Download File - Mrs. Sturges APES and Environmental Systems

Loss of Biodiversity Lab
Adapted from Carolina ©
Background
Tropical rainforests support a vast array of organisms, many of them still undiscovered by humans. However, the
rainforest is quickly diminishing, both in size and biodiversity. Other ecosystems experience similar losses.
Reasons include habitat destruction, pollution, overharvesting, invasive species and climate change.
Biodiversity refers to the number, variety and populations of species within a particular geographic area. A
decrease in biodiversity refers mainly to a loss of species. A population decrease indicates the potential for a
species’ disappearance from a community. A species that has disappeared from a particular community is said to
be extirpated, or locally extinct. A species whose population is so low that can no longer perform its ecological
service is said to be ecologically extinct.
Probably more biodiversity is lost to the degradation of habitat than to any other factor. As human populations
grow, they consume more resources, clearing forests to build farms, damming waterways, crowding coastal areas
with houses and hotels and mining mountains and prairies for minerals. The resident organisms either continue to
survive in the remaining natural areas of adapt to living amount humans. Some species cannot thrive in the altered
or fragmented habitats and eventually die out.
Pollution and disease contribute in several ways to the loss of biodiversity. A sudden chemical spill or waste
discharge may devastate a pond or lake community, eliminating many species at once. A chronic low level of an
environmental toxin often becomes dangerous as it accumulates in organisms over time. The concentration is
magnified in the tissues of consumers of these organisms. A classic example of this biomagnification of a toxin is
the decline of raptors and fish-eating seabirds in the 1960s due to their extensive feeding on fish that had already
accumulated some of the pesticide DDT into their own tissues. Mercury is a toxin that bioaccumulates and is
magnified in top predators such as tuna and swordfish. Disease agents, such as fungal parasites of plants, can
devastate a species, particularly, if the disease is introduced suddenly into a population without any inherited
immunity. For example, a fungus from Asian chestnut trees introduced to the eastern U.S. in the early 1990s
decimated the population of American chestnuts, a tree species of huge ecological and economic importance in the
eastern U.S.
Overharvesting reduces biodiversity as a species are removed from their habitat for human use or consumption.
Overharvesting has reduced populations of whales and American bison and has eliminated the passenger pigeon.
In many cases, direct losses indirectly affect other species, such as those that depend on the overharvested species
as a food source. Over collection of certain animals or plants whose parts are seen to have medicinal or other
traditional use often leads to a rapid decline in population. Populations as different as rhinoceroses and ginseng
plants have been depleted for this reason. Ironically, the rarer such a species becomes, the more profitable it
becomes to collect and sell on the black market.
Exotic species are organisms introduced deliberately or accidently into a habitat to which they are not native. Some
of those alien species are introduced and temporarily thrive before dying out, and some maintain small, localized
populations. Others, called invasive species, expand their range with increasing ecological, economic and
environmental consequences. The kudzu vine for example, was introduced to the U.S. in the late 1800’s as an
ornamental and later encouraged as an effective means of erosion control. Kudzu thrived too well in the Southeast,
where it has covered many native plant communities under its vast tangles. Nonnative animals may also
outcompete native species for food or habitat. The zebra mussel was accidently introduced to the Great Lakes in
the 1980’s, probably through the release of ballast water from a European ship that has traveled up the St.
Lawrence seaway. The muscle multiplied and spread so rapidly that it brought many native mussel species to the
brink of extinction. Not only does it outcompete the native mollusk for food, it grows upon their shells in such
numbers that the native mollusks’ shells cannot open and close effectively and they are smothered. In the Great
Lakes, the few native predators that eat the zebra mussels have not eaten them fast enough, and the mussel
population continues to grow. Zebra mussels present a direct problem for people, too, because they attach not only
to other mollusks, but also to underwater machinery at dams and power stations. Ecologists do not know how the
presences of the mussels will ultimately change the ecosystem. The mussels may bring about an increase in some
species, just as they have caused a decline in others. Regardless, they have altered the biodiversity for the
foreseeable future.
Recently, climate change has been recognized as a threat to biodiversity. The Fourth Assessment Report of the
United Nations Intergovernmental Panel on Climate Change, published in 2007, concluded that in the next century
climate change might be catastrophic for many ecosystems, noting that extinction becomes increasingly likely for a
larger percentage of the earth’s species as temperatures rise. Record temperature increases documented in the
Arctic and Antarctic already are changing the scale and pattern of seasonal ice melts, altering the habitat available
to polar species, possibly faster than they can adapt.
