Ecology

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Ecology is the study of how living things (biotic factors) interact with their non-living environment (abiotic factors). This includes the study of the various ecosystems and biomes. The event is in the form of a written test. For both of the biomes, competitors should know the main nutrients found there and their cycles, animals and plants found there along with their adaptations, life zones, and other common processes found there. However, it's also really good to know the other types of biomes as well since they always seem to appear on the tests. Know the relationships between the biomes you're studying and the biomes you are NOT studying.

Ecology rotated out after 2011 when it was replaced by Water Quality. It has returned to the rotation for the 2017 season.

Basics of Ecology

Food Web

On many of the Ecology tests, you may be given around a dozen organisms which you need to organize into a food web. For 2010, the theme is grasslands and taiga, so you should have a general idea of the organisms that inhabit both areas, and which organisms consume others (ex. shrub -> shrew -> snake -> hawk).

Ecology Definitions

Know how to apply all of the below terms to defining variables, analyzing data from graphs and tables, presenting data in graphs and tables, forming hypotheses, and making calculations and predictions .

Succession: The replacement of one community by another, developing toward a climax
- Primary: The ecological succession of vegetation that occurs in passing from barren earth or water to a climax community
- Secondary: The development of biotic communities in an area where the natural vegetation has been removed or destroyed but where soil is present

More Terms

Extinction: No remaining living organisms; gone forever

Selection: In the context of evolution, certain traits or alleles of a species may be subject to selection. Under selection, individuals with advantageous or "adaptive" traits tend to be more successful than their peers reproductively--meaning they contribute more offspring to the succeeding generation than others do
- Natural: The differential survival and reproduction of organisms with genetic characteristics that enable them to better utilize environmental resources
- Stabilizing: Stabilizing selection is a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait
- Disruptive: Disruptive selection is a type of natural selection that simultaneously favors individuals at both extremes of the distribution. When disruptive selection operates, individuals at the extremes contribute more offspring than those in the center, producing two peaks in the distribution of a particular trait
- Directional: In population genetics, directional selection occurs when natural selection favors a single allele and therefore allele frequency continuously shift in one direction.
- Artificial: The process in which breeders choose the variants to be used to produce succeeding generations

Limiting Factors: A factor that limits a population's growth; i.e. resources, shelter, food and disease

Biodiversity: The number and variety of organisms within one region (biome)

Ecology Graphs and Charts

Survival Curves: Graph of the probability of survival (y-axis) versus time (x-axis). Some basic life history strategies can be seen from the basic shape of this graph. Type I organisms have lower mortality rate at low ages which gradually increases with age. Type II organisms have mortality rates that stay the same throughout life. Type III organisms have the largest mortality rates at birth. Most survival curves are combinations of more than one type of organism. The three general shapes can be seen below.

Life Table: An age-specific death schedule. Such a schedule is often converted to a more palatable survivorship schedule. For each age interval there is an predicted life expectancy or survivorship. From a life table, one can produce a survival curve.

Biomes: See a biome resource

Population Growth

Population growth deals with how the size of a population changes over time. One more thing: HUMANS DON'T HAVE EXPONENTIAL GROWTH (it's pretty close though) Intrinsic rate of growth (r-max) is the rate of growth under ideal conditions (in red below).

Exponential growth occurs when the growth rate remains the same while the population grows. It creates a J shaped curve (shown)
Logistic growth occurs when the growth rate decreases as the population grows due to density-dependent factors (factors increasing mortality rate as population grows such as predation rates, competition, and disease). This creates an S-shaped curve (shown in blue below). It is the most common type of population growth.

Determining the Population Growth

Logistical Growth (the most common): dN/dt = rmaxN((K - N)/(K))

Where dN/dt is basically the change in population divided by change in time, and K being the carrying capacity, and rmax being the maximum growth rate (biotic potential of the organisms) (rmax is sometimes just r). N is population size.

Exponential Growth (less common): P(t) = P(initial)e^(rt)

Life History Strategies

Age of reproduction: The average age in an organism when it becomes capable of reproduction (For example, population A might have many more members than population B. However, all the members of A might be post-reproductive, whereas population B might consist of mostly pre-reproductive and reproductive age individuals. Population A might be in danger of extinction).
- r-selected organisms: Put most of their energy into rapid growth and reproduction. This is common of organisms that occupy unpredictable environments, e.g. weeds are usually annuals with rapid growth and early reproduction. They produce large number of seeds containing few stored nutrients
- K-selected organisms: Put most of their energy into growth. They are common in stable environments near carrying capacity, e.g. long lived trees such as redwoods take many years of growth to reach reproductive age

Geographic Range: Where the members of a species' populations live, feed, and reproduce. Geographic ranges can change due to the establishment and extinction of species.
- Cosmopolitan Species: Species that have ranges that stretch over several continents.
- Endemic Species: Species that have ranges that are isolated to a small area on a single continent.

