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World Geography 3202/3200
Unit Notes
Unit Three: Ecosystems
Definitions;
Ecosystem
Decomposers
Food Pyramid
Desertification
1.
Producers
Food Chain
Climax Vegetation
Consumers
Food Web
Biological Amplification
Examine a diagram of a food web and identify a food chain.
Example:
Food Chain:
Grass – Rabbit - Owl
2.
Describe energy flow through an ecosystem.

3.
Using figure 6.5 on page 95 you can summarize the main energy
flows in an ecosystem.
o Sun = source of all ecosystem energy
o Producers make food via photosynthesis
o Consumers eat plants and other consumers to get energy
o Each time energy moves from one organism to another,
energy leaves the system in the form of heat.
o Decomposers return nutrients to the soil but energy is not
recycled.
Explain why there are fewer organisms at each trophic level.
There are fewer organisms at each trophic level because the amount of energy decreases
at each new level of the food pyramid, fewer organisms can obtain the necessary energy
to live. Thus, the number of organisms decreases at each successive level.
4.
Explain how pesticides can reach toxic levels for organisms at
a higher trophic level.
A food pyramid helps to illustrate how pesticides such as DDT can reach
toxic (i.e poison) levels for organisms at a higher trophic level.
Organisms at higher trophic levels consume larger numbers of
organisms at lower levels in order to obtain the necessary food energy.
Thus, because these toxins tend to accumulate in the higher-level
organisms each time a lower-level organism is consumed, more and
more toxins are found in these higher-level organisms as they consume
more and more lower-level organisms.
Example of the accumulation of toxins in higher level organisms. (Biological
Amplification)
5.
Describe the effect that the introduction of a new organism
has on a particular ecosystem.
For each of these you will have to examine the feeding habits of
organisms in the ecosystem and then decide if the introduction of the
new species will cause an increase or decrease in the number of a
selected species. For example, Capelin eat shrimp and krill. The favorite food of
cod is capelin. Exports of capelin to Asian countries have been steadily increasing over
the past ten years. Hence, codfish stocks may decrease, while shrimp and
krill may increase.
6.
Describe the general characteristics of a given ecosystem.
The following table summarizes the general characteristics of the
different ecosystems.
Ecosystem
Savanna
Climate Conditions
High temperatures most
of the year, light to
moderate precipitation
usually during one
season
Boreal Forest Temperate cold winter
climate: warm summers,
moderate precipitation
Vegetation
Tall grasses with
occasional trees
Location
At low latitudes in;
Central South
America, Central
Africa, India, and
parts of Australia.
Thick forests of
evergreen trees
with small thin
needle leaves.
High latitudes in
northern North
America and
Northern Europe and
Asia.
Central and eastern
North America,
Europe and western
Asia, and Eastern
Asia.
Temperate
Forest
Mild winters, quite warm Broad-leafed
to hot summers,
trees, which lose
moderate to heavy
their leaves in
precipitation
winter ETC.
Temperate
Grasslands
Light precipitation
usually in summer,
warm to hot summer
temperatures, cold
winters.
Grass (short &
tall)
Central parts of North
America, South
western part of South
America,
Mediterranean Asia
and Australia.
Tropical
Rainforest
High temperatures all
year, heavy precipitation
most of the year.
Many varieties of
broad-leafed
evergreen trees
of all sizes ETC.
Low latitudes, near
the equator in South
America, Africa, and
South-east Asia. Also
in Australia.
Tundra
Short summers,
temperatures always
colder than 10 C, very
cold long winters, light
precipitation.
High temperatures all
year, very light
precipitation
No trees, limited
plant growth
ETC.
In very high latitudes
Xerophytes such
as cactus and
other species,
plants tend to
have thick skins
or extended root
systems.
Varied climate; generally
cold, quite similar to
tundra at highest
elevations.
Varied
depending of
elevation,
highest
elevations have
tundra-like
vegetation.
