Ecology

Ecology is the study of the various ecosystems and biomes. After you have studied these, you take a written test. Last year's topic was Forests and Estuaries; this year it is forests and Deserts. For both of the biomes, you 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.

Forests: This area of ecology is great for the people who participated in Forestry. You will have to know the different parts of the forest, and various kinds of forests and information about them. The main subdivisions that you need to learn for this biome would be taiga/boreal forest, rainforest, and deciduous forests.

Deserts: Presumably you will have to know various water conservation and temperature regulation strategies organism have developed to cope with the extremely arid environment.

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

Ecological Roles

 * Producers:Any organism that is capable of producing its own food, usually through photosynthesis


 * Consumers:An organism that feeds on other living organisms, for example animals and parasitic plants would be considered producers.
 * Primary:consumes a producer
 * Secondary:consumes a primary consumer
 * Tertiary:consumes a secondary consumer


 * Decomposers:an organism that breaks down organic matter into inorganic form, plants often uses this material as fuel


 * Carrying Capacity:the maximum number of individuals of a given species that a site can support during the most unfavorable time of year, without causing deterioration of the site

Community Interactions

 * Predator and Prey:one organism eats another organism (frog eats fly)
 * Symbiosis:two organisms living in direct contact with one another


 * Mutualism:two organisms living together in a relationship in which both benefit from the association. (bee pollinates flower)


 * Parasitism:two organisms in a relationship in which one benefits and one is harmed (dog has heartworms)


 * Commensalism:Two organisms in a relationship in which one benefits and the other is unaffected (shark and remora)


 * 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-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


 * Biodiversity:The number and variety of organisms within one region

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 survivalship 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 http://www.ucmp.berkeley.edu/glossary/gloss5/biome/index.html]

Population Growth
Population growth deals with how the size of a population changes over time. Intrinsic rate of growth (r-max) is the rate of growth under ideal conditions.
 * Exponential growth occurs when the growth rate remains the same while the population grows. It creates a J shaped curve (shown in red below).
 * 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).



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 However, all the members of A might be post-reproductive, whereas population B might consist of mostly prereproductive 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


 * 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
 * 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 ( it is important the fire reaches the right temperature) is crucial to the seeds dispersal. 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. Instead, thanks to greenhouse gases, the earth�s average temperature is a more hospitable 60�F.

Possible Causes: Problems arise when the atmospheric concentration of greenhouse gases increases. Since the 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

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 and often impossible 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.

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?



1. Why are similar warblers in the above diagram able to coexist in the same ecosystem?

2. This strategy that allows them to live together is known as __________.

2007 Resources
Forest:

http://www.ucmp.berkeley.edu/exhibits/biomes/forests.php

http://www.mbgnet.net/sets/rforest/index.htm

Marine:

http://darter.ocps.net/classroom/klenk/Contents.htm

http://www.connaughton.washcoll.edu/academics/marine/marinelectures.html

http://www.mbgnet.net/salt/sandy/indexfr.htm

Estuaries:

http://www.estuaries.gov/pdf/energyflow.pdf

http://inlet.geol.sc.edu/estecohp.html

http://www.estuaries.gov/about.html

2009 Resources
Deserts:

http://www.desertusa.com/life.html (Introductory desert material)

http://www.western.edu/faculty/jsowell/desertecology/index.html (good study guide!)

Grasslands: