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50 Cards in this Set
- Front
- Back
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community
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community is a group of species that occupy a given area, interacting either directly or indirectly
~A spatial (空間的)concept Or, Community is a subset of species. A community has attributes that differ from those of its components –Number of species –Relative abundance of species –Nature of species interactions –Physical structure |
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Species richness (S)
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Species richness (S) is the count of the number of species occurring within the community
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Relative abundance
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Relative abundance represents the percentage each species contributes to the total number of individuals of all species
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How to compare the patterns of species richness and relative abundance?
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A common method for comparing patterns of species richness and abundance between communities is to plot the relative abundance of each species against rank (called a rank-abundance diagram)
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Species evenness
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Species evenness indicates the distribution of species richness.
A community with a greater species evenness would have a more gradual slope of the rank-abundance curve |
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Diversity indexes
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Diversity indexes provide a way to quantify the relationship between species number and relative abundance
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Dominant species
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When a single or few species predominate within a community, these species are referred to as dominants.
Dominant species are usually defined separately for different taxonomic (分類的) or functional groups of organisms within the community. Dominant species are typically the dominant competitors under the prevailing (major/ common) environmental conditions. |
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keystone species
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A keystone species has a disproportionate (不均衡的) impact on the community relative to its abundance.
The removal of a keystone species initiates changes in the community structure and often results in significant loss of diversity |
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Food Chain
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A food chain is a descriptive diagram that represents the flow of energy from prey (the consumed) to predator (the consumer)
The food chain is a Model. |
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Food webs
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Feeding relationships in nature are more complex (than food chains)
Food webs are highly interwoven, with linkages representing a wide variety of species interactions |
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food web structure
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–Links are the arrows from one species to another and indicate the consumed and the consumer
–Basal species feed on no other species but are fed upon by others –Intermediate species feed on other species, and they themselves are prey of other species –Top predators prey on intermediate and basal species |
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Trophic 營養 levels
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Ecologists often simplify the representation of food webs by grouping species into broader categories that represent general feeding groups (trophic levels) based on the source from which they derive energy
–Autotrophs or primary producers –Heterotrophs or secondary producers –Herbivore –Carnivore –Omnivore |
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Guilds (互助性的)團體
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Guilds are groups of species that exploit 剝削a common resource in a similar fashion
Eg. Nectar-feeding (花蜜) or seed-eating birds |
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functional type
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The functional type defines a group of species based on their common response to the environment
Shade (陰涼處) tolerant versus shade intolerant |
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Communities Have a Characteristic Physical Structure
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The physical structure of a community reflects abiotic and biotic factors
The form and structure of terrestrial (Earth) communities are defined primarily by their vegetation. The physical structure of aquatic communities is defined by features of the abiotic environment. |
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vertical structure
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Every community has an associated vertical structure.
Terrestrial vertical structure is determined by the growth form of plants which controls the vertical gradient of light Aquatic vertical structure is determined largely by light penetration through the water column |
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Terrestrial vertical structure (Different Layers)
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–The upper layer (canopy) is the primary site of energy fixation through photosynthesis
–The understory is situated under the canopy and will only form if enough sunlight can reach these lower layers –The nature of the herb layer depends on various abiotic conditions (e.g., soil moisture) and density of the canopy and understory –The forest floor is where decomposition takes place and nutrients and minerals are recycled |
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Aquatic vertical structure (Different Layers)
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–The photic zone is where the availability of light supports photosynthesis
–The aphotic zone is an area without light –The benthic zone is where decomposition is most active |
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species and community in each layer
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Various types of consumers and decomposers occupy all levels of the community
–Decomposers are typically found in greater abundance in the forest floor and sediment (benthic) layers Interchange takes place among the vertical strata though many highly mobile animals restrict themselves to only a few layers The composition of species in each layer shifts during the day, with season, in response to weather or climate, in response to abiotic conditions (oxygen, light, etc.) |
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Zonation of a salt marsh (濕地) in response to microtopography, water depth, sediment oxygenation, and salinity
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Zonation of a salt marsh (濕地) in response to microtopography, water depth, sediment oxygenation, and salinity
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Intertidal (潮間帶) zonation is determined by tidal action
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Intertidal (潮間帶) zonation is determined by tidal action
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Zonation
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Zonation Is Spatial Change in Community Structure
For example, the changes in biological structure that occur in a hilly forest from hilltop to bottomland. Zonation are common to all environments, aquatic and terrestrial |
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Defining Boundaries between Communities
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How different must two adjacent areas be before we call them separate communities?
–The answer is based on the degree of similarity or difference and can be rather subjective –The distinction between communities is arbitrary (chosen at random), based on the criteria for classification. |
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Broad-scale descriptions
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Broad-scale descriptions are used for landscape community structure.
(For examples, map which seperates different forest by different colors) |
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association
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An association is a type of community with
–Relatively consistent species composition –A uniform, general appearance (physiognomy) –A distribution that is characteristic of a particular habitat |
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Two Contrasting Views of the Community
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Two major views — the difference between the views is the importance of interactions, current and evolutionary, in the structuring of communities
–Organismic concept of communities –Individualistic or continuum concept |
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Individualistic or continuum concept
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The individualistic or continuum concept states that the relationship among coexisting species (species within a community) is due to similarities in their requirements and tolerances, not to strong interactions or common evolutionary history
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Organismic concept of communities
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Communities are integrated units — organismic concept of communities (F. Clements)
In this view, transitions between communities are narrow, with few species in common This view suggests a common evolutionary history and similar fundamental responses and tolerances for the component species |
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global climate change
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Changes include:
The amount of tilt in Earth’s rotation affects the amount of sunlight striking the different parts of the globe. Variations in Earth’s climate have been affecting life and its evolution for millions of years The human species has the ability to alter Earth’s climate |
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Greenhouse gases
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It includes water vapor, carbon dioxide, and ozone.
