54 Community Ecology Flashcards
1
Q
What does ‘interspecific interactions’ refer to?
A
How species of a community affect each other.
2
Q
What does symbiosis refer to?
A
It can refer to two species which live together beneficially.
More broadly it refers to two species with live in direct and intimate contact with each other.
Note that competition etc. isn’t symbiosis as the predator and prey do not live together, unlike in parasitism
3
Q
What are the main forms of ‘interspecific interaction?
A
Competition, Predation, Herbivory, Parasitism, Mutualism, Communalism and Faciliation
4
Q
What type of interaction is competition?
A
-/-
5
Q
What type of interaction is predation?
A
+/-
6
Q
What type of interaction is herbivory?
A
+/-
7
Q
What type of interaction is parasitism?
A
+/-
8
Q
What type of interaction is mutualism?
A
+/+
9
Q
What type of interaction is commensalism?
A
+/0
10
Q
What type of interaction is facilitation?
A
+/+ or +/0
11
Q
What is competition?
A
When two organisms of the same or different species compete for a limited resource.
12
Q
What can competition be divided into?
A
‘Interspecific competition’ between organisms of the same species and ‘intraspecific competition’ between organisms of different species.
13
Q
What are some examples of resources fought over in competition?
A
Food, water, shelter and light (plants)
In ‘intraspecific competion’ mates can also be fought over.
14
Q
What does ‘niche’ refer to?
A
The sum of a species’ use of the biotic and abiotic resources in its environment
15
Q
What fundamental concepts does competition lead to?
A
‘competitive exclusion’, ‘resource partitioning’ and ‘character displacement’
16
Q
What is ‘competitive exclusion’?
A
If two species with a similar niche compete it is possible that one species outcompetes the other and thus removes it from that niche.
17
Q
What is ‘resource partitioning’?
A
If two species inhabit similar niches they may undergo ‘resource partitioning’ in which one species occupies one part of that niche and the other occupies a different area of that niche.
18
Q
What is an example of ‘resource partitioning’?
A
If two snakes occupy a similar niche i.e. eating mice in the same niche.
In this case ‘resource partitioning’ could occur in that one species eats mice in the bushes whereas the other species eats mice in the trees.
‘Resource partitioning’ can also be temporal for example inesct-eating birds could come out at day and insect-eating bats might come out at night.
19
Q
What is ‘character displacement’?
A
If two sympatric (overlapping geographically) species compete for the same niche they may undergo ‘character displacement’.
This leads to the similar species gaining different features.
20
Q
What drives ‘character displacement’?
A
Natural selection as it is not beneficial to the species to be competing.
21
Q
What is an example of character displacement?
A
If two bird species moved to the same island they might undergo ‘character displacement’ so that their beaks differ.
The species that develops a shorter beak would eat small seed whereas the species with the long beak would eat larger seeds.
In this way the competition has been reduced.
22
Q
What is predation?
A
An interspecific relation in which one species (the ‘predator’) kills its ‘prey’ for food.
23
Q
What are some typical adaptions of predators?
A
Acute senses to find their prey.
Many have adaptations such as claws, teeth, fangs, stingers, or poison that help them catch and kill their food.
Often speed so that they can catch their prey
24
Q
What are some typical adaptions prey?
A
Many are fast so that they can escape. They may have claws and horns etc. to defend them self.
Many exploit the various forms of ‘defensive coloration’
25
What are the basic forms of ‘defensive coloration’?
‘cryptic coloration’, ‘aposematic coloration’, ‘Batesian mimicry’ and ‘Müllerian mimicry'
26
What is ‘cryptic coloration’?
Coloration that acts as camouflage to make the species blend into its surrounding.
May be used as a defines by prey or by predators to sneak up on their prey.
27
What is ‘aposematic coloration’?
Typically bright colours which warn and predators that the potential prey is dangerous.
For example the ‘Poison dart frog’ is bright orange
28
What is ‘batesian mimicry’?
A harmless species mimics a harmful one and thus causes the predator to mistakenly avoid it.
29
What is ‘Müllerian mimicry’?
Two unpalatable species mimic each other. This is beneficial as it means that the predator learn to avoid these species faster.
For example bees and wasps are both yellow and black.
Note that this differs from ‘Batesian mimicry’ in that both are actually dangerous.
30
What is an example of mimicry used by predators?
The 'alligator snapping turtle’ moves its tongue so that it appears to be a worm.
31
What is herbivory?
An interspecific interaction in which an animal eats a plant.
32
What are some example of adaptions animals have to facilitate herbivory?
Teeth and digestive systems specialised to digest cellulose.
Chemical sensors on their feet or a developed sense of smell to determine if plants are palatable or toxic.
33
What are some examples of adaptions that plants have to prevent herbivory?
