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68 Cards in this Set
- Front
- Back
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What is a community? |
Assemblage of populations of various species that live close enough for potential interaction. |
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Community interactions can either ______, _________ or _____________ on the species involved. |
Help; harm; have no effect. Positive, negative, or no effect on fitness. |
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What are relationships between species in a community called, and what are some examples? |
Interspecific interactions. Examples are competition, predation, parasitism, and herbivory. |
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When does interspecific competition occur? |
When species compete for a resource in short supply. (-/-) |
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What is an ecological niche and what are the two types? |
The total of a species use of biotic and abiotic resources. 1) Fundamental niche: potentially occupied by species 2) Realized niche: niche actually occupied by species Due to competition, realized niche is usually smaller than fundamental niche. |
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What is the competitive exclusion principle? What leads to competitive exclusion, and why does this happen? |
No two species can coexist if they share the same ecological niche. Strong competition will lead to competitive exclusion and local elimination of a competing species, and this is a result of asymmetric competition. |
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What is niche differentiation and what does it include? |
Niche differentiation (also known as resource partitioning) is the differentiation of ecological niches, enabling similar species to coexist within a community. It includes spatial partitioning, temporal partitioning, and character displacement.
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What are two types of resource partitioning and give an example! |
1) Spatial partitioning - DIfferent lizard species rest on different branches upon the same trees. 2) Temporal partitioning - Common spiny mouse and golden spiny mouse are both nocturnal, but in places where they co-exist, golden will become diurnal. |
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What is character displacement? |
A tendency for characteristics to be more divergent in sympatric populations of two species, than in allopatric populations of the same species. |
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What are the three types of consumption? |
(+/-): Predation, herbivory, parasitism. |
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What are two types of defensive adaptations that prey can display? |
Constitutive (always there) or inducible. |
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What are examples of defensive adaptations that prey can display? |
Behavioural defenses: fleeing, hiding, forming herds, alarm calls Morphological defenses: spines, hooves Cryptic coloration/camouflage: (ex sea dragon or canyon tree frog) Aposematic coloration: Animals with toxins emit color warnings (ex ring necked snake). Mimicry. |
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What are the two types of mimicry? |
1) Batesian: harmless species mimics a harmful/unpalatable one 2) Mullerian mimicry: two or more unpalatable species resemble each other |
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What is an example of parasite and human co-evolution? |
Plasmodium causes malaria in humans. Humans with the HLA-B53 allele is able to beat malarial infections, however plasmodium is starting to evolve strains that counters HLA-B53. |
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Why don't herbivores eat all available food on the planet? |
1) Top down control (predation) 2) Bottom up control (nitrogen limitation) 3) Plant defenses |
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What are the three interspecific interactions that make up symbiosis? |
1) Parasitism (+/-): endoparasites, ectoparasites 2) Mutualism (+/+): obligate (one cannot live without the other, fungus and alga) or facultative (can live alone, ants and aphids) 3) Commensalism (+/0) |
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What is facilitation? |
(+/+) or (0/+). Interaction in which one species has a position affect on other species WITHOUT intimate and direct contact |
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What is allelopathy? |
Chemical inhabition of one species by another. |
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Two fundamental features of community structure are ________ and __________. |
Species diversity; feeding relationships (trophic structure - aka conceptualization of feeding relationships). |
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What are the two components of species diversity? |
Species richness (# of different species in the community), and relative abundance (proportion each species represents of all individuals in community). |
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What are four ways of calculating species diversity? |
1) Shannon diversity index (H). 2) Simpson diversity index (D). These two take into account evenness and species diversity. The more even, the higher diversity score is given. Evenness is D/Dmax, up to a max of 1. 3) Rank abundance plots - the longest curve and smallest slope is the most diverse. 4) Species accumulation curves - repeated sampling of a type of organism in a certain place. x: # of samples, y: number of species. Curve steep at beginning, slows down cause harder to find new species. |
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What are two ways that a species can have a very large impact on the community structure? |
1) Dominant species 2) Keystone species |
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What do you know about dominant species? |
They are the most abundant species, or have the highest biomass/basal area. They CAN exert powerful control over other species, for example sugar maples impact shading and soil nutrient availability. They are dominant because they are superior, can evade predation, and are usually plants. |
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What are keystone species? |
They are species that exert influence disproportionate to their abundance within a community. |
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What are the three types of keystone species, and give an example! |
1) Keystone predator: sea otters (eats sea urchins that eat kelp, which is an important habitat for others), pisaster (eats mussels that would otherwise grow and stop other species from establishing themselves. 2) Keystone prey: Pacific salmon (is eaten by a lot of diverse species, and help act as fertilizer when they die). 3) Keystone modifier/ecosystem engineers: armadillo burrows (are used by ocelots, foxes, birds); beaver dams (help filter water, act as habitat for other wildlife); wolves in Yellowstone park |
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What is a trophic structure, and what links them? |
Feeding relationships between organisms in a community. Food chains link trophic levels from producers to top carnivores. Many interacting chains is called a food web. |
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Normally more diversity = more ____________. |
Functional redundancy. |
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What is bottom-up and top-down control? |
Two methods of COMMUNITY structure control. 1) Bottom-up: unidirectional influence from lower to higher trophic levels, with basal resources determining structure 2) Top-down or trophic cascade: control comes from above! They usually work together in a combo! Ex. abundance of clovers increase rabbit abundance. Wolves notice increase... and drives rabbit abundance back down! |
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How can we manage community structures? |
Use biomanipulation - addition or removal of species to alter ecosystem! We can use this to help restore polluted communities. It will depend on # of trophic levels, and need to understand each community's dynamics. |
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Communities have a biological structure (the mix of species and interactions among them). They also have a physical structure, reflecting ___________ and ___________ factors. |
Abiotic (such as water depth) and biotic (such as spatial arrangement of trees) factors.
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What is zonation? |
Change in community structure across a landscape. They are very often associated with a gradient in an abiotic factor - example is moisture or elevation). Zonation is caused by both physical constraints (tolerance) and interspecific interactions. Aquatic zonation: water flow, temp, salinity gradients. |
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What are the two zonation boundaries? |
1) Environmental tolerance. 2) Competitive exclusion/ability. |
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What is a disturbance? |
An event that changes a community by removing organisms or altering resource availability. Disturbances reset succession and promote diversity! |
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What are the two factors of disturbance, and what do you know about them? |
Type, frequency, severity. These three factors are predictable in most communities and define a disturbance regime. |
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What is the Intermediate Disturbance Hypothesis (IDH) and explain the graph. |
We know that communities have to experience their natural disturbance regime. One hypothesis is that moderate levels of disturbance is best for species diversity than small or large level disturbances. x: index of disturbance, y: # of taxa low disturbance: competitive species survive (K-selected) moderate/intermediate: both survive high disturbance: better colonists survive, r-selected |
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Why is IDH on its way out? |
Small and large disturbances are still important. Small: creates patches of habitats like vernal pools. Big: certain areas require large disturbances such as delta lakes requiring flooding |
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What do we know about past ecologists and beliefs of community structure and equilibrium? |
Clements believed that communities were in a state of equilibrium, and was predictable and stable - species behave as groups in response to environmental gradients. He thought it was all about the biotic interactions and climate. However, if communities are predictable, then every community should be made up of the same group of species - not true!). Gleason believed that it was random and depends on who gets there first. He was closer to being right! Chance and history are important in community structures. We now know that communities constantly change due to disturbances - nonequilibrium model. |
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In terrestrial communities, ecologists often classify them based on their _______________. In marine communities... |
Dominant growth forms due to their impact on physical structure. Marine communities use abiotic features mainly to define physical structure. |
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What is vertical stratification? |
A physical framework in which different animals are adapted to live. |
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What are the 5 layers of terrestrial vertical stratification? |
Growth form determines the # of layers: Canopy: top most layer where most photosynthesis occurs. If open, lots of light in the lower layers - well-developed understory and shrub strata. Understory: tall shrubs, small trees Shrub layer: tall shrubs Herb layer: grasses, mosses, etc. Depends on light and soil traits, exposure and slope position. Forest floor: decomposition occurs. |
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What are the layers in the vertical strata of aquatic systems? |
Strata is largely determined by light penetration, then temp and O2. From the top: Epilimnion, Metalimnion, hypolimnion. There's also bottom sediments: benthic zone, upper photoic zone (with phyotosynth and phytoplankton, and deeper waters (aphotic zone). |
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What is succession and its two types? |
Predictable, directional change in species composition over time. Primary and secondary. |
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What are the two types of deterministic hypotheses regarding the processes driving succession? |
1) Monoclimax hypothesis: there is one climax stage which is in equilibrium, for each climate 2) polyclimax hypothesis: similar climates support different climate states, depending on substrate |
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The Initial Floristic Composition hypothesis says: |
The IFC says that succession is partly indeterminate (random) and depends on which species comes first. |
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Early arriving species can ___________ later-coming species. |
1) Facilitate - pioneers modify environment to make it more suitable for later species, while making the site less favourable to themselves. More common in primary successions. 2) Inhibit - common in secondary succession. There is a "priority effect", first comers holds the site. Pioneers make the site less suitable for later species and themselves. Short-lived species will eventually give way to long-lived ones, which may be present at the onset but are surpressed until the colonizers die.