Measure of diversity has been of historical significance and their importance still remains today given the obvious
declines in habitat quality in almost every ecological system. The Shannon-Wiener diversity index, historically, has
been used to measure the effects of habitat quality.) Though the results of the Shannon Wiener index needs to be
used with caution, it provides a good learning tool for comparing two distinct habitats. The S-W index is a measure
of the likelihood that the next individual will be the same species as the previous sample. When pollution is present
or a human disturbance has occurred in a community, biodiversity is typically lower than in an undisturbed
community.
Species diversity is a combination of species richness and species evenness. Species richness is the total number of
species present in the community. Species evenness is the relative distribution of individuals among the species
present in a community. The evenness contrasts with dominance and is maximized when all species have the same
number of individuals. Evenness also looks at species equitability (how even are the numbers of individuals of
each species). For instance, say we have a sample of 100 fish containing only 2 species. We would say that the
species are equitable if there were 50 of each species. Conversely, if there were 99 of 1 species and only 1 of the
other, there would be no equitability. Given this second scenario, we would be pretty confident in our prediction
that if we were to sample 1 more individual that it would be the same as the 99 in that sample. Conversely, in the
previous scenario, we would have a 50/50 chance at predicting the next species sampled.
The S-W Index calculates the uncertainty of predicting a species (H). The H value will range from 0 (a community
with a single species) to over 7 for a very diverse community. A rich ecosystem with a high species diversity has a
large H value, while an ecosystem with little diversity has a low H value.
Species evenness (E) is a measure of how similar the abundance of different species are. When there are similar
proportions of all species then evenness is one, but when the abundance is very dissimilar (some rare species and
some common species) then the value increases. The higher the E value the more even a community is.
The Diversity Indices:
Species Richness (R): The species richness is based solely on the number of species found in the given area and
does not reflect the relative dominance of species.
R=s
Where:
s = the number of species
Shannon-Wiener Index (H)
H= -sum (Pi ln(Pi))
or
𝑆
𝐇 = − ∑𝑖=1 Pi(ln(Pi)) (H is a positive number!!)
Pi = relative abundance = ni/N
ni = number of individuals of species “i ”
N= total number of individuals of all species
Evenness:
E = H/ (lnR)
Overview
As you play the Loss of Biodiversity game, you simulate a forest ecosystem undergoing changes that affect its
biodiversity. Your group begins with a cup of assorted cubes, each color representing a different organism in a
deciduous forest community. Each round represents 1 year. At the beginning of each year, draw an event card,
which represents a condition or action that poses a threat to various organisms. If the drawn card corresponds
with a threat to an organism, remove the corresponding cubes, symbolizing the population loss causes by that
threat. Each cube represents a percentage of the population, Keep track of the number of cubes and the species of
organisms that are removed from the community over the course of 15 rounds. At the end of the game, graph the
populations over the 15-year period and answer the Laboratory Questions.
The game includes nine representative species of a temperate forest ecosystem—the American toad, grasshopper,
red-tailed hawk, oak, sedge, cottontail rabbit, field mouse, red-headed woodpeckers and a black rat snake. The
populations are interdependent in a complex food web. The grasshopper, cottontail rabbit and field mouse feed on
sedge. The grasshopper, field mouse, and red-headed woodpecker feed on oak. The American toad and red-headed
woodpecker feed on grasshoppers. Black rat snakes and red-tailed hawks feed on cottontail rabbits, field mice, redheaded woodpeckers and American toads. In addition, red-tailed hawks feed on black rat snakes.
Pre-Lab Questions:
Answer the following in complete sentences
1. Draw a food web of the forest community described in the Overview section. Since you are turning your lab
in through turnitin.com, you may draw it by hand and take a picture of it to insert into your lab (insert 
photo change text wrap to “tight” drag into place ). You do not have to draw actual animals- their
names will suffice. Remember, the arrow points in the direction of energy flow, “arrow to the mouth”
2. What are the main factors that contribute to a loss of biodiversity outlined in the background information?
3. Of those factors, which is the most detrimental to biodiversity loss?
4. What is the difference between an alien species and an invasive species?
5. If an ecosystem has an H value close to 0 what does that tell you about the diversity of that ecosystem?
6. Three communities have the same R value but differ in their H values. Community one has an H value of
3.35, community two has an H value of 1.56 and Community three has an H value of 4.94. Which
community is the most diverse? How can you tell?
7. Complete Table 1 to determine the R, H and E values of the community below. Some numbers have been
provided in order for you to check your method and understanding. You may take a picture of the final
version and insert into your lab (insert  photo change text wrap to “tight” drag into place ) or
recreate the table digitally.
A sample community of 256 individuals is comprised of 5 different species and the frequency of each species is
recorded below. Complete the table and determine the R, H and E value.
Table 1
Fish Species
Frequency
Pi
Species #1
84
0.3281 -1.1144
Species #2
4
0.0156 -4.1589
Species #3
91
0.3555
Species #4
34
Species #5
43
Sum=
1
Calculate:
R=
H=
E=
ln(Pi)
Pi*ln(Pi)
-0.3656
H
value, it’s
positive!