Spines and thorns. Using ‘recruitment’
Also releasing toxins such as ’strychnine’ from ’tropical vine’ and ’nicotine’ form the tobacco plant.
‘Astragalus’ aka ‘locoweeds’ accumulate Selenium to a level toxic to animals like sheep.
34
What is parasitism?
An interaction in which one organism, called the ‘parasite’ derives nutrition from the ‘host'
35
What can parasitism be divided into?
Endoparasites that live inside the host and ‘ectoparasites’ which live on its surface
36
What is a specific form of parasitism?
‘Parastoid’ insects lay eggs inside a host. The lava then eat part of that host for nutrition before emerging.
37
Besides consuming the hosts resources, how can parasites affect an organism?
Some parasites change the behavior of their hosts in a way that increases the probability of the parasite being transferred from one host to another.
For instance, the presence of parasitic acanthocephalan (spiny-headed) worms leads their crustacean hosts to engage in a variety of atypical behaviors, including leaving protective cover and moving into the open.
This changed behaviour gives them a greater chance of being eaten by the birds that are the second host in the parasitic worm’s life cycle.
38
What is facilitation?
An interspecific interaction in which one species increases the survival or reproduction of another species without necessarily living in direct contact with the host like in mutualism/commenalism
39
What are some examples of facilitation?
Trees release oxygen which allows animals to live. (+/0)
Worms break down soil to recycle nutrients for plants and animals (+/+)
40
What is ‘mutualism’?
When two species live in a close association for which both benefit.
41
What are some examples of ‘mutualism’?
Pollinators gain nutritious nectar from flowers which also benefit as their pollen has been dispersed.
42
What is ‘commensalism’?
When two species live in a close association yet only one species benefits.
43
What are some examples of ‘commensalism’?
Barnacles that live on a whale and thus get a free ride. This is called ‘hitchhiking’
44
What is a specific form of ‘commensalism’?
‘Hitchhiking’ in which one species (or pollen etc) gets a free ride.
For example algae on a turtles shell. barnacles on a whale
45
What is the variety of species in a community called?
’Species diversity'
46
What are the components of species diversity?
’Species richness’ and ’relative abundance'
47
What is ’species richness'?
The total number of species in a community.
48
What is ‘relative abundance’?
The proportion each species represents of all individuals in the community.
49
What is typically used to quantify species diversity?
’Shannon diversity'
50
How is Shannon diversity calculated?
H = - (Pa ln Pa + Pb ln Pb + Pc ln Pc ...)
Where Px refers to the population of species x and ‘ln’ refers to the natural logarithm
51
What is the symbol used for Shannon diversity?
H
52
Does a high Shannon diversity value represent high or low diversity?
High diversity
53
What are the general advantages of a diverse community?
They are generally more productive, able to recover from environmental stress like droughts and are more resilient to ‘invasive species'
54
Define ‘invasive species’?
A species which occupies a community outside its normal range.
55
What are the feeding relationship between organisms of a population called?
The ’trophic structure'
56
What are species which feed at multiple trophic levels called?
’Non-exclusive consumers'
57
What is the typical maximum number of trophic levels commonly seen in a community?
Rarely up to 7
58
What hypothesis explains the limit of the number of trophic levels
The ‘energetic hypothesis’ and the ‘dynamic stability hypothesis'
59
How does the ‘energetic hypothesis’ explain the limit of trophic levels?
Energy transfer between trophic levels is typically only around 10% efficient. Therefore as each trophic level is added the biomass of the producers must increase by a factor of 10.
60
Define ‘biomass’
The total mass of all the organisms in a population/community.
61
What is the total mass of the organisms in a population/community called?
The ‘biomass'
62
What is the ‘dynamic stability hypothesis’ of the limit to trophic levels?
The longer the food chain is, the more unstable it is. For example a food shortage of the primary consumers would be magnified to the point it would likely lead to the extinction of any extremely high level predators.
63
What can species that have a large impact on the community be divided into?
‘Dominant species’ and ‘keystone species'
64
What are dominant species?
Species in the community that are the most abundant or have the greatest biomass.
For example trees are the dominant species in a forest, even though there are many more insects.
65
What are ‘keystone species’?
Species which are not as abundant as ‘dominate species’ but play a critical role.
For example the sole producer might have a single rare pollinator. If that pollinator was lost it would cause the ecosystem to collapse as the sole produce would not reproduce.
66
What are ‘ecosystem engineers’?
Organisms which profoundly affect their environment, such as damn building beavers.
67
What are organisms which profoundly affect their environment called?
‘Ecosystem engineers'
68
What does 'foundation species’ refer to?
An ‘ecosystem engineer’ i.e. profound impact on environment.
69
What are the two models used to analyse the impacts of factors changing in the environment?
