What Is An Ecosystem

What Is An Ecosystem  An ecosystem is a natural unit consisting of all plants, animals and micro-organisms (biotic factors) in an area functioning together with all of the non-living physical (abiotic) factors of the environment.

 Aquatic systems are those that contain plants and animals that predominantly Examples Of Ecosystem depend on Include: a significant amount of water to be present for at least part of the year.

CHAPARRAL • A dense, impenetrable thicket of shrubs or dwarf trees. A vegetation type dominated by shrubs and small trees, especially evergreen trees with thick, small leaves.

CORAL REEF A large underwater formation created from the calcium carbonate skeletons of coral animals; can also refer to the animals living on and near the coral reef.

DESERT  A desert is a landscape form or region that receives very little precipitation. Deserts can be defined as areas that receive an average annual precipitation of less than 250 mm (10 in), or as areas in which more water is lost than falls as precipitation.In the Köppen climate classification system, deserts are classed as BWh (hot desert) or BWk (temperate desert).

GREATER YELLOWSTONE ECOSYSTEM  Greater Yellowstone is the last remaining large, nearly intact ecosystem in the northern temperate zone of the Earth and is partly located in Yellowstone National Park. Conflict over management has been controversial, and the area is a flagship site among conservation groups that promote ecosystem management. The Greater Yellow Ecosystem (GYE) is one of the world's foremost natural laboratories in landscape ecology and geology and is a worldrenowned recreational site. It is also home to the animals of Yellowstone.

HUMAN ECOSYSTEM  Human ecosystems are complex cybernetic systems that are increasingly being used by ecological anthropologists and other scholars to examine the ecological aspects of human communities in a way that integrates multiple factors as economics, socio-political organization, psychological factors, and physical factors related to the environment.

LARGE MARINE ECOSYSTEM  Any marine environment, from pond to ocean, in which plants and animals interact with the chemical and physical features on the environment.

LITTORAL ZONE  The region of the shore of a lake or sea or ocean / the shore of a sea or ocean.

MARINE ECOSYSTEM  Any marine environment, from pond to ocean, in which plants and animals interact with the chemical and physical features of the environment.

RAINFOREST  Mixed rainforest or mixed forest) is a rainforest classification where eucalypt forest grows in combination with Cool Temperate rainforest species.

SAVANNA • A tropical or subtropical grassland containing scattered trees and droughtresistant undergrowth.

SUBSURFACE LITHOAUTOTROPHIC MICROBIAL ECOSYSTEM  A minute life form; a microorganism, especially a bacterium that causes disease.

TAIGA • A moist sub arctic coniferous forest that begins where the tundra ends and is dominated by spruces and firs.

TUNDRA • A type of ecosystem dominated by lichens, mosses, grasses, and woody plants. Tundra is found at high latitudes (arctic tundra) and high altitudes • A treeless plain characteristic of the arctic and sub arctic regions.

URBAN ECOSYSTEM  Is the subfield of ecology which deals with the interaction of plants, animals and humans with each other and with their environment in urban or urbanizing settings. Analysis of urban settings in the context of ecosystem ecology (looking at the cycling of matter and the flow of energy through the ecosystem) can result in healthier, better managed communities. Studying the factors which allow wild plants and animals to survive (and sometimes thrive) in built environments can also create more livable spaces. It allows people to adapt to the changing environment while preserving the resources.

• The diagram above shows how both energy and inorganic Energy Flow Through the Ecosystem nutrients flow through the ecosystem. The dark arrows represent the movement of this energy . The movement of the inorganic nutrients is represented by the open arrows.

To summarize: In the flow of energy and inorganic nutrients through the ecosystem, a few generalizations can be made: 1. 2. 3. 4. 5.

The ultimate source of energy (for most ecosystems) is the sun The ultimate fate of energy in ecosystems is for it to be lost as heat. Energy and nutrients are passed from organism to organism through the food chain as one organism eats another. Decomposers remove the last energy from the remains of organisms. Inorganic nutrients are cycled, energy is not.

Food Chains and Webs: • A food chain is the path of food from a given final consumer back to a producer. For instance, a typical food chain in a field ecosystem might be: grass

grasshopper

mouse

snake

hawk

The real world, of course, is more complicated than a simple food chain. While many organisms do specialize in their diets (anteaters come to mind as a specialist), other organisms do not. Hawks don't limit their diets to snakes; snakes eat things other than mice. Mouse eats grass as well as grasshoppers, and so on.

A more realistic depiction of who eats whom is called a food, web; an example is shown below:

 It is when we have a picture of a food web in front of us that the definition of food chain makes more sense. We can now see that a food web consists of interlocking food chains, and that the only way to untangle the chains is to trace back along a given food chain to its source.

• The food webs you see here are grazing food chains since at their base are producers which the herbivores then graze on. While grazing food chains are important, in nature they are outnumbered by detritus-based food chains. In detritus-based food chains, decomposers are at the base of the food chain, and sustain the carnivores which feed on them. In terms of the weight (or biomass) of animals in many ecosystems, more of their body mass can be traced back to detritus than to living producers.

PYRAMIDS • The concept biomass important.

It is a general principle that the further removed a trophic level is from its source (detritus or producer), the less biomass it will contain (biomass here would refer to the combined weight of all the organisms in the trophic level).

of is

This Reduction In Biomass Occurs For Several Reasons: 1. Not everything in the lower levels gets eaten. 2. Not everything that is eaten is digested. 3. energy is always being lost as heat.

• It is important to remember that the decrease in number is best detected in terms or biomass. Numbers of organisms are unreliable in this case because of the great variation in the biomass of individual organisms. • A generalization exists among ecologists that on average, about 10% of the energy available in one trophic level will be passed on to the next; this is primarily due to the 3 reasons given above. Therefore, it is also reasonable to assume that in terms of biomass, each trophic level will weigh only about 10% of the level below it, and 10x as much as the level above it.

Roles Of Organisms In An Ecosystem • Organisms can be either producers or consumers in terms of energy flow through an ecosystem. • Producers convert energy from the environment into carbon bonds, such as those found in the sugar glucose. Plants are the most obvious examples of producers; plants take energy from sunlight and use it to convert carbon dioxide into glucose (or other sugars). Algae and cyanobacteria are also photosynthetic producers, like plants. Other producers include bacteria living around deep-sea vents. These bacteria take energy from chemicals coming from the Earth's interior and use it to make sugars. Other bacteria living deep underground can also produce sugars from such inorganic sources. Another word for producers is autotrophs.

Consumers get their energy from the carbon bonds made by the producers. Another word for a consumer is a heterotroph. Based on what they eat, we can distinguish between 4 types of heterotrophs: consumer

trophic level

food source

Herbivores

primary

plants

Carnivores

secondary or higher

animals

Omnivores

all levels

plants & animals

Detritivores

-----------

detritus

• A trophic level refers to position in the food chain. • Autotrophs are at the base. eat autotrophs are called primary consumers.

the organisms Organisms that herbivores or

• An organism that eats herbivores is a carnivore and a secondary consumer. • A carnivore which eats a carnivore which eats a herbivore is a tertiary consumer, and so on. • It is important to note that many animals do not specialize in their diets. • Omnivores (such as humans) eat both animals and plants. Further, except for some specialists, most carnivores don't limit their diet to organisms of only one trophic level. Frogs, for instance, don't discriminate between herbivorous and carnivorous bugs in their diet. If it's the right size, and moving at the right distance, chances are the frog will eat it. It's not as if the frog has brain cells to waste wondering if it's going to mess up the food chain by being a secondary consumer one minute and a quaternary consumer the next.

Components of an Ecosystem ABIOTIC COMPONENTS

BIOTIC COMPONENTS

Sunlight

Primary producers

Temperature

Herbivores

Precipitation

Carnivores

Water or moisture

Omnivores

Soil or water chemistry (e.g., P, NH4+)

Detritivores

etc.

etc.

All of these vary over space/time

Processes of Ecosystems • This figure with the plants, zebra, lion, and so forth illustrates the two main ideas about how ecosystems function: ecosystems have energy flows and ecosystems cycle materials. These two processes are linked, but they are not quite the same (see Figure 1).

• Figure 1. Energy flows and material cycles. • Energy enters the biological system as light energy, or photons, is transformed into chemical energy in organic molecules by cellular processes including photosynthesis and respiration, and ultimately is converted to heat energy. This energy is dissipated, meaning it is lost to the system as heat; once it is lost it cannot be recycled. Without the continued input of solar energy, biological systems would quickly shut down. Thus the earth is an open system with respect to energy.28

• During decomposition these materials are not destroyed or lost, so the earth is a closed system with respect to elements (with the exception of a meteorite entering the system now and then). The elements are cycled endlessly between their biotic and abiotic states within ecosystems. Those elements whose supply tends to limit biological activity are called nutrients.

The Transformation of Energy • The transformations of energy in an ecosystem begin first with the input of energy from the sun. Energy from the sun is captured by the process of photosynthesis. Carbon dioxide is combined with hydrogen (derived from the splitting of water molecules) to produce carbohydrates (CHO). Energy is stored in the high energy bonds of adenosine triphosphate, or ATP (see lecture on photosynthesis).

• Figure 2 portrays a simple food chain, in which energy from the sun, captured by plant photosynthesis, flows from trophic level to trophic level via the food chain. A trophic level is composed of organisms that make a living in the same way, that is they are all primary producers (plants), primary consumers (herbivores) or secondary consumers (carnivores). Dead tissue and waste products are produced at all levels. Scavengers, detritivores, and decomposers collectively account for the use of all such "waste" -consumers of carcasses and fallen leaves may be other animals, such as crows and beetles, but ultimately it is the microbes that finish the job of decomposition. Not surprisingly, the amount of primary production varies a great deal from place to place, due to differences in the amount of solar radiation and the availability of nutrients and water. • For reasons that we will explore more fully in subsequent lectures, energy transfer through the food chain is inefficient. This means that less energy is available at the herbivore level than at the primary producer level, less yet at the carnivore level, and so on. The result is a pyramid of energy, with important implications for understanding the quantity of life that can be supported.

• Usually when we think of food chains we visualize green plants, herbivores, and so on. These are referred to as grazer food chains, because living plants are directly consumed. In many circumstances the principal energy input is not green plants but dead organic matter. These are called detritus food chains. Examples include the forest floor or a woodland stream in a forested area, a salt marsh, and most obviously, the ocean floor in very deep areas where all sunlight is extinguished 1000's of meters above. In subsequent lectures we shall return to these important issues concerning energy flow. • Finally, although we have been talking about food chains, in reality the organization of biological systems is much more complicated than can be represented by a simple "chain". There are many food links and chains in an ecosystem, and we refer to all of these linkages as a food web. Food webs can be very complicated, where it appears that "everything is connected to everything else", and it is important to understand what are the most important linkages in any particular food web.

Controls on Ecosystem Function • There are two dominant theories of the control of ecosystems. The first, called bottom-up control, states that it is the nutrient supply to the primary producers that ultimately controls how ecosystems function. If the nutrient supply is increased, the resulting increase in production of autotrophs is propagated through the food web and all of the other trophic levels will respond to the increased availability of food (energy and materials will cycle faster). • The second theory, called top-down control, states that predation and grazing by higher trophic levels on lower trophic levels ultimately controls ecosystem function. For example, if you have an increase in predators, that increase will result in fewer grazers, and that decrease in grazers will result in turn in more primary producers because fewer of them are being eaten by the grazers. Thus the control of population numbers and overall productivity "cascades" from the top levels of the food chain down to the bottom trophic levels.

The Geography of Ecosystems • There are many different ecosystems: rain forests and tundra, coral reefs and ponds, grasslands and deserts. Climate differences from place to place largely determine the types of ecosystems we see. How terrestrial ecosystems appear to us is influenced mainly by the dominant vegetation. • The word "biome" is used to describe a major vegetation type such as tropical rain forest, grassland, tundra, etc., extending over a large geographic area. It is never used for aquatic systems, such as ponds or coral reefs. It always refers to a vegetation category that is dominant over a very large geographic scale, and so is somewhat broader than an ecosystem.

Figure 3: The distribution of biomes.

A schematic view of the earth shows that, complicated though climate may be, many aspects are predictable (Figure 4). High solar energy striking near the equator ensures nearly constant high temperatures and high rates of evaporation and plant transpiration. Warm air rises, cools, and sheds its moisture, creating just the conditions for a tropical rain forest. Contrast the stable temperature but varying rainfall of a site in Panama with the relatively constant precipitation but seasonally changing temperature of a site in New York State. Every location has a rainfall- temperature graph that is typical of a broader region.

• •

Figure 4. Climate patterns affect biome distributions. We can draw upon plant physiology to know that certain plants are distinctive of certain climates, creating the vegetation appearance that we call biomes. Note how well the distribution of biomes plots on the distribution of climates (Figure 5). Note also that some climates are impossible, at least on our planet. High precipitation is not possible at low temperatures -- there is not enough solar energy to power the water cycle, and most water is frozen and thus biologically unavailable throughout the year. The high tundra is as much a desert as is the Sahara.

What are the 2 kinds of ecosystem? • NATURAL ECOSYSTEM - ecosystem made naturally & occurred naturally with no influence by man ( ex. forest, backyard) • MAN-MADE ECOSYSTEM - ecosystem with the influence of man, this is usually controlled ( ex. fishpond, zoo)

The Ten Global Threats to Ecosystem Viability 1) 2) 3) 4) 5) 6)

Loss of crop & grazing land Depletion of world's tropical forests Extinction of species Rapid population growth Shortage of fresh water resources Over fishing, habitat destruction, & pollution in the marine environment. 7) Threats to human health 8) Climate change 9) Acid rain 10) Pressures on energy resources

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