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it is very nice subject
I agree with Ibrahim, it is a nice subject. Very interesting and well presented. I'm puzzled by the answer to the first review question of Topic 1: "What is a re-created ecosystem in a laboratory environment known as? a. mesocosm, b. simulation, c. microcosm, d. reproduction" "Answer. A) Experimental systems involved in partitioning a part of a natural ecosystem that can be used for experiments, is termed a mesocosm." The Glossary (and the body of the course) states: "microcosm - a re-creation of natural ecosystems entirely in a laboratory environment to be used for experiments." "mesocosm - portion of a natural ecosystem to be used for experiments" I think mesocosm might be the right answer for a different question! Anyway thanks again, I'm looking forward to the rest of the course
components of its physical and geographic environment and available specie.
I agree with Ibrahim, it is a nice subject. Very interesting and well presented. I'm puzzled by the answer to the first review question of Topic 1: "What is a re-created ecosystem in a laboratory environment known as? a. mesocosm, b. simulation, c. microcosm, d. reproduction" "Answer. A) Experimental systems involved in partitioning a part of a natural ecosystem that can be used for experiments, is termed a mesocosm." The Glossary (and the body of the course) states: "microcosm - a re-creation of natural ecosystems entirely in a laboratory environment to be used for experiments." "mesocosm - portion of a natural ecosystem to be used for experiments" I think mesocosm might be the right answer for a different question! Anyway thanks again, I'm looking forward to the rest of the course. Phil
Types of Ecosystems
Life in an ecosystem is often about competition for limited resources, a characteristic of the theory of natural selection. The resources for which organisms compete include organic material from living or previously living organisms, sunlight, and mineral nutrients, which provide the energy for living processes. Other critical factors influencing community dynamics are the components of its physical and geographic environment and available species. These are all important environmental variables that determine which organisms can exist within a particular area.
In 1993, an interesting example of ecosystem dynamics occurred when a rare lung disease struck inhabitants of the southwestern United States. This disease had an alarming rate of fatalities, killing more than half of patients from respiratory failure.
The disease was unknown, and the Centers for Disease Control (CDC), the United States government agency responsible for managing potential epidemics, was brought in to investigate. The cause of the disease, determined within a few weeks by the CDC investigators, was the hantavirus.
The scientists could have learned about the disease earlier had they known to talk with the Navajo healers (American Indians), who lived in the area and who had observed the connection between rainfall and mice populations, thereby predicting the 1993 outbreak.
An ecosystem is a community of living organisms and their interactions with their abiotic (nonliving) environment. Ecosystems can be small, such as the tide pools found near the rocky shores of many oceans, or large, such as the Amazon Rainforest in Brazil. There are three broad categories of ecosystems based on their general environment: freshwater, ocean water, and terrestrial. Within these broad categories are individual ecosystem types based on the organisms present and the type of environmental habitat.
Ocean ecosystems are the most common, comprising 75 percent of the Earth's surface and consist of three basic types: shallow ocean, deep ocean water, and deep ocean surfaces (the low depth areas of the deep oceans). The shallow ocean ecosystems include coral reef ecosystems, and the deep ocean surface is known for large numbers of plankton and krill (small crustaceans) that support it. Although not as diverse as the other two, deep ocean ecosystems contain a wide variety of marine organisms. Such ecosystems exist even at the bottom of the ocean where light is unable to penetrate through the water.
Overall freshwater ecosystems are the rarest, occurring on only 1.8 percent of the Earth's surface. Lakes, rivers, streams, and springs comprise these systems; they are quite diverse, and they support a variety of fish, amphibians, reptiles, insects, phytoplankton, fungi, and bacteria.
Terrestrial ecosystems, also known for their diversity, are grouped into large categories called biomes, such as tropical rain forests, savannas, deserts, coniferous forests, deciduous forests, and tundra. Grouping these ecosystems into just a few biome categories obscures the great diversity of the individual ecosystems within them. For example, Desert ecosystems, like all ecosystems, can vary greatly. The desert in Saguaro National Park, Arizona, in the US, has abundant plant life, while the rocky desert of Boa Vista island, Cape Verde, Africa, is devoid of plant life.
The impact of environmental disturbances caused by human activities is as important as the changes wrought by natural processes. Human agricultural practices, air pollution, acid rain, global deforestation, overfishing, eutrophication, oil spills, and illegal dumping on land and into the ocean are all issues of concern to conservationists.
Equilibrium is the steady state of an ecosystem where all organisms are in balance with their environment and with each other.
In ecology, two parameters are used to measure changes in ecosystems:
The ability of an ecosystem to remain at equilibrium in spite of disturbances is called resistance. The speed at which an ecosystem recovers equilibrium after being disturbed, called its resilience.
