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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.

Basics of Ecology

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

Any organism that is capable of producing its own food, usually through photosynthesis
An organism that feeds on other living organisms, for example animals and parasitic plants would be considered producers.
consumes a producer
consumes a primary consumer
consumes a secondary consumer
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)
two organisms living in direct contact with one another
two organisms living together in a relationship in which both benefit from the association. (bee pollinates flower)
two organisms in a relationship in which one benefits and one is harmed (dog has heartworms)
Two organisms in a relationship in which one benefits and the other is unaffected (shark and remora)
The replacement of one community by another, developing toward a climax
the ecological succession of vegetation that occurs in passing from barren earth or water to a climax community
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
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
The differential survival and reproduction of organisms with genetic characteristics that enable them to better utilize environmental resources
Stabilizing selection is a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait
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
In population genetics, directional selection occurs when natural selection favors a single allele and therefore allele frequency continuously shift in one direction.
The process in which breeders choose the variants to be used to produce succeeding generations
The number and variety of organisms within one region

Ecology Graphs and Charts

Survival Curves
a graph of the probability of survival versus time
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. For life tables, see

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
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.
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.
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.
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.
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.

Human Impact on Ecosystems

Global Warming

--lived in the atmosphere and vary regionally.Why are greenhouse gas concentrations increasing? 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.What has changed in the last few hundred years is the additional release of carbon dioxide by human activities. 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.Estimating future emissions is difficult, because it depends on demographic, economic, technological, policy, and institutional developments. Several emissions scenarios have been developed based on differing projections of these underlying factors. For example, by 2100, in the absence of emissions control policies, carbon dioxide concentrations are projected to be 30---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----

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

What is Acid Rain and What Causes It? "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.


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.


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.

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 (see Enviro Facts "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 (see Enviro Facts "Desertification"). It is very difficult and often impossible to restore desertified land.


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 (see Enviro Facts "Wetlands" and "River Catchments").

Ecosystems for 2007 Resources Forest: