Life tables

Question 1

populations have a spacial structure which includes:

Answer 1

1. their range
2. spatial arrangement of individuals within and among the range
   - density
   - patterns of movement among individuals

Question 2

Populations also have genetic variation
among individuals throughout the population
… or represented in

Answer 2

subpopulations

Question 3

Another component of populations is

associated with age structure

Answer 3

and the
rates at which births and deaths occur
within a population

Question 4

who invented life tables and why

Answer 4

the Insurance and Health Care Industry to monitor mortality and survivorship in human populations

Question 5

When was the first life table developed

Answer 5

in 1921 by Pearl and Parker

Question 6

In order to construct a life table in the first place,

one must have some knowledge of the

Answer 6

age structure within a population

Question 7

the first column of the life table is

Answer 7

x

Question 8

x usually represents

Answer 8

age (could be in days, weeks, years, hours, etc.)

Question 9

individuals that make up x are referred to as a

Answer 9

cohort

Question 10

two inherent weaknesses in life tables

Answer 10

1. only age is considered when allocating individuals to classes (not size, social status, and genotype)
2. life tables almost always include only females for species having distinct males and females. This is because one of the key parameters in a life table is the rate of production

Question 11

the male’s contribution to sexual reproduction

Answer 11

difficult to measure in terms of the numbers of young produced

Question 12

how is birth accounted for in life tables

Answer 12

by counting the number of female offspring produced per breeding season or age interval per female in the population (fecundity)

Question 13

Life tables

Answer 13

tables that contain class-specific survival and fecundity data

Question 14

x

Answer 14

age class

Question 15

nx

Answer 15

the number of individuals in each age class immediately after the population has produced offspring

Question 16

sx

Answer 16

the survival rate from one age class to the next age class

Question 17

bx

Answer 17

the fecundity of each age class

Question 18

what is the fecundity of each age class denoted by

Answer 18

bx (b for birth)

Question 19

what does the column bx indicate

Answer 19

new offspring cannot reproduce, but 1-year-olds can each produce one offspring, 2-year-olds can each produce three offspring, and 3-year-olds can each produce two offspring

Question 20

Number surviving to next age class

Answer 20

(nx) x (sx)

Question 21

Number of new offspring produced

Answer 21

(nx) x (sx) x (bx)

Question 22

if we do these calculations for every age class…

Answer 22

we can find the number of individuals that we will have after one time interval

Question 23

the number of individuals in a population after one time interval divided by the initial number of individuals provides…

Answer 23

lambda

Question 24

A POPULATION WITH A FIXED LIFE TABLE
ASSUMES A STABLE AGE DISTRIBUTION AND
GROWS

Answer 24

at a constant rate

Question 25

When age-specific birth bx and survival, sx, rates remain unchanged for a sufficient length of time, a population will assume

Answer 25

a stable age distribution

Question 26

``` Under such conditions, each age class in the population grows or declines at the same rate; and so, therefore, does the ```

Answer 26

total size of the population

Question 27

lambda

Answer 27

the growth rate of the population

Question 28

``` Under stable age distribution conditions, each age class grows at the ```

Answer 28

same rate from year to year

Question 29

Stable age distribution

Answer 29

when the age structure of a population doesn't change over time

Question 30

when does a stable age distribution occur

Answer 30

when survival and fecundity of each age class stays constant over time

Question 31

survivorship

Answer 31

the probability of surviving from birth to any later age class (lx); survivorship in the first age class is always set at 1

Question 32

survivorship to the second year (l2) is calculated as

Answer 32

l1s1

Question 33

net reproductive rate (R0)

Answer 33

the total number of female offspring that we expect an average female to produce over the course of her life

Question 34

R0 =

Answer 34

Sigmalxbx

Question 35

``` lx is the number at the beginning of a particular age class divided by ```

Answer 35

the number at the beginning of the cohort

Question 36

Generation time (T)

Answer 36

the average time between the birth of an individual and the birth of its offspring

Question 37

T =

Answer 37

Sigma X x X lx X bx / Sigma X lx X bx

Question 38

When λ or r is estimated from a life table, it is assumed that the life table has

Answer 38

a stable age distribution

Question 39

Age distributions fluctuate due to environmental conditions, so any approximation of λ or r is restricted to

Answer 39

the environmental conditions that the population experiences at the time of measurement

Question 40

To calculate an approximate (denoted as a) λ | λa =

Answer 40

R0^(1/T)

Question 41

to calculate an approximate r

Answer 41

ra = logeR0 / T

Question 42

populations grow when

Answer 42

R0 > 1

Question 43

populations decline when

Answer 43

R0 < 1

Question 44

Net reproductive rate (R0)

Answer 44

the total number of female offspring that we expect an average female to produce over the course of her life

Question 45

Generation time (T)

Answer 45

the average time between the birth | of an individual and the birth of its offspring.

Question 46

We can provide close approximations, denoted as λa and ra (where the letter “a” indicates an approximation), based on our estimates of net reproductive rate (R0 ) and generation time (T):

Answer 46

λa = R0^(1/T)

Question 47

Kinds of Life Tables

Answer 47

1. cohort/dynamic life tables | 2. static/time-specific life table

Question 48

Cohort life table

Answer 48

a life table that follows a group of individuals born at the same time from birth to the death of the last individual

Question 49

Cohort life tables are readily applied to

Answer 49

sessile organisms that can be tracked over the course of their life

Question 50

Environmental changes can affect survival and fecundity of a cohort

Answer 50

it is difficult to separate the effects of age and the environment

Question 51

Rosemary and Peter Grant

Answer 51

1978 marked 210 cactus finch fledglings and followed them for 15 years

Question 52

The cohort life table does not work well for

Answer 52

species that are highly mobile or for species with very long life spans, such as trees

Question 53

One of the problems in using a cohort life | table is that

Answer 53

a change in the environment during one year can affect survival and fecundity of the cohort that year. This makes it difficult to disentangle the effects of age from the effects of changing environmental conditions

Question 54

Static life table

Answer 54

a life table that quantifies the survival and fecundity of all individuals in a population during a single time interval

Question 55

age is not confounded with

Answer 55

time

Question 56

Static life tables can be applied to

Answer 56

highly mobile organisms, and species with long life spans

Question 57

Life tables may not be representative of years with different environmental conditions

Answer 57

tables for multiple years should be constructed

Question 58

A life table may also be constructed from the | distribution of the ages at death in a population

Answer 58

For example, one could obtain the age of death for each person in a local cemetery by examining the headstones. Using the total number of occupants of the cemetery, we could determine the number of individuals surviving at the beginning of each age interval, and from that, survivorship

Question 59

Some biases though (life table)

Answer 59

For example, it assumes that an equal number of newborns forms the basis for each age class. This assumption is violated in expanding and declining populations in which younger and older age classes, respectively, are over-represented.

Question 60

Sea turtle populations have declined by more than

Answer 60

99% over the past several centuries

Question 61

Once life tables were created, population modelers realized that

Answer 61

few hatchlings survive in nature anyway, so protecting eggs would not benefit the population

Question 62

Instead, life tables indicated that

Answer 62

improving the survivorship of adult turtles would grow the population

Question 63

what has been proven to be a tremendous success in conserving the sea turtles

Answer 63

turtle excluder devices on fish trawling nets