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IB Biology > C.5 Population ecology > Flashcards

C.5 Population ecology Flashcards

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1
Q

What are the four factors that determine the change in the size of a population?

A

Natality
Immigration
Mortality
Emigration

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2
Q

What is the population size equation?

A

population size = (immigration + natality) - (mortality + emigration)

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3
Q

How does natality affect population size?

A

Increases through reproduction

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4
Q

How does immigration affect population size?

A

Increases population size from external populations

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5
Q

How does mortality affect population size?

A

Decreases as a result of death

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6
Q

How does emigration affect population size?

A

Due to loss to external populations

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7
Q

What is a population?

A

All the individuals of a given species living in the same area at the same time

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8
Q

What are populations subject to?

A

Continual change

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9
Q

When are populations not impractical to count?

A

When the species is large and the target area is small

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10
Q

What does population sampling involve?

A

Identifying individual numbers in small areas and then extrapolating to estimate population totals

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11
Q

When population sampling what must be done to avoid selection bias?

A

Sampled areas must be chosen randomly

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12
Q

What would selection bias cause?

A

A misrepresentation of the population size

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13
Q

What does more samples taken mean?

A

That the more accurate population estimates are likely to be

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14
Q

When are different sampling techniques used for?

A

Non-motile and motile species

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15
Q

How can non-motile species be sampled?

A

Using quadrats

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16
Q

How can motile species be sampled?

A

Using the capture mark release recapture method

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17
Q

When marking a species what must marking not be?

A

Easily removable or affect the animals survival prospects

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18
Q

What is the first half of capture mark and release technique?

A

Area is defined and a selection of individuals are captured counted are marked and released

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19
Q

When is a second capture made in the capture mark release method?

A

After sufficient time to allow marked individuals to reintegrate in the population

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20
Q

What is counted in the second capture of the capture mark release method?

A

Unmarked individuals and marked individuals

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21
Q

What are the three values generated in the capture mark release method?

A

1st collection of marked individuals
2nd capture of both marked and unmarked individuals
2nd capture of just the marked individuals

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22
Q

How is an estimated population size derived from the capture mark release method?

A

The Lincoln index

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23
Q

How can you increase the accuracy of the Lincoln index?

A
  • increasing the size of the capture samples
  • taking repeated samples
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24
Q

What is the equation of the lincoln index?

A

(n1 x n2) / n3

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25
Q

What assumptions must be true for the lincoln index to require?

A
  • all individuals in a given area have an equal chance of being captured
  • that marked individuals are randomly distributed after release
  • that marking individuals will be randomly distributed after release
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26
Q

When will exponential population growth occur?

A

In an ideal, unlimited environment

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27
Q

When will a logistic population growth occur?

A

When environmental pressures slow the rate of growth

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28
Q

In an environment of exponential growth what will there be none of to place limits on rate of growth?

A

No competition

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29
Q

Why will population growth initially be slow in an exponential population growth?

A

As there is a shortage of reproducing individuals that may be widely dispersed

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30
Q

What is the maximal growth rate for a given population known as?

A

Its biotic potential

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31
Q

Where can exponential growth be seen?

A

In populations that are very small or in regions that are newly colonised by a species

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32
Q
A
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33
Q

In an exponential growth, what will increase as population numbers increase?

A

The rate of growth

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33
Q
A
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34
Q

What is the carrying capacity?

A

The maximum number of a species that can be sustainably supported by the environment

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35
Q

What is population numbers approaching in a logistic population growth?

A

Carrying capacity

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36
Q

What happens when a population approaches carrying capacity?

A

Environmental resistance occurs

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37
Q

When does the graph plateau on logistic population growth?

A

At carrying capacity

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38
Q

Where will logistic growth eventually be seen?

A

In any stable population occupying a fixed geographic space

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39
Q

What are limiting factors?

A

Environmental conditions that control the rate at which a process can occur

40
Q

What two types of environmental factors can population growth can be determined by?

A

Density dependent factors and density independent factors

41
Q

What type of environmental factors are influenced by the relative size of a population?

A

Density dependent environmental factors

42
Q

What are density dependent factors? (panda)

A

Predators
Availability of resources
Nutrient supply
Disease
Accumulation of wastes

43
Q

What are density independent factors? (paw)

A

Phenomena
Abiotic factors
Weather conditions

44
Q

What do stable populations occupying a fixed geographic space demonstrate?

A

A sigmoidal population growth curve

45
Q

What are the three stages of a sigmoidal population growth curve?

A

Exponential growth phase
Transitional phase
Plateau phase

46
Q

Why will natality greatly exceed mortality in the exponential growth phase?

A

As there is a rapid increase in population size

47
Q

Why is mortality low in the exponential growth phase?

A

Because there are abundant resources and minimal environmental resistance

48
Q

What causes competition for survival in the transitional phase?

A

As the population grows resources eventually become limited

49
Q

What begins to fall during the transitional phase?

