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

depend on a significant amount of

water to be present for at least part of

the year.

Examples Of Ecosystem

Include:

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 regionthat receives very little precipitation.Deserts can be defined as areas thatreceive an average annual precipitationof less than 250 mm (10 in), or as areasin which more water is lost than falls asprecipitation.In the Köppen climateclassification system, deserts areclassed as BWh (hot desert) or BWk(temperate desert).

GREATER YELLOWSTONE

ECOSYSTEM

�Greater Yellowstone is the last remaininglarge, nearly intact ecosystem in the northerntemperate zone of the Earth and is partlylocated in Yellowstone National Park.Conflict over management has beencontroversial, and the area is a flagship siteamong conservation groups that promoteecosystem management. The Greater YellowEcosystem (GYE) is one of the world'sforemost natural laboratories in landscapeecology and geology and is a world-renowned recreational site. It is also home tothe 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.

�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 drought-

resistant 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 theinteraction of plants, animals and humans witheach other and with their environment in urban orurbanizing settings. Analysis of urban settings inthe context of ecosystem ecology (looking at thecycling of matter and the flow of energy throughthe ecosystem) can result in healthier, bettermanaged communities. Studying the factors whichallow wild plants and animals to survive (andsometimes thrive) in built environments can alsocreate more livable spaces. It allows people toadapt to the changing environment whilepreserving the resources.

�The dark arrows represent the movement

of this energy .

�The movement of the inorganic nutrients

is represented by the open arrows.

Energy Flow Through the

Ecosystem

• The diagram

above shows

how both

energy and

inorganic

nutrients flow

through the

ecosystem.

To summarize: In the flow of energy and

inorganic nutrients through the ecosystem, a

few generalizations can be made:

1. The ultimate source of energy (for mostecosystems) is the sun

2. The ultimate fate of energy in ecosystems isfor it to be lost as heat.

3. Energy and nutrients are passed fromorganism to organism through the food chainas one organism eats another.

4. Decomposers remove the last energy fromthe remains of organisms.

5. 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 typicalfood 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; snakeseat 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 foodchains since at their base are producers whichthe herbivores then graze on. While grazingfood chains are important, in nature they areoutnumbered by detritus-based food chains. Indetritus-based food chains, decomposers are atthe base of the food chain, and sustain thecarnivores which feed on them. In terms of theweight (or biomass) of animals in manyecosystems, more of their body mass can betraced back to detritus than to living producers.

PYRAMIDS

• The concept of

biomass is

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 thetrophic level).

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 decreasein number is best detected in terms orbiomass. Numbers of organisms areunreliable in this case because of the greatvariation in the biomass of individual

organisms.

• A generalization exists among ecologists thaton average, about 10% of the energyavailable in one trophic level will be passedon to the next; this is primarily due to the 3reasons given above. Therefore, it is alsoreasonable to assume that in terms ofbiomass, each trophic level will weigh onlyabout 10% of the level below it, and 10x asmuch 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 environmentinto carbon bonds, such as those found in thesugar glucose. Plants are the most obviousexamples of producers; plants take energy fromsunlight and use it to convert carbon dioxide intoglucose (or other sugars). Algae and cyanobacteriaare also photosynthetic producers, like plants.Other producers include bacteria living arounddeep-sea vents. These bacteria take energy fromchemicals coming from the Earth's interior and useit to make sugars. Other bacteria living deepunderground can also produce sugars from suchinorganic sources. Another word for producers isautotrophs.

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:

• A trophic level refers to the organismsposition in the food chain.

• Autotrophs are at the base. Organisms thateat autotrophs are called herbivores orprimary consumers.

consumer trophic level food source

Herbivores primary plants

Carnivores secondary or higher animals

Omnivores all levels plants &

animals

Detritivores - - - - - - - - - - - detritus

• An organism that eats herbivores is a carnivoreand a secondary consumer.

• A carnivore which eats a carnivore which eats aherbivore is a tertiary consumer, and so on.

• It is important to note that many animals do notspecialize in their diets.

• Omnivores (such as humans) eat both animals andplants. Further, except for some specialists, mostcarnivores don't limit their diet to organisms ofonly one trophic level. Frogs, for instance, don'tdiscriminate between herbivorous and carnivorousbugs in their diet. If it's the right size, and movingat the right distance, chances are the frog will eatit. It's not as if the frog has brain cells to wastewondering if it's going to mess up the food chainby being a secondary consumer one minute and aquaternary 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 inorganic molecules by cellular processes includingphotosynthesis and respiration, and ultimately isconverted to heat energy. This energy is dissipated,meaning it is lost to the system as heat; once it is lostit cannot be recycled. Without the continued input ofsolar energy, biological systems would quickly shutdown. Thus the earth is an open system with respectto energy.28

• During decomposition these materials are notdestroyed or lost, so the earth is a closedsystem with respect to elements (with theexception of a meteorite entering the systemnow and then). The elements are cycledendlessly between their biotic and abiotic stateswithin ecosystems. Those elements whosesupply tends to limit biological activity are called

nutrients.

