Download Biology 1001 Laboratory 1 INTRODUCTION TO ECOLOGY OR LIFE

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Biology 1001
Laboratory 1
INTRODUCTION TO ECOLOGY
OR
LIFE IN THE QUAD
PREPARATION
Read this exercise before you come to the laboratory.
Be sure to bring a Lab Coat to next week’s lab!
TEXTBOOK READING
Campbell and Reece, Chapt. 52, 53.
OBJECTIVES
After completing this laboratory exercise, the student should be able to:
1. Make a proper graph, if given a set of numerical data.
2. Explain or define the terms ecosystem, population, community, niche, competition.
LABORATORY ASSIGNMENTS
1. Participate in the "species" competition exercise.
2. Plot the graphs using the data from this exercise. Ask your lab instructor to check them for
errors. Final copies must be passed in for marking before you leave today.
3. Answer the questions on the lab assignment page.
INTRODUCTION
Ecology is the study of the interrelationship of living organisms and their environment. The
environment includes both the physical environment - such as temperature, humidity. pH, and light
intensity - and the biotic environment of all of the other organisms that interact with one another.
The interactions can take place at various levels, such as populations (all members of the same
species in an area), communities (all of the populations of an area), or ecosystem (both the
living communities and their nonliving components).
Populations of different species exhibit different distributional patterns. The most common type
is a clumped distribution, in which the members of a population are grouped together. Some
aggregations are short term, such as schools of fish or flocks of birds; others are seasonal, such as a
frog chorus; and still others are semipermanent, such as elephant herds or baboon troops. Some
plants are found clustered around a needed resource such as water or light. Others show an even
distribution. This is commonly demonstrated by territorial animals and plants such as the creosote
bush, which secretes poisons from its root systems to prevent competition. Many man-made
communities exhibit even distribution. Random distribution is rare in nature and occurs in areas
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where resources are somewhat evenly available and there is no biological or physical control over
distribution. One place where this pattern is observed is the tropical rain forests.
In addition to spatial distribution, many forms exhibit temporal patterns. Often these patterns
are associated with some aspect of reproduction, such as mating, hatching, flowering, seed set, and
migration.
Population size is controlled by many factors, including immigration and emigration,
birth rate, death rate, and carrying capacity (ability of the environment to support a
particular population size).
The maximum rate of reproduction of a species is called its reproductive potential if there
are no limiting factors (e.g., food or space) affecting its growth. Both the physical and biological
environments place limits on the reproductive potential. These limits, such as availability of
nutrients, home sites, food, and competition with other organisms, are collectively known as
environmental resistance and exert a dampening effect on growth. These limits tend to stabilize
and balance a population at a level somewhat below the carrying capacity of the environment.
Whenever addition to a population (from birth and immigration) exceeds subtraction (from
death and emigration), it will show growth. All successful species reproduce enough to ensure
replacement. Unless this happens, the species will be faced with extinction. As a population
increases, more organisms join the breeding population, and the number of offspring increases
proportionately. A number of obvious factors affect the rate of growth, including: (1) age of
reproduction, (2) frequency of reproduction, (3) number of offspring, and (4) number of times during
a lifetime that the organism reproduces. All organisms have the reproductive potential for
exponential growth. In this form of growth, more organisms are added to the population during
each succeeding time period, causing it to increase at faster and faster rates.
These exponential J-shaped growth curves are short-lived phenomena, characterized by
explosive, rapid growth followed by a massive die-off called a population crash. The spring
turnover in lakes, the addition of fertilizer, or the addition of a new ingredient to the environment
may trigger a massive response in the biotic community. Also, if a species is introduced into a new
environment, it may explode; this has occurred many times. If a population has been held in check
by a biological factor (e.g., parasite or predator) or a physical factor (e.g., lack of oxygen), the
population may experience exponential growth when the restricting factor has been removed.
Eventually, environmental resources become limiting factors once more, competition becomes
greater, the death rate increases, the birth rate declines, and the growth rate approaches zero.
Exponential growth has ended, and the population levels off close to a sustainable level. This
sustainable level is usually referred to as the carrying capacity of the environment for the species
being considered. The level is controlled by competition for the limiting environment factors. If the
population rises above this level, the ecosystem will become damaged and eventually the population
level will drop. If the damage is not too great, the system can recover (environmental homeostasis).
Some factors controlling population size are density dependent, and the larger the population,
the greater their effect. For example, limited food supply, predators, and parasites are much more
debilitating when populations are large. Other factors, such as freezing temperatures, are density
independent and exert their effects regardless of population size.