3) Tolerate - later species are able to invade due to tolerancing a lower level of resources. More common in secondary succession. |
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What is the resource-ratio hypothesis? |
Theory that succession is due to altered relative competitive abilities of species as a result of shifts in available resources over time. Nutrients become more available during succession as light becomes less available. Altered ratios of these resources affect species performance and competitive ability. |
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What are alternative stable states? |
Outcomes of succession that involve different configurations of a community than formerly present. The ecosystem can exist under many states. This is connected to resistance (ability to stay unchanged) and resilience (ability to resist damage and recover) in communities. |
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What is niche packing? |
Pattern of the number and relationships (including overlap) among niches of co-occuring species in a community. |
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During succession, species richness is the net balance of ___________ and ______________. These also change __________ niches. |
Colonization (which increases richness) and replacement (which decreases richness). These species-species interactions also change realized niches. |
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Life history affects the rate of replacement. What are the two factors of life history? |
Growth rate and longevity. Example: Long-living species have low growth rates due to resources limitation, so low replacement as well. |
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Which two things prevent competitive exclusion? |
Changing resource availability and disturbance. |
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If the population is kept below carrying capacity, and disturbances occur, |
more species can co-exist! |
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What happened when we surpressed natural fires in national parks? |
We prevented a natural disturbance regime - which is bad because then catastrophic fires occur, and lack of fire also limits some natural species. Now we do controlled burns. |
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What is an edge? |
Place where different communities meet. |
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What are the two types of edges? |
Inherent edge: natural present and stable. This is due to long-term natural elements. Induced edge: transitory, either natural disasters or human activity. These undergo succession. |
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What is a border? |
Region where edges of two patches meet. |
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What is an ecotone? |
Wide borders that act as a transition zone between patches. |
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What is an edge affect? |
Response of communities or individuals to environmental conditions present at an edge. Inherent: likely increases diversity. |
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What are interior species? |
Species that require the conditions of interior habitats: edge:interior ratio! Humans are reducing interior habitats. |
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Why do we study island biogeography? |
It offers good insights into habitat patches and can be applied to many different fragmented habitats. It is important to remember that islands are terrestrial land surrounded by water, and habitat patches are surrounded by other land habitats. |
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The number of species on an island depends on _________ and ___________. |
Immigration and extinction. |
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What effect does island sizes have on extinction and immigration rates? |
x: # of species y: rate Immigration: -greater rate with large islands Extinction/extirpation: -greater rate with small islands |
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What effect does nearness to mainland have on extinction and immigration rates? |
Immigration: -higher when close to mainland Extinction: -slight changes but similar to large/small islands. |
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What are some things that island biogeography does not take into account? |
We call it the equilibrium theory of island geography. It is only meant to study short-term patterns of diversity, ignores island shape (orientation, % edge, distance to other islands), and species composition (mutualist, etc). |
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What is the LDG? |
Latitudinal diversity gradient - where species richness and diversity is greater in equator, and decreases as latitude increases. |
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Why does LDG exist? |
It is due to climate - which is made up of both seasonality and evapotranspiration. Seasonality is more important though. |
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What is evapotranspiration? |
Sum of evaporation and plant transpiration from land to air. Involves temperature and water. |
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Why does seasonality describe the LDG? |
With higher latitudes, there is more seasonality (changing seasons). Organisms that deal with it have bigger niches which means less species. |
