Final Exam Flashcards
(237 cards)
1
Q
Competition
A
An interaction between individuals in which each is harmed by their shared use of a limiting resource.
2
Q
Interspecific competition
A
Interaction between individuals of different species
3
Q
Intraspecific competition:
A
Between individuals of a single species.
4
Q
Competition for Resources
A
Competition occurs between species that share the use of a resource that limits the growth, survival, or reproduction of each species.
5
Q
Resources
A
are features of the environment required for growth, survival, or reproduction, and which can be consumed to the point of depletion.
6
Q
Exploitation competition
A
Species compete indirectly: Individuals reduce the availability of a resource as they use it (= Scramble).
7
Q
Interference competition
A
Species compete directly for access to a resource (= Contest). Individuals may perform antagonistic actions
Examples: when two predators fight over a prey
8
Q
natural experiment
A
is a situation in nature that is similar in effect to a controlled removal experiment.
9
Q
Competitive Exclusion
A
- Competing species are more likely to coexist when they use resources in different ways.
- If the ecological niches of competing species are very similar, the superior competitor may drive the other species to extinction
10
Q
Resource partitioning
A
Species using a limited resource in different ways.
11
Q
α & β
A
competition coefficients
12
Q
Equilibrium densities =
A
Isoclines –> dN / dt = 0
13
Q
How can we model competition?
A
Lotka-Volterra competition models
14
Q
N1
A
population density of species 1.
15
Q
r1
A
intrinsic rate of increase of species 1.
16
Q
K1
A
carrying capacity of species 1.
17
Q
α and β
A
competition coefficients—constants that describe effect of one species on the other.
18
Q
Zero population growth isoclines
A
- The population does not increase or decrease in size for any combination of N1 and N2 that lies on these lines.
- Zero growth isoclines can determine the conditions under which each species will increase or decrease.
19
Q
Presence of herbivores can lead to
A
competitive reversals.
ie) In the absence of the flea beetles, ragwort is a superior competitor
20
Q
fugitive species
A
must disperse from one place to another as conditions change.
21
Q
Altering the Outcome of Competition
A
Disturbances such as fires or storms can kill or damage some individuals, while creating opportunities for others.
22
Q
Competition can cause
A
evolutionary change, and evolution can alter the outcome of competition
23
Q
Natural selection can
A
influence the morphology of competing species and result in character
-phenotypes of competing species become more different over time.
24
Q
Hypotheses to explain changes in hare
birth and survival rates: 1
A
1. Food supplies become limiting when hare population density is high, but… • some declining hare populations do not lack food • experimental addition of food does not prevent decline
25
Hypotheses to explain changes in hare
| birth and survival rates: 2
```
2. Predation by lynx and other predators
can explain drop in survival rates, but…
• hare birth rates drop during the decline
phase.
• Hare numbers rebound slowly after
predator numbers plummet.
• The physical condition of hares worsens
as hares decrease in number
```
26
exploitation
a relationship in
which one organism benefits by feeding
on, and directly harming, another:
+ / - relationship
27
Herbivore
eats tissues of living plants
| or algae.
28
Predator
kills and eats other
| organisms, referred to as prey
29
Parasite
```
lives in or on another organism
(its host), feeding on parts of it. Usually
doesn’t kill the host.
-Some parasites (pathogens) cause
disease.
```
30
Parasitoids
are insects that lay an
egg on or in another insect host.
After hatching, larvae remain in the
host, which they eat and usually kill.
31
sit-and-wait predators
remaining in one place and attacking
prey that move within striking distance
ie) sessile animals, such as
barnacles, and carnivorous plants
32
Crypsis
The prey is camouflaged, or resembles its background.
33
Mimicry
The prey resembles another organism that is toxic or very fierce.
34
Behavior
• Not foraging in open
areas.
• Keeping lookouts.
• Defensive circles.
35
Masting
some produce huge numbers of seeds in
| some years and hardly any in other years
36
Compensation
Removal of plant tissue stimulates
| new growth.
37
Full compensation
no net loss of plant tissue.
38
Structural defenses
tough leaves, spines
and thorns, saw-like edges, pernicious
(nearly invisible) hairs that can pierce the
skin.
