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1. Understand how materials and energy enter, pass through, and exit an ecosystem
2. Describe how communities are organized, how they develop and how they diversify
3. Understand the various trophic roles and levels.
4. Diagram the principal biogeochemical cycles.
5. Understand the factors that affect population density, distribution and change
6. Understand the meaning of exponential growth
7. Understand the significance and use of life tables
8. Describe the factors that have encouraged growth in some cultures and limited growth in others
9. Understand the magnitude of pollution problems in the United States
10. Describe the effects of modern agriculture on desert, grassland and tropical rain forest ecosystems.
11. Describe how fossil fuels and nuclear energy affect the ecosystem.
1. Crepes for Breakfast, Pancake Ice for Desert
2. Introduction to Principles of Ecology
1) A habitat is the place where a species normally lives: it is characterized by distinctive physical features and vegetation.
2) A community is the collection of all populations in a given habitant.
3) The niche refers to a range of physical and biological conditions under which a species can live and reproduce.
a) specialist species have narrow niches.
b) Generalist have broad ranges of habitats and niches.
1) Communities of organisms make up the biotic, or living , portions of an ecosystem.
2) Succession is the orderly progression of species changes that leads to a climax community.
a) In primary succession, changes begin when pioneer species colonize a barren habitat.
b) In secondary succession, a community reestablishes itself toward a climax state after a disturbance.
3. Ecosystem Organization
A. Regions on the earth function as systems running on energy form the sun processed through various organisms.
1) autographs are producers that capture sunlight energy and incorporate it into organic compounds.
2) Heterotrophs are organisms that depend directly or indirectly on energy stored in the tissues of producers.
a) consumers are heterotrophs that feed on tissues of other organisms.
I) herbivores eat plants.
II) Carnivores eat animals.
III) Parasites reside in or on living hosts and extract energy form them.
IV) Omnivores eat a variety of organisms.
b) detritivores include small invertebrates that feed on partly decomposed particles of organic mater (detritus)
c) Decomposers are also heterotrophs and include fungi and bacteria that extract energy form the remains or products of organisms.
3) Ecosystems are open systems through which energy flows and materials are cycled.
a) Ecosystems require energy and nutrient input and generate energy (usually as heat) and nutrient output.
b) Energy cannot be recycled: most is lost as heat to the environment.
1) Trophic (“feeding”) levels are a hierarchy of energy transfers, or bluntly stated, “Who eats whom?”
2) Level 1 (closest to the energy source consists of primarily producers, level 2 is composed of herbivores, and level 3 and above are carnivores.
3) Decomposers feed on organisms form all levels.
1) A sequence of who eats whom is called a food chain: example: algaeà fishà fishermenà shark.
2) Cross connecting food chains make up food webs in which the same food resources is often, part of more than one food chain.
4. Energy Flow through Ecosystems
A. Primary productivity.
1) primary productivity is the total rate of photosynthesis for the ecosystem during a specified interval.
2) Net primary productivity is the rate of energy storage in plant tissues in excess of the rate of respiration by the plants themselves.
1) Energy flows into ecosystems form the sun (one-way)
2) Energy flows through ecosystems by way of grazing food webs (consumption of autographs) and detrital food webs (use of wastes and bodies of autographs and consumers)
3) Energy leaves ecosystems through heat losses generated by metabolism.
1) Trophic structure can be diagrammed as a pyramid in which producers from a base for successive tiers of consumers above them.
2) Pyramids can be of two basic types:
a) A pyramid of biomass makes provision for differences in size of organisms by using the weight of members in each trophic level.
b) A pyramid of energy reflects tropic structure more accurately because it is based on energy losses at each level.
5. Case Study: Energy flow at silver springs Florida.
A. Energy inputs and outputs are calculated to show energy flow per unit of area per unit of time.
6. Biogeochemical cycles—An overview
A. Biogeochemical cycles influence the availability of essential elements in ecosystem.
1) elements are available to producers as ions.
2) Nutrient reserves are maintained by environmental inputs and recycling activities.
3) The amount of nutrient being recycled through major ecosystems is greater than the amount entering or leaving in a given year.
4) Inputs to an ecosystem’s nutrient reserves are by precipitation, metabolism and rock weathering: outputs include losses by runoff.
1) In the hydrologic cycle, oxygen and hydrogen move as water molecules.
2) In the atmospheric cycles, elements can move in the gaseous phase: examples include carbon and nitrogen.
3) In sedimentary cycles, the element does not have a gaseous phase: example phosphorus.
7. The Hydrologic cycle
A. Water is moved or stored by evaporation, precipitation, retention, and transportation.
1) A watershed funnels rain or snow into a single river.
2) Nutrients are absorbed by plants to prevent their loss by leaching.
8. The Carbon cycle
A. Carbon enters the atmosphere (when it exists as carbon dioxide) by aerobic respiration, fossil fuel burning and volcanic eruptions.
9. Nitrogen cycle
A. nitrogen is needed for proteins and nucleic acids.
1) it is abundant in the atmosphere (80 %) but not in the earth’s crust.
2) Of all the nutrients needed for plant growth, nitrogen is the scarcest.
1) in nitrogen fixation, bacteria convert N2 to NH3, which is then used in the synthesis of proteins and nucleic acids.
2) In assimilation and biosynthesis, fixed nitrogen becomes incorporated into plant, then animal tissues.
3) Decomposition of dead nitrogen fixers release nitrogen-counting compounds.
4) Ammonificaiton occurs when bacteria and fungi decompose dead plants and animals and release excess ammonia or ammonium ions.
5) Nitrification is a type of chemosynthesis where NH3 or NH4+ is converted to NO2 other nitrifying bacteria use the nitrite for energy and release NO3-
C. Nitrogen scarcity
1) nitrogen fixing bacteria are constantly adding nitrogen compounds to the soil.
2) But soil nitrogen is still scarce due to leaching, denitrificaiton and farming methods that emphasize synthetic fertilizers.
3) Denitrificaiton is the release o f nitrogen gas to the atmosphere by the action of bacteria (NO2- and NO3-à N2)
1) air pollutants including oxides of nitrogen contribute to soil acidity.
2) Heavy nitrogen applications not only are costly and are lost in runoff and harvested crops.
10 The phosphorus cycle.
A. Phosphorus moves form land to sediments in the seas, and back to land in its long term geochemical phase of the cycle.
B. In the ecosystem phase, plants take up the phosphorus form the soil it is then transferred to herbivores and carnivores, which excrete it in wastes and their own decomposing bodies.
1. A Nightmare of numbers
1) For example India is increasing at two percent a year and now accounts for nearly one fifth of the world’s population.
2) Birth control programs have not been successful.
2. Introduction to population dynamics
1) population density is the number of individuals per unit of area or volume
2) distribution refers to the general pattern in which the population members are dispersed—clumped, random or uniform
3) Age structure defines the relative proportions of individuals of each age
a) the three categories are: prerepraductive, reproductive and postreproductive.
b) The reproductive base for a human population includes individuals aged 15-44
B. Population Size and Patterns of growth
1) population size is equal to (births plus immigration) minus (deaths plus emigration): zero population growth designates a near balance of births and deaths.
a) a population’s rate of increase ®= births minus deaths divided by total population.
b) As long as r is positive, the population will continue to increase at ever increasing rates—easily measured by noting the ‘doubling time.”
c) A graphic plot of exponential growth results in a J shaped curve that becomes steeper with advancing time.
3. A closer Look at Growth Patterns
1) The biotic potential of a population is its maximum rate of increase under ideal nonlimiting conditions.
2) The biotic potential varies form species to species, depending on:
a) when individuals start reproducing
b) how often reproduction occurs
c) how many offspring are born each time.
3) the actual rate of increase of a population is influenced by environmental circumstances.
B. Limiting Factors and Carrying capacity
1) Environmental circumstances prevent full biotic potential.
2) Any essential resource that is in short supply becomes a limiting factor, such as predation (including disease) competition for living space, and pollution.
3) The number of individuals that can be sustained by the resources in a given area is the carrying capacity.
4) The carrying capacity can vary over time and is expressed graphically in the S-shaped curve pattern called logistic growth.
C. Checks on population Growth
1) Density dependent controls (such as diseases) are limiting factors that exert their effects with respect to the number of individuals present.
2) Density independent controls, such as natural disasters, tend to increase the death rate without respect to the number of individuals present.
D. Live history patterns
1) Demography is the study of age specific patterns such as time of reproduction and death
2) Survivorship schedules are summarized in life tables.
4. Human Population Growth
1) The world population has passed the 5.7 billion mark (1995).
2) Each year over 100 million more people are born about 273,000 per day
a) It took about 200,000 million years for the world’s human population to reach 1 billion: it took only 12 years to reach the fifth billion
b) Even at a growth rate of 1.6% the human population is rapidly reaching a size that may not be sustainable.
1) In The preindustrial stage, living conditions are harsh, birth and death rates are high: there is little increase in population size.
2) In the transitional stage, living conditions improve, death rates drop, birth rates remain high
3) In the industrial stage growth slows
4) In the postindustrial stage, zero population growth is approached: birth rate falls below death rate
5) Some developed countries are in the industrial stage (USA, Canada, Japan) some countries (ex Mexico ) are in the transitional stage.
1) each day 700,000 metric tons of pollutants are dumped into the atmosphere in the United States alone.
2) Air pollutants include oxides of carbon, sulfur, and nitrogen as well as the CFCs.
a) Industrial smog is gray air found in industrial cities that burn fossil fuels.
b) Photochemical smog is brown air found in large cities in warm climates: for example, gases form car exhaust.
B. Acid Deposition
1) burning coal produces sulfur dioxides
2) burning fossil fuels and fertilizers results in nitrogen oxides
3) tiny particles of these oxides can fall to earth as dry acid deposition or wet acid deposition—acid rain.
C. Damage to the ozone layer
1) Ozone (O3) n the lower stratosphere absorbs most of the ultraviolet radiation form the sun.
2) The thinning of the ozone layer has produced an ozone hole over Antarctica
3) In response, skin cancer has increased, cataracts may increase, and phytoplankton my be affected.
4) Chlorofluorocarbons (CFCs) seem to be the cause—one chlorine atom can convert 10,000 ozone molecules of oxygen.
6. Water Scarcity and Water Pollution
1) about one third of all food is raised on irrigated land
2) problems resulting form wide scale use of irrigation include salt buildup (salinizaiton) waterlogged soil and subsidence (sinking of land as ground water is withdrawn).
B. Problems with Water Quality
1) Human waste, insecticides, herbicides, chemicals, radioactive materials, and heat can pollute water
2) Most liquid wastes form urban populations in the United States undergo treatment but some are released into waterways untreated.
7. Coping with solid wastes and problems of land use
1) We face a challenge to move form a “throwaway” society to one of conservation and reuse.
2) Paper is easily recycled and not only conserves trees but also saves production energy.
3) Finding enough space for burying our wastes is becoming a problem and the dump sites can leak toxic materials into the soil and water.
B. conversion of marginal lands for Agriculture
1) Almost 21% of land is used for agriculture: another 28% is available but its conversion to agriculture may not be worth the cost.
2) The green revolution has increased crop yields but uses many times more energy and mineral resources
3) Large scale desertification is caused by overgrazing on marginal lands.
8. Destruction of Forests
1) deforestation can reduce fertility, change rainfall patterns, increase temperatures, and increase carbon dioxide.
2) Removing trees form tropical forests to make more crop land is counterproductive because of the poor soils.
1) fossil fuels are a limited resource, extraction costs are increasing, and atmospheric levels of carbon dioxide and sulfur dioxides are increasing.
2) Petroleum and natural gas reserves may be depleted during the next century
3) Extraction and use of abundant reserves of coal are not environmentally attractive.
C. Nuclear Energy
1. with nuclear energy, the net energy produced is low and the cost high compared with generation methods.
2. Meltdown may release large amounts of radioactivity to the environment.
3. Waste is so radioactive that it must be isolated for 10,00 years
D. Alternative energy sources
1) Breeder reactors make their own fuel but can explode like a small atomic bomb.
2) Fusion power is possible but many obstacles make the technology a distant possibility
3) Solar-hydrogen energy is an attractive technology because it depends on the renewable energy source—the sun.
10. The idea of sustainable living
A. A sustainable society is one that manages its population growth and economic activities in ways that prevent serous damage to the environment.
Interesting literature:
National Geiographic: Population October 1998 #4. Gives a really good overview on the human population over time and what will happen in the future with the human population.
David M. Schwartz. Birds, Bees and Even Nectar-Feeding Bats Do It. Smithsonian April 2000. Volume 31 number1. Pp58 to 71. This intreguing article discusses how the ecosystems and humans are intertwined. And that most of our food requires organisms to polinate, that is move the male gamet to the female part of the flower. It describes how through habitad destruciton, pesticides and ignorance many of the organisms that actually move the polen from plant to plant are starting to disappear and that we will not really notice that they are gone untill our crops fail.
http://www.api.org/edu/oilsup.htm an interesting website by the american protrolium institute, stateing in essence that we will never run out of oil.
http://www.solstice.crest.org/index.shtml A site for the introduciton of a sustainable energy culture.
Quiz (No quiz available at this time)
Pitcarin island and its story. A population of 9 englishmen and 12 Tihitian women. Infighting left 1 englisman and the women alive to start a new colony
http://www.time.com/time/magazine/article/0,9171,883297-2,00.html