brine shrimp lab

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Kevin Sung

Mr. Teer

AP Biology 4

Brine Shrimp Lab (Habitat Selection)

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I. Background

Every organism in this world has a preference as to the best and ideal habitat to

live and breed in. To study these inclinations, scientists study ethology, which is the

study of animal behavior. In order to study ethology, observation of animal behavior is

vital and interpreting their action is essential. By learning an organism’s behavior,

scientists can then piece together the organism’s entire lifestyle and its predilection of a

certain habitat. Since animals cannot alter the environment, they tend to position

themselves in a favorable milieu. This process is called habitat selection. Habitat

selection allows organisms to produce and live abundant lives in the preferred

environment.

As the common man knows, too much of anything will more than likely kill you.

Too little-just as dangerous. For example, if a person decides to never ingest any

Vitamin C, he or she will suffer from sicknesses like scurvy or bleeding gums. Likewise,

if a foolhardy individual decides to take too many Vitamin C tablets, he/she will soon

learn that they serve as a perfect laxative. Shelford’s Law of Tolerance describes this

relationship between quantities and resulting effects; except in science terms it is

stated: “too much of an environmental factor can be just as bad as too little.” The

tolerance range of most organisms is portrayed as a bell curve on the chart.

There are two main types of animal orientation behavior, that is, animal

movement caused by sensory input. The first of these is taxis, which is when an animal

moves directionally in response to a stimulus. For example, a female tick has a

photosensitive body surface. When she senses light, she moves to the end of a branch

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or twig to wait for a mammal to feed off of. This movement toward the light can be

considered taxis. The second type of orientation behavior is kinesis. In kinesis, the

stimulus causes a random change in the animal’s speed or direction, but the animal

does not move toward or away from a stimulus. For example, in wood lice, the speed at

which the animal moves is altered by a kinetic response.

In this particular experiment/lab, the test subjects are called brine shrimp, or

Artemia salina. (Their other names include sea monkey and fairy shrimp.) They are

crustaceans much similar to lobsters. At around 1 cm or so in length, they glide with

“wings” that are actually 11 pairs of appendages that act as paddles. These shrimps

require salt (brine) in their water in order to survive. In addition, they are quite fragile

and die off easily, hence the mass reproduction. Extra facts include that they feed on

algae and other microscopic organisms.

II. Overview

The point of this experiment is to examine the habitat preferences of the brine

shrimp, Artemia (salina). We will use controlled experimentation to determine the

thermal, pH and light environment preferences of the brine shrimp.

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III. Objectives and Questions

Do brine shrimp prefer certain thermal, pH and light ranges over others?

At the completion of this lab, we should be able to:

Design and conduct an experiment to measure the effect of environmental

variables on habitat selection

Describe the relationship between dependent