ECOSYSTEMS

Earth’s Major Biomes

Ecology= “study of one’s house”

eco = Greek for "house", ology = Greek for "study of”

“Study of organisms in relation to the environment” (American Ecological Association)

Biosphere = Intersection of:

Atmosphere Hydrosphere Lithosphere Pedosphere

Together = Ecosphere

Living inhabitants of earth: an estimated 5 to 100 million. About 2.55 million have

been scientifically named and described so far, including:   250,000 flowering plant species 800,000 lower plant species (1.05 million plant species altogether) 45,000 vertebrate animal species 950,000 insect species (1.5 million animal species altogether)   About 10,000 new species are identified each year,

mostly insects.

Processes which sustain ecosystems:

  A) energy flows B) stable biotic structure

C) nutrient cycling  

Energy flows:

Energy is the capacity to do work Forms of energy all trace back to radiant

energy from the sun Radiant energy from sun is converted to

1) heat 2) chemical energy (stored in chemical

bonds of molecules)3) mechanical energy4) electrical energy

Thermodynamics: Study of energy and its changes

1st Law of Thermodynamics: Energy cannot be created or destroyed, but can be transformed from one form to another

Example: Photosynthesis

6CO2 + 12H20 + radiant energy from sun

C6H12O6 (glucose or sugars) + 6H20 + 6O2   Plants use green pigment (chlorophyll) to absorb radiant energy and convert

radiant energy into chemical energy

Notice: CO2 is essential for all life on earth and the process of photosynthesis gives off the O2 that all animals need to breath.

 

2nd Law of Thermodynamics (the law of entropy)

As energy is transformed from one state to another, some is changed to heat energy which is dissipated and given off to the environment

Example: In the process of cell respiration, chemical energy stored in food molecules (glucose) is released within cells of plants and animals. Now food molecules are broken down and mechanical energy is produced.

In the process of energy transformation, some is lost.  

C6H12O6 (glucose) + 6O2 + 6H20

6CO2 + 12H20 + mechanical energy and heat

Oh My God! Let’s tax those CARBON EMISSIONS from the respiration of

plants and animals and people! Call out the EPA!

Question:

How is it possible that in 2007 the U.S. Supreme Court voted 5-4 that CO2 is an “air pollutant” that could be regulated by the Environmental Protection Agency? Didn’t these people go to high school and college?

A Carbon Tax? Carbon is the basis of all life on earth

And yet, U.N.’s “Greenhouse Development Rights Framework (GDR) (2007, Bali) plan proposes a “consumption luxury tax” to be levied on everyone on the planet who makes over $9,000/year. Americans would pay about $780 per year, or $212 billion in “climate reparations” to poorer countries with the Plan.

Reason magazine’s Rob Bailey ran the numbers: the total “climate reparation” from rich to poor countries = $600 billion/year.

The Obama energy bill of 2009 is far more expensive. It squeaked by the house but has not passed the Senate.

Example 2 of 2nd law: In the conversion of stored energy in

coal to electricity that occurs in a coal-fired power plant, 2/3 of original energy in coal is lost to waste heat.

Carbon is also oxidized to form CO2.

(But the real pollutants are from impurities in the coal, including mercury and sulfur dioxide, which can form sulfuric acid, a component of acid rain.)

Conundrum:

Living organisms have a high degree of organization and complexity.

Thus, the evolution of life to more complex forms seems to refute the 2nd law.

Life can only become more complex if it consumes high amounts of energy.

This is true also for industrialized societies such as ours- which get 85% of their energy from fossil fuels (ancient sunlight).

Stable biotic structure

Producers are autotrophs (Greek; auto = self, troph = nourishment, so self-nourishing).

Autotrophs get their energy from the sun via photosynthesis. Plants are the most important producers on land, and algae and certain types of bacteria are the most important producers in aquatic areas.

Consumers are heterotrophs (Greek for “different nourishers”).

