Performance Benchmark L.12.C.1
Students know relationships of organisms and their physical environment. E/S
Ecology is the study of the interaction between organisms and their environment. Biotic factors
are the living components of an ecosystem including interactions between organisms. Abiotic
factors are the nonliving components that affect the living including water, oxygen, light,
temperature, soil, and nutrient cycles. The abiotic factors collectively dictate where ecosystems
exist.
Figure 1. Locations of world biomes.
http://library.thinkquest.org/11922/habitats/h
abitats.htm
Abiotic Factors
Light: The energy that drives life on earth originates from the sun. The amount of sunlight
dictates the growth of plants. Therefore, energy directly relates to where biomes are located.
Both the intensity and duration of light varies with latitude. Radiant energy is greatest at the
equator and decreases as you travel to the poles. Areas near the equator receive approximately
12 hours of daylight everyday. Areas near the poles receive 24 hours of weak intensity light in
“summer” and 24 hours of darkness in “winter”. Figure 2 shows how one unit of energy from
the sun at the equator covers a smaller area than the same unit of energy at the poles creating the
weaker intensity of light at the poles. Day length varies with the seasons, lengthening as you
approach the summer solstice and shortening as you move toward the winter solstice.
Figure 2. A unit of energy from the sun at the equator covers a
smaller unit of area than the same unit of energy at the poles.
From: http://www-class.unl.edu/geol101i/15a_climate.htm
Sunlight is also affected by depth of water. As light penetrates water, certain wavelengths are
absorbed. The zone which is penetrated is called the photic zone and below that is the aphotic
zone. Most of earth’s photosynthesis takes place in the photic zones of the oceans and the
organisms that live in the aphotic zone are heterotrophic and feed off on the photic zone
organisms that migrate to deeper depths.
Figure 3. (left) and Figure 4 (below) Red and yellow light are absorbed in the first 15 meters while blue light
can penetrate 37.5 meters. http://www.photo.net/learn/optics/edscott/cf000030.htm
Fig. 4 http://daac.gsfc.nasa.gov/oceancolor/scifocus/oceanColor/oceanblue.shtml
Temperature: Temperature patterns are affected by both latitude and altitude. There is a direct
relationship between the decreasing light energy received (as latitude increases) and the decrease
in temperature. The hottest regions of earth are equatorial and the coldest regions are polar. As
you travel away from the equator, these zones have decreasing average annual temperatures.
Conversely, there is an inverse relationship between altitude and temperature. As altitude
increases, average temperature decreases within the troposphere. As a result even the tops of
equatorial mountains may have snow.
Water: Water is essential to life and is recycled through the water cycle (See Benchmark
L.12.C.3). The amount of precipitation (including rain, snow, hail, and sleet) that an area
receives dictates the type of vegetation. Precipitation is affected by latitude, altitude,
topographic features, and proximity to large bodies of water.
Figure 5. Why are deserts at 300 N/S of equator?
http://www.earlham.edu/~biol/desert/whatis.htm
The equatorial regions tend to be very wet while many deserts are located around 30 degrees
north and south latitudes. Air over the equator is disproportionately heated because of the
increased solar energy. This results in air masses that expand creating low pressure systems. As
the air mass rises, it cools, and it loses its moisture. These air masses then move away from the
poles, cool, condense, and sink creating a high pressure system. The increased air pressure and
dryness causes the air mass to draw water out of the environment creating deserts.
Soil and Minerals: Soil is another non-living component important to the health of an
ecosystem. Soil is defined as the unconsolidated mineral or organic material on the immediate
surface of the earth that serves as a natural medium for the growth of land plants
(http://soils.usda.gov). There are many types of soils and each one has unique characteristics,
like color, texture, structure, and mineral content. The type of soil dictates the type of
vegetation.
