Chapter 3 ContinuedTHE BIOSPHERE

3.3 Energy Flow in Ecosystems

How does energy flow through an ecosystem?Energy flows through an ecosystem in a one-way

stream-like path, from primary producers to various levels of consumers.

Food Chains & Food Webs

A food chain is a series of steps in which organisms transfer energy by eating and being eaten.

(can vary in length considerably)Grass is eaten by herbivore (antelope),

which is then eaten by carnivore (coyote)Grass is primary producer,

antelope=primary consumer, and coyote=secondary consumer.

Food Chains and Food Webs

In the previous examples of the grass-antelope-coyote food chain, it can be said that the coyote is two steps removed from the primary producer (grass)

Food Chains and Food Webs

In aquatic food chains, primary producers are a mixture of floating algea (known as phytoplankton) and attached algea

Both of which are autotrophsi.e. of aquatic food chain: algae are eaten by

flagfish which are eaten by largemouth bass which are eaten by anhinga(large bird), which are then eaten by alligators.

How many times removed is the alligator?

Food Chains and Food Webs

In most ecosystems the feeding relationships of organisms are not as linear as food chains describe them,

Reason being that many animals eat more then one kind of food.

So these interconnected networks of food chains form what ecologist call “food webs”

Food Chains within Food Webs

Think of the Everglades, aquatic and terrestrial organisms interact in many over lapping feeding relationships.Algae and plants can both be primary

producers simultaneouslyThere are various path from primary

producer to final consumer, and there are also various final consumers as well.

Decomposers and Detritivores in Food Webs

Even though part of primary producers are eaten by consumers, a very large part of producers die with out ever being eaten.In the detritus path way of the

Everglades FOOD WEB, the decomposers convert dead material to detritus.

Decomposers and Detritivores in Food Webs

That detritus material is then consumed by detrivores (worms, shrimp, and crayfish).

The decomposition process is the driving force of the nutrient cycle, and it does so by releasing nutrients that can be used by primary consumers and are introduced back into the food web. (we will cover later “Carbon & nitrogen cycles).

Food Web and Disturbance

Food Webs are so complex that it is often difficult to predict exactly how they will respond to environmental change (or stimuli).

Disscuss possible effect of oil spill that results in the decline of decomposers as well as bacteria and algea that produce detritus from dead matter?

Food Web and Disturbance

If decomposers die and detritus is never produced, along with the death of bacteria and algae, then flag fish, grass shrimp, and worms would have no food source. (cray fish would also experience a decrease in food availability)

Then the largemouth bass, the killifish, and the pig frog would have extremely limited food source (if any), and raccoons would have to adjust their diet to plants leaves seeds and fruits.

With the absence of decomposers there is no release of nutrients and the regular nutrient cycles are halted to a stop (think about the niche of decomposers), then the soil that plants grow on will cease to get the nutrients plants need and they eventually die.

Food Web and Disturbance

In conclusion, a disturbance at any level of the food web, no matter how insignificant or unimportant it might seem, can have very serious long term effects on an extensive food web.

Zooplankton

Zooplankton are mostly important in aquatic ecosystem and food webs,

They are similar to phytoplankton in the sense that they are small, but they are predators to algae and even phytoplankton.

They are not producers, they are primary consumers.

They are a diverse group of swimming, multicellular organism classified under the kingdom Animalia (so they are animals)

Trophic Levels and Ecological Pyramids

Each step in the food web or food chain is called a trophic level. Primary producers = first trophic level

Ecological pyramyds show the relative amounts of energy or matter contained within each trophic level of a food web/chain.

Pyramids of Energy?!?!

Pyramids of Energy

There’s no limit to number of trophic levels, or the number of organisms that live on each level.

But only a small portion of the energy that passes through a trophic level is ultimately stored in the bodies of organisms at the next level.(about 1/10th or 10% of energy makes it to the next trophic level)

Pyramids of Energy

Why is that energy lost? Because organisms use most of the energy they

acquire in order to breath, move around, grow, digest food and so on.

