Population Ecology Flashcards
(128 cards)
1
Q
What is population ecology?
A
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
Q
What is a population?
A
The total number of individuals of one species in a defined area
3
Q
What is a community?
A
All the populations of all species in a defined area
4
Q
What do population ecologists seek to understand?
A
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
Q
What is the name for the study of population growth, regulation and dynamics?
A
Demographics
6
Q
What does population ecology explore?
A
How biotic and abiotic factors influence the density, distribution, size and age structure of populations
7
Q
What is adaptation?
A
The evolutionary process whereby organisms become better suited to their environments
8
Q
What are life histories?
A
The role of the changing environment on events affecting growth, survival, development and reproduction
9
Q
What are the two types of cause that lead to a species occurring where they do?
A
Ultimate cause
Proximate cause
10
Q
What is the ultimate cause?
A
Through natural selection organisms become adapted to maximise their fitness in a particular environment
11
Q
What are the three types of fitness?
A
Direct fitness
Indirect fitness
Inclusive fitness
12
Q
What is direct fitness?
A
The number of offspring an individual produces relative to others in the population
13
Q
What is indirect fitness?
A
Derived from shared genes with kin other than the individuals direct offspring such as cousins, nieces and nephews
14
Q
What is inclusive fitness?
A
The sum of direct and indirect fitness gains
15
Q
What is a proximate cause?
A
The current environmental factors (both biotic and abiotic) which determine where an organism can live
16
Q
What are biotic factors?
A
Other organisms
17
Q
What are the two types of biotic factors?
A
Intra-specific: competition (within species)
Inter-specific: competition, predation, parasites and disease (between species)
18
Q
What are abiotic factors?
A
The environment: water temperature wind weather light salinity pH These factors are often entangled
19
Q
What is a response curve?
A
Shows how the abiotic features of the environment affect how well an organism functions
20
Q
What is an ecological niche?
A
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
Q
What is the name for a niche in the absence of other organisms?
A
Fundamental niche
22
Q
What is the name for a niche in which other organisms are present?
A
Realised niche
23
Q
What is a habitat?
A
An objective description of an environment
24
Q
What is the result of environmental variability?
A
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
