Population Ecology Flashcards Preview

Year 1 Biology Ellie M > Population Ecology > Flashcards

Flashcards in Population Ecology Deck (128):
1

What is population ecology?

The scientific study of the distribution and abundance of organisms, the interactions that determine that distribution and abundance, and the relationships between organisms and the transformation and flux of energy and matter

2

What is a population?

The total number of individuals of one species in a defined area

3

What is a community?

All the populations of all species in a defined area

4

What do population ecologists seek to understand?

Variation in life histories
Evolutionary forces which produce patterns in communities
How populations interact with each other and the environment
Species distributions
Population growth, regulation and dynamics

5

What is the name for the study of population growth, regulation and dynamics?

Demographics

6

What does population ecology explore?

How biotic and abiotic factors influence the density, distribution, size and age structure of populations

7

What is adaptation?

The evolutionary process whereby organisms become better suited to their environments

8

What are life histories?

The role of the changing environment on events affecting growth, survival, development and reproduction

9

What are the two types of cause that lead to a species occurring where they do?

Ultimate cause
Proximate cause

10

What is the ultimate cause?

Through natural selection organisms become adapted to maximise their fitness in a particular environment

11

What are the three types of fitness?

Direct fitness
Indirect fitness
Inclusive fitness

12

What is direct fitness?

The number of offspring an individual produces relative to others in the population

13

What is indirect fitness?

Derived from shared genes with kin other than the individuals direct offspring such as cousins, nieces and nephews

14

What is inclusive fitness?

The sum of direct and indirect fitness gains

15

What is a proximate cause?

The current environmental factors (both biotic and abiotic) which determine where an organism can live

16

What are biotic factors?

Other organisms

17

What are the two types of biotic factors?

Intra-specific: competition (within species)
Inter-specific: competition, predation, parasites and disease (between species)

18

What are abiotic factors?

The environment:
water
temperature
wind
weather
light
salinity
pH
These factors are often entangled

19

What is a response curve?

Shows how the abiotic features of the environment affect how well an organism functions

20

What is an ecological niche?

The role and position a species has in its environment; how it meets its needs for food and shelter, how it survives and how it reproduces. Includes its interactions with all biotic and abiotic factors of its environment

21

What is the name for a niche in the absence of other organisms?

Fundamental niche

22

What is the name for a niche in which other organisms are present?

Realised niche

23

What is a habitat?

An objective description of an environment

24

What is the result of environmental variability?

Natural selection always has a ‘moving target’

25

What different characteristics can environmental variability have?

It can be temporal or spatial
It can be deterministic and predictable or stochastic and unpredictable

26

Features of deterministic environmental change

Gradual shift, long term changes
Often predictable
Distributions of species tend to shift

27

What is acclimation or acclimatisation?

The process by which and individual organism adapted to a gradual change in its environment. This happens in a short period within the organism’s lifetime.
It may occur discretely or in a periodic cycle e.g. moulting

28

What is phenotypic plasticity?

The ability of an organism to change its phenotype in response to changes in the environment.
Includes all types of environmentally induced changes, which may or may not be permanent.
More important for immobile that mobile organism

29

How do species move to avoid adverse condition?

Migration or dispersal

30

What is hibernation?

A state or arrested development which allows organisms to survive periods of adverse condition and synchronise their life cycle development within the environmental conditions

31

What is the life history theory?

The pattern and duration of key events in an organisms lifetime which affect the number of offspring produced - natural selection shapes their life history to produce the most offspring

32

What is an iteroparous organism?

An organism that can reproduce many times in its life

33

What is a semelparous organism?

An organism that only breeds once in its life
Some semelparous species are annual - they have a single generation in a year

34

What is the cost of reproduction?

Resources used for reproduction cannot be used for other important processes such as growth

35

What is the Latin name for the hard beech?

Nothofagus truncata

36

How is growth visible in hard beech trees?

Growth is visible as rings
The thickness of the ring represents the investment in growth

37

What was the name for good years when the hard beech trees produced heavy crops of seeds?

Masting

38

Who studied the trade-off between growth and reproduction in hard beech?

Monks and Kelly (2006)

39

What were the results about trade-off between growth and reproduction?

On years of high seedfall, the annual ring growth was depressed relative to the previous year

40

What is a K-selected life history?

Subsist near the carrying capacity of the environment (K)
Produce low number of offspring over longer span of time
High parental investment
Favours evolution of timed life history strategies such as seasonal or diurnal resting stage
Complex life cycles

41

Features of stochastic environmental change

Highly unpredictable
Catastrophic events cause high levels of mortality
Ephemeral habitats - only available for short periods of time

42

What is an R-selected life history?

Have populations that fluctuate in response to unpredictable changes in the environment
High growth rate (r)
Tend to produce a high number of offspring with minimal parental care
Shorter lifespan

43

What type of environment are K selected organisms best suited for?

Stable environment

44

What type of environment are r-selected organisms best suited to?

Unstable environment

45

What is abundance in population ecology?

The number of individuals in a population

46

What is density in population ecology?

Number of individuals per unit area/volume

47

What is dispersion in population ecology?