39
Induced defenses
produced in response
to herbivore attack. Some cacti increase
spine production after being grazed.
40
Secondary compounds
```
toxic chemicals to reduce herbivory.
-Other compounds attract predators or
parasitoids that will attack the herbivores.
-Some are produced all the time; others
are induced.
```
41
Herbivores can use behavior to circumvent plant defenses:
- Plants in the genus Bursera store toxic resins in canals in the leaves.
- Beetles in the genus Blepharida have evolved a counter-defense
42
The Lotka–Volterra predator–prey model
dN/dt = rN-aNP
43
N
number of prey
44
P
number of predators
45
r
population growth rate
46
a
Capture efficiency
47
When P = 0,
the prey population grows exponentially.
48
With predators present (P ≠ 0),
```
the rate of prey capture depends on:
• how frequently they encounter each
other (NP)
• efficiency of prey capture (a).
The overall rate of prey removal is aNP.
```
49
The Lotka–Volterra predator–prey model with mortality
dP/dt= baNP mP
50
m
mortality
51
If N = 0,
predator population decreases
| exponentially at death rate m.
52
When prey are present (N ≠ 0),
individuals are added to the predator population according to:
• the number of prey killed (aNP)
• efficiency (b).
53
Zero population growth isoclines
can predict changes in predator and prey
| populations over time.
54
Prey population
decreases if P > r/a; it
| increases if P < r/a.
55
Predator population
decreases if N < m/ba;
| it increases if N > m/ba.
56
experiments with a rotifer predator and algal prey species, Hairston et al. found that populations cycled, but not
synchronously. 4 possible mechanisms
```
1. Rotifer egg viability increases with prey
density.
2. Algal nutritional quality increases with
nitrogen concentrations.
3. Accumulation of toxins alters algal
physiology.
4. The algae might evolve in response to
predation.
```
57
Symbionts
organisms
that live in or on other
organisms
58
parasite
consumes the tissues or body fluids of the organism on which it lives (the host).
59
Pathogens
are parasites
| that cause diseases.
60
Herbivores
aphids or nematodes that feed on one or a few host plants
61
Parasitoids
insects whose larvae feed on a single
| host and almost always kill it.
62
Macroparasites
large species such as arthropods and worms
63
Microparasites
microscopic, such
| as bacteria
64
haustoria
Dodder gets water and food from the host plant via specialized
roots
65
hemiparasitic
they get water and nutrients from the host but can also photosynthesize.
ie) mistletoes
66
ectoparasites
many fungi are this
67
endoparasites.
Many disease organisms
68
Mycobacterium tuberculosis,
the bacterium that causes
| tuberculosis
69
ectoparasitism advantage
- change host
| - don't have to counteract immune defenses
70
ectoparasitism disadvantage
-exposed to predators
71
endoparasitism advantage
- protected
| - stable enviroment
72
endoparasitism disadvantage
-find host
73
Parasites exert strong selection pressure
on their
| host organisms, and vice-versa.
74
parasite impact on communities
Parasites can reduce the sizes of host populations
and alter the outcomes of species interactions,
thereby causing communities to change.
75
Ecosystem engineer
species can change the physical character
| of the environment, as when a beaver builds a dam
76
dynamics and spread of disease formula
dI/dt = βSI - mI
77
β
transmission coefficient (how effectively the disease spreads)
78
m
mortality and recovery rate
79
A disease will spread when
dI/dt > 0
80
ST = m/β
A disease will establish and spread when
the number of susceptible individuals
exceeds threshold density,
81
Climate change impact on spreading of disease
```
Range shifts may put more or fewer
people at risk
• Control efforts
• Ecological interactions involving
pathogens and hosts
```
82
From Chemicals to Evolution and
| Ecosystems
Interactions between enslaver parasites and
their hosts provide evidence of previous
evolutionary change:
• Enslaver parasites have many adaptations
to cope with host defenses.
• A parasite that uses a chemical is well
adapted to take advantage of the body
chemistry of its host.
83
Positive interactions
-occur when neither species is
harmed and the benefits of the interaction are
greater than the costs for at least one species.
-are those in which one or both species benefit
and neither is harmed. (= Facilitation)
84
Mutualism
Mutually beneficial interaction between individuals of two
| species (+/+).
85
Commensalism
Individuals of one species benefit, while individuals
| of the other species do not benefit and are not harmed (+/0).
86
Symbiosis
A relationship in which the two species live in close
| physiological contact with each other, such as corals and algae.
87
Symbioses
can include parasitism (+/–), commensalism (+/0), and
| mutualism (+/+).
88
Most plants form mycorrhizae
-Symbiotic associations between the roots
and various fungi.
-The fungi increase the surface area for the plant to take up water and soil
nutrients
89
Ectomycorrhizae
The fungus grows between root cells and
forms a mantle around the
root.
90
Arbuscular mycorrhizae
The fungus grows into the soil, extending away from the root; and also penetrates into some of the plant root
cells.
91
Ecological interactions can evolve into
| commensalism or mutualism
• Lichens on tree leaves -> initially harm the tree by blocking
sunlight.
• The Australian palm has adapted by increasing the
concentration of chlorophyll in leaves with lichens.
92
Obligate mutualisms
```
Tropical figs are pollinated by fig wasps.
• Neither species can
reproduce without the
other.
• The wasps and the figs
have coevolved.
```
93
Facultative Mutualism
```
Some ants protect treehoppers from predators
• the treehoppers secrete
“honeydew” (sugar solution),
which the ants feed on.
• Treehoppers always secrete
honeydew, so ants always
have this resource.
```
94
Each partner in a mutualistic interaction
acts
in ways that serve its own ecological and
evolutionary interests.
95
Trophic mutualisms:
Mutualist receives energy or nutrients from its partner.
96
Habitat mutualisms
One partner provides the other with shelter, living space, or favorable habitat
97
Service mutualisms:
One partner performs an ecological service for the other.
98
Cheaters
are individuals that increase offspring production by overexploiting their mutualistic partner
99
“Penalties”
may be imposed on cheaters
100
Communities
communities are groups of interacting species that
| occur together at the same place and time
101
A physically defined community
might encompass all the species in a sand dune, a mountain stream, or a desert.
102
biologically defined community
might include all the species associated with a kelp forest, a freshwater bog, or a coral reef.
103
Taxonomic affinity
e.g., all bird species in a community
104
Guild
group of species that use the same resources. (typically in the same way)
105
Functional group
species that function in similar ways, but do not necessarily use the same resources.
106
Interaction webs
describe both trophic (vertical) and non-trophic (horizontal)
interactions
107
Community structure
is the set of characteristics that shape communities
108
Species richness
the number of species in a community.
109
Species evenness
relative abundances compared with one another.
110
Species diversity
combines species richness and species evenness.
111
Shannon diversity index
```
pi = proportion of individuals in the ith species
s = number of species in the community
```
112
Biodiversity
describes diversity at multiple spatial scales, from genes to species to communities.
113
Species diversity
(and biodiversity) often used broadly to mean the number of species in a community.
114
Rank abundance curves
plot the proportional abundance of each species (pi) relative to the others in rank order.
115
Species accumulation curves
species richness is plotted as a function of the total number of individuals that have been counted.
116
Species composition
identity of species in a community.
117
Communities can be characterized by
complex networks of direct and indirect interactions that vary in strength and direction.
118
Direct interactions
occur between two species (e.g., competition, predation, and facilitation).
119
Indirect interactions
occur when the relationship between two species is mediated by a third (or more) species
120
Trophic cascade
Effect across more than onetrophic level
121
Trophic facilitation
A consumer is indirectly facilitated by a positive interaction between its prey and another species.
122
Competitive networks
Competitive interactions among multiple species in which every species negatively interacts with every other species.
123
Indirect effects
can arise from horizontal interactions at one trophic level.
124
Interaction strength
Magnitude of the effect of one species on the abundance of another species
-Measured by removing one species (the interactor species) from the community and observing the effect on the other species (the target species)
125
Dominant species, or foundation species
have large effects due to high abundance or biomass.
