# Life tables Were first used to estimate insurance risk in human populations Divides the population into age specific classes Estimates the age-specific.

## Presentation on theme: "Life tables Were first used to estimate insurance risk in human populations Divides the population into age specific classes Estimates the age-specific."— Presentation transcript:

Life tables Were first used to estimate insurance risk in human populations Divides the population into age specific classes Estimates the age-specific mortality risk in each class

A life table for a town in the East Midlands
age pop death % death 1 death in <1 2533 20 127 1-4 11130 1 5-9 15519 2 7760 10-14 16409 4 4102 15-19 16133 9 1793 20-24 21482 10 2148 25-29 15997 22 727 30-34 16026 35 458 35-39 19800 34 582 40-44 16076 39 412 45-49 13404 59 227 50-54 13027 108 121 55-59 10051 136 74 60-64 10220 176 58 65-69 9190 320 29 70-74 7427 445 17 75-79 5231 414 13 80-85 2884 355 8 85+ 1840 347 5

Assembling a life table
Cohort or Dynamic life table Assembled by following the fate of a cohort from birth to death. Static life table Assembled estimating the age specific death risks from the age structure at a given time

Dynamic life table Static life table age 1999 2000 2001 2002
survivorship lx 1000 1.00 1 400 0.40 2 100 0.10 3 20 0.02 Static life table estimated age 1999 survivorship lx 1000 1.00 1 400 0.40 2 100 0.10 3 20 0.02

However a static life table assumes the population is stable which is usually not true
estimated age 1999 survivorship lx 1000 1.00 1 400 0.40 2 100 0.10 3 20 0.02 Original estimates estimated age 1999 original population survivorship lx survivorship 1000 1.00 1 400 1200 0.40 0.33 2 100 1400 0.10 0.07 3 20 1600 0.02 0.13 But what if the population is decreasing? Decreasing population

Population increasing
estimated age 1999 original population survivorship lx survivorship 1000 1.00 1 400 900 0.40 0.44 2 100 800 0.10 0.13 3 20 600 0.02 0.03 Population increasing

Phlox drummondii (annual phlox) is native to central and eastern Texas
Phlox drummondii (annual phlox) is native to central and eastern Texas. It is a winter annual and grows abundantly in sandy fields and on roadside verges. It germinates in response to cool rainy weather.

qx=lx-lx+1 the proportion of individuals that have died over a time period = the mortality rate.

Mortality analysis time days time days Average mortality rate per day
Log scale time days

Where bx seed=number of seed per plant (Bx/Nx)

Fecundity analysis Number of seed produced per plant time days

Diagrammatic dynamic life table for Phlox drummondii
Rectangles=stages in the life-cycle Inverted triangles= transition probabilities Diamond=seed production

A more complex diagrammatic life table of the biennial ragwort Senecio jacobea
Dispersal Seed bank dynamics germination immigration establishment Biennial lives for 2 years reproducing at the end of the second year

Survivorship curves Type I = Found where there are ample resources e.g. human population in developed countries Type II = A constant risk of death throughout lifespan e.g. seeds in a buried seedbank Type III = High early mortality e.g. many plants reproducing by seed

Survivorship curve for Phlox drummondii

Survivorship curves of Erophila verna at different densities
b=5-10 c=15-20 d=35-50 e=>50 1000s m-2 Survivorship curves for a species depend on a range of conditions

In plants stage of development can be a more useful definition of progress than age. Data are for a perennial Ranunculus acris juveniles immature vegetative generative dead

Similar presentations