Life Tables

Question 1

Define demography

Answer 1

the study of the processes that change the size of a population (ex. birth, death, and dispersal) with particular respect to sex and age

Question 2

Define surviorship

Answer 2

the probability of a newborn individual living to a particular age

Question 3

Define mortality rate

Answer 3

the probability of dying at a particular age

Question 4

What is the slope related to on survivorship graphs (# of survivors vs. age) and explain

Answer 4

related to the mortality rate
a steep slope implies high mortality vs. shallow slope meaning lower mortality rate

Question 5

Define life tables function

Answer 5

allow for enumerating age and sex specific vital rates.
allow for understanding age-structured population growth and life-history evolution

Question 6

In life tables, how is lx often displayed

Answer 6

by multiplying by 1000 often shown on log scale

Question 7

sometimes survivorship curves are separated by _____

Answer 7

cohort (age or by year)

Question 8

Why is the correction factor necessary in the life expectancy equation

Answer 8

because without it, is saying that all individuals are dying at the end of their lifespan

Question 9

Explain the 3 types of survivorship curves

Answer 9

Type 1 = age specific mortality INCREASES with age (humans)
Type 2 = age specific mortality is CONSTANT with age (squirrels)
Type 3 = age specific mortality DECREASES with age (turtles)

Question 10

When generating a life table, we either need _____ or ____ data

Answer 10

number surviving to interval
number dying during interval

Question 11

what kind of organisms are cohort life tables typically applied to

Answer 11

short lived and/or sessile organisms that can be tracked reliably for their whole lives

Question 12

Cohort life tables can be applied to population at any phase of population ______

Answer 12

growth
(growing, shrinking, stationary)

Question 13

Cohort life tables are typically the _____ but they usually require ____

Answer 13

most powerful and accurate
more effort

Question 14

Define static life tables

Answer 14

data is collected at a single point in time, applied to long-lived and/or mobile organisms that are difficult to track reliably their whole lives

Question 15

What are the subtypes of static life tables

Answer 15

1. time specific 2. stationary based on ages at death within a population

Question 16

Define time-specific life tables

Answer 16

builds life table by estimating the survival of individuals of known age during a single time interval, uses yearly mortality (qx)

Question 17

What is a stationary life table based on

Answer 17

ages at death within a population, the number dying in each class (Dx)

Question 18

How was the stationary life table for Dall mountain sheep built

Answer 18

they used the horns of dead sheep to create their data and the total number to create their cohort size

Question 19

What are the very strict assumptions of the stationary life table example of using Dall mountain sheep

Answer 19

1. can accurately age the skulls
2. probability of finding skills does not change with age
3. population is stationary in size (if the population was growing, young individuals would be overrepresented)

Question 20

Sx

Answer 20

number alive at the start of interval

Question 21

Dx

Answer 21

Number dying in interval
Sx-Sx+1

Question 22

lx

Answer 22

probability of survival from birth to certain interval
Sx/S0

Question 23

qx

Answer 23

probability of dying in the interval (mortality)
lx-lx+1/lx

Question 24

dx

Answer 24

fraction dying in the interval
Dx/S0

Question 25

ex

Answer 25

mean expectation of life
[(sum of all survive of time and older)/survived to that exact time] -0.5