Chapter 11: Population Structure Important Concepts to Review: · Population structure, survivorship curves and the three types · Life table types · Understanding examples of patterns of survival(Dall sheep, birds, desert shrub) · Age distribution and understanding examples(oak, cottonwood) · Sex ratios and understanding and frequency-dependent selection Notes: Introduction · Population Structure: can be defined by a number of factors including patterns of mortality, age distributions, sex ratios and dispersal. o Population study is conducted via combining the understanding gained through natural history and scientific study. o Adolph Murie - foundational figure in population ecology (read the first page of chap11 for the explanation, its mostly stupid but either way. 11.1 Patterns of Survival - A survivorship curve summarizes the pattern of survival in a population · Mortality and Survival - most fundamental descriptions of population ? Patterns of survival vary a lot between species o Some species produce millions of offspring and may have a high death rate, others produce very little and invest heavily in their care - thus resulting in high rates of young survival. ? Life Tables - bookkeeping devices that ecologists use that list the births, survivorship and deaths in populations. · Estimating patterns of survival ? The first and most reliable way to estimate patterns of survival is to identify a large number of individuals born at the same time and keep records of them from birth to death. o Cohort - a group born at the same time o Cohort Life Table - data collected from the cohort observation ? However, collecting data using this method is Time-consuming Difficult to keep track off with mobile animals · Some animals live longer than the average human lifespan - hence impossible to keep track off. o The second way to estimate patterns of survival in wild populations is to go and record the death age for some individuals for a short period of time. This method differs as individuals are born at different times. ? Static Life Tables - contains the age groups in a population at one particular period of time Estimating the age of death is crucial however it's not easy, some individuals were tagged at birth then the tags would be recovered after death. However, this is not practical. Estimates of death can be useful (sometimes) . Mountain sheep can be aged by counting the growth of rings on their horns. Growth rings are also present on the carapaces of turtles, trunks of trees and in the "stems" of corals o The third way of determining patterns of survival is age distribution. Age distribution consists of the proposition of individuals of different ages within a population. This can be used to calculate the estimate of survival by subtracting the difference in population in the succeeding age classes. . This method assumes that the difference in the number from one age to the next is due to mortality · It assumes that the population is neither growing or declining through migration or emigration.