Pattern of spacing between individuals within the population

48

Methods of measuring abundance?

Most sampling based on measures of RELATIVE abundance:
Number per sample
Catch per unit effort
Trapping
Counts in quadrants
Counts on transacts

49

What are examples of indirect measures of abundance?

Footprints
Nests
Burrows
Vocalisations
Faecal counts / scats
Feeding signs

50

What are the 4 factors that must be considered when picking a sampling technique?

1. Quantitative
2. Comparable
3. Cost effective
4. Biologically relevant

51

What types of markings are used in organisms during mark release recapture?

Paint marks
Hair tuft removal
Microchips
Recognition of individual colour patterns

52

What is the equation used to calculate the total population size in mark release recapture?

Total population size =
(no. marked in sample 1 x total caught in 2nd sample ) / no. marked animals in 2nd sample

53

How does distribution affect the probability of detection?

The pattern of distribution is not permanent for each species - distribution patterns often change seasonally

54

What are the three observed types of population distribution?

Uniform
Random
Aggregated/clumped

55

Features of aggregated distributions

Most common type
Found in environments with patchy resources - animals clump around resources
Also clustered due to social factors such as family groups
Prey clumped in areas where they can hide from predators

56

Features of uniform distributions

Evenly spaced
Need to maximise space between individuals due to competition or direct social interactions
Plants can exhibit uniform distributions

57

What is an example of a plant which exhibits uniform distributions?

Creosote bushes in Southwest USA - releases terpenes to inhibit the growth of other plants around it

58

Features of random distributions

Least common
Rare because biotic and abiotic factors cause organisms to be either clustered or spread apart
Can occur in plants with wind-dispersed seeds and marine larval forms dispersed by sea currents that settle randomly

59

What does sample distribution affect?

How many samples we need to take to measure the abundance accurately
Our ability to compare populations
How we handle, analyse and interpret the data

60

What is the change in population size equivalent to?

Births + immigrants - deaths - emigrants

61

What is the k-value?

‘Killing power’ - uncovers which life phase has the highest mortality

62

What is R(0)?

Basic reproductive rate - mean number of offspring produced by an individual by the end of the cohort

63

What is r?

The intrinsic rate of natural increase - the per capita rate of increase

64

What is a cohort life table?

Dynamic, follows a cohort over time

65

What is a static life table?

Snapshot of the population at one time

66

What is age structure?

Relative number of individuals of each age in the population. They can be used to predict a population’s growth trend, and illuminate social conditions in humans

67

What is a survivorship curve?

y-axis: number of organisms surviving in logarithmic scale
x-axis: age, as a proportion of maximum life span
Informs us about causes of mortality
Reflects r/K strategies

68

What is the relationship between body size and abundance?

Bigger species are less abundant

69

What is the population growth rate when resources are unlimited?

Geometric or exponential

70

What is exponential growth?

Continuous, occurs if reproduction happens at any time

71

What is geometric growth?

Pulsed, occurs if reproduction is seasonal

72

What is the name for growth rate as it slows and stops and resources are depleted?

Logistic or sigmoidal growth

73

What is the name for the population size at which growth stops?

Carrying capacity

74

what is K?

The number of individuals that the environment can support - birth rate is equal to death rate and population growth is zero

75

What are the primary demographic factors affecting population abundance?

Birth rate
Death rate
Immigration rate
Emigration rate

76

What are the secondary demographic factors affecting population abundance?

Weather
Food
Breeding sites
Shelter
Biotic factors

77

What are density-independent demographic factors?

Factors that act in a density-independent manner have an effect on births and deaths which is not related to the size of the population

78

What are examples of density-independent factors?

Pollutants in environment
Climate extremes
Seasonal cycles such as monsoons
Catastrophic factors such as fires and hurricanes

79

Example of species affected by density-independent population growth

Thrips in Australia
Eat rose pollen, which is available all year
In winter, the cold temperatures lower the development and fecundity of thrips, so population decreases
In spring, rates increase and populations rise
Growth checked by summer heat before density-dependent factors important
Weather accounts for 78% of population size variance

80

Density-independent factors on amphibians

Pollutants cause environmental stress, limiting population growth
Pesticides and other toxins disrupt their endocrine system
Direct increases in mortality l, indirect limitation in growth, development and fecundity
Increases deformities, delays development so more vulnerable to predators
Limits population growth irrespective of population size

81

Density-dependent factors

Factors that act in a density-dependent manner have an effect on births and deaths which is directly related to population size

82

What are 5 mechanisms of density-dependent regulation?

Competition for resources - high density means higher competition
Disease - increased density increases disease transmission rates
Predation - predator catches more prey as prey population increases
Territoriality - increased competition for space
Intrinsic factor - higher densities can result in aggressive interactions s and hormonal changes affecting reproductive rates

83

What correlation do density-dependent factors have to population size?

Positive or negative

84

What is the allee effect?

Negative density dependence
Population growth rate low at low density due to low chance of animals finding mates or plants being pollinated
As a result newly established populations grow very slowly

85

What are factors that determine a population’s abundance?

