring produced that survive, on average, to a particular age Cohort: a group of the same age that can be followed through time To analyze general patterns in survivorship, biologist plot the logarithm of the number of survivors versus age creates the survivorship curve, 3 general curves exist o Type I: survivorship throughout life is high, most individuals approach the species’ max life span. Ex. Humans o Type II: occurs in species where individuals have about the same probability of dying in each year of life. Ex. Blackbirds and songbirds
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o Type III: extremely high death rates for seeds and seedlings but high survival rates for later in life. Ex. Plants Fecundity Fecundity: the number of female offspring produced by each female in a population Number of males present rarely affects population dynamics Age-specific fecundity: the average number of female offspring by a female in age class x Age class: a group of individuals of a specific age The Role of Life History Key aspects of the life table vary dramatically among populations for the L. vivipara Box 52.1 Quantitative Methods: Using Life Tables to Calculate Population Growth Rates Survivorship of an age class is determined by dividing the number of females in that age class by the number of
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This note was uploaded on 02/12/2012 for the course SCI 2341 taught by Professor Yates during the Spring '11 term at Alabama.

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Chapter 52 Notes - Chapter 52 Notes Population Ecology...

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