Materials
- container of 250 cubes, 25 each of 10 different colors
- loss of biodiversity game cards
- colored pencils
Procedure
1. Put all red cubes aside to start. The red cubes represent invasive species.
2. Start with 25 cubes of all other colors. Note the color of cube that represents each of the native
species. This information is provided to you in Table 2.
3. Each single cube represents 10 individuals- make sure to account for
this in all tables and graphs.
4. Shuffle the game cards and lay them face-down in a stack.
5. Draw the top card and red it aloud.
6. Remove or add the corresponding cubes, as indicated by the instructions on the card. Place the
card into a discard pile. Place the removed cubes into the container. These organisms are dead and
cannot be returned to your ecosystem.
7. Record in Table 2 how many of each cube remains in the data table. Remember that you start with
25 of each of the 9 native species and no invasives.
8. Keep track of the names and number of each invasive species introduced to the community. In the
data table, write these names under “Invasive Species” and record the numbers added during each
year
9. Repeat steps 3-6 until you have completed 15 rounds (years) of the game. Note: If a population is
extirpated, disregard that species in any following rounds that refer to it.
10. Before you put up your discard pile TAKE A PICTURE of what their information. This will help you
answer the first conclusion question.
11. For each round calculate the R, H and E values for the community using the tables provided.
Include the round number (round 1, round 2, etc), write in the names of the invasive species as
they appear in your game and the subsequent i value (10, 11, 12, and 13 respectively).
12. Use Table 2 to graph (a line graph) the populations of the various species (include invasives
collectively as one group) over time . Use a colored pencil corresponding to the color of each
species. Make sure to include an appropriate title and label the X and Y axis with appropriate
titles.
Some of your lab will be turned in, hard copy, in person while other components will be
turned in through turnitin.com. Here is the breakdown:
Physical, Hard Copy:
- Table 2
- S-W Index Tables (15 total)
- Line graph
Turnitin.com:
- Prelab questions (take pictures of your food web and Q#6 and insert into your lab
in the appropriate places—you may try to recreate them digitally but it is not
required)
- All conclusion questions
Table 2
Year
Organism
Color
0
American toad
Blue
250
Grasshopper
Black
250
Red-tailed hawk
Brown
250
Oak
Orange
250
Sedge
Light
green
250
Cottontail rabbit
Pink
250
Field mouse
Yellow
250
Red-headed
woodpecker
White
250
Black rat snake
Dark
Green
250
Invasive
species:
0
Red
0
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Species
i
American Toad
1
Grasshopper
2
Red-tailed hawk
Oak
3
4
Sedge
5
Cottontail rabbit
6
Field mouse
7
Red-headed
woodpecker
8
Black-rat snake
9
Invasive species
1:
Invasive Species
2:
Invasive Species
3:
Invasive Species
4:
ni
Round _____
pi
ln pi
pi ln pi
____
____
____
____
S=
N=
R=
i = the number of different species
S= total number of different species
ni = number of individuals (population)
N = total individuals
𝑛𝑖
pi = 𝑁
ln = use the “ln” button on your calculator
and then plug in pi
H=
1.00
E=
pi ln pi = multiply the pi column by the ln
pi column
H = -sum(Pi ln(Pi)) --- H IS POSITIVE!!
R = S (the number of different species)
𝐻
E=
(𝑙𝑛𝑅)
Conclusion Questions
Please write in COMPLETE, thoughtful sentences.
1. Examine the discarded stack of cards and categorize the cards according to the factors that
contributed to a loss of biodiversity in the forest community. List the factors in order of how
frequently they occurred over the 15 years, beginning with the most frequent and ending with the
least.
2. Which factor that contributes to a loss of biodiversity was not listed that can cause all other
factors?
3. Which event had the most devastating immediate consequence to a population? Describe what
happened.
4. Which event caused a population to decline the most over the long term? Describe what
happened.
5. Which round had the greatest biodiversity?
6. How can you tell?
7. Which round had the least amount of biodiversity?
8. How can you tell?
9. Which round was the most even?
10. Which round was the least even?
11. On the basis of the game’s results, calculate the percent change in each species’ population in the
ecosystem. You MUST show your setup/equation. To insert an equation (insert  equation 
start typing  adjust as necessary).
Percent Change =
𝑁𝑒𝑤 𝑃𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛−𝑂𝑙𝑑 𝑃𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛
𝑂𝑙𝑑 𝑃𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛
x 100
Note: A negative number is a decline in population, while a positive number is an increase
Your answer must IDENTIFY if it is a increase in population or a decrease in population. For example:
44−55
American Toad =
= -0.2 = A 2% decline in population
55