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ECO3A: Individs, Popns, Commun > Population Ecology (W5) > Flashcards

Population Ecology (W5) Flashcards

1
Q

What do resources & conditions do for the hierarchy of ecology?

A

Set the stage for how all the different levels of hierarchy interact with one another.

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2
Q

Resources?

A

= things that individuals consume throughout their growth & reproduction.

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3
Q

Conditions?

A

= physiochemical features of an environment that affect the physiology of individuals.

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4
Q

Egs of Conditions? (2)

A

• Temperature.
• Salinity (in aquatic environments).

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5
Q

Questions we ask/focus on in population ecology? (2)

A

• What affects the abundance of a population?

• What affects the distribution of a population?

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6
Q

Applied population ecology definitions? (2)

A

= the use of population ecology principles to achieve a management goal.

OR

= the manipulation/protection of a population to achieve a goal.

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7
Q

Eg of Manipulative management regime?

A

Kruger National Park (culled animals & water points).

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8
Q

Custodian management regime?

A

= protecting an area with a goal that the natural processes that occur there will carry on operating without human interaction.

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9
Q

Eg of Custodian management regime?

A

North American National Parks.

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10
Q

Types of management approaches? (2)

A

• Manipulative management regime.
• Custodian management regime.

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11
Q

Goals of applied ecology? (4)

A

• Conservation.
• Pest control.
• Sustained harvest.
• Monitoring.

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12
Q

Conservation?

A

= make a population increase.

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13
Q

Eg of Conservation?

A

Roan & Sable antelope.

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14
Q

Pest control?

A

= make a population decrease.

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15
Q

Eg of Pest control?

A

Reducing abundance of rats in the city.

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16
Q

Sustained harvest?

A

= manage for a continuing yield.

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17
Q

Eg of Sustained harvest?

A

Harvesting fish from fish stock in a sustainable manner.

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18
Q

Monitoring?

A

= leave it alone but keep an eye on it.

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19
Q

Eg of Monitoring?

A

In organisms that are not a problem (manipulative management in a way through surveys).

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20
Q

Manipulative management regime attribute?

A

Does something to a population’s numbers directly or indirectly by altering the habitat, food, predators or disease.

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21
Q

Custodian management regime attributes? (3)

A

• Preventative.
• Protective.
• Aimed at minimizing the external influences on the population or its habitat.

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22
Q

How to decide which goal to use? (2)

A

• Value judgement.
• Technical judgement.

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23
Q

Value judgement (VJ)?

A
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24
Q

VJ attributes? (2)

A

• Word “should” indicates opinion.
• Depends on background of the opinion giver.

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25
Q

Egs of people deciding on the goal? (3)

A

• Ministers.
• Politicians.
• Management board.

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26
Q

Who are the people deciding on the goal?

A

= people responsible to the people they’re protecting.

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27
Q

Eg of VJ statement?

A

“Local survival of Acacia trees justifies the proposed reduction of elephants.”

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28
Q

Technical judgement (TJ)?

A

= judgement that is phrased in a way that makes it testable (practical).

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29
Q

TJ attributes? (2)

A

• Posed as a testable hypothesis.
• Allows us to learn from our failures & successes.

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30
Q

Egs of people who make technical judgements? (3)

A

• Managers.
• Scientists.
• Ecologists.

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31
Q

Eg of TJ?

A

“Elephants must be culled because, otherwise, they will eliminate Acacia trees from an area”.

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32
Q

Population?

A

= a group of individuals of the same species for which it is meaningful to consider density and distribution, rates of birth and death, sex and age structure, and other demographic parameters.

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33
Q

Population attribute?

A

The boundaries of the population are defined according to administrative convenience.

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34
Q

How do we characterize a population? (2)

A

Using:

• Static manners.
• Dynamic manners.

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35
Q

Static manners of characterizing a population? (4)

A

• Open/closed population.
• Movement in and out of the population.
• Density of population.
• Counts of abundance.

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36
Q

Dynamic manners of characterizing a population? (3)

A

• Population growth rate.
• Sex structure.
• Age structure.

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37
Q

Open population?

A

= presence of immigration & emigration.

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38
Q

Closed population?

A

= absence of immigration & emigration.

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39
Q

Density?

A

= number of animals per unit area.

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40
Q

Counts of abundance?

A

= numbers of individuals.

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41
Q

Sex structure?

A

= proportions of males & females.

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42
Q

Age structure?

A

= proportions of young & old.

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43
Q

What makes populations change over time? (4)

A

Levels of:

• Births.
• Immigration.
• Deaths.
• Emigration.

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44
Q

Factors that add to/increase the population number? (2)

A

• Births.
• Immigration.

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45
Q

Factors that decrease population number? (2)

A

• Deaths.
• Emigration.

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46
Q

If births & immigration are larger than deaths & emigration, what happens to the population?

A
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47
Q

If deaths & emigration are larger, what happens to the population?

A
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48
Q

What happens to the population if births and immigration & deaths and emigration are equal?

A
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49
Q

Births?

A

= flow of individuals into the population/added to the population number.

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50
Q

Nt?

A

= population size.

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51
Q

Nt+1?

A

= population size in the next time-step.

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52
Q

ΔN attributes? (2)

A

• Total amount of change from one year to the next.
• Increment.

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53
Q

ΔN formula before BIDEN model?

A

ΔN = B+I–D–E

where:

• ΔN = increment.
• B = births.
• I = immigration.
• D = deaths.
• E = emigration.

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54
Q

BIDEN model?

A

= model that assumes that there’s no immigration or emigration (no movement in & out of the area), ie., I-E=0.

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55
Q

ΔN formula according BIDEN model?

A

ΔN = B–D

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56
Q

Per capita rate?

A

= average birth or death rate per individual.

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57
Q

ΔN formulas under BIDEN model? (2)

A

• ΔN = B–D

• ΔN = Nt+1 – Nt

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58
Q

R?

A

= per capita change in population size.

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59
Q

Why divide births (B) & deaths (D) by the population size (Nt)?

A

It’s because births & deaths happen to individuals.

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60
Q

b?

A

= per capita birth rate.

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61
Q

d?

A

= per capita death rate.

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62
Q

R equations? (2)

A

• R = b–d

• R = ΔN/Nt

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63
Q

ΔN equations? (4)

A

• ΔN = B+I–D–E

• ΔN = B – D

• ΔN = Nt+1 – Nt

• ΔN = RNt

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64
Q

ΔN = B+I–D–E?

A

Before BIDEN model.

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65
Q

ΔN = B–D?

A

BIDEN model.

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66
Q

ΔN = Nt+1 – Nt?

A

2nd BIDEN model equation.

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67
Q

ΔN = RNt?

A

Relates to per capita rates.

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68
Q

λ ?

A

= finite rate of change.

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69
Q

λ > 1?

A

Population is increasing.

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70
Q

λ < 1?

A

Population is decreasing.

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71
Q

λ equations? (2)

A

• λ = 1+R

• λ = 1+b–d

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72
Q

How did λ = 1+R come about? (4)

A

ΔN = RNt

Nt+1 – Nt = RNt

Nt+1 = Nt + RNt

Nt+1 = Nt (1+R)

Therefore, λ = 1+R.

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73
Q

How did λ = 1+b–d come about? (4)

A

Nt+1 – Nt = RNt

Nt+1 – Nt = (b–d) Nt

Nt+1 = Nt + (b–d) Nt

Nt+1 = Nt + (1+b–d)

Therefore, λ = 1+b–d.

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74
Q

Types of population models? (2)

A

• Discrete population model.
• Continuous population model.

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75
Q

When is the Discrete population model appropriate to use? (2)

A

• Where estimates of population abundance occur at fixed intervals (eg., annually).

• Where important demographic events happen at fixed intervals.

76
Q

When is the Continuous population model appropriate to use? (2)

A

• Populations where there is continuous change.
• No fixed intervals between demographic events.

77
Q

What could you use for Continuous population models?

A

Calculus & differential equations.

78
Q

Discrete models vs Continuous models in terms of Abundance representation?

A

● Discrete models
= Nt.

● Continuous models
= N.

79
Q

Discrete models vs Continuous models in terms of Max. growth rate?

A

● Discrete models
= R.

● Continuous models
= r.

80
Q

Discrete models vs Continuous models in terms of Increment?

A

● Discrete models
= ΔN.

● Continuous models
= dN/dt.

81
Q

Discrete models vs Continuous models in terms of Observed per capita rate of change in the population?

A

● Discrete models
= ΔN/Nt.

● Continuous models
= dN/Ndt.

82
Q

Discrete models vs Continuous models in terms of Time change?

A

● Discrete models
= whole time stops.

● Continuous models
= instantaneous time stops.

83
Q

Discrete models vs Continuous models in terms of Biology?

A

● Discrete models
= fixed demographic events.

● Continuous models
= no fixed demographic events (continuous).

84
Q

Discrete models vs Continuous models in terms of Data?

A

● Discrete models
= fixed surveys.

● Continuous models
= continuous.

85
Q

List of differences between Discrete models & Continuous models? (7)

A

• Abundance.
• Max. growth rate.
• Increment.
• Per capita rate of change.
• Time change.
• Biology.
• Data.

86
Q

Equation showing relationship between Discrete models & Continuous models?

A

r = loge (1–R)
r = loge (λ)

Therefore, λ = e^r

87
Q

Uses of λ = e^r ?(2)

A

• Helps us predict how population is going to change from one year to the next.

• Helps you get growth rate from an exponential growth graph.

88
Q

How do you get growth rate from an Exponential growth graph? (3)

A

● Log the Exponential growth graph to a linear graph.

● r is the slope for the line graph.

● Use equation: e^r = λ.

89
Q

How do we predict how the population is going to change from one year to the next? (2)

A

● Over the next year equation:

Nt+1
= Ntλ
= Nt e^r

● Over t number of years equation:

Nt
= No λ^t
= No e^rt

90
Q

Exponential population growth model attributes? (2)

A

• Appropriate in new populations placed in empty habitats.
• Used where populations have been reduced, either by disease or harvest.

91
Q

Why do we want the simplest model that adequately explains the patterns?

A

In order to understand a natural phenomenon.

92
Q

What happens if a model is not simple?

A

Adds unnecessary complexity & confusion.

93
Q

If simple model doesn’t match the patterns we observe in the real world?

A

Add complexity only where necessary.

94
Q

Problem with Exponential population growth model?

A

Doesn’t depict that in the real world there are limited resources.

95
Q

How might high density affect the growth rate of a population? (4)

A

High density leads to:

• decrease in per capita food availability,
• increase in intraspecific competition,
• decrease in reproduction or survival,
• decrease in population growth rate.

96
Q

Vital rates?

A

= involve change in either birth or death rates.

97
Q

Graph 1/3 of vital rates graphs attributes? (3)

A

• Birth rate decreases.
• Death rate increases.
• ED or K is vertical dotted line where they cross/meet.

98
Q

Graph 2/3 of vital rates graphs attributes? (3)

A

• Birth rate decreases.
• Death rate stays constant.
• ED or K is vertical dotted line where they cross/meet.

99
Q

Graph 3/3 of vital rates graphs attributes? (3)

A

• Birth rate stays constant.
• Death rate increases.
• ED or K is vertical dotted line where they cross/meet.

100
Q

Density dependence?

A

= there is a relationship between density & some vital rate (eg. births, deaths, i, e, R).

101
Q

Types of density dependence? (2)

A

• Negative density dependence.
• Positive density dependence.

102
Q

Negative density dependence?

A

= relationship between density & vital rate reduces growth rate.

103
Q

Positive density dependence?

A

= relationship between density & vital rate increases growth rate.

104
Q

Negative density dependence = …?

A

Decreases R.

105
Q

Positive density dependence = …?

A

Increases R.

106
Q

What mechanisms could cause these relationships (density dependence)? (3)

A

• Predation pressure.
• Disease pressure.
• Space for settlement.

107
Q

Explain Predation pressure mechanism? (3)

A

High abundance of prey, More predators, High predation pressure.

108
Q

Explain Disease pressure mechanism? (3)

A

High abundance of individuals, High rates of contact, High transmission of disease.

109
Q

Explain Space for settlement mechanism? (5)

A

High abundance needing space, High competition, Low reproduction, Low survivability, Decreased population growth.

110
Q

Predation pressure?

A

= where a higher abundance of individuals attracts more predators & more predation pressure.

111
Q

Types of competition? (3)

A

• Exploitation competition.
• Interference competition.
• Intraspecific competition.

112
Q

Exploitation competition?

A

= removal of resources such that others cannot use them.

113
Q

Interference competition?

A

= behavioural exclusion from an area & the resources it contains (eg. territories).

114
Q

Types of density growths? (2)

A

• Density dependent growth.
• Density independent growth.

115
Q

Density independent growth?

A

= no relationship between density & growth rate.

116
Q

Density dependent growth?

A

= relationship between density & growth rate.

117
Q

Graph 1/2 for Density independent growth attributes? (4)

A

• x-axis = t.
• y-axis = N.
• Exponential growth/increase.
• Equation: dN/dt = rN.

118
Q

Graph 2/2 for Density independent growth attributes? (4)

A

• x-axis = N.
• y-axis = dN/Ndt
• Constant horizontal line (r).
• Equation: dN/dt = rN.

119
Q

ED stands for?

A

Equilibrium Density.

120
Q

ED is AKA?

A

K.

121
Q

ED or K?

A

= carrying capacity.

122
Q

Graph 1/2 for Density dependent growth attributes? (5)

A

• x-axis = N.
• y-axis = dN/Ndt.
• Decreasing line graph.
• r is at top of line on y-axis.
• ED is at bottom of line on x-axis.

123
Q

Graph 2/2 for Density independent growth attributes? (4)

A

• x-axis = t.
• y-axis = N.
• ED is the horizontal dotted line on y-axis.
• S-shaped.

124
Q

Interpretation of Graph 1/2 for Density dependent growth attributes? (3)

A

• As N increases,
• Resources per individual decrease (due to competition),
• Per capita growth rate decreases until it reaches zero growth.

125
Q

Line general equation?

A

y = a + bx

126
Q

Slope of a line general equation from line graph equation?

A

b = rise/run = Δy/Δx

127
Q

Slope equation for Graph 1/2 for Density dependent growth?

A

b = -r/K

128
Q

Types of graph models that we talk about? (2)

A

• Exponential population growth model.
• Logistic population growth model.

129
Q

Equation for Logistic population growth model?

A

dN/dt = rN (1– N/K)

130
Q

Elaborate how we got the Logistic population growth model equation? (6)

A

• y = a + bx

• dN/Ndt = r + (-r/K)N

• dN/Ndt = Kr/K – Nr/K

• dN/Ndt = (Kr–Nr)/K

• dN/Ndt = r (1–N/K)

Therefore,

• dN/dt = rN (1–N/K)

131
Q

Large N attributes in terms of Logistic population growth model? (3)

A

• Little change in population size.
• Little change in dN/Ndt.
• N/K approaches 1, therefore (1–N/K) becomes (1–1) = 0.

132
Q

Small N attributes in terms of Logistic population growth model? (2)

A

• N/K approaches 0, therefore (1–N/K) becomes (1–0) = 1.
• Population grows close to exponential rate.

133
Q

Graphs of Logistic model? (3)

A

• Observed per capita growth rate.
• Increment (# of individuals added).
• Population size vs Time.

134
Q

Observed per capita growth rate graph attributes? (7)

A

• x-axis = N.
• y-axis = dN/Ndt.
• r is at top of line on y-axis.
• K is at bottom of line on x-axis.
• Decreasing line graph.
• Equation for Continuous model.
• Equation for Discrete model.

135
Q

Observed per capita growth rate graph equation for Continuous model?

A

dN/Ndt = r (1–N/K)

136
Q

Observed per capita growth rate graph equation for Discrete model?

A

ΔN/Nt = R (1–Nt/K)

137
Q

Increment (# of individuals added) graph attributes? (6)

A

• x-axis = N.
• y-axis = dN/dt.
• K is at the bottom of “hill” on x-axis.
• Hill looking from bottom, tip of hill then back down.
• Equation for Continuous model.
• Equation for Discrete model.

138
Q

Increment equation for Continuous model?

A

dN/dt = rN (1– N/K)

139
Q

Increment equation for Discrete model?

A

ΔN = RNt (1–Nt/K)

140
Q

Population size vs Time graph attributes? (3)

A

• x-axis = t.
• y-axis = N(t).
• S-shaped graph.

141
Q

Population size vs Time equation for Continuous model?

A

N(t) = K/ [1+ e^(a–rt)]

142
Q

Population size vs Time equation for Discrete model?

A

Nt+1 = Nt + RNt (1–Nt/K)

143
Q

Blue circle (at beginning of graphs) on Increment & Population size vs Time graphs attributes? (2)

A

• Lots of resources.
• Few individuals breeding & adding numbers to the population.

144
Q

Orange circle (at middle of graphs) on Increment & Population size vs Time graphs attributes? (2)

A

• Fair number of resources.
• Fair number of individuals breeding (with maximum added individuals).

145
Q

Green circle (at end/top of graphs) on Increment & Population size vs Time graphs attributes? (2)

A

• Few resources.
• Lots of individuals breeding (but few numbers being added to population).

146
Q

Important concepts related to Logistic model? (2)

A

• Population regulation.
• Population limitation.

147
Q

Population regulation question?

A

What processes halt population increase?

148
Q

Population limitation question?

A

What factors or process can change the average density.

149
Q

Egs of Population regulation vs Population limitation? (2)

A

• Game reserve.
• Animal density in relation to food abundance.

150
Q

Regulating factors attributes? (3)

A

• Exert a negative feedback on population growth rate.
• Negative density dependent.
• Causes the return of a population size to an equilibrium (eg. K).

151
Q

Limiting factors attributes? (4)

A

• Determine the ED.
• Affect births or deaths.
• Can be density dependent or density independent.
• They are often resources.

152
Q

Eg of Regulating factor?

A

Decrease in per capita food reduces survival-intensity of the effect (density dependent).

153
Q

Eg of limiting factor?

A

Rainfall affecting food & determining the upper limit of the population (density independent).

154
Q

As line gets closer to K, what happens? (4)

A

• Intraspecific competition,
• Leads to low b and high d,
• Density dependent.
• Regulating factor.

155
Q

Assumptions of the Logistic model? (7)

A

• Population growth rate is directly affected by density.

• Relationship between growth rate & density is linear.

• No time lag.

• Ignores environmental influences.

• ED or K is constant.

• Population is closed (I–E=0).

• Age structure is not considered.

156
Q

How to add complexity to models to make them realistic (modification)? (3)

A

• Non-linear density dependence.
• Time lags.
• Variable environment.

157
Q

Logistic model assumption addressed in Non-linear density dependence?

A

“Relationship between growth rate & density is linear”.

158
Q

Model under Non-linear density dependence?

A

θ-logistic model (theta).

159
Q

θ-logistic model equation?

A

dN/Ndt = r (r– [N/K]^θ)

160
Q

θ-logistic model graphs? (3)

A

• θ < 1.
• θ > 1.
• θ = 1.

161
Q

θ < 1 graph attributes? (6)

A

• x-axis = N.
• y-axis = dN/Ndt.
• Concave up relationship (exponential decrease).
• Undercompensatory DD.
• Growth rates decrease but not fast enough to equilibriate.
• Outbreaks.

162
Q

θ > 1 graph attributes? (6)

A

• x-axis = N.
• y-axis = dN/Ndt.
• Concave down relationship (cliff).
• Overcompensatory DD.
• Growth rates decrease but way too much to equilibriate.
• Fluctuate at K.