126
Keystone species
have a strong effects because of their roles in the community. Large effect in proportion to their
abundance
127
Ecosystem engineers
species that create, modify, or maintain physical habitat for themselves and other species
128
Succession
is change in species composition in communities over time.
129
Disturbance
Events that injure or kill some individuals and create opportunities for other individuals.
130
Stress
An abiotic factor reduces the growth or reproduction of individuals.
131
Primary succession
involves the colonization of habitats devoid of life (e.g., volcanic rock).
132
Secondary succession
involves reestablishment of a community in which some, but not all, organisms have been destroyed (fires, storms, logging, etc.).
133
Climax stage
a stable end point that changes little
134
Space fro substitution
Could predict how communities would change over time without actually waiting for the pattern to unfold.
135
Early stages showed aspects of facilitation
plants modified the habitat in positive ways for other plants and animals.
136
As succession progresses, larger,
slow-growing and long-lived species begin to
| dominate.
137
Biogeography
is the study of patterns of species composition and diversity across geographic locations
138
species richness and composition vary:
- by latitude
| - continent to continent
139
Alpha diversity
species diversity at the community level
140
Beta diversity
Change in species number and composition, or turnover of species, from one community type to another.
-connects local and regional scales
141
Gamma diversity
Regional species pool —all the species contained within a region.
142
Alfred Russel Wallace
father of biogeography
| -co-discoverer of natural selection
143
The six biogeographic regions correspond roughly to Earth’s
six major tectonic plates.
144
Vicariance
evolutionary separation of species by barriers such as those formed by continental drift.
ex) The large flightless birds (ratites) had a common ancestor from Gondwana.
145
Global patterns of species richness should be controlled by three processes:
Speciation, extinction, and dispersal.
146
1. Species diversification rate:
• The tropics have the most land area on Earth
• Speciation by geographic isolation would be more
likely.
-Temperatures are very stable.
147
2. Species diversification time
The tropics more climatically stable over time,
species have had more time to evolve.
• Temperate and polar regions have undergone
severe climatic changes such as glaciation,
disrupting species diversification.
148
3. Productivity or Carrying Capacity
-Productivity is highest in the tropics (terrestrial).
-High productivity promotes large population sizes
because carrying capacity is larger.
149
An important concept in biogeography is the species–area relationship
species richness increases with area sampled.
150
species-area relationship
Species–area curves plot species richness (S) of a sample against area (A) of the sample.
-The relationship between S and A is estimated by linear regression:
151
equilibrium theory of island biogeography.
The number of species on an island depends on a balance between immigration or dispersal rates and
extinction rates.
152
Habitat fragmentation
also creates large edge effects at the transition between forest and matrix habitat.
153
Biofuels
liquid or gas fuels from plant material (biomass).
154
“filters"
exclude species from communities.
155
Biotic resistance
occurs when interactions with the native species exclude the invader.
156
Resource partitioning
Competing species coexist by using resources in different ways
157
Resource ratio hypothesis
Species coexist by using resources in different proportions.
158
Species diversity should be the greatest when?
at intermediate levels of disturbance
159
Low levels of disturbance
competition reduces diversity
160
Intermediate levels of disturbance
species involved in positive interactions are released from competition and can increase diversity
161
High levels of disturbance
positive interactions are common and help to increase diversity.
162
Lottery models
emphasize the role of chance in maintaining species diversity.
163
Lottery Model
Most relevant in very diverse communities
where many species overlap in their
resource requirements.
• Its relevance decreases in communities in
which species have large disparities in
interaction strength.
164
Species diversity can control community functions,
such as plant productivity, soil fertility, water quality,
| etc.
165
Community stability
the tendency of a community to remain the same in structure and function.
166
Four hypotheses
have been proposed to explain the positive relationship between species diversity and community function.
167
Two variables in all the hypotheses
• Degree of overlap in ecological function of species.
• Variation in strength of the ecological functions of
species.
168
Complementarity hypothesis
-As species richness increases, there will be a
linear increase in community function.
•Each species added has an equal effect.
169
Redundancy hypothesis
-The functional contribution of additional
species reaches a threshold.
•As more species are added, there is overlap in
their function, or redundancy among species.