Types of Movement: There are two main types of movement that organisms do.
- Active Movement: Movement that requires an organism to use some appendage to move (walking, flying, swimming, etc).
- Passive Movement: Movement in which an organism uses an external force to cause transit (wind, water, etc).

Seed Dispersal: The method by which a plant scatters its offspring away from the parent plant to reduce competition. Methods include: wind, insects, animals, tension, and water. Seed dispersal is a form of passive movement.
- Wind: Some seeds are carried to a new place by the wind. These seeds are very light. The seeds of the orchid are almost as fine as dust. Many have hairy growths which act like little parachutes and carry the seeds far away from the parent plant.
- Water: Fruits which float such as those of the water lily and the coconut palm are carried by water. Coconuts can travel for thousands of kilometers across seas and oceans. The original coconut palms on South Sea islands grew from fruits which were carried there from the mainland by ocean currents.
- Animals/Insects: The animal eats the fruit but only the juicy part is digested. The stones and pips pass through the animal's digestive system and are excreted to form new plants. This can be far away from the parent plant.
- Explosions/Tension/Mechanical: Some plants have pods that explode when ripe and shoot out the seeds. Lupins, gorse and broom scatter their seeds in this way. Pea and bean plants also keep their seeds in a pod. When the seeds are ripe and the pod has dried, the pod bursts open and the peas and beans are scattered.
- Fire: To survive fire some plants have adaptive traits that allow them to reproduce or regenerate. An adaptive trait is a behavior, physical feature or some other characteristic that helps a plant or animal survive and make the most of its habitat. When fire occurs, animals have the ability to fly, run away or burrow deep into the ground. Plants cannot do this and so have adapted other ways of surviving. The way a plant stores its seeds and disperses them is an example of a fire adaptive strategy. The intensity of the fire is crucial to the seeds dispersal (it is important the fire reaches the right temperature). Also important is how often the fires occur.

Human Impact on Ecosystems

Global Warming

Greenhouse Effect: Energy from the sun drives the earth’s weather and climate, and heats the earth’s surface; in turn, the earth radiates energy back into space. Atmospheric greenhouse gases (water vapor, carbon dioxide, and other gases) trap some of the outgoing energy, retaining heat somewhat like the glass panels of a greenhouse. Without this natural “greenhouse effect,” temperatures would be much lower than they are now, and life as known today would not be possible. (Understatement) Instead, thanks to greenhouse gases, the earth’s average temperature is a more hospitable 60°F. The most important gases are carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons.

Possible Causes: Problems arise when the atmospheric concentration of greenhouse gases increases. Since the industrial revolution, atmospheric concentrations of carbon dioxide have increased nearly 30%, methane concentrations have more than doubled, and nitrous oxide concentrations have risen by about 15%. These increases have enhanced the heat-trapping capability of the earth’s atmosphere. Sulfate aerosols, a common air pollutant, cool the atmosphere by reflecting light back into space; however, sulfates are short-lived in the atmosphere and vary regionally. Scientists generally believe that the combustion of fossil fuels and other human activities are the primary reason for the increased concentration of carbon dioxide. Plant respiration and the decomposition of organic matter release more than 10 times the CO2 released by human activities; but these releases have generally been in balance during the centuries leading up to the industrial revolution with carbon dioxide absorbed by terrestrial vegetation and the oceans. Fossil fuels burned to run cars and trucks, heat homes and businesses, and power factories are responsible for about 98% of U.S. carbon dioxide emissions, 24% of methane emissions, and 18% of nitrous oxide emissions. Increased agriculture, deforestation, landfills, industrial production, and mining also contribute a significant share of emissions. In 1997, the United States emitted about one-fifth of total global greenhouse gases.