163
Q

θ = 1 graph attributes? (4)

A

• x-axis = N.
• y-axis = dN/Ndt.
• Linear relationship (decreasing).
• Exactly compensatory DD.

164
Q

Eg of θ < 1 graph?

A

Lemmings.

165
Q

Eg of θ > 1 graph?

A

Wildebeest.

166
Q

Eg of θ = 1 graph?

A

Warblers.

167
Q

Why undercompensatory DD?

A

It’s because changes in births & deaths are not happening fast enough to keep the population from halting increase at the equilibrium density (ED).

168
Q

Why overcompensatory DD?

A

It’s because changes in births & deaths happen so fast that it pulls the population down below equilibrium density (ED), resulting in fluctuation at K.

169
Q

What do Time lags depend on? (2)

A

• How quickly the population grows (r).
• How long the lag is (L).

170
Q

Logistic model assumption addressed in Time lags?

A

“No time lag”.

171
Q

Time lags graphs? (3)

A

• rL is small.
• rL is moderate.
• rL is large.

172
Q

rL is small graph attributes? (6)

A

• Little change from standard model.
• Either population is growing very slowly (r).
OR
• Little lag between population size & growth rate (L).
• x-axis = t.
• y-axis = N.
• S-shaped/Sigmoid shape.

173
Q

rL is moderate graph attributes? (5)

A

• Dampened oscillations until K is reached.
• Moderate growth rate (r).
OR
• Moderate lag between population size & growth rate (L).
• x-axis = t.
• y-axis = N.

174
Q

rL is large graph attributes? (6)

A

• Lot of growth rate (r).
OR
• Lot of lag (L).
• Stable limit cycles.
• x-axis = t.
• y-axis = N.
• Fluctuations at K.

175
Q

DD stands for?

A

Density dependent.

176
Q

Logistic model assumption addressed by Variable environment?

A

“Ignores environmental influences”.

177
Q

Explain Variable environment graph regarding theoretical vs realistic graph? (3)

A

● Graph is of birth rate (b) decrease & death rate (d) increase with K being vertical dotted line where they cross/meet.

● Theoretically, the b & d lines are straight however, in reality they are fluctuating as b decreases & d increases.

● Theoretically, K is a vertical dotted line where b & d lines meet/cross but, in reality K is an equilibrium band zone (square/2 vertical dotted lines where b & d cross).

178
Q

X-axis for b & d graphs?

A

N.

179
Q

Y-axis for b & d graphs?

A

Rate.

180
Q

What is a fluctuating equilibrium due to/ What causes fluctuating equilibrium? (2)

A

• K itself fluctuating.
• K relatively constant, but other factors push the population away from K.

181
Q

Explain discussion:

Have a look at the population growth for wildebeest in the Serengeti.
¹ What is happening to this population before the peak?
² What could be causing the pattern in abundance after the peak?

A

● Before the peak
= exponential growth.

● After the peak
= population size decreases.

182
Q

From discussion, why does the population size decrease after the peak? (4)

A

• Environmental variability.
• Lagged effect.
• Overshoot, then settling at K.
• K is constant, but other factors are pushing population away from K.

183
Q

dN/dt = rN (1– Nt-L/K) represents…?

A

Delayed density dependence (seen in L for lag).

184
Q

dN/dt = rN (1–[N/K]^θ) represents…?

A

Non-linear density dependence (seen by θ).

185
Q

dN/dt = rN represents…?

A

Unlimited resources.

186
Q

Imagine that a scientist experimentally reduces one population to half its ED. Show a detailed progression of mechanisms by which the reduced population returns to a regulated state? (8) [in order]

A

• Reduced population size.
• Reduced competition for resources.
• Improved body conditions.
• Improved reproduction & survival.
• Increase in population size.
• Increased competition.
• Reduced body conditions.
• Reduced population growth.

ECO3A: Individs, Popns, Commun (11 decks)

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