Populations Growth pt. 1

Question 1

What determines population growth?

Answer 1

the number of births, deaths, immigration, and emigration

Question 2

Exponential population growth

Answer 2

a constant, positive rate of growth, r, causes the # of individuals in the population to grow exponentially because there are more individuals contributing to the population later in time

Question 3

Total population growth rate =

Answer 3

of NEW individuals added per unit time

Question 4

Per capita growth rate (r) =

Answer 4

of new individuals added (b, birth rate) MINUS # of individuals removed (d, death rate) per individual over time

Question 5

Exponential growth equation

Answer 5

Nt = No (e^rt)

Question 6

Nt = No (e^rt)

What does each unit stand for?

Answer 6

Nt = population size at future time, t
No = current population size
e = 2.72 (Euler’s constant)
r = growth rate per individual (b-d, birth-death)
t = amount of time over that passed between No and Nt

Question 7

To find the growth rate at any one instant in time (dN/dt) you use the formula:

Answer 7

dN/dt = r x N

or

dN/dt = (b-d) x N

Question 8

What is dN/dt also known as?

Answer 8

Instantaneous growth rate

slope of the line at Instant A or instant B

Question 9

Exponential population growth:

r<0

Answer 9

population size decreases, slope is negative

dN/dt = -0.5 x 30
decreases by 15 individuals per unit time when N = 30

Question 10

Exponential population growth:

r=0

Answer 10

population size does not change, slope is constant

dN/dt = 0 x 30
changes by 0 individuals per unit time when N = 30

Question 11

Exponential population growth:

r>0

Answer 11

population size increases, slope is positive

dN/dt = 0.5 x 30
increases by 15 individuals per unit time when N = 30

Question 12

What is the geometric growth equation?

Answer 12

Nt = Nolambda^t

Question 13

What do the units stand for

Nt = Nolambda^t

Answer 13

Nt = population size at future time, t
No = current population size
lambda = a ratio of a population’s size in year 0 to its size in year 1
t = amount of time over which population grows (1 year, 2 years, etc.)

Question 14

What does the geometric growth model describe?

Answer 14

it still describes exponential growth, but allows us to describe population growth for species that have specific breeding seasons

Question 15

Geometric population growth:

lambda<1

Answer 15

population size decreases, slope is negative

lambda = 0.5
for every 1 individual in the population in year 1, there are only 0.5 individuals in year 2

Question 16

Geometric population growth:

lambda=1

Answer 16

population size does not change, slope is constant

lambda = 1
for every 1 individual in the population in year 1, there is still 1 individual in year 2

Question 17

Geometric population growth:

lambda>1

Answer 17

population size increases, slope is positive

lambda = 1.5
for every 1 individual in the population in year 1, there are 1.5 individuals in yer 2

Question 18

What is the exponential growth model used to describe?

Answer 18

species that can breed continuously through the year

Question 19

What is the geometric growth model used to describe?

Answer 19

species that have breeding seasons