population size into the future, next time period. If the birth and immigration exceed the numbers of death and emigration, the population number should grow. If it was vice versa then the population will decline. The BIDE processes. If r is positive, population size increases and vice versa. Population demography. Study of the effect of age-structure and other population parameters (b,i,d,e) on population growth. Age structure is the proportion of individuals in each age class. Example of 2 age distributions, one in France and one in India. India higher rate for reproduction. Because it produced more newborns. Life tables. (on exam 20% constructing life table and answering questions about them) Consist of age specific survivorship and fecundity (reproduction) which are the vital rates. Idea that survivorship and fecundity varies on age of population. Known as vital rates of population. Can make some predictions, one from lifespan of specific individual. Predict how long an individual will live. Can predict age distribution over time and future population size. Estimate what value of little r is. Used by insurance companies want to know when you’ll die given your health risks. Developed by Egyptian in 200bc to know how many slaves they had. Ancient romans used it for tax purposes. Determining age specific survivorship. In sea turtles 75-95% mortality rate in hatchling stage. Decreases when they are older. Survivorship varies with age. Hard to age turtles. X can represent life stage or age. Cohort analysis, even age group of individuals. Follow a cohort during lifespan of tarantulas. Life tables typically focus on females because it is often hard to keep track of reproduction of males. Calculate lx is proportion surviving. Always start with 0.
Construct as survivorship curves. Make sure how to label your axis. Plot from life table, age (x) against number alive (nx). 3 basic kinds of survivorship curves. Type I,II,III. Most of the time scale to 1000 so its easier to compare among examples, Multiply nx by 10 so everything scales to 1000. Type I shows that the number survived drops at a lower rate. Juvenile survival is high and most mortality occurs among older individuals. Type II shows linear decline in survivorship so mortality is decreasing constantly. Individuals die at equal rates, regardless of age. Type III, we see high mortality rates in the beginning like the turtles but then levels off late on. Darwin’s ground finch. Small, isolated volcanic island. Original cohort had 210 birds, after one year 91 remained and after 2 years 78 remained. 9/1/16 Look at life table example on Moodle. Age-specific survivorship- first half of life table. Second half is to determine the age specific fecundity schedules. Which is reproduction. Want to make predictions about how big or small the population is going to be at some time in the future. Reproduction is age dependent. bx is number of female offspring produced per female at age x. Harder to track reproductive success for males than females. In chart, it only looks at daughters from female parent. Potential fecundity is the total number of daughters produced by mother if the mother survived to the end of last age class. 54, if mom survives to the end of the maximum life span, it would produce
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