These are animals which eat plants and other animals as sources of food energy and body-building material.

a) primary consumers eat producers (plants). These are herbivores (plant eaters, such as cattle, deer, giraffs, etc.)

b) secondary consumers eat primary consumers and are the carnivores, such as lions, tigers, etc.

c) Tertiary Consumers- omnivores eat both primary and secondary consumers. These include bears, humans, pigs.

Detrivores and Decomposers Detritivores or detritus feeders feed off of dead organic

matter, detritus, or decomposed animal and plant material. Examples include earthworms, vultures, termites, ants,

millipedes, soil insects   Decomposers (saprotrophs – Greek sapro means “rotten”,

troph means “nourishment”) microbial heterotrophs, which break down organic material and use the decomposition products to feed themselves with energy. In the process, they often release simple molecules like CO2 and salts that can be used by producers. Examples include bacteria and fungi. These are extremely important for converting dead organic matter into humus for the soil, breaking down of dead wood, etc.

Energy flow in ecosystems occurs in food chains

Trophic levels Each level is called a trophic level (trophic =

feeding).

However, because most organisms feed on

several kinds of food, food chains are less common than food webs, which are a complex of interconnected food chains in an ecosystem.

Each ecosystem has about 3 or 4 trophic levels.

Food Web

Biomass pyramid: another example of 2nd law in action

Bo

2nd law in action:

whereas a primary consumer like a rabbit might need a fairly small range for foraging (about 15 acres), a secondary consumer like a tiger needs a much larger home range (almost 100 square miles)

The Carbon Cycle

Carbon Cycle:

Carbon exists in gaseous, liquid and solid forms and occurs in five main reservoirs:

Reservoir billion metric tons

1) Atmosphere- as CO2 (380 ppm 766

Or (0.038%) of atmospheric gases

2) Ocean - as CO2, CaCO3, and HCO3. 39,000

(about 50 times more CO2 in the oceans than

atmosphere).

3) vegetation, animals, soils, peat, etc. 2,100

4) fossil fuels (oil, coal, natural gas) 4,000

5) carbonate rocks as CaCO3 (about 100X more) 80,000

Photosynthesis: Plants remove CO2 from the atmosphere and form glucose (sugars).

6CO2 + 12H20 --> C6H12O6 + 6O2 + 6H2O   Again, sugars are used in cell respiration of

living things:   C6H12O6 + 6O2 + 6H20 --> 6CO2 + 12H20 +

energy for biological work

More CO2 in the atmosphere means more biomass!

Many greenhouses increase levels of CO2 to 2 to 4 times normal levels (700 to 1400 ppm)

This results in faster growth rates, longer growing seasons, larger plant size and larger yields of crops (by 20 to 50%)

Increased CO2 means agricultural crops need less water and adapt better to drought and pollution.

Fossil Fuels are, in effect, ancient sunlight, and are non-renewable

Combustion of wood, peat, and fossil fuels causes oxidation of solid carbon to form gaseous CO2

About 210 billion metric tons of CO2 are added to atmosphere each year from all sources; human activities add about 7 billion metric tons, or about 3% of the total. Other sources (97%) are oceans, vegetation, soils, and volcanoes.

96.9% of all greenhouse gases in atmosphere are water vapor, whereas CO2 makes up less than 2%.

66 to 86% of the total greenhouse effect is due to water vapor and clouds, and only 9 to 27% is due to CO2.

Humans are responsible for less than 3% of CO2 emissions, and less than 1% of total greenhouse effect.

Margaret Hillman (2007): “When the chips are down I think

democracy is a less important goal than is the protection of the planet from the death of life, the end of life on it. (Carbon rationing) has got to be imposed on people whether they like it or not.”

From “A Plan to Save the Planet, But is Anyone Willing to Pay the Price?,” Local Transport Today

David Bellamy, Botany Professor, Great Britain’s best-known environmentalist:

“What a load of poppy-cock! Global warming- at least the modern nightmare version- is a myth.

  (CO2) is in fact, the most important airborne fertilizer in the world, and

without it there would be no green plants at all. Even a doubling of CO2 in the atmosphere would produce a rise in plant productivity. Call me a biased old plant lover, but that doesn’t sound like much of a killer gas to me. Hooray for global warming is what I say, and so do a lot of my fellow scientists.

