Chapter 9

Question 1

What are the 4 factors that affect population size?

Answer 1

Birth/Immigration and Emigration/Death

Question 2

What is the formula for population growth rate with no immigration/emigration?
What do the variables mean?

Answer 2

N(t+1) - N(t) = (b-d)N(t)
b = birthrate
d = deathrate
N(t) = number of individuals in the population at a given time

Question 3

What is the variable for the growth rate of a population? What does it mean compared to 0?

Answer 3

r = b-d
If r=0, then b=d, so population is constant
If r>0, then b>d, so population is increasing
If r<0, then b<d, so population is decreasing

Question 4

Define life table

Answer 4

An age-specific account of mortality. Systematic patterns of mortality and survivorship within populations.

Question 5

Define cohort

Answer 5

A group of individuals in a population born in the same period of time

Question 6

Define survivorship. What variable is used for this?

Answer 6

The number of individuals surviving to a given age versus the entire original cohort size
lx

Question 7

Define age-specific mortality. What variable is used for this?

Answer 7

Difference between the number of individuals alive for an age class and the next older age class.
dx

Question 8

Define age-specific mortality rate. What variable is used for this?

Answer 8

Determined by the number of individuals dying during a given time by dividing the number alive at the beginning of each intervals
qx

Question 9

Define life expectancy. What variable is used for this?

Answer 9

Average number of years an individual is expected to live from the time of it’s birth
E

Question 10

What do each of these columns on a life table represent?
x
nx
lx
dx
qx
E
ex

Answer 10

x - age classes in years
nx - number of individuals of the cohort that are alive at age x
lx - survivorship
dx- difference between number of individuals alive for an age class and the next age class
qx - age-specific mortality rate
e - life expectancy
ex - average number of years an individual of a certain age is expected to live into the future

Question 10

Define Age-specific life expectancy. What variable is used for this?

Answer 10

The average number of years an individual of a certain age is expected to live into the future.
Ex

Question 11

Define a dynamic life table

Answer 11

The fate of a single cohort from birth to death.

Question 12

Define dynamic composite life table

Answer 12

Constructed from individuals born over several time periods, not just one.

Question 13

Define static life tables. What assumptions are made?

Answer 13

Sampling a population to obtain a distribution of age classes during a single period of time.
Assume: Ech age class sampled is in proportion to its numbers in the populations. AND age-specific births and mortality rates are constant over time.

Question 14

What does a mortality curve represent?

Answer 14

It plots mortality rates against age

Question 15

What does a survivorship curve plot?

Answer 15

Survivorship against age.
*Plotted on a log10 scale.

Question 16

Define a Type I survivorship curve

Answer 16

High survival rate throughout life, most mortality occurring at the end.

Question 17

Define a Type II survivorship curve

Answer 17

Survival rates do not vary much with age

Question 18

Define a Type III survivorship curve

Answer 18

Mortality rate is very high early in life

Question 19

Define birthrate

Answer 19

Births per 1000 individuals of a population per unit of time

Question 20

Define crude birthrate

Answer 20

Number of birth during some time period divided by the estimated population size at the beginning of the time period multiplied by 1000

Question 21

Define age-specific birthrate

Answer 21

Function of the number of females in the population. This further modifies the birthrate estimate for dimorphic species.

Question 22

Define fecundity table

Answer 22

Shows fertility adjusted for morality.
Multiplies bx by death rate for each age cohort to find fecundity

Question 23

What does bx represent?

Answer 23

Number of females born to each female in an age group

Question 24

Define net productivity rate, its variable, and the variable in its relation to 1

Answer 24

The average number of females produced by a newborn female during her lifetime
R0
R0 = 1 ; population is stable
R0 > 1 ; population is growing
R0 < 1 ; population is declining

Question 25

A population that is increasing in size has an intrinsic rate of population growth (r) that is

Answer 25

<0

Question 26

What value do mortality rate curves end on?

Answer 26

1.0

Question 27

Why are population projection matrices so complicated?

Answer 27

Because some species can move back and forth between life stages

Question 28

The leading cause of current species extinctions is….

Answer 28

habitat destruction

Question 29

A dynamic composite life table is different from a dynamic life table in that it uses individuals…

Answer 29

born over several time periods

Question 30

Why is the b0 = 0 at time period x0 for some species?

Answer 30

Some species do not reproduce during the first time period

Question 31

A population reaches a stable age distribution when the…

Answer 31

The proportion of individuals in each age group remains the same.

Question 32

In a population projection matrix, S34 would represent…

Answer 32

the probability an individual in stage class 4 would revert to 3.