In mid-latitudes.
south-western North
America, Western
South America,
Northern and
Southern Africa,
Central Asia, and
Australia.
In mountainous
regions of the world;
ex. Rocky Mountains
in North America,
Andes Mountains in
South America,
Himalayas in Asia.
Desert
Mountains
7.
Analyze patterns in the distribution of world ecosystems.
Here, students should be able to identify (using a map) patterns such as;
 The most predominant ecosystem in the high latitudes
 The name of the forest ecosystem in the low latitudes
 The most predominant ecosystem in South America
 The continents that do not experience a tundra ecosystem
 The name of the ecosystem in your local area.
8.
State the relationship between climatic conditions and the type of ecosystem
they produce.
Major ecosystems are classified by their dominant vegetations. The
dominant vegetation is determined largely by climatic conditions.
Therefore major ecosystems parallel climatic conditions. For example,
the Prairie vegetation region receives light rainfall and therefore the
dominant vegetation in that ecosystem is short and tall grasses
9.
Describe the structure of the equatorial rainforest.
An estimated 70-90% of life in the rainforest exists in
the trees, above the shaded forest floor. Primary
tropical rainforest is vertically divided into at least five
layers: the overstory , the canopy, the understory, the
shrub layer, and the forest floor. Each layer has its own
unique plant and animal species interacting with the
ecosystem around them. The overstory refers to the
crowns of emergent trees which soar 20-100 feet
above the rest of the canopy. The canopy is the dense
ceiling of closely spaced trees and their branches,
while the understory is the term for more widely
spaced, smaller tree species and juvenile individuals
that form a broken layer below the canopy. The shrub
layer is characterized by shrubby species and juvenile
trees that grow only 5-20 feet off the forest floor. The
forest floor is the ground layer of the forest made up of
the trunks of trees, fungus, and low growing vegetation.
These layers are not always distinct and can vary from
forest to forest, but serve as good model of the
vegetative and mechanical structures of the forest.
10.
Predict the ecosystem once given the rainfall and temperature combination.
For example, Average Annual Temperature = 18 oC – 27 oC
Average Annual Precipitation = 60 cm – 190 cm
11.
Ecosystem = SAVANNA (See Figure 6.9 on page 103.)
Write a sentence to describe the CLIMAX VEGETATION of the local area.
“The climax vegetation of the local area is the coniferous tree. It is conical in
shape. It has needles for leaves and has a thick bark.
12.
Identify the ecosystem represented by a climate graph
Example:
This graph illustrates climate
Conditions (i.e. high temperatures
year round and two distinct seasons –
a dry season followed by a wet season.
These conditions are found in a
SAVANNA ecosystem.
13.
Describe the factors that affect soil quality.
Soil fertility is measured in terms of a soil’s humus content relative to the amount of
ground-down bedrock it contains. Several factors determine this mixture:
i)
ii)
iii)
iv)
Leaching of soil will decrease the quality of soil and reduce
the thickness of the topsoil layer (horizon “A”).
Eluviation will decrease the quality of the soil and the
thickness of the topsoil layer. (horizon “A”)
The higher the rate of accumulation of humus, the better the
quality of the topsoil layer.
Capillary Action increases the thickness of the topsoil layer
(Horizon “A”) and therefore increases the quality of the soil.
14.
How would climatic conditions affect soil fertility in each of
the following regions?
i)
Rainforest: Have a soil known as LATOSOL, which although it
does experience a great deal of accumulation of humus from the
warm wet conditions, it also experiences a great deal of leaching
and eluviation which causes the soil to be VERY INFERTILE.
Temperate Grasslands: Moderate precipitation and temperate
temperatures allow for the accumulation of humus, little leaching
& eluviation, but a moderate amount of capillary action.
Combined, this leads to a VERY FERTILE soil known as
CHERNOZEM.