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Greenhouse effect
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The average surface air temperature of the earth is 30°C higher than it would be without the absorption and reradiation of thermal energy
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atmospheric concentration of CO2
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The atmospheric concentration of CO2 has increased by more than 25 percent over the past 100 years.
Currently, 70 percent of the total CO2 emissions from the burning of fossil fuels come from the developed countries Deforestation is also a major cause |
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Atmospheric CO2 Concentrations Affect CO2 Uptake by Oceans
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Although the oceans have the potential to absorb most atmospheric carbon derived from fossil fuel combustion and deforestation, this does not happen
–Thin layer of warm water floating on a much deeper layer of cold water –Mixing of CO2 does not extend into the deep waters because of the thermocline |
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Plants Respond to Increased Atmospheric CO2
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Elevated atmospheric CO2 affects plants
Direct, short-term effects –CO2 fertilization effect is the increase in the rate of photosynthesis because of higher rates of diffusion of CO2 from the atmosphere into the leaf –Reduction in water loss because plants increase their water-use efficiency Long-term effects –Plant growth and development The enhanced effects of elevated CO2 levels on plant growth may be short-lived –Downregulation results as plants produce less rubisco –More carbon is allocated to roots –Fewer stomata are produced |
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General circulation models GCMs
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General circulation models (GCMs) have been developed to help scientists determine how increasing concentrations of greenhouse gases may influence large-scale patterns of global climate
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What does GCMs suggest now?
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–Predict an increase in the average global temperature and precipitation
–Expect warming to be greatest during the winter months in the northern latitudes –Predict increased variability of climate (e.g., more storms and hurricanes) |
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Aerosols
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Aerosols, small particles suspended in the atmosphere, absorb solar radiation and scatter it back to space reduction in the amount of radiation reaching Earth’s surface
Natural sources of aerosols –Winds blowing dust particles –Sea spray –Biomass burning –Volcanoes Human sources of aerosols –Burning of fossil fuels sulfate particles |
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Changes in Climate Will Affect Ecosystems at Many Levels
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–Physiological and behavioral response of organisms
–Birth, death, growth rates of populations –Relative competitive abilities of species –Community structure –Productivity –Cycling of nutrients |
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research focuses on the response of ...to greenhouse warming
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research focuses on the response of individuals, populations, communities, and ecosystems to greenhouse warming
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The distribution and abundance of animals are directly related to ....
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features of the climate
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Changes in the growth and reproductive rates of species in response to climate change may influence...
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the nature of species interactions and this could alter patterns of zonation and succession
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Vegetation is indirectly affected by climate change, and these indirect effects could cause a significant rise in CO2 emissions from soils
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Vegetation is indirectly affected by climate change, and these indirect effects could cause a significant rise in CO2 emissions from soils
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How do we know the Earth’s climate is changing?
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Direct measures from instruments (instrumental record) and observations of other surface ―weather variables‖
–Land surface –Sea surface –Upper atmosphere |
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Fact about global warming
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The global average surface temperature has increased by 0.74°C since the early 20th century
–Minimum temperatures (0.2°C/decade) are increasing about twice the rate of maximum temperatures (0.1°C/decade) Global ocean heat content has increased significantly since the late 1950s |
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Why is the climate changing?
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May be because instrumentation is located in urban areas that are typically warmer than surrounding rural areas.
Maybe the current warming is still in recovery following the last glacial maximum (18,000 to 20,000 years ago) –IPCC has stated that increase in global average temperature is ―very likely‖ due to observed changes in greenhouse gas concentrations the distribution and abundance of organisms (and their communities and ecosystems) have changed |
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Changing Climate Will Shift the Global Distribution of Ecosystems
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As Earth’s climate has changed in the past, the distribution and abundance of organisms (and their communities and ecosystems) have changed
Tropical rain forest distribution would be reduced by 25 percent under conditions of doubled CO2 A warming of the world’s oceans would alter the potential range of waters in which reef development is possible |
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Global Warming Would Raise Sea Level and Affect Coastal Environments
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Over the past 100 years, sea level has risen.
A sea-level rise will have major effects on coastal ecosystems –Direct inundation of low-lying wetlands and dryland areas –Erosion of shorelines –Increased salinity of estuaries and groundwater –Rising coastal water tables –Increased flooding and storm surges Estuarine and mangrove ecosystems would no longer be able support the coastal fisheries. |
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Climate Change Will Affect Agricultural Production
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The regions suitable for growing these crops (wheat, corn) will change.
Increasing concentrations of CO2 may benefit these crop plants –Cotton yield increased by 60 percent and wheat by more than 10 percent under elevated CO2 and irrigation |
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Climate Change Will Directly Affect Human Health
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Direct
–Increased heat stress, asthma, cardiovascular and respiratory ailments Indirect –Increased incidence of communicable diseases, increased mortality/injury due to increased natural disasters, changes in diet/nutrition The distribution and rates of transmission for various infectious diseases will be influenced by climate patterns |
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Understanding Global Change Requires the Study of Ecology at a Global Scale
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Understanding Global Change Requires the Study of Ecology at a Global Scale
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