170
Driver and passenger hypothesis
• Strength of ecological function varies greatly:
• “driver” species have a large effect
• “passenger” species have a minimal effect.
• Addition of driver and passenger species will have
unequal effects on community function.
171
A variation on the driver and passenger
| hypothesis
It assumes there could be overlap between driver and passenger functions.
172
biofuels and agriculture
-These lands could produce enough fuel to
substitute for 13% of global oil consumption and
19% of electricity; and reduce CO2 emission by
15%.
• Biofuels vary in the biomass and energy required to
make them.
-This is 4–5 months of driving for the average individual in the United States.
– The same amount of corn could feed one person
for 20–27 years.
173
Ecosystem
all the components of an ecological system, biotic and abiotic, that influence the flow of energy and elements.
174
Primary production
is the chemical energy generated by autotrophs during photosynthesis and chemosynthesis (source of energy for all organisms, from bacteria to humans)
175
Primary productivity
is the rate of primary production.
176
Gross primary production (GPP)
total amount of carbon fixed by autotrophs.
| • GPP depends on photosynthetic rate.
177
```
Photosynthetic rate is influenced by climate and leaf
area index (LAI)
```
leaf area per unit of ground area.
178
Net primary production (NPP):
```
NPP = GPP – Respiration
• NPP represents biomass gained by the
plant.
• NPP is the energy left over for plant
growth, and for consumption by
detritivores and herbivores.
• NPP represents input of carbon in
ecosystems.
```
179
It is important to be able to measure NPP
- NPP is the ultimate source of energy for all organisms in an ecosystem.
- Variation in NPP is an indication of ecosystem health.
- NPP is associated with the global carbon cycle.
180
Harvest techniques
Measure biomass before and after growing season
181
Measuring belowground NPP is more difficult
-Fine roots turn over more quickly than
shoots—they die and are replaced quickly.
• Roots may exude carbon into the soil, or
transfer it to mycorrhizal or bacterial
symbionts.
• Harvests must be more frequent, and
additional correction factors are needed
182
Chlorophyll absorbs
- blue and red wavelengths and has a characteristic spectral signature
- Plants also reflect near-infrared wavelengths
183
NDVI (normalized difference vegetation index):
-NIR = Near-infrared wavelengths (700-100 nm)
| • red = red wavelengths (600 – 700 nm)
184
NDVI and remote sensing
can be used to estimate CO2 uptake and NPP, deforestation, desertification, atmospheric pollution, and other phenomena.
185
The net change in CO2 is GPP minus total respiration
Net ecosystem production or exchange (NEE).
186
What does most of the photosynthesis in aquatic habitats?
Phytoplankton
-Phytoplankton have short life spans, so biomass at
any given time is low compared with NPP; harvest
techniques are not used
187
What is NPP constrained by?
both physical and biotic factors
188
What controls NPP in terrestrial ecosystems?
nutrients, particularly nitrogen
189
NPP in lakes
- limited by phosphorus and nitrogen
| - NPP is measured as change in chlorophyll concentrations or number of phytoplankton cells
190
limnocorrals
- used in lake experiments
| - clear containers with open tops to which nutrients can be added.
191
NPP in rivers
-NPP is often low
-Most of the energy is derived from terrestrial organic
matter
-Suspended sediment in rivers can limit light penetration, thus water clarity often controls NPP
-Nitrogen from agricultural and industrial practices
can result in blooms of algae and “dead zones.”
192
Estuaries
usually nutrient-rich; variation in NPP is correlated with nitrogen inputs from rivers
193
NPP in Oceans
- open ocean, NPP is mainly from phytoplankton
- Picoplankton (cells < 1 μm) contribute as much as 50% of the total marine NPP
- coastal areas, kelp forests may have leaf area indices and rates of NPP as high as those of tropical forests.
- “Meadows” of seagrasses such as eelgrass (Zostera) are also important in nearshore zones.
194
open-ocean NPP is limited by what?
nitrogen
195
NPP in the equatorial Pacific Ocean
limited by iron
196
Iron and global warming
-Martin suggested that fertilizing the oceans with iron could reduce global warming because CO2 uptake by phytoplankton would increase
-unlikely to be the solution
-iron is lost quickly from the photic zone, sinking to deeper layers where it is unavailable to support phytoplankton
growth
197
Secondary production
Heterotrophs get their energy by consuming organic
| compounds that were produced by other organisms
198
Detritivores
eat dead organic matter (detritus)
199
Net secondary production
Ingestion – Respiration – Egestion
200
egested
lost in urine and feces
201
Net secondary production
in most ecosystems is a small fraction of NPP. The fraction is greater in aquatic ecosystems than terrestrial.
202
Inuit women had PCB concentrations in their breast milk
seven times higher than in women in Quebec
203
allochthonous inputs
external energy inputs in aquatic systems
204
Detritus
dead organic matter
205
autochthonous energy
Energy produced by autotrophs within the system
206
Second law of thermodynamics
in transfer of energy, some is dispersed and becomes unusable:
-Energy will decrease with each trophic level.
207
Trophic pyramid
relative amounts of energy or biomass of each trophic level
208
Why don’t terrestrial herbivores consume more
| of the available biomass?
1. Herbivores limited by predators, never reach carrying
capacity. Green World Hypothesis
2. Autotrophs have defenses against herbivory, such as
secondary compounds, spines, etc.
3. Phytoplankton are more nutritious for herbivores than
terrestrial plants.
209
Trophic efficiency
Amount of energy at one trophic level divided by
| the amount of energy at the trophic level immediately below it
210
Assimilation efficiencies
- herbivores and detritivores ~ 20%–50%
| - carnivores ~ 80%.
211
Animals have carbon:nutrient ratios similar to
the animals consuming them
212
Endotherms digest food more completely than ectotherms
and thus have higher assimilation efficiencies
213
Trophic cascade
A series of trophic interactions that result in changes in biomass and species composition on levels not immediately adjacent
214
Hypotheses on the number of trophic levels
1. The amount of energy entering via primary production: More production should allow more trophic levels.
2. Frequency of disturbances: Higher trophic levels depend on lower levels, and take time to re-establish after disturbance
3. Ecosystem size: Larger ecosystems support larger
populations, have more habitat heterogeneity, and higher species diversity
215
Food webs
are static descriptions of energy flow and trophic interactions
216
Bioaccumulation
Some chemicals are not metabolized or excreted, and
| become progressively more concentrated in tissues over an organism’ s lifetime
217
Biomagnification
Concentration of these compounds increases in animals at higher trophic levels
218
Landscape ecology
examines spatial patterns and their relationship to ecological processes and changes
219
Landscape
An area in which at least one element is spatially heterogeneous; often includes multiple ecosystems.
220
Heterogeneity
different types of landscape elements, and arrangement: mosaic
221
Landscape composition
The kinds of elements or patches and how much of each kind is present.
222
Landscape structure
Physical configuration of the landscape elements
223
Scale
the spatial or temporal dimension of an object or process, characterized by grain and extent
224
Grain
size of the smallest homogeneous unit of study (e.g., a pixel in a digital image); it determines resolution.
225
Extent
boundary of the area or time period encompassed by the study.
226
Disturbance can create landscape
heterogeneity
227
Edges
(total length of habitat boundary) increase as fragmentation increases.
228
Edge effects
biotic and abiotic changes associated with the boundary
229
Abiotic edge effects
included higher temperatures and diurnal extremes, higher wind speeds, and more light penetration.
230
Habitat fragmentation tends to increase rates of
of inbreeding and genetic drift and alters selection regimes for species confined to fragments
231
Core areas
surrounded by buffer zones to mitigate human impacts
232
Biological reserves
are smaller reserves with conservation of a single species or ecological community as the main objective
233
Connectivity
can reduce the effects of fragmentation by preventing isolation of populations
234
Corridors may also facilitate movement of
pathogens and invasive species
235
Ecosystem management
attempts to maintain ecosystem sustainability, set explicit goals and policies, and use science to evaluate and adjust management practices over time
236
adaptive management
Policies can then be adjusted as needed— an iterative process
237
Three main parts of ecosystem management
ecological, socioeconomic, and institutional
