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BIO205 > Chapter 12 - Population Growth and Regulation > Flashcards

Chapter 12 - Population Growth and Regulation Flashcards

1
Q

What is demography?

A

The study of populations.

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2
Q

What is the growth rate of a population?

A

The number of new individuals that are produced in a given amount of time minus the number of individuals that die.

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3
Q

What is the intrinsic growth rate (r) of a population?

A

The highest possible per capita growth rate for a population.

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4
Q

What is the exponential growth model?

A

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

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5
Q

Pictured is the equation for the exponential growth model. Define what each variable represents.

A

Nt = Size of future population at time t
N0 = Current population size
e = base of natural log = 2.72
r = the population’s intrinsic growth rate
t = time over which the population grows

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6
Q

When is a population’s growth rate less than the intrinsic growth rate? Give examples.

A

When conditions are less than ideal. For example, low resource availability or increased disease.

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7
Q

What is the shape of exponential growth when graphed?

A

J-shaped curve

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8
Q

Pictured is the equation to determine the change in population per unit time. What does this tell us about the rate of change in population at any particular point in time?

A

The rate of change in population size at any particular point in time depends on the population’s intrinsic growth rate and the population’s size at that point in time.

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9
Q

What does a constant intrinsic growth rate result in for a population?

A

Exponential growth.

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10
Q

What type of species can the exponential growth model be applied to? What types of species does this model not apply to?

A

Can be applied to species that reproduce throughout the year. Not particularly helpful for species with discrete breeding seasons.

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11
Q

What is the geometric growth model?

A

A model of population growth that compares population sizes at regular time intervals.

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12
Q

What does lambda in the geometric growth model represent?

A

The ratio of a population’s size in 1 year (or some other time interval) to its size in the preceding year (or some other time interval).

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13
Q

What can be said about a population if its lambda value is greater than 1? Less than 1? Can it ever be negative?

A

If greater than 1, the population size has increased due to more births than deaths.
If less than 1, the population has decreased because there have been more deaths than births.
Since there cannot be a negative number of individuals, lambda is always positive.

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14
Q

This is the equation for the geographic growth model. Define each variable.

A

Nt = population size at t intervals
N0 = population size at t = 0
lambda = ratio
t = number of intervals/time

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15
Q

How are geometric and exponential growth related?

A
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16
Q

Knowing the relationship between geometric and exponential growth, what would happen if we graphed a population’s growth using both models?

A

Identical graphs would be produced.

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17
Q

What are the values of lambda and r when a population is
a) decreasing
b) constant
c) increasing

A

a) lambda < 1; r<0
b) lambda = 1; r = 0
c) lambda >1; r>0

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18
Q

What is the doubling time of a population?

A

The time required for a population to double in size.

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19
Q

Can exponential growth be sustained indefinitely?

A

No.

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20
Q

What are density-independent factors? Provide examples.

A

Factors that limit population size regardless of the population’s density. Examples: natural disasters, extreme temperatures, droughts.

21
Q

What are density-dependent factors? Provide examples.

A

Factors that affect population size in relation to the population’s density. Examples: limited resources/competition, stress, disease, predators.

22
Q

Differentiate between negative and positive density dependence.

A

Negative - When the rate of population growth decreases as population density increases.
Positive - When the rate of population growth increases as population density increases.

23
Q

What is a self-thinning curve?

A

A graphical relationship that shows how decreases in population density over time lead to increases in the size of each individual in the population.

24
Q

What does negative density dependence do to a population?

A

Tends to bring populations under control and to maintain their abundances at a level close to the maximum number that can be supported by the environment.

25
Q

When does positive density dependence usually occur?

A

When population densities are very low.

26
Q

Does positive density dependence cause slow or fast population growth?

A

Slow.

27
Q

Are positive and negative density dependence entirely isolated phenomena?

A

No, populations can be regulated by both processes.

28
Q

What is the carrying capacity (K) of a population?

A

The maximum population size that can be supported by the environment.

29
Q

What is the logistic growth model?

A

A growth model that describes slowing growth of populations at high densities.

30
Q

What shape does the logistic growth model produce when graphed?

A

S-shaped curve.

31
Q

What is the inflection point?

A

The point on a sigmoidal growth curve at which the population achieves its highest growth rate.

32
Q

What is the age structure of a population?

A

The proportion of individuals that occurs in different age classes.

33
Q

What do each of these age structures indicate about a population:
a) high proportion of young people
b) similar numbers from 0-50
c) Fewer younger than middle-aged people

A

a) growing population
b) stable population
c) possible decline in population

34
Q

What are life tables?

A

Tables that contain class-specific survival and fecundity data.

35
Q

Describe what each type of survivorship curve indicates.

A

Type I: Population that experiences very little mortality early in life and high mortality late in life.
Type II: Population experiences relatively constant mortality throughout its life span.
Type III: Population with high mortality early in life and high survival later in life.

36
Q

What type of survivorship curves do most populations have?

A

Combinations of type I and type III.

37
Q

How could it be helpful for ecologists to be able to predict how a population will change in abundance over time?

A

Managing populations that humans consume, conserving species, controlling pest populations.

38
Q

Why are life tables typically based on females?

A

It can be difficult to determine paternity in many species.

39
Q

What is a stable age distribution?

A

When the age structure of a population does not change over time.

40
Q

How do you determine the survivorship at any given age class?

A

Multiple the prior year’s survivorship by the prior year’s survival rate.

41
Q

What is the net reproductive rate?

A

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

42
Q

What is the generation time (T)?

A

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

43
Q

Differentiate between cohort and static life tables.

A

Cohort - A life table that follows a group of individuals born at the same time from birth to the death of the last individual. Does not work well for highly mobile species or those with long life spans.
Static - life table that quantifies the survival and fecundity of all individuals in a population during a single time interval. Can be used on highly mobile and species with long life spans.

44
Q

In the logistic growth model, what does a larger K value do?

A

Growth tends towards exponential

45
Q

In the logistic growth model, what does a smaller K value do?

A

Growth tends towards 0

46
Q

What happens as K approaches N in the logistic growth model?

A

Growth rate slows.

47
Q

What happens to a population when the n/k value is at 1?

A

growth stabilizes

48
Q

What is a flaw of the logistic growth model?

A

It cannot calculate extinction.

49
Q

Differentiate between deterministic and stochastic models.

A

Determinate - does not include random variation
Stochastic - include random variation in demographic and environmental variables.

BIO205 (12 decks)

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