Determination of the precise abundance of individuals will reflect the combined affects of all the factors and all the processes that affect a population, whether they are dependent or independent of density

86

What are factors that regulate a population’s abundance?

Regulation is the tendency of a population to decrease in size when it is above a particular level, but to increase in size when below that level

87

What is the problem if births and deaths are density-independent?

There is no stability - there will either be a continuous growth or continuous decline to extinction

88

What type of factors regulate abundance?

Density-dependent factors

89

What is monotonic damping?

When there is a low intensity of density dependence, abundance plateaus around carrying capacity

90

What can Harcourt’s life tables be used for?

To distinguish the importance of density dependent and density independent factors

91

What is an example of density dependent and independent factors interacting?

Weather effects on population are density independent, but the effects are more significant when a population is at K and resources per individual are in short supply

92

What is maximum sustainable yield?

The largest theoretical yield (sustainable harvest) over an indefinite period
MSY aims to maintain population size at point maximum growth by harvesting individuals that would normally be added to the population

93

What are the 5 problems with applying maximum sustainable yield?

1. Very difficult to get accurate estimates of population size
2. Carrying capacity changes; impossible to estimate
3. Basic demographic data rare; varies between populations
4. Difficult to get measured of other forms of mortality - what regulates the population naturally?
5. Social systems and mating strategies often unknown

94

Example of MSY applied wrongly

Has caused collapse of many fisheries worldwide
Ignores several key demographic factors - size and age of fish being taken and their reproductive status. Also ignores ecosystem damage by exploitation and bycatch

95

What are direct biological interactions?

Consumption of another individual, mutual benefit (mutualism e.g. symbiosis)

96

What are indirect biological interactions?

Shared resources
Common enemies - shared predator

97

What is mutualism?

+/+
Both species benefit from interaction

98

What is commensalism?

+/0
One species benefits, the other is unaffected

99

What is competition?

-/-
Each species affected negatively from interaction

100

What is antagonism?

+/-
One species benefits, one disadvantaged

101

What is amensalism?

-/0
One species affected nagatively, the other is unaffected

102

Examples of mutualism?

Cleaner fish
Birds removing parasites
Nitrogen fixation by fungi (lichen)
Photosynthesis by algae living within coral polyps

103

What does it mean when a species is obligate?

That species can not survive without interactions with another species in the long or short term

104

What is the problem with commensalism?

Close interaction of two organisms unlikely to be completely neutral

105

What is the definition of competition?

Competition is an interaction between individuals brought about by a shared requirement for a resource in limited supply and leading to a reduction in the survivorship, growth or reproduction in the individuals concerned

106

Example of commensalism?

Epiphytes may intercept nutrients that otherwise would go to host plant; may shade host tree

107

What are the two types of competition?

Interspecific
Intraspecific

108

What are the features of competitive interactions?

1. Need spatial and temporal co-occurrence
2. Increase in intensity as the density, phylogenetic similarity and niche overlap of competing species increase

109

What is interference competition?

Direct
Between individuals if they interfere with other’s foraging/reproduction

110

What is exploitation competition?

Indirect
Use of resources depletes the amount available to others

111

What is apparent competition?

Occurs indirectly between two species which are both preyed upon by the same predator

112

What is contest competition?

Usually the result of interference competition
One species ‘wins’ and monopolises all of the resource - other species population crashes

113

What is scramble competition?

Usually result of exploitation competition
Resource shared equally between both species, but due to resource being finite, both populations eventually crash

114

What outcome is usually seen in a stable environment?

K-selected organisms have a higher competitive ability as they are specialists
Contest outcome

115

What outcome is usually seen in an unstable environment?

r-selected organisms have a lower competitive ability as they are generalists
Scramble outcomes

116

What is resource petitioning?

Differentiation of niches leading to species coexistence

117

What is the competitive exclusion principle?

One much can only carry a single species, which is why competition leads to exclusion of all but one species

118

How is a fundamental niche found?

Remove all competing species, and see what niche the species occupies

119

What is a realised niche?

A niche occupied with competing species present - many be smaller than fundamental niche

120

What is bottom-up control?

Where resources are limited, populations decline as individuals compete for access to the limiting resources

121

What are examples of antagonism?

Predation
Parasitism
Herbivory
Cannibalism

122

What form of antagonism is the largest factor in evolutionary time changing phenotypes?

Predation

123

What is top-down control?

Predation influencing the size of a prey population
Works together with bottom-up control

124

What is predator-mediated coexistence?

Predator feeds on competitively dominant prey species
By reducing its numbers the predator releases competitive inferior prey from suppression by dominant species
Predator therefore allows more species to coexist than possible in absence of predator

125

What can be the opposite problem of predation?

If a predator feeds preferentially on competitively inferior prey species, predation further reduces the number of species in the community

126

What are predator-prey cycles characterised by?

Regular increases and decreases in numbers of predator and prey
Lag between population responses

127

Extrinsic factors affecting cycles in population

Weather
Food
Predators
Parasites

128

Intrinsic factors affecting population cycles

Hormonal change
Behavioural change