A

Natality rates

50
Q

What rises during the transitional phase?

A

Mortality rates

51
Q

What does the decrease in natality rates and increase in mortality rates cause?

A

Slowing of population growth

52
Q

What is the plateau phase?

A

When the mortality rate equals the natality rate

53
Q

What has been reached at the plateau phase?

A

The carrying capacity

54
Q

What is not constant at the plateau phase?

A

The population size

55
Q

What keeps the population stable in the plateau phase?

A

Limiting factors

56
Q

How can the exponential growth phase be summarised?

A

N + I&raquo_space;> M + E

57
Q

How can the transitional phase be summarised?

A

N + I > M + E

58
Q

How can the plateau phase be summarised?

A

N + I = M + E

59
Q

What simple organisms can be used to model population growth curves?

A

Yeast or duckweed

60
Q

Where is yeast grown?

A

On agar plates

61
Q

Where is duckweed grown?

A

In cups of water

62
Q

Why is using yeast or duckweed good for modelling population growth?

A
  • organisms are small and can populate small easy to store containers
  • nutritional requirements are low
  • experiments inexpensive to conduct
  • reproduce rapidly so results generated quickly
63
Q

What will yeast and duckweed demonstrate?

A

The phases of a sigmoidal growth curve

64
Q

What are the two ways limiting population factors can exert their influence?

A

Either top down or bottom up control

65
Q

What are top down factors?

A

Pressures applied by a higher trophic level to control the population dynamics of the ecosystem

66
Q

What does the top predator do to its prey to limit its rate of population growth?

A

Suppresses the abundance of its prey or alters its behaviour to limit its rate of population growth

67
Q

What does top down control result in?

A

Oscillating trophic cascade

68
Q

What commonly exerts top down control by preventing lower trophic levels from monopolising essential resources?

A

Keystone species

69
Q

What are bottom up factors?

A

Pressures that limit the availability of resources to lower trophic levels

70
Q

What suppresses the abundance of organisms at higher trophic levels?

A

A lack of resources at lower trophic levels

71
Q

Why will population growth be reduced for all higher levels in bottom up control?

A

As the suppression of the bottom restricts energy supply to the top

72
Q

What can inadvertently exert bottom up pressure on an ecosystem?

A

Human activity

73
Q

What causes algal blooms?

A

Eutrophication

74
Q

What is an algal bloom?

A

A rapid increase in the population of algae in a water system

75
Q

What can algal blooms be limited by?

A

Measures that exert bottom up or top down control

76
Q

What type of control would be the most successful?

A

Bottom up and top down control

77
Q

How can algal blooms be reduced?

A

By limiting the supply of nutrients like nitrogen and phosphorus

78
Q

How can you implement bottom up control in algal blooms?

A

Reducing the use of fertilisers for agricultural practices

79
Q

How can you implement top down control?

A

Introducing fish eating fish into the aquatic ecosystem

80
Q

How does introducing fish eating reduce algal bloom?

A

They eat zooplanktivores and they eat the algae

81
Q

Why should you be careful when introducing piscivorous into the aquatic environments?

A

As they have unintended consequences

82
Q

What is sustainability?

A

The capacity for a biological system to remain diverse and productive indefinitely

83
Q

What is a sustainable yield?

A

The amount of a natural resource that can be taken from an ecosystem without reducing the base stock

84
Q

What is the maximum sustainable yield (MSY) in fishing?

A

The highest proportion of fish that can be removed from the total population without jeopardising the maximum yield in the future

85
Q

What should the MSY be?

A

Half the carrying capacity of the species

86
Q

Why should the MSY be half the carrying capacity of the species?

A

This is the stage when population growth is highest

87
Q

What does the MSY represent?

A

The optimum balance between reproductive growth rates and losses to harvesting and death

88
Q

What will harvesting above the MSY do?

A

Reduce the possible sizes of future yields

89
Q

What are the three ways commercial stock can be estimated?

A

Capture mark release recapture
Echo sounders
Analysing Fish Catch Data

90
Q

How may fish be captured in the capture mark release recapture method?

A

Electro shocking

91
Q

Where would you use and not use the capture mark release recapture method?

A

Use in rivers and lakes but not in oceans

92
Q

What is echo sounding?

A

The transmission of sound waves in water to identify the sizes of schools of fish via sonar

93
Q

Why is echo sounding good?

A

It is a non-invasive way of collecting data

94
Q

When can you use echo sounding?

A

If the species of fish form shoals

95
Q

What can data collected from fish catches be used to estimate?

A

Population size

96
Q

What are the factors that must be considered when developing and implementing sustainable fishing practices?

A

Population size
Age
Reproductive status

97
Q

If a population is growing will the the relative proportion of older fish be higher or lower?

A

Lower

98
Q

If a population is in decline, will the relative proportion of older fish be higher or lower?

A

Higher

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