Figure 6: Soil profiles from various ecosystems. Notice how the differences in soils correlates to the
type of vegetation supported. From: http://jimswan.com/111/soil/soils.jpg
The process of soil formation in an ecological sense is called primary succession (see Benchmark
L.12.C.2). In general, as soil forms, three distinct layers can be distinguished. The uppermost
layer is the topsoil or A Horizon. This includes organic matter and various living organisms. It
is often dark in color from the high organic content (humus) which is from the decay of dead
plant and animal matter. The middle layer, or B Horizon is called the subsoil and consists of
partially weathered rock particles and an accumulation of water soluble minerals leached from
the topsoil. The bottom layer or C Horizon, consists of partially weathered parent rock with little
organic matter.
Figure 7. A generic soil labeled profile http://www.mo15.nrcs.usda.gov/features/wissoil/sld005.htm
Climatograms: A climatogram is a graphical way to highlight the differences between biomes.
The graph shows a biome’s average monthly temperature and average monthly precipitation data
on a single graph. The precipitation is presented as a bar graph using the left axis and the
temperature data is plotted as a line graph using the right axis.
Figure 8: Two examples of climatograms. The data from Indonesia represents a tropical rainforest. The data from
Arizona represents a desert. Indonesia: http://www2.kpr.edu.on.ca/cdciw/biomes/indonesia/abiotic_description.htm
Arizona: http://www2.kpr.edu.on.ca/cdciw/biomes/sonorandesert.htm
Biotic Factors
Ecological Hierarchy: Organisms in an ecosystem do not live in isolation. They interact with
their environment and with other organisms. Therefore, an understanding of the organization of
an ecosystem is necessary in the field of ecology. The hierarchy starts with the individual. The
simplest grouping of organisms is a population. A population is defined as a group of organisms
of the same species that have the potential to interact and interbreed with each other. For
example, all of the mountain lions that live in the southern Sierra Nevada Mountains would be a
population and the mountain lions in northern Nevada would be a separate population. A
community consists of all the populations of different organisms in a given location. The
community level of study looks at the inter-specific relationships, like predator prey relationships
or competition. Food webs are another way to think about an ecological community. Food webs
are covered in detail in Benchmark L.12.C.3. Lastly, the zone on Earth where life can exist is
the Biosphere. The Biosphere is about 20km thick extending from the floor of the ocean and
reaching up to the limits of life in the atmosphere. An extended definition form Wikipedia.org
defines the biosphere as the outermost part of the planet's shell — including air, land, surface
rocks and water — within which life occurs, and which biotic processes in turn alter or
transform.
Individual
Population
Community
Ecosystem
Figure 9: An example of an ecological hierarchy from population to ecosystem.
Ecological relationships: Again, organisms do not live in isolation. They must interact with
their environments and other organisms. Ecological relationships are relationships in which two
different organisms interact regularly to the benefit of at least one of them. There are three basic
types of ecological relationships: mutualism, commensalisms, and parasitism. The following
table illustrates each type of relationship. A + sign represents a benefit, a 0 represents no effect,
and a – sign represents a harmful effect.
Mutualism
Commensalism
Parasitism
Organism #1
+
+
+
Organism #2
+
0
-
An example of a mutualistic relationship is between termites and the bacteria that live in their
digestive tract. Termites cannot digest cellulose and depend on the bacteria to release the
nutrients in the wood while the termites give the bacteria nutrition and a place to live.
Barnacles have a commensalistic relationship with whales. The whales are not bothered by the
barnacles but the barnacles rely in the water currents created by the whale’s swimming to filter
feed.
Tapeworms are parasitic and live inside the digestive tract of a host organism. The worm steals
nutrients from the host to grow and reproduce. Consequently, the host loses nutrients, energy,
and can suffer from tissue damage from the infestation.
Competition: Resources are limited in an ecosystem. Therefore, individuals must compete with
individuals of their own species (intraspecific competition) and with other species (interspecific
competition) to meet their survival needs.
Performance Benchmark L.12.C.1
Students know relationships of organisms and their physical environment. E/S
Common misconceptions associate with this benchmark:
1. Species live independently of each other and there environment.
Organisms are constantly interacting with their environments abiotic factors, such as,
water, light, soil, and air. Plants, for example, take the radiant energy from the
sunlight, carbon dioxide and water to make their food through the process of
photosynthesis. These are all abiotic factors. Animals must obtain their energy from
other organisms like plants and other animals. These interactions are very specific
and are important for stability in an ecosystem.