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Organisms that have the same ecological requirements fit in the same ecological niche. If we
let a circle represent the niche of an organism, everything within it is required for the organism to
survive. Thus, circle A represents the niche of a squirrel and circle B the niche of a whale. The
niches are completely separate, and it would be hard to imagine anything in nature that the two
have in common.
Concept of the niche.
B
A
If we compared the niche of the squirrel with the niche of a chipmunk, they would overlap.
A
B
The stippled area represents where the niches overlap and where the two organisms have the
same needs. This area represents a zone of competition between them (e.g., food, nesting sites,
escape from predators, and parasites), and the one with the best adaptations (fit) would have the
greater chance of surviving. What organism would have the greatest competition with the squirrel?
The answer is another squirrel. We find that the more closely two forms are related, the more
competition there is between them. Intraspecific competition (between members of the same
species) is greater than interspecific competition (between members of different species). This
presentation is an oversimplification of the niche concept (which is more like an ever-changing
polygon), but it may enable you to visualize competition more clearly.
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PART I - 'SPECIES' COMPETITION
In this exercise we will look at some aspects of competition by examining the interaction of two
artificial "species" competing for a number of common resources.
-----------------------------------------------------LABORATORY ASSIGNMENT 1
The class will be divided into two groups corresponding to the two "species" - forks and spoons.
Within each species you will be working in groups of two - one will have the fork or spoon and the
food pouch and the other will do the counting and recording. (You may change jobs at any time
you wish).
There are five "resources" - toothpicks, pasta noodles, string, pistachio nuts and rice, spread
over a large area. A unit of energy will consist of one toothpick, one pasta noodle, one string, two
pistachio nuts or five pieces of rice.
After each 30 second trial, the number of units collected by each individual will be counted and
recorded. Neither of these species is reproducing at this time and so an individual only requires
enough "food" for its own survival. If an individual collects less than 5 units in any one trial, it
will die from lack of food. If it collects 5 units or more, it survives. However, if it collects more
than 7 units it also dies, this time from overeating. The experiment will continue until one
"species" becomes extinct.
Each pair of students will record the units of food they collect and will decide if they "survived"
or "perished". The lab demonstrator will keep track of the overall survival of the two "species" as
well as time the intervals.
------------------------------------------------------LABORATORY ASSIGNMENT 2
l. Using the data that were recorded from the "species-competition" exercise (which will be
compiled on the chalk board in the lab), plot extinction curves for both "species" (number surviving
with respect to time). See Appendix page A-3 for help in making graphs. You should be able to
plot both species on the same graph. Use a piece of graph paper from the front bench. After you
have constructed your graph, have an instructor check it.
2. Using the data you recorded yourself, make a bar graph (not a histogram) to show the total
units 'eaten' for each type of energy unit. Use a piece of graph paper from the front bench. After
you have constructed your graph, have an instructor check it.
3. Redraw your final corrected graphs on the graph paper provided in your lab
manual. Pass these in for evaluation before you leave today.
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LABORATORY ASSIGNMENT 3
Be sure that you can answer the questions on page 1-7 before you leave the lab today.
-----------------------------------------------------TABLE 1-1
TRIAL
(30 sec)
INDIVIDUAL FEEDING DATA: “SPECIES” FORK
# of
toothpicks
# of
pastas
# of
strings
# of
pistachio nuts
SPOON
kernels
of rice
TOTAL
UNITS
1
2
3
4
5
6
7
8
9
10
11
12
TOTAL
UNITS
S=SURVIVED
P=PERISHED
N.B. A “unit” consists of l toothpick or l pasta noodle or l piece of string or 2 pistachio nuts or 5
grains of rice.
Survived = 5 to 7 units;
Perished = under 5 units or over 7 units
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TABLE 1-2 SURVIVAL OF FEEDING INDIVIDUALS
TRIAL
(time in 30 sec
intervals)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
# FORKS
SURVIVING
# SPOONS
SURVIVING
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LAB ASSIGNMENTS - LABORATORY 1
l. Which 'species' - forks or spoons - was more successful?
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2. What was your reasoning in answering question 1?
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3. Based on your own bar graph, state which energy units were easier to capture. Why?
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4. Why is a histogram not an appropriate type of graph for these data? __________________
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5. Look at the data from someone of the other ‘species’ than you. Compare it with your data.
Discuss the relative advantages and disadvantages of forks and spoons with regard to the
various kinds of energy units available.
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