G2: Ecosystems and Biomes
1. Define the following terms:
Gross production: the total amount of organic matter produced by plants in an ecosystem.
Net production
Biomass
2. Explain why gross production is always higher than net production.
3. State the calculation for determining gross production, net production and respiration.
4. The following passage outlines some of the energy flow in an ecosystem.
From the IB Biology QuestionBank CDRom
a. Calculate the efficiency (in %) of the conversion of light energy into gross production.
b. Draw a pyramid of energy for the ecosystem.
c. Explain the shape of the pyramid of energy.
5. Study the energy flow diagram below.
From the IB Biology QuestionBank CDRom
a. Calculate the net production of the autotrophs.
b. Calculate the percentage of energy lost as heat in:
i.
Autotrophs
ii.
Heterotrophs
c. Suggest reasons for the differences in energy loss as heat between autotrophs and heterotrophs.
6. Explain the small biomass and low numbers of organisms in higher trophic levels.
7. Discuss the difficulties of classifying organisms into trophic levels
8. Describe what is meant by ecological succession.
9. Describe the effects of succession on the following factors:
Productivity
Biomass
Biodiversity
10. Explain the following ways in which living organisms affect the abiotic environment in primary succession:
Soil composition & strength
Organic nutrients
Mineral Nutrients
Water uptake
11. Distinguish between primary and secondary succession, with examples:
Primary
Secondary
Example
Differences
Similarities
12. Try the succession reading exercise below
Succession, a series of environmental changes, occurs in all ecosystems. The stages that any ecosystem passes through are
predictable. In this activity, you will place the stages of succession of two ecosystems into sequence. You will also describe
changes in an ecosystem and make predictions about changes that will take place from one stage of succession to another.
The evolution of a body of water from a lake to a marsh can last for thousands of years. The process cannot be observed
directly. Instead, a method can be used to find the links of sttages and then to put them together to develop a complete
story.
The water level of Lake Chinolawa in Chiapas was once 18 meters higher than it is today. As the water level fell, land was
exposed. Many small lakes or ponds were left behind where there were depressions in the land. Below are illustrations and
descriptions of four ponds as they exist today. Use the illustrations and descriptions to answer the questions about the
ponds.
Pond A: Cattails, bulrushes, and water lilies grow in the pond. These plants have their roots in the bottom of the pond, but
they can reach above the surface of the water. This pond is an ideal habitat for the animals that must climb to the surface
for oxygen. Aquatic insect larvae are abundant. They serve as food for larger insects, which in turn are food for crayfish,
frogs, salamanders, and turtles.
Pond B: Plankton growth is rich enough to support animals that entered when the pond was connected to the lake. Fish
make nests on the sandy bottom. Mussels crawl over the bottom.
Pond C: Decayed bodies of plants and animals form a layer of humus over the bottom of the pond. Chara, a branching green
algae, covers the humus. Fish that build nests on the bare bottom have been replaced by those that lay their eggs on the
Chara.
Pond D: The pond is so filled with vegetation that there are no longer any large areas of open water. Instead, the pond is
filled with grasses. The water dries up during the summer months.
a) Write the letters of the ponds in order from the youngest, to the oldest.
b) Black bass and bluegill make their nests on sandy bottoms. In which pond would you find them?
c) What will happen to the black bass and blue gill as the floor of the ponds fills with organic debris?
d) Golden shiner and mud minnows lay their eggs on Chara. In which pond would you find them?
e) Some amphibians and crayfish can withstand periods of dryness by burying themselves in mud. In which pond(s)
would they survive?
f)
Dragonfly nymphs spend their early stages clinging to submerged plants. Then, they climb to the surface, shed their
skins and fly away as dragonflies. Which pond is best suited for dragonflies?
g) In which pond will gill breathing snails be replaced by lung breathing snails that climb to the surface to breathe?
h)
Some mussels require a sandy bottom in order to maintain an upright position. In which pond will they die out?
13.
Succession cloze exercise – use the words form the word bank to complete the statements below. Words can be
used more than once.
__________________ is the orderly, natural changes and species replacements that take place in the communities of an
ecosystem.
* Succession occurs in stages that are somewhat predictable.
* Succession is difficult to observe because it takes __________________ _________ __________________ to see the
community succeed from one to another.
Two types of succession:
1. __________________ __________________ is the colonization of new land that is exposed by avalanches,
volcanoes, or glaciers by pioneer organisms. (Starts from rocks)
2. __________________ __________________ is the sequence of community changes that take place after a
community is disrupted by natural disasters or human actions. (Start from soil & left over organisms)
Characteristics of primary succession:
1. The first species to colonize an area in primary succession are __________________ __________________ .
2. The final community in succession that is a stable, mature community that undergoes little or no change in
species is called a __________________ __________________ .
Characteristics of secondary succession:
1. Secondary succession begins in places that have had communities of organisms exist before. They also begin with
soil instead of rock. This means they take __________________ time to change than primary succession.
2. Secondary succession begins with __________________ __________________ and ends with a
__________________ __________________ just like primary succession communities.
Comparing and contrasting primary and secondary succession:
1. Similarities: Both are changes that occur to whole ecosystems, both begin with pioneer species, and both end with
similar climax communities for a given area.
2. Differences: Primary begins with __________________ and no __________________ while secondary begins
with soil left from a previous community. Secondary has had living things while primary has not had living things.
Primary takes longer than secondary.
Causes of plant succession:
1. Plants immigrate by means of __________________ __________________ (spread) and then germinate in new
locations.
2. Plants __________________ with each other for light, water, and nutrients. The best “competitor” wins.
3. __________________ __________________ : plants add organic matter to the topsoil which alters the soil.
This in turn changes the plants and animals that live in that site.
4. __________________ : As plants slowly modify the site, this leads to some stable state. Succession “seeks”
stability.
WORD BANK
site modification
compete
less
decades to centuries
rocks
climax community
soil
succession
primary succession
stabilization
secondary succession
seed dispersal
pioneer species
14. Distinguish between biome and biosphere.
15. Explain how rainfall and temperature affect the distribution of biomes.
16. Whittaker’s Climograph is a well-known representation of temperature, rainfall and distribution of biomes in the
world:
From http://www.zoology.ubc.ca/~etaylor/413www/commun_dist2.html
Identify the biomes likely to be found under these conditions:
i.
180cm y-1, 10oC ii.
0-50cm y-1,0-30oC
-1
o
iii.
60cm y , 10 C
-1
o
iv.
250-450cm y , 20-30 C v.
0-50cm y-1,-15-0oC
-
17. Describe the characteristics of the following biomes, using individual climographs and including details of
vegetation. You may adjust the graph axes as required.
18. Biome Map Coloring Exercise -Color the map according to the clues listed below.
a) The dotted lines represent the border between the U.S. and Mexico and Canada. All other lines show biome
borders. Color the country borders (dotted line) red.
b) Northern Canada and Alaska are tundra - color the tundra light blue
c) Most of Canada is boreal forest. Color the boreal forest dark green.
d) The west coast of the U.S. is mainly temperate forest where California is. The east coast, all the way to the center of
the country is also temperate forest. Color the temperate forest light green.
e) The Midwest (middle of the U.S.) is temperate grassland. Color the grassland yellow.
f) The eastern edge of Mexico and Central America, Hawaii, and the Caribbean Islands are all tropical rain forests.
Color those purple.
g) There is a northwest coniferous forest located in the far corner of the U.S (northwest). Color the northwest
coniferous forest brown.
h) The great lakes and the lakes in Canada are freshwater. Find each freshwater lake and color it pink.
i) The bodies of water surrounding the continent are salt water. Color the coastal areas dark blue.
j) The western region of the U.S. as well as Northern Mexico is desert. Color the desert orange.
k) The western edge of Mexico is temperate forest. Color it the same color as you did the other temperate forests.
l) Color code the squares at the bottom to match your biome colors.
m) Label the countries: U.S.A., Canada, Mexico
Boreal Forest