Effects of Climate Change: Mean surface temperatures have increased 0.5-1.0°F since the late 19th century. The 20th century's 10 warmest years all occurred in the last 15 years of the century. Of these, 1998 was the warmest year on record. The snow cover in the Northern Hemisphere and floating ice in the Arctic Ocean have decreased. Globally, sea level has risen 4-8 inches over the past century. Worldwide precipitation over land has increased by about one percent. The frequency of extreme rainfall events has increased throughout much of the United States. Increasing concentrations of greenhouse gases are likely to accelerate the rate of climate change. Scientists expect that the average global surface temperature could rise 1-4.5°F (0.6-2.5°C) in the next fifty years, and 2.2-10°F (1.4-5.8°C) in the next century, with significant regional variation. Evaporation will increase as the climate warms, which will increase average global precipitation. Soil moisture is likely to decline in many regions, and intense rainstorms are likely to become more frequent. Sea level is likely to rise two feet along most of the U.S. coast.

Invasive Species

A species that has moved into an area and reproduced so aggressively that it has replaced some of the original species. For example if we introduced one species to a new environment the already adapted species to that area would be forced out. This practice can be produced by lost of habitat.

Acid Rain

Acid rain is a broad term used to describe several ways that acids fall out of the atmosphere. A more precise term is acid deposition, which has two parts: wet and dry. Wet deposition refers to acidic rain, fog, and snow. As this acidic water flows over and through the ground, it affects a variety of plants and animals. The strength of the effects depend on many factors, including how acidic the water is, the chemistry and buffering capacity of the soils involved, and the types of fish, trees, and other living things that rely on the water. Dry deposition refers to acidic gases and particles. About half of the acidity in the atmosphere falls back to earth through dry deposition. The wind blows these acidic particles and gases onto buildings, cars, homes, and trees. Dry deposited gases and particles can also be washed from trees and other surfaces by rainstorms. When that happens, the runoff water adds those acids to the acid rain, making the combination more acidic than the falling rain alone. Prevailing winds blow the compounds that cause both wet and dry acid deposition across state and national borders, and sometimes over hundreds of miles.

Scientists discovered, and have confirmed, that sulfur dioxide (SO₂) and nitrogen oxides (NO_x) are the primary causes of acid rain. In the US, About 2/3 of all SO₂ and 1/4 of all NO_x comes from electric power generation that relies on burning fossil fuels like coal. Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds. Sunlight increases the rate of most of these reactions. The result is a mild solution of sulfuric acid and nitric acid.

Erosion

The wearing away of land or soil by the action of wind, water, or ice. Soil erosion is a natural process. It becomes a problem when human activity causes it to occur much faster than under natural conditions.

Causes of Soil Erosion

Wind and water are the main agents of soil erosion. The amount of soil they can carry away is influenced by two related factors:

Speed - The faster either moves, the more soil it can erode;
Plant cover - Plants protect the soil, and in their absence, wind and water can do much more damage.

The Importance of Plants

Plants provide protective cover on the land and prevent soil erosion for the following reasons:

Plants slow down water as it flows over the land (runoff) and this allows much of the rain to soak into the ground;
Plant roots hold the soil in position and prevent it from being washed away;
Plants break the impact of a raindrop before it hits the soil, thus reducing its ability to erode;
Plants in wetlands and on the banks of rivers are of particular importance as they slow down the flow of the water and their roots bind the soil, thus preventing erosion.

The loss of protective vegetation through deforestation, over-grazing, ploughing, and fire makes soil vulnerable to being swept away by wind and water. In addition, over-cultivation and compaction cause the soil to lose its structure and cohesion and it becomes more easily eroded. Erosion will remove the top-soil first. Once this nutrient-rich layer of soil is gone, few plants will grow in the soil again. Without soil and plants the land becomes desert-like and unable to support life. This process is called desertification. It is very difficult- often impossible, in fact- to restore desertified land.

Preventing Soil Erosion

Preventing soil erosion requires political, economic and technical changes. Political and economic changes need to address the distribution of land in South Africa as well as the possibility of incentives to encourage farmers to manage their land sustainably. Aspects of technical changes include:

The use of contour ploughing and wind breaks;
Leaving unploughed grass strips between ploughed land;
Making sure that there are always plants growing on the soil, and that the soil is rich in humus (decaying plant and animal remains). This organic matter is the "glue" that binds the soil particles together and plays an important part in preventing erosion; ->* avoiding overgrazing and the over-use of crop lands;
Allowing indigenous plants to grow along the river banks instead of ploughing and planting crops right up to the water's edge;
Encouraging biological diversity by planting several different types of plants together;
Conservation of wetlands.

History of Environmental Protection

1854 - Henry David Thoreau writes Walden, inspiring many to live simply and in harmony with nature
1864 - George Perkins Marsh publishes Man and Nature, described by some environmentalists as the fountainhead of the conservation movement.
1872 - Yellowstone becomes the nation's first National Park
1892 - John Muir founds Sierra Club to protect the Sierra Nevada
1905 - National Audubon Society formed
1949 - Aldo Leopold publishes A Sand County Almanac, in which he sets guidelines for the conservation movement and introduces the concept of a land ethic.
1962 - Rachel Carson writes Silent Spring, about the use of DDT as a pesticide and how it hurt bird species' eggs
1969 - Garrett Hardin writes Tragedy of the Commons, showing that although an area might not be abused by its users, without a true limit and caretakers its resources eventually are depleted
1970 - EPA Act passed by Nixon, creating the Environmental Protection Agency
1970 - Clean Air Act bans certain aerosols in the USA
1973 - Endangered Species Act Passed
1979 - Three Mile Island meltdown in Pennsylvania of nuclear reactor
1984 - Bhopal poisoning in India
1986 - Chernobyl incident in Ukraine
1987 - Montreal Protocol signed by Reagan and Thatcher - attacks CFC disruption of ozone layer
1989 - Exxon Valdez spill in Prince William Sound off Alaska dumps millions of gallons of crude oil
1997 - Kyoto Protocol in Japan confronts global warming, USA doesn't sign
2010 - BP oil spill in Gulf of Mexico, biggest oil spill in US history
2010 - The Cove, documentary, released, revealing the horrors of Japanese cetacean killing

Biomes

Each year, the rules for Ecology include biomes that specific questions can be asked about that year.

Season	Biomes
2018	Deserts, Grasslands
2017	Taiga, Tundra, Deciduous Forests
2011	Taiga, Tundra
2010	Grasslands, Taiga
2009	Deserts, Grasslands
2008	Forests, Deserts