  It would be terrible if billions or trillions of dollars were wasted “on a

problem that doesn’t exist- money that could be used in umpteen better ways: fighting world hunger, providing clean water, developing alternative energy sources, improving our environment, creating jobs.”

 

Nitrogen Cycle: nitrogen also occurs in gas, liquid and solid forms

Critical for soils and for life itself because nitrogen is an essential part of proteins, enzymes, hormones and nucleic acids, which store genetic information about an organism's traits.

Nitrogen (N2) makes up about 78% of

earth's atmosphere. This gas is inert, highly stable and unusable.

Nitrogen

Cycle

Five steps in the process of nitrification: 1) Nitrogen fixation mostly occurs by bacteria in soil. N2 is converted to ammonia

(NH3). Rhizobium is the most important nitrogen-fixing bacteria and lives on nodules on the roots of plants like beans or peas.

2) In the process of nitrification, ammonia (NH3) is converted to nitrite (NO2) then to nitrate (NO3) by other types of soil bacteria called nitrifying bacteria.

3) In the process of assimilation, plant roots absorb NO3 and/or ammonia (NH3) and incorporate the nitrogen of the molecules into plant proteins and nucleic acids. When animals eat the plants, they are able to convert these to animal compounds.

4) Ammonification, When living things produce N-containing waste products like urea (in urine) and uric acid, the N is released as NH3- ammonia. This process again is accomplished by bacteria.

5) Denitrification. Nitrate (NO3) is reduced to gaseous N again by bacteria which are aneorobic, i.e., can live in areas without free oxygen. 

Nitrogen fertilizer adds valuable nitrate and ammonia to soils and is used by humans to increase agricultural productivity.

Nitrate can leach through soils and contaminate groundwater. This is especially hazardous for infants and is a serious pollutant in agricultural areas in the Midwest.

Overuse of commercial fertilizers can cause a buildup of nitrate and ammonia in nearby waters, where it stimulates growth of algae in the process of eutrophication.

When dead algae decompose, free oxygen in water is consumed.

When the dissolved oxygen (DO) in the water falls below a critical level, other aquatic organisms, like fish, can no longer breathe and so they die off.

Nitrogen cycle

Net primary productivity

Amount of biomass produced from photosynthesis in excess of the amount broken down by a plant's cell respiration.

This relates to the amount of photosynthesis in a given time.

The most productive ecosystems in terms of biomass are continental shelves and tropical rainforests.

Tropical forests cover only about 7% of earth's land surface but include over half of world's species.

Global net primary productivity- June

Global net primary productivity- December

Law of Limiting Factors Limiting factors are the variables which tend

to restrict the niche of an organism. Different species have different tolerance levels for environmental extremes like heat, cold, etc.

If any factor lies outside the organisms range of tolerance the organism can't live there. So for each factor (temperature, pH, etc.), an organism will have:

Law of Limiting Factors

optimum range - point of maximum growth range of tolerance- range of max. to min. for

each factor limits of tolerance- death occurs when factor

reaches this level zone of stress- between optimum range and limit

of tolerance.   Any factor which exceeds an organism's limits of

tolerance can remove the organism

Law of Limiting Factors

law of the minimum The 19th Century agricultural chemist Von Liebig

postulated that the growth of each organism is limited by whatever essential factor is in shortest supply or is present in harmful excess.

Von Liebig did his work on the effects of

chemical nutrients on plant growth.

Other limiting factors can include competition

from other species, acid rain, drought, temperature changes, etc.

Plant Succession

Biomes = major ecosystems comprised of distinct assemblages of plants and animals

Seven major terrestrial biomes:

Temperate Forests occur in Western Europe, east Asia, and the eastern U.S. where mean annual precipitation (MAP) is 30 to 80 inches.

Most commonly, forests include either deciduous or mixed deciduous and coniferous trees.