Most of the remaining energy after life processes is lost as heat to the environment.

So pyramids of energy so the relative amounts of energy available at each trophic level of a food web/chain.

Pyramids of Biomass

Biomass: total number of living tissue within a given trophic level.(measured in grams of organic matter per unit area)

The amount of biomass a given trophic level can support is determined, in part, by the amount of energy available.

A pyramid of biomass illustrates the relative amount of living organic matter available at each trophic level in an ecosystem.

Pyramids of NumbersEcologists

interested in the number of organisms at each level use pyramids of numbers.

Shows the relative number of individual organisms at each trophic level.

When pyramid of numbers is upsidedown

Think of thousands of insects feeding on one tree, or a countless number of mosquitos feeding on one deer.

Even though the pyramid of biomass remains the same because the tree and the deer have much more biomass, there is a much larger number of insects at the higher trophic level.

Which means the Pyramid of numbers will appear as “upside-down”

ClassWorkWorkBook section 3.3 ALL

3.4 Cycles of Matter

How does matter move through the biosphere?

unlike the one way flow of energy, matter is recycled within and between ecosystems.

Recycling in the biosphere

Elements pass from one organism to another among part of the biosphere through closed loops called Biogeochemical Cycles.

These cycles are powered by the flow of energy

Recycling in the biosphere

These cycles of matter include:Biological processes.Geological processes.Chemical processes.

As matter moves through these cycles it is transformed, but it is never created nor destroyed--- just changed.

Biological Processes

Any and all activities performed by living organisms.

Include eating, breathing, “burning” calories, and eliminating waste products (decomposition)

Geological Processes

Include: Volcanic eruptionsformation/breakdown of rockMajor movements of matter within and below earths surface (plate tectonics, subduction, and the rock cycle)

Chemical and Physical Processes

The formation of clouds and precipitation

Flow of running waterThe action of lightning.

Recycling in the biosphere

Carbon atoms in your body may once have been part of a rock on the ocean floor, the tail of a dinosaur or even part of a historical figure.

FYI: Technically, all the matter on earth, including the atoms that make up the molecules in our body, are composed or star dust.

The Water Cycle

Water continuously moves between the oceans, the atmosphere, and land– sometimes outside living organisms and sometimes inside them.

The Water Cycle

Water typically enters the atmosphere in one of two ways:the first is as water vapor molecules

produced by evaporation directly from bodies of water.

The second is still water vapor, but instead of simply evaporating, it was a result of transpiration (aka sweating) of plants and animals.

Water Cycle

If water vapor is carried along in winds that are heading either towards the poles, or towards higher altitudes, as temperatures drop eventually the water vapor will condense tiny droplets that form clouds.

When those droplets become large enough they fall to Earth’s surface as precipitation. (rain, snow, sleet, hail)

Water CycleOnce precipitation exceeds the rate of

recharge (the rate at which water can penetrate soil), water become runoff as surface waters

Runoff surface waters flow as streams or rivers and eventually make their way back to the ocean

The water that penetrates soil is called ground water, groound water form aquifer (underground bodies of water) which may eventually flow into ponds, lakes and rivers.

The Water Cycle

Nutrient Cycles

Nutrients: chemical substances that organisms need to sustain life.

Every organism needs them to build tissue and carry out bodily functions. Nutrients pass through organisms and the environment through biogeochemical cycles.

Thethree pathways, or cycles, that move carbon, nitrogen and phosphorus through the biosphere are especially critical for life on earth.

The Carbon Cycle

Carbon is a major component of all organic compounds, including carbohydrates, lipids, proteins, and nucleic acids (the building block of proteins).

Life on Earth can be described as Carb-based life. Calcium carbonate (CaCO3) is a component in the

skeletons of many animals and is also found in many kinds of rocks (i.e limestone).

Carbon and Oxygen form carbon dioxide(CO2), which is an important atmospheric gas (greenhouse gas), even though the majority of CO2 on earth is dissolved in the oceans.

The Carbon Cycle

Coal, oil, and natural gas = fossilized carbon

Coal reservoirs = atmosphere, ocean, rocks, fossil fuels and forests

The Carbon Cycle

Autotrophs take in CO2, and combine it with Hydrogen from water(H2O) to produce Carbohydrates, some organisms combine carbon with calcium and oxygen to produce CaCO3 to produce skeletons.

The Carbon Cycle

All organisms release Carbon Dioxide gas through respiration

When organisms die, decomposers break down organic matter and release carbon into the environment.

Geologic forces can turn carbon into carbon containing rocks, or fossil fuels

Carbon Dioxide is released into the atm by volcanic or human activities.

The Nitrogen Cycle

Nitrogen is necessary to produce RNA and DNA (all living things have RNA and/or DNA

Nitrogen = 78% of atmosphere Nitrates and nitritites are found in soils, biological

waste, and decaying organic matter. (that’s why compost is so good for plants)

Specific bacteria are able to combine gaseous nitrogen into compounds through a process called nitrogen fixation.

Some live in the soil on the roots of plants (legumes)

The Nitrogen Cycle

Some bacteria obtain energy by converting nitrates into nitrogen gas which is released into the atmosphere (denitrification)

Small part of nitrogen gas converted into usable forms by lighting (atmospheric nitrogen fixation)

The Nitrogen Cycle

The Phosphorus Cycle Phosphorus is also used in the structure of

DNA and RNA. Does not enter atmosphere in significant

amounts. Remains mostly on land in the form of

inorganic phosphates (mostly in minerals that make up rocks)

In oceans as dissolved phosphates and phosphate sediment

As rocks are weathered, phosphates are released

The Phosphorus Cycle

Organic phosphates move through food webs Others wash into rivers and streams

Eventually makes it to ocean, where organisms process it and incorporate into biological compounds. (Chitinophosphates make up the exoskeleton of crustaceans and insects)

Nutrient LimitationPrimary productivity of an ecosystem

might be limited by the availability of nutrients in that ecosystem.

Even if a single nutrient is limited, there is a limit on the whole, over all primary productivity.(LIMITING NUTRIENT)

6.2 Using Resources Wisely

Healthy soils supports both agriculture and forestry

Good top soil is produced by long-term interactions between soils and the plants growing on it.

Can be renewable resource if managed properly (crop Cycling)

6.2 Soil Erosion

Soil erosion is the removal of soil by water or wind. (worse when land is plowed and left barren, plant roots help prevent soil erosion)

Organic matter and nutrients that make soil fertile are carried away with soil erosion.

In dry climates: farming, overgrazing, seasonal drought, and climate change can change farmland into desert. (Desertification)

Deforestation: loss of forest. (healthy forest provide wood and hold soil in place, protect quality of fresh water and absorb CO2)

Old-Growth forest = never been cut, half of these have been lost to deforestation.

6.2 Water Pollution

Pollutant = harmful material that can enter the biosphere

Pollutants can enter water supply from many smaller sources called non-point sources

The primary sources = industrial and agricultural chemicals, residential sewage, and non-point sources.

Biological Magnification: occurs if a pollutant is picked up by an organism and is not broken down or eliminated from its body. Instead the pollutant collects, and the next trophic level (which must eat more) has 10X the concentrations of these pollutants.

6.2 Acid Rain

Burning of fossil fuels release nitrogen and sulfur as gasses into the air, when compounds combine with water vapor in the air. They form nitric acid and sulfuric acid.

Airborne acids can drift for many km before falling as acid rain.

Acid precipitation can dissolve and release mercury and other toxic elements from soil, freeing those elements to enter other parts of the biosphere.