2005	Freshwater, Estuaries

Deciduous Forests

Deserts

Grasslands

Taiga

Tundra

Ecology Glossary

A basic glossary of ecology terms.
Word	Definition
Abiotic	Non living (Water, wind, rocks)
Acid precipitation	Includes acid rain, acid fog, acid snow, and any other form of precipitation that is more acidic that normal (i.e., less that pH 5.6).
Adaptation	Any genetically controlled structural, physiological, or behavioral characteristic that helps an organism survive under a given set of environmental conditions
Aerobic	Living or occurring only in the presence of oxygen
Amensalism	Two organisms in a symbiotic relationship in which one is unaffected and one is harmed (the black walnut tree secretes juglone which kills the plants living at base of tree, but the lack of competition doesn't help or harm the tree). This is a very rare type of symbiosis.
Ammonification	The process by which decomposers change nitrogen in detritus to ammonium (NH4+)
Anaerobic, adj.	Lacking or seriously depleted of oxygen
Assimilation	The process by which plants absorb nitrate or ammonium through root hairs to be used within the plant
Autotroph	Organism that uses solar or chemical energy to manufacture the organic compounds it needs as nutrients from simple inorganic compounds obtained from its environment (think producers)
Batesian Mimicry	Resemblance of an unpalatable species by an edible species to deceive predators
Biodiversity	Variety of different species (species diversity), genetic variability among individuals within a species (genetic diversity), variety of ecosystems (ecological diversity), and functions such as energy flow and matter cycling needed for the survival of a species and biological communities
Biomass	Organic matter produced by plants and other photosynthetic producers; total dry weight of all living organisms that can be supported at each trophic level in a food chain or web; dry weight of all organic matter in plants and animals in an ecosystem
Biome	Terrestrial regions inhabited by certain types of life, certain climate and vegetation
Biosphere	Zone of earth where life is found. It consists of parts of the atmosphere (the troposphere), hydrosphere (mostly surface and ground water), and lithosphere (mostly soil and surface rocks and sediments on the bottoms of oceans and other bodies of water) where life is found.
Biotic	Living or once living organisms.(Bunny, Dead Bunny)
Biotic potential	Maximum rate at which the population of a given species can increase when there are no limits on its rate of growth
Carbon Cycle	Cyclic movement of carbon in different chemical forms from the environment to organisms then back to the environment
Carrying Capacity	The maximum number of organisms that an environment can support
Chemosynthesis	Process in which certain organisms (mostly specialized bacteria) extract inorganic compounds from their environment and convert them into organic nutrient compounds without the presence of sunlight
Climax community	Fairly stable, self-sustaining community in an advanced stage of ecological succession; usually has a diverse array of species and ecological niches; captures and uses energy and cycles critical chemicals more efficiently than simpler, immature communities
Clumped Distribution	The most common type of population distribution where many members of the population live close together
Cohort	A group of individuals born around the same time
Commensalism	An interaction between organisms of different species in which one type of organism benefits and the other is neither helped nor harmed to any great degree
Community	Populations of all species living and interacting in an area at a particular time
Competition	Two or more individual organisms of a single species (intraspecific competition) or two or more individuals of different species (interspecific competition) attempting to use the same scarce resources in the same ecosystem
Consumer	Organism that cannot synthesize the organic nutrients it needs and gets its organic nutrients by feeding off of the tissues of producers or of other consumers
Decomposer	Organism that digests parts of dead organisms and cast-off fragments and wastes of living organisms by breaking down the complex organic molecules in those materials into simpler inorganic compounds and then absorbing the soluble nutrients
Deforestation	Removal of trees from a forested area without adequate replanting
Denitrification	The reduction of nitrates back into nitrogen gas (N2), completing the nitrogen cycle. This process is performed by bacterial species such as Pseudomonas and Clostridium in anaerobic conditions.
Desert	Biome in which evaporation exceeds precipitation and the average amount of precipitation is less than 25 centimeters a year. Such areas have little vegetation or have widely spaced, mostly low vegetation.
Desertification	Conversion of rangeland, rain-fed cropland, or irrigated cropland to desert-like land, with a drop of agricultural productivity of 10% or more
Detritivore	Consumer organism that feeds on detritus, parts of dead organisms, and cast-off fragments and wastes of living organisms
Detritus	Parts of dead organisms and cast-off fragments and wastes of living organisms
Distribution	Area over which we can find a species
Ecology	Study of the interactions of living organisms with one another and with their nonliving environment of matter and energy, study of the structure and functions of nature
Ecosystem	Community of different species interacting with one another and with the chemical and physical factors making up its nonliving environment
Environment	All external conditions and factors, living and nonliving, that affect an organism or other specified system during its lifetime
Exponential growth	Growth in which some quantity, such as population size or economic output, increases at a constant rate per unit of time
Extant	A species that is still alive and reproducing
Extinct	A species that is no longer living on earth
Food chain	Series of organisms in which each eats or decomposes the preceding one
Food web	Complex network of many interconnected food chains and feeding relationships
Gene pool	The sum total of all the genes that exist among all the individuals of a species
Global warming	Warming of the earth’s atmosphere because of increases in the concentrations of one or more greenhouse gasses primarily as a result of human activities
Grassland	Biome found in regions where moderate annual average precipitation (25-76 cm) is enough to support the growth of grass and small plants but not enough to support large stands of trees
Greenhouse effect	A natural effect that releases heat in the atmosphere near the earth’s surface. Water vapor, carbon dioxide, ozone, and several other gasses in the lower atmosphere absorb some of the infrared radiation radiated by the earth’s surface. This will eventually increase the temperature of the earth if there are enough of the greenhouse gasses
Gross primary productivity	The rate at which an ecosystem's producers capture and store a given amount of chemical energy as biomass in a given length of time
Habitat	Place or type of place where an organism or population of organisms lives
Herbivore	Plant-eating organism
Heterotroph	Organism that cannot synthesize the organic nutrients it needs and gets its organic nutrients by feeding off of the tissues of producers or of other consumers
Indicator Species	A species that gives an early warning that an ecosystem is in a state of flux, often times fish and amphibians or apex predators
Interspecific competition	Attempts by two or more species to use the same resources in an ecosystem
Intraspecific competition	Attempts by two or more organisms of a single species to use the same limited resources in an ecosystem
J-shaped curve	Curve with a shape similar to that of the letter J; can represent prolonged exponential growth
Keystone species	Species that play roles affecting many other organisms in an ecosystem
K-selected species	Species that produce a few, often fairly large offspring but invest a freat deal of time and energy to ensure that most of those offspring reach reproductive age
Limiting factor	Single factor that limits the growth, abundance, or distribution of the population of a species in an ecosystem
Muellerian Mimicry	Resemblance of two equally unpalatable species in order to increase the concentration of individuals with the warning appearance to increase its efficiency
Muskeg	An acidic soil type common in Arctic and boreal areas, more-or-less synonymous with bogland
Mutualism	A symbiotic relationship in which both participate species generally benefit
Niche	Total way of life or role of a species in an ecosystem. It includes all physical, chemical, and biological conditions a species needs to live and reproduce in an ecosystem
Nitrification	The process of oxidizing ammonia to create nitrite (NO2−)then oxidizing the nitrite to create nitrate (NO3-)
Nitrogen Cycle	Cyclistic movement of nitrogen in different chemical forms from the environment to organisms and then back to the environment
Nitrogen fixation	The process of chemically converting nitrogen gas (N 2 ) from the air into compounds, such as nitrates (NO 3 ), nitrites (NO 2 ), or ammonia (NH 3 ), that can be used by plants in building amino acids and other nitrogen-containing organic molecules.
Nutrient	Any food or element an organism must take in to live, grow, or reproduce
Omnivore	Animal that can use both plants and animals as a food source
Organism	Any form of life
Parasitism	Interaction between species in which one organism, called the parasite, preys on another organism, the host
Perennial Herbaceous	A perennial plant that has stems that die at the end of the growing season, but parts of the plant survive under or close to the ground from season to season (for biennials, until the next growing season, when they flower and die). New growth develops from living tissues remaining on or under the ground, including roots, a caudex (a thickened portion of the stem at ground level) or various types of underground stems, such as bulbs, corms, stolons, rhizomes and tubers.
Phosphorus Cycle	Involves the uptake of phosphorus by organisms. Phosphorus in the environment is mainly found in rocks, and natural weathering processes can make it available to biological systems. Phosphorus is an essential nutrient for plants and animals in the form of ions PO43- and HPO42- . It is a part of DNA-molecules and RNA-molecules, molecules that store energy (ATP and ADP) and of fats of cell membranes.
Pioneer community	First integrated set of plants, animals, and decomposers found in an area undergoing primary ecological succession
Population	Group of individual organisms of the same species living in a particular area
Predation	A symbiotic relationship in which an organism kills another organism
Primary consumer	Organism that feeds on all or part of plants or on other producers
Primary succession	Ecological succession in a bare area that has never been occupied by a community of organisms
Producer	Organism that uses solar or chemical energy to manufacture the organic compounds it needs as nutrients from simple inorganic compounds obtained from its environment
r-selected species	Species that reproduce early in their life span and produce large numbers of usually small and short-lived offspring in a short period
Rhizobia	Soil bacteria that fix nitrogen after becoming established inside root nodules of legumes
Scavenger	Organism that feeds on dead organisms that were killed by other organisms or died naturally
Second law of thermodynamics	In any conversion of heat energy to useful work, some of the initial energy input is always degraded to lower quality, more dispersed, less useful energy
Secondary Consumer	An organism that consumes a primary consumer
Secondary succession	Ecological succession in an area in which natural vegetation has been removed or destroyed but the soil is not destroyed
Species diversity	Number of different species and their relative abundances in a given area
S-shaped curve	Leveling off of an exponential, J-shaped curve when a rapidly growing population exceeds the carrying capacity of its environment and ceases to grow
Sustainability	Ability of a system to survive for some specified time
Symbiosis	Any intimate relationship or association between members of two or more species
Symbiotic relationship	Species interaction in which two kinds of organisms live together in an intimate association. Members of the participating species may be harmed by, benefit from, or be unaffected by the interaction
Synergy	Is the term used to describe a situation where the final outcome of a system is greater than the sum of its parts.
Taiga	The largest land biome. Characterized by conifer forests and cold temperatures. Boreal forest is usually used to refer to the more southerly part of the biome.
Tertiary Consumer	An organism that consumes a secondary consumer.
Trophic level	All organisms that are the same number of energy transfers away from the orginal source of energy that enters the ecosystem
Uniform Distribution	A rare type of population distribution where the population is evenly spread out

Sample Questions

The graph above relates nitrate concentration in runoff water near a forest to time. In this experiment, forest A experienced deforestation completed in 1925. Forest B experienced little to no deforestation.

1.Explain the cause for the different concentrations of nitrate in the two ecosystems.

2.What is a possible cause for the increase of nitrate concentration in the runoff water in ecosystem B?