Ecosystem resistance and resilience are especially important when considering human impact. The nature of an ecosystem may change to such a degree that it can lose its resilience entirely. This process can lead to the complete destruction or irreversible altering of the ecosystem.
Food Chains and Food Webs
In ecology, a food chain is a linear sequence of organisms through which nutrients and energy pass: The bottom of the food chain consists of photosynthetic organisms, which are called primary producers. The organisms that consume the primary producers are herbivores: the primary consumers. Secondary consumers are usually carnivores that eat primary consumers. Tertiary consumers are carnivores that eat other carnivores. There is a single path through the chain. Each organism in a food chain occupies what is called a trophic level. Depending on their role as producers or consumers, species or groups of species can be assigned to various trophic levels.
One major factor that limits the length of food chains is energy. Energy is lost as heat between each trophic level due to the second law of thermodynamics. Thus, after a limited number of trophic energy transfers, the amount of energy remaining in the food chain may not be great enough to support viable populations at yet a higher trophic level.
The loss of energy between trophic levels is illustrated by the pioneering studies of Howard T. Odum in the Silver Springs, Florida, ecosystem in the 1940s. The primary producers generated 20,819 kcal/m2/yr (kilocalories per square meter per year), the primary consumers generated 3368 kcal/m2/yr, the secondary consumers generated 383 kcal/m2/yr, and the tertiary consumers only generated 21 kcal/m2/yr. Thus, there is little energy remaining for another level of consumers in this ecosystem.
Even when all organisms are grouped into appropriate trophic levels, some of these organisms can feed on species from more than one trophic level. Therefore, the linear model of ecosystems, the food chain, is not completely descriptive of ecosystem structure. A holistic model - which accounts for all species interactions - is a more accurate and descriptive model for ecosystems. A food web is a graphic representation of a holistic, non-linear web of primary producers, primary consumers, and higher-level consumers.
A comparison of the two types of structural ecosystem models shows strength in both.
Food chains are more flexible for analytical modeling, are easier to follow, and are easier to experiment with, whereas food web models more accurately represent ecosystem structure and dynamics, and data can be directly used as input for simulation modeling.
Two general types of food webs are often shown interacting within a single ecosystem. A grazing food web has plants or other photosynthetic organisms at its base, followed by herbivores and various carnivores. A detrital food web consists of a base of organisms that feed on decaying organic matter, called decomposers or detritivores. These organisms are usually bacteria or fungi that recycle organic material back into the biotic part of the ecosystem as they themselves are consumed by other organisms.
As all ecosystems require a method to recycle material from dead organisms, most grazing food webs have an associated detrital food web.
The three-spines stickleback (Gasterosteus aculeatus) is a freshwater fish that evolved from a saltwater fish to live in freshwater lakes about 10,000 years ago, which is considered a recent development in evolutionary time. Over the last 10,000 years, these freshwater fish then became isolated from each other in different lakes.
Depending on which lake population was studied, findings showed that these sticklebacks then either remained as one species or evolved into two species. The divergence of species was made possible by their use of different areas of the pond for feeding called micro niches.
Dr. Harmon and his team from the University of Idaho, created artificial pond microcosms in 250-gallon tanks and added muck from freshwater ponds as a source of zooplankton and other invertebrates to sustain the fish. In different tanks they introduced one species of stickleback from either a single-species or double-species lake.
It turned out that the water from the tanks with two-species fish contained larger particles of dissolved organic carbon (DOC) than water with single-species fish. This increase in DOC blocked the sunlight and prevented algal blooming. Water from the single-species tank contained smaller DOC particles, allowing more sunlight penetration to fuel the algal blooms.
This change in the environment, which is due to the different feeding habits of the stickleback species in each lake type, probably has a great impact on the survival of other species in these ecosystems, especially other photosynthetic organisms.
Experimentation and Modelling
A holistic ecosystem model attempts to quantify the composition, interaction, and dynamics of entire ecosystems; it is the most representative of the ecosystem in its natural state. A food web is an example of a holistic ecosystem model. However, this type of study is limited by time and expense. Ecosystems are characterized using a variety of research methodologies. Some ecologists study ecosystems using controlled experimental systems, while some study entire ecosystems in their natural state.
These systems usually involve either partitioning a part of a natural ecosystem that can be used for experiments, termed a mesocosm, or by re-creating an ecosystem entirely in an indoor or outdoor laboratory environment, which is referred to as a microcosm.
A major limitation to these approaches is that removing individual organisms from their natural ecosystem or altering a natural ecosystem through partitioning may change the dynamics of the ecosystem. These changes are often due to differences in species numbers and diversity and also to environment alterations caused by partitioning (mesocosm) or re-creating (microcosm) the natural habitat.
Thus, these types of experiments are not totally predictive of changes that would occur in the ecosystem from which they were gathered.
Conceptual models are useful for describing ecosystem structure and dynamics and for demonstrating the relationships between different organisms in a community and their environment. The organisms and their resources are grouped into specific compartments with arrows showing the relationship and transfer of energy or nutrients between them. Thus, thus these diagrams are sometimes called compartment models.
In a terrestrial ecosystem near a coal deposit, carbon will be available to the plants as carbon dioxide gas in a short-term period, not from the carbon-rich coal itself.
However, over a longer period, micro organisms capable of digesting coal will incorporate its carbon or release it as natural gas, changing this unavailable organic source into an available one. This conversion is greatly accelerated by the combustion of fossil fuels by humans, which releases large amounts of carbon dioxide into the atmosphere. This is thought to be a major factor in the rise of the atmospheric carbon dioxide levels in the industrial age.
The carbon dioxide released from burning fossil fuels is produced faster than photosynthetic organisms can use it. This process is intensified by the reduction of photosynthetic trees because of worldwide deforestation. Most scientists agree that high atmospheric carbon dioxide is a major cause of global climate change.
Analytical and Simulation Models
Analytical models often use simple, linear components of ecosystems, such as food chains. However they are known to be complex mathematically; therefore, they require a significant amount of mathematical knowledge and expertise.
Although analytical models have great potential, their simplification of complex ecosystems limits their accuracy. Ecosystems are dynamic entities and subject to a variety of abiotic and biotic disturbances caused by natural forces and/or human activity.
Simulation models that use computer programs are better able to deal with the complexities of ecosystem structure.
A recent development in simulation modeling uses supercomputers to create and run individual based simulations, which accounts for the behavior of individual organisms and their effects on the ecosystem as a whole. These simulations are considered to be the most accurate and predictive of the complex responses of ecosystems to disturbances.
As most ecosystems are subject to periodic disturbances and are often in a state of change,they are usually either moving toward or away from their equilibrium state. There are many of these equilibrium states among the various components of an ecosystem, which affects the ecosystem overall.Furthermore, as humans have the ability to greatly and rapidly alter the species content and habitat of an ecosystem, the need for predictive models that enable understanding of how ecosystems respond to these changes becomes more crucial.
What is a re-created ecosystem in a laboratory environment known as?
a. mesocosm, b. simulation, c. microcosm, d. reproduction
Answer. A) Experimental systems involved in partitioning a part of a natural ecosystem that can be used for experiments, is termed a mesocosm.
What term describes the use of mathematical equations in the modeling of linear aspects of ecosystems?
a. analytical modelling, b. simulation modelling, c. conceptual modeling
d. individual-based modelling
Answer A) Analytical models often use simple, linear components of ecosystems, such as food chains. However they are known to be complex mathematically; therefore, they require a significant amount of mathematical knowledge and expertise.
acid rain corrosive rain caused by rainwater falling to the ground through sulfur dioxide gas, turning it into weak sulfuric acid; can damage structures and ecosystems
analytical model ecosystem model that is created with mathematical formulas to predict the effects of environmental disturbances on ecosystem structure and dynamics
apex consumer organism at the top of the food chain
chemoautotroph organism capable of synthesizing its own food using energy from inorganic molecules
conceptual model (also, compartment models) ecosystem model that consists of flow charts that show the interactions of different compartments of the living and non-living components of the ecosystem
detrital food web type of food web in which the primary consumers consist of decomposers; these are often associated with grazing food webs within the same ecosystem
ecosystem dynamics study of the changes in ecosystem structure caused by changes in the environment or internal forces
ecosystem community of living organisms and their interactions with their abiotic environment
equilibrium steady state of an ecosystem where all organisms are in balance with their environment and each other
food chain linear representation of a chain of primary producers, primary consumers, and higher- level consumers used to describe ecosystem structure and dynamics
food web graphic representation of a holistic, non-linear web of primary producers, primary consumers, and higher-level consumers used to describe ecosystem structure and dynamics
grazing food web type of food web in which the primary producers are either plants on land or phytoplankton in the water; often associated with a detrital food web within the same ecosystem
holistic ecosystem model study that attempts to quantify the composition, interactions, and dynamics of entire ecosystems; often limited by economic and logistical difficulties, depending on the ecosystem
mesocosm portion of a natural ecosystem to be used for experiments
microcosm re-creation of natural ecosystems entirely in a laboratory environment to be used for experiments
resilience (ecological) speed at which an ecosystem recovers equilibrium after being disturbed
resistance (ecological) ability of an ecosystem to remain at equilibrium in spite of disturbances
simulation model ecosystem model that is created with computer programs to holistically model ecosystems and to predict the effects of environmental disturbances on ecosystem structure and dynamics
trophic level position of a species or group of species in a food chain or a food web
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