The ’bottom up model’ and the ’top down model'
70
What is the ‘bottom-up model’?
It analyses the effects based on the philosophy that Nutrients (N) affects plant (V) numbers which influence Herbivores (H) and thus Predators (P)
Fundamentally it views expects a a unidirectional influence from lower to higher trophic levels.
Therefore the ‘bottom up model’ can be summarised as: N → V → H → P.
With arrows reflecting the direction of influence.
71
What are implications does the ‘bottom up model suggest’?
It can be summarised as: N → V → H → P.
Therefore if the nutrient levels increase so will the number of plants (V) and thus so will the population of herbivores.
Similarly if the number of herbivores decrease so will the population of predators.
72
What is the ’top down model’?
It views the ecosystem as a unidirectional flow of influence from the top trophic level to the bottom so that:
“Predation mainly controls community organization because predators limit herbivores, herbivores limit plants, and plants limit nutrient levels through nutrient uptake.”
Therefore the ’top-down’ model can be represented as; N→ V→ H→ P
73
What implications does the ‘bottom up’ model suggest?
As the population of a secondary consumer increases the population of primary consumer decreases. This causes the population of producers to increase and thus nutrients decrease.
Therefore it predicts a sequence of alternating +/- effects known as a ’trophic cascade'
74
What is a ’trophic cascade’?
An alternating series of +/- effects when an organism in a high trophic level increases or decreases in population.
For example: As the population of a secondary consumer increases the population of primary consumer decreases. This causes the population of producers to increase and thus nutrients decrease.
75
What it called when an increase in population causes the trophic level below to decrease in population and the one below that increase and so on?
A ’trophic cascade’
76
What factor is believed to be extremely important in an ecosystem?
'Disruption'
77
What is the model which states that disruption is important to an ecosystem called?
The ’non-equilibrium’ model.
78
What does the ’non equilibrium model’ suggest?
Most healthy communities are continuously changing as new species are introduced etc.
79
What can high-level of disturbance be caused by?
Events which have a high frequency or a high intensity.
80
What is the ’non-equilibrium’ model?
A model which states that most communities are constantly affected by disruption and thus constantly change.
81
What hypothesis predicts the optimum level of disturbance in a community?
The ‘intermediate disturbance hypothesis'
82
What does the ‘intermediate disturbance hypothesis predict’?
That communities which have a greater level of disturbance will have a greater level of species diversity.
83
What it the logic behind the ‘intermediate disturbance hypothesis’?
In ecosystems with a low rate of disturbance the diversity will tend to be low as this makes it easy for one species to take over.
In communities with a high level of disturbance only the fast growing species or those that appear quickly (migratory birds etc) will be present.
Disturbances like fire provide space by removing dead material
84
What happens after severe disruption?
‘Ecological succession’ in which fast-growing species / migratory species that appear quickly will appear then be replaced by more dominant species.
85
Define ‘ecological succession’?
A phenomena after disruption in which the fast-growing species appear first. They are then replaced with slower growing but more dominant species.
86
What is ’succession’ divided into?
‘Primary succession’ and ’secondary succession'
87
What is ‘primary succession’?
Succesion which occurs in a region which did not have life in it before.
88
What is secondary succession?
Succession which occurs in a region which previously had life but which was lost through disruption.
89
What are some examples of conditions which could cause primary succession?
A glacier retreating (melting) and thus revealing new land.
A volcano releasing lava and thus forming a new island.
90
What are some examples of situation which could lead to secondary succession?
A storm/tsunami wipes out a large forrest.
Humans deforest a large are.
91
What factors result in the multiple steps of succession?
- Some species grow faster than others and thus appear first
- Some species i.e. mammals are less able to travel long distances than birds etc. Therefore it will take longer for them to appear.
-Particularly in during primary succession one species might be needed before the other can appear. For example legumes might appear first to add nitrates to the soil. Only after this could more dominant species appear as they need the soil nitrates.
92
What does resource partitioning lead to in terms of a species niche?
The ‘fundamental niche’ of a species is the niche that could possibly occupied by a species.
The ‘realised niche’ is the actual niche occupied by a species.
Because resource partitioning partitions the niche it makes the ‘realised niche’ smaller and thus limited nutrient availability and ultimately population size.
93
What does ‘fundamental niche’ refer to?
The niche that could possibly occupied by a species.
94
What does ‘realised niche’ refer to?
The actual niche occupied by a species.
95
What is the niche that could possibly occupied by a species called?
The ‘fundamental niche'
96
What is the niche that is actually occupied by the species called?
Its ‘realised niche'
97
What factors could make the ‘realised niche’ smaller than the ‘fundamental niche’?
‘Resource partition’
Competitive exclusion
Also the fact that the species has not been introduced to that environment. For example the realised niche becomes closer to the ‘fundamental niche’ when invasive species are introduced to new regions.
