Ecology

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 returned to the rotation for the 2017 and 2018 seasons.

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). It is also very important to know how a change in the population of one organism will affect other organisms in the food web.

Trophic Pyramid
Like food webs, trophic pyramids are also commonly found on Ecology tests. These diagrams are designed to show the comparative biological productivity for each level of the food chain. That is, as one gets further up the food chain, the energy gained from that level decreases by about 10%. An example trophic pyramid is shown at right.

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)

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

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 loss 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 (NOx) are the primary causes of acid rain. In the US, About 2/3 of all SO2 and 1/4 of all NOx 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: 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.
 * 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.

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.

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?




 * 3. Why are similar warblers in the above diagram able to coexist in the same ecosystem?
 * 4. This strategy that allows them to live together is known as __________.

Links
Earth and Environmental Systems podcast show notes, look for episodes 29, 33-38

2007 Resources
Forest
 * Berkeley Forest Resources
 * Forests

Marine
 * Marine Information
 * Marine Lectures
 * Marine Resources

Estuaries
 * Estuary Energy Flow
 * South Carolina Estuary Information
 * About Estuaries

2009 Resources
Deserts
 * Introductory desert material
 * Good study guide!

Grasslands
 * Ecology Glossary

2010 Resources

 * 2011 Official Powerpoint
 * Basic Ecology

Taiga
 * Blue Planet Tiaga Biomes
 * Berkeley Resources

Tundra
 * Blue Planet Tundra Biomes
 * Berkeley Resources
 * National Geographic Resources