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General Ecology > Chapter 12 Lecture 1 > Flashcards

Chapter 12 Lecture 1 Flashcards

1
Q

under ideal conditions…

A

populations can grow rapidly

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2
Q

demography

A

the study of populations

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3
Q

growth rate

A

in a population, the number of new individuals that are produced per unit of time minus the number of individuals that die

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4
Q

Intrinsic growth rate (r)

A

the highest possible per capita growth rate for a population.

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5
Q

what do individuals experience under ideal conditions

A

maximum r (i.e., maximum reproductive rates and minimum death rates

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6
Q

what does the strength of a reproductive population depend on

A
  1. the number of individuals of reproductive age
  2. the availability of resources such as food and mates
  3. the presence or absence of predators, disease, etc.
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7
Q

how may individuals be added to populations

A
  1. continuous reproduction

2. discrete reproductive periods

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8
Q

what does the periodicity with which offspring are produced result in

A

important differences in the way in which population growth is conceptualized mathematically

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9
Q

in many species, young are added only during certain times of the year during…

A

discrete reproductive periods - such populations undergo geometric growth

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10
Q

in geometric growth

A

the rate of increase is proportional to the number of individuals present in the population at the beginning of the discrete reproductive period

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11
Q

what is the typical form of population growth in the wild

A

geometric growth

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12
Q

species that reproduce continually

A

they can add young at any time of the year

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13
Q

what do populations with continual reproduction undergo

A

exponential growth

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14
Q

exponential growth model

A

a model of population growth in which the population increases continuously at an exponential rate

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15
Q

what equation describes the exponential growth model

A

Nt+ N0e^rt

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16
Q

Nt

A

future population size

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17
Q

N0

A

current population size

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18
Q

r

A

intrinsic growth rate

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19
Q

t

A

time over which a population grows

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20
Q

e

A

2.7183

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21
Q

J-shaped curve

A

the shape of the exponential growth when graphed

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22
Q

the rate of a population’s growth at any point in time is the derivative of this equation

A

dN/dt = rN

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23
Q

e^r

A

the factor by which the population increases during each unit of time, and is sometimes symbolized with a lambda

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24
Q

exponential growth

A

results in a continuous curve of increase (or decrease, when the rt term is negative) whose slope varies in direct relation to the size of the population

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25
Q

the rate of increase of a population undergoing exponential growth at a particular instant in time, the instantaneous rate of increase =

A

dN/dt = rN

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26
Q

dN/dt = rN

this equation encompasses two principles (A)

A
  1. the exponential growth rate (r) expresses the population increase (or decrease) on a per individual basis
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27
Q

dN/dt = rN

this equation encompasses two principles (B)

A
  1. the rate of increase (dN/dt) varies in direct proportion to the size of the population (N)
28
Q

the rate of the change in population size equals

A

the contribution of each individual to population growth times the number of individuals in the population

29
Q

the individual contribution (per capita) to population growth is the difference between

A

the birth rate (b) and the death rate (d) calculated on a per capita basis

30
Q

dN/dt = bN - dN or

A

dN/dt = (b-d)N

31
Q

since r is the difference between birth rate and death rate (b-d),

A

dN/dt (rate of increase) = rN

32
Q

when the death rate exceeds the birth rate…

A

r is negative, and the population declines

33
Q

what equation represents exponential population growth

A

Nt = N0e^rt

34
Q

when young are added to populations during certain time frames (discrete population growth), what is the best way to represent growth

A

geometric growth model

35
Q

which growth is most common among wild populations

A

discrete

36
Q

overall, within each year, the population growth rate of a discretely growing population varies with

A

seasonal changes in the balance of birth and death processes

37
Q

seasonal

A

discrete

38
Q

why do populations initially grow slowly

A

because there is a small number of reproductive individuals

39
Q

what does growth rate increase with

A

the number of reproductive individuals

40
Q

what kind of breeding seasons do most species have

A

discrete

41
Q

geometric growth model

A

a model of population growth that compares population sizes at regular time intervals

42
Q

expressed as a ratio of a population’s size is one year to its size in the preceding year (lambda)

A

geometric growth model

43
Q

when lambda is greater than 1

A

population size has increased

44
Q

when lambda is less than 1

A

population size has decreased

45
Q

lambda cannot be…

A

negative

46
Q

growth in populations with discrete breeding seasons is treated somewhat differently than…

A

growth in populations with continual growth

47
Q

the size of the populations with discrete breeding seasons must be measured consistently at…

A

a particular time of the year to have any meaning

48
Q

when populations are augmented periodically…

A

it is most convenient to express the growth rate as a ration of the population in one year to that of the preceding year (N1/N0)

49
Q

demographers have assigned lambda to N1/N0 and call it

A

the geometric growth rate

50
Q

lambda =

A

N1/N0

51
Q

lambda represents

A

a factor of population increase

52
Q

if one wants, then to project the size of a population into the future (t=1), it could be written as

A

N(t+1) = N (1) lambda

53
Q

in order to project the growth of a population…

A

the original number N(0) is multiplied by the geometric growth rate lambda once for each unit of time passed

54
Q

N(t) =

A

N(0) lambda^t

55
Q

the equation for geometric growth is identical to the one for exponential growth, except that…

A

lambda, the geometric growth rate, takes the place of e^r (the amount of exponential growth accomplished in one time period)

56
Q

N(t) =

A

N(0) lambda ^t

57
Q

exponential and geometric growth models are identical except

A

e^r takes the place of lambda

58
Q

when a population is decreasing

A

lambda < 1

r < 0

59
Q

when a population is constant

A 
lambda = 1
r = 0
60
Q

when a population is increasing

A

lambda > 1

r >0

61
Q

decreasing populations have…

A

negative exponential growth rates and geometric growth rates greater than 0 but less than 1

62
Q

increasing populations have

A

positive exponential growth rates and geometric growth rates that are greater than 1

63
Q

doubling time

A

the time required for a population to double in size

64
Q

how can doubling time be estimated

A

by rearranging the exponential growth model

65
Q

Nt = N0e^rt —>

A

e^rt = Nt/N0

66
Q

When a population doubles, Nt/N0 =

A

2

67
Q

for the geometric model, the equation for doubling time is

A

t2 = loge2/loge(lambda)

General Ecology (16 decks)

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