98
What are geographical features which affect a community called?
Biogeographic factors
99
What are ‘biogeographic factors’?
Geographic factors wich affect a community
100
What is an example of a biogeographical factor?
‘Evapotranspiration’ which is the total amount of water which evaporates from the soil plus the amount of water transpired by plants.
101
What is evapotranspiration divided into?
‘Potential evapotranspiration’ and ‘actual evapotranspiration'
102
What is ‘potential evapotranspiration’?
The total amount of evapotranspiration which could occur if water was not a limiting factor. Therefore it is closely linked to the amount of sunlight.
103
What is ‘actual evapotranspiration’?
The total amount of evapotranspiration which actually occurs.
Most often water is the limiting factor.
104
What are some examples of how evapotranspiration affects communities?
As potential evapotranspiration increases so does the number of vertebrate species found in a community.
As ‘actual transpiration increases’ so does the number of tree species found in a community.
105
What are patterns in which something is high or low at the equator then gets progressively less as one travels north and south called?
A latitudinal gradient.
106
What is a 'latitudinal gradient’?
A gradual change of a property as the latitude increases or decreases from the equator to the poles.
Therefore environments at the small latitude will have similar properties. The further a region is in terms of latitude, the greater the difference in properties will be.
A region at 25ºS would also have similar properties to one at 25ºN.
107
What is an example of a ‘latitudinal gradient’?
Temperature: It tends to be highest at the equator but progressively gets colder as one travels to the poles.
Also evapotranspiration
108
Besides evapotranspiration, what is an example of a biogeographic fact which affects species richness?
Land area of the community.
109
What predicts the effect of land area on species richness?
The ’species-area curve'
110
What does the ’species area curve predict'?
As the area of a community increases, so does the number of species found on it.
111
Besides the ’species area curve’, what predicts the number of species that will be found on an island?
The ‘island equilibrium model'
112
What is the ‘island equilibrium model’?
The equilibrium i.e. stable number of species on an island will be occur when the immigration rate matches the extinction rate.
(i.e. when the immigration and extinction line on the graph intercept)
Therefore it is the factors which affect the rate of extinction and immigration which affect the total number of species on an island.
Not that 'migration' is the rate of new species in this context.
113
What factors affect immigration in the ‘island equilibrium model’?
Island size: the larger the island, the greater the rate of immigration as birds etc. are more likely to randomly come across it.
Distance form mainland: As distance from mainland increases the rate of immigration decreases as some species won’t wonder that far and it decrease the rate of any this far form seeing it.
114
What factors affect extinction in the ‘island equilibrium model’?
Island size: A larger island will have a lower rate of extinction because more members of a species will come and thus replenish the population
Distance from mainland: As the instance from mainland increases less birds etc. of the same species come. This means the population on the island is smaller so more vulnerable to extinction.
115
Based on the ‘island equilibrium model’ what will happen when island size increases?
The number of species will increase
116
Based on the ‘island equilibrium model’ what will happen when the distance from mainland increases?
The number of species will decrease
117
How does an increase in island size affect migration and extinction?
Migration: increase, Extinction: decrease
118
How does an increase in distance from mainland affect migration and extinction?
Migration: decrease, Extinction: increase
119
What things are classed as pathogens?
Disease-causing microorganisms, viruses, viroids and prions.
120
What are ‘prions’?
Infectious proteins
121
What are ‘viroids’?
Infectious RNA molecules
122
Where do most human diseases arise?
From animal diseases which mutated to become infectious to humans.
123
What is a disease carried by animals which can infect humans called?
A ‘zoonotic pathogen'
124
What is a carrier of a disease called?
A ‘vector'
125
What is a ‘zoonotic pathogen’?
A disease carried by animals which can infect humans.
126
What are the most common vectors for zoonotic diseases?
Parasites such as mosquitos and ticks.
127
How is malaria carried?
Mosquitos are infected with the plasmodium parasite ‘plasmodium’ which is spread when mosquitos suck blood from various animals/humans, causing them to be injected with ‘plasmodium’.
128
What does 'sympatic' refer to?
Living together i.e. sympatic species have overlapping ranges
129
What does 'allopatric' refer to?
Not living together i.e. species which do not have overlapping ranges
130
What are species with overlapping ranges called?
Sympatric
131
What are species without overlapping ranges called?
Allopatric
132
What are camouflage and mimicry collectively known as?
'Defensive coloration'
133
What does parastoid refer to?
The group of parasitic insects which lay there eggs insider the host.
134
What are insects which lay eggs inside the host called?
Parastoid
135
What are 'non exclusive consumers'?
Those which feed at multiple levels
136
What does H refer to in ecology?
Shannon diversity