2. Symbiosis is limited to parasitism, where the parasite goal is to kill its host.
There are three types of symbiotic relationship, parasitism, commensalism, and
mutualism. In a parasitic symbiotic relationship one organism benefits by getting
food, shelter, and or protection at the expense of a second organism, it’s host. The
parasite’s intention is not to kill the host because without the host the parasite will die
as well. In a commensal symbiotic relationship, one organism is helped but the other
is unaffected. In a mutualistic symbiotic relationship both organisms benefit from the
relationship.
3. Biotic factors, like plants and animals, determine the biome.
Biomes are characterized by the predominant vegetation, but the two major
determining factors of biomes are temperature and precipitation. Organisms must be
adapted to live in the climate that is determined by temperature and precipitation.
Many organism adaptations are driven by abiotic factors, for examples, some cactuses
have spines that help to reduce water loss and to help shade from excessive sun. This
adaptation is ideal for living in high temperatures with low precipitation.
Performance Benchmark L.12.C.1
Students know relationships of organisms and their physical environment. E/S
Sample Test Questions
1. Which statement illustrates a biotic factor interacting with an abiotic factor?
a. A sea turtle transporting a pilot fish to a source of food.
b. A rock moving during an earthquake
c. A plant absorbs sunlight, which is used for photosynthesis.
d. Wind cause waves to form on a lake.
2. The presence of a parasite in an animal will result in
a. the parasite purposely killing the host animal.
b. the host animal becoming ill from nutrients lost to the parasite.
c. the parasite and the host animal both benefiting from the relationship.
d. the host animal is unaffected by the parasitic relationship.
3. Identify the group that consists of abiotic factors.
a. Temperature, light, precipitation, and soil
b. Individual, population, community, and ecosystem
c. Rock, soil, tree, and squirrel
d. Mountain lion, soil, and sunlight
4. The study of interaction between organisms and their interrelationships with the physical
environment is known as
a. Symbiosis
b. Biology
c. Ecology
d. Abiotic
5. Many different species of organisms interacting in a particular environment are an
example of a
a. Species
b. Biosphere
c. Ecosystem
d. Community
Performance Benchmark L.12.C.1
Students know relationships of organisms and their physical environment. E/S
Answers to Sample Test Questions
1.
2.
3.
4.
5.
(c)
(b)
(a)
(c)
(d)
Performance Benchmark L.12.C.1
Students know relationships of organisms and their physical environment. E/S
Intervention Strategies and Resources:
The following list of intervention strategies and resources will facilitate student understanding of
this benchmark.
1. Current Marine Ecology projects with real life data that students can access.
This is a great website that examines the historical as well as current abiotic data of
Racerock Ecological Preserve, Southern Vancouver Island, BC. There are several current
marine ecological projects under way so students can observe ecological research in
action.
To access this site, visit: http://www.racerocks.com/
2. Biomes of the world, including biotic and Abiotic factors.
This website presents a very easy to navigate and easy to read about the biomes of the
world. It includes land, fresh water, and marine biomes. The information includes both
abiotic and biotic description of each biome.
To access this site, visit: http://www.mbgnet.net/
3. Soil property Webquest
This website is a fairly involved webquest that allows students to investigate the
properties of soil. It can be easily adapted to fit the needs of any classroom teacher.
To access this site, visit:
http://cte.jhu.edu/techacademy/web/2000/ravenscroft/WEBQUEST.HTM
4. Soil webquest more appropriate for ELL students
This webquest is very simple but may be appropriate for low level students or second
language students as an introduction to soils.
To access this site, visit: http://www.ecps.k12.nc.us/dfw/ebaker/SoilWebquest.htm
5. Printable climatograms
This is a printable climatogram activity to give students practice graphing and
interpreting climatic data.
To access this site, visit:
http://www.pbs.org/americanfieldguide//teachers/prairie/studinst.pdf
Other American Field Guide activities can be found at
http://www.pbs.org/americanfieldguide/teachers/