In the Pacific Northwest, because precipitation is very high (MAP = 80 to over 200 inches) there is temperate rainforest. Here, we have a tremendous supply of timber, especially in the old growth forests. The spotted owl controversy is here.

Grassland Biome MAP is about 10 to 30 inches.

short grass prairie occurs in drier areas, tall grass prairie in wetter areas.

Soils developed under grassland (predominantly Mollisols) are extremely fertile and these areas are generally good or great for agriculture.

They include the "breadbaskets of world": the U.S. Midwest, Ukraine, Pampas).

Desert Biome Conditions are dry. True deserts are found in different latitudes

wherever MAP is less than 10 inches.

Desert plants have a wide range of adaptations. Some (like the mesquite tree) have very long roots to tap water deep underground. Others have spines and thorns or toxins to defend themselves from competitors. Others, such as cactus, have little or no leaves through which they could lose water by transpiration.

Desert animals are also adapted to drought. The Kangaroo rat can live without drinking water its entire life. It metabolizes water from its food.

When watered, deserts can be good for human agriculture; soils

(Aridisols) are nutrient-rich. But salts (a limiting factor) can build up in desert soils in process of salinization and most plants have a hard time surviving.

Coniferous Forest Biome

(Also, called boreal forest or “taiga”). Stretches across North America and Eurasia (most of Canada, Russia, Scandanavia).

Climate is cool (with cold, harsh winters) and generally dry (MAP about 20 inches).

Trees are mostly coniferous (spruce, fir, etc.) but also include some deciduous trees (aspen, birch).

These areas are good for timber production and pulp wood, but poor for agriculture.

Soils are thin and acidic (Spodosols). Permafrost is common.

Tundra Biome includes the cold boggy plains of the far north.

Generally very cold and dry. During the short summers with long days, the snow and upper layer of permafrost melt.

Vegetation is small and stunted due to the cold and is dominated by grasses, mosses, lichens, sedges. It is generally too cold for tree growth. Average temperature in July is generally less than 10˚ C or 50° F (the minimum limit for tree growth.)

Savanna Biome includes tropical grasslands with widely scattered

trees.

Often found in Mediterranean climates (climates with cool, moist winters and a prolonged dry summer). They include hot areas, with seasons regulated by precipitation variations.

Great assemblages of wildlife mammals live in the African savanna and include lots of hoofed mammals and predators.

When converted to rangeland for cattle, etc., these areas can be rather easily overgrazed and desertified.

Tropical forest biome Climate is warm and wet year round. MAP is 80 to 180

inches and mean annual temperature (MAT) is over 18˚ C.

The world's greatest species diversity. These forests cover only about 7% of earth's land surface but contain over half of all species. One tree in Peru may have 43 different ant species (and 26 genera), equivalent to the entire ant fauna of the British Isles. One hectare in Borneo had 700 species of trees, the same number as in all of North America.

Soils (Oxisols) are generally very old, leached, and nutrient poor.

Biological diversity Includes:  

1) genetic diversity within species

2) species diversity (# of different species)

3) ecosystem diversity (variety within and between ecosystems)

  Biological diversity contributes to more robust ecosystems because

ecosystems with a high amount of diversity are best able to adapt to environmental stressors and provide the best defense against extinction.

Extinction: Species live an average of 1 to 10 million years

Some like the shark have lived as long as about 400 million years. And, of course, simple bacteria, algae, etc. have been with us for probably 3.8 billion years.

There have been numerous mass extinction events. Some have estimated that of every 2000 species which have lived on the earth 1999 have already gone extinct. Or 99.9% of all species are extinct.

In addition to extinction events, there is a fairly continuous, low-level rate of extinction going on all the time which we call background extinction.

Extinction Intensity

Endangered Species Act (1973) Authorizes the U.S. Fish and Wildlife Service to

protect endangered and threatened species from extinction.

The Endangered Species Act (ESA) makes it

illegal to sell or buy products made from endangered species.

The act was updated in 1982, 1985, 1988 and is considered one of the strongest pieces of environmental legislation in the U.S. It has been very controversial because it has interfered with several big governmental projects.