The Transformation of

Energy

• The transformations of energyin an ecosystem begin firstwith the input of energy fromthe sun. Energy from the sunis captured by the process ofphotosynthesis. Carbondioxide is combined withhydrogen (derived from thesplitting of water molecules) toproduce carbohydrates (CHO).Energy is stored in the highenergy bonds of adenosinetriphosphate, or ATP (seelecture on photosynthesis).

• Figure 2 portrays a simple food chain, in which energy fromthe sun, captured by plant photosynthesis, flows fromtrophic level to trophic level via the food chain. A trophiclevel is composed of organisms that make a living in thesame way, that is they are all primary producers (plants),primary consumers (herbivores) or secondary consumers(carnivores). Dead tissue and waste products are producedat all levels. Scavengers, detritivores, and decomposerscollectively account for the use of all such "waste" --consumers of carcasses and fallen leaves may be otheranimals, such as crows and beetles, but ultimately it is themicrobes that finish the job of decomposition. Notsurprisingly, the amount of primary production varies agreat deal from place to place, due to differences in theamount of solar radiation and the availability of nutrientsand water.

• For reasons that we will explore more fully in subsequentlectures, energy transfer through the food chain isinefficient. This means that less energy is available at theherbivore level than at the primary producer level, less yetat the carnivore level, and so on. The result is a pyramid ofenergy, with important implications for understanding thequantity of life that can be supported.

• Usually when we think of food chains we visualize greenplants, herbivores, and so on. These are referred to asgrazer food chains, because living plants are directlyconsumed. In many circumstances the principal energyinput is not green plants but dead organic matter. Theseare called detritus food chains. Examples include theforest floor or a woodland stream in a forested area, a saltmarsh, and most obviously, the ocean floor in very deepareas where all sunlight is extinguished 1000's of metersabove. In subsequent lectures we shall return to theseimportant issues concerning energy flow.

• Finally, although we have been talking about food chains,in reality the organization of biological systems is muchmore complicated than can be represented by a simple"chain". There are many food links and chains in anecosystem, and we refer to all of these linkages as a foodweb. Food webs can be very complicated, where itappears that "everything is connected to everything else",and it is important to understand what are the mostimportant 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, statesthat it is the nutrient supply to the primary producers thatultimately controls how ecosystems function. If thenutrient supply is increased, the resulting increase inproduction of autotrophs is propagated through the foodweb and all of the other trophic levels will respond to theincreased availability of food (energy and materials willcycle faster).

• The second theory, called top-down control, states thatpredation and grazing by higher trophic levels on lowertrophic levels ultimately controls ecosystem function. Forexample, if you have an increase in predators, thatincrease will result in fewer grazers, and that decrease ingrazers will result in turn in more primary producersbecause fewer of them are being eaten by the grazers.Thus the control of population numbers and overallproductivity "cascades" from the top levels of the foodchain down to the bottom trophic levels.

The Geography of Ecosystems

• There are many different ecosystems: rain forestsand tundra, coral reefs and ponds, grasslands anddeserts. Climate differences from place to placelargely determine the types of ecosystems we see.How terrestrial ecosystems appear to us isinfluenced mainly by the dominant vegetation.

• The word "biome" is used to describe a majorvegetation type such as tropical rain forest,grassland, tundra, etc., extending over a largegeographic area. It is never used for aquaticsystems, such as ponds or coral reefs. It alwaysrefers to a vegetation category that is dominant overa very large geographic scale, and so is somewhatbroader than an ecosystem.

Figure 3: The distribution of biomes.

A schematic view of the earth shows that, complicated though climatemay be, many aspects are predictable (Figure 4). High solar energy

striking near the equator ensures nearly constant high temperaturesand 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 rainfallof a site in Panama with the relatively constant precipitation but

seasonally changing temperature of a site in New York State. Everylocation has a rainfall- temperature graph that is typical of a broader

region.

• Figure 4. Climate patternsaffect biome distributions.

• We can draw upon plantphysiology to know thatcertain plants are distinctiveof certain climates, creatingthe vegetation appearancethat we call biomes. Note howwell the distribution of biomesplots on the distribution ofclimates (Figure 5). Note alsothat some climates areimpossible, at least on ourplanet. High precipitation isnot possible at lowtemperatures -- there is notenough solar energy to powerthe water cycle, and mostwater is frozen and thusbiologically unavailablethroughout the year. The hightundra is as much a desert asis 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 Viability1) Loss of crop & grazing land

2) Depletion of world's tropical forests

3) Extinction of species

4) Rapid population growth

5) Shortage of fresh water resources

6) Over fishing, habitat destruction, & pollution in themarine environment.

7) Threats to human health

8) Climate change

9) Acid rain

10) Pressures on energy resources

Thank you!!!END SHOW