Tundra: Cold year-round temperatures provide for little plantgrowth and therefore little accumulation of humus. Cold
temperatures also slow down the decay of plants and animals,
while permafrost prevents adequate water drainage. Together this
all creates a soil, known as TUNDRA SOILS, which are VERY
INFERTILE.
ii)
iii)
iv)
Boreal Forest: Short summers and long cold winters, combined
with high precipitation results in a soil type known as PODZOL.
This soil is moderately leached and eluviated with little capillary
action. In addition the soil has increased acidity from the falling
needles of the coniferous trees that dominate. All of this adds up
to a soil that is INFERTILE.
15.
If given a picture of TWO soil profiles, identify which one
would be more fertile.
Soil profile “B”
would be most fertile
because it has the
thicker “A” horizon
containing the
nutrients and minerals
needed by plants for
growth.
16.
If given a picture of TWO soil profiles, identify which one
would have experienced Leaching/eluviation and Capillary
Action?
In this comparison soil
profile “A” would have
experienced leaching
and eluviation, while
soil profile “B” would
have experienced
capillary action
17.
Students should know how to determine the soil texture by
using a triangular graph, similar to the one shown below.
Procedure:
1.
Find clay % along the left side of the
triangle and read parallel to the
triangle base.
2.
Find the sand % along the triangle’s
base by reading the lines parallel to
the triangle side labeled as “%silt”
3.
Find silt % along the right side of the
triangle and reading lines parallel to
the “% clay” side of the triangle.
18.
Which type of soil texture is best suited for farming and why?
LOAM soils are best suited for farming. They enable the easy
penetration of plant roots and nutrients. Plant roots can find
plenty of air, water and nutrients.
19.
Which type of soil texture is LEAST suited to farming?
Clay soil would be least suitable for farming. Its thick, heavy
composition and poor drainage makes clay unsuitable for farming.
20.
Which TWO regions of the world suffer most from
desertification?
Africa and Asia
21.
What is the main cause of desertification?
It results when unpredictable climate variation (i.e. years of
adequate rainfall are followed by prolonged periods of drought) are
combined with unsustainable land-use practices (i.e. large increase
in population in an area, overgrazing of animals, over cutting of
forests etc.)
22.
Why does Africa and Asia suffer most from the threat of
desertification?
These regions have extensive dryland regions. These regions have
experienced huge increases in population over the past fifty years.
This has lead to overuse of the land in terms of overgrazing, water
usage and deforestation. Hence desertification is occurring in
these regions.
23.
Evaluate the validity of the following statement:
“Soil is a plentiful resource”
Currently there is enough arable land to meet the demands placed
upon it. Therefore it can be considered a plentiful resource. As
humanity’s needs change and as the amount of arable land
changes (through desertification, for example), soil may well cease
to be a plentiful resource.
24.
Using a map of the world that shows the soil types and
ecosystems found on each continent, state why patterns like
the following are true:
“In Africa, only 16% of the land is suitable for farming”
Answer:
Most of the land in Africa is desert or savanna, with
some patches of tropical rainforest or scrub. None of these
ecosystems are well suited for farming. Also, a large part of the
continent has a dry climate – either desert or semi-arid.
In answering these questions you need to focus on the types of
soils found in that continent (i.e. which ones are good for farming
and those that are not), and you should pay attention to the
climate of the continent to identify climates that support farming
(i.e. warm and moist) and those that do not (i.e. dry and/or cold)
25.
What is a worldview? What are the two world views? Which of
these do you support? Why?
Worldview: Is a conception of life, the beliefs about the world that
people hold when they say, “This is how it is” or “This is the way things
are.”
Worldview #1: The traditional European (Western) point of view, which sees the natural
world existing to serve the needs of humans, and therefore should be exploited to its
fullest. An example of this point of view would be:
Worldview #2:
Another worldview that has been deeply held for
thousands of years by aboriginals is the view that the earth is in delicate
balance and humans are merely a part of the balance. The emphasis is
NOT on human need but is on maintaining the balance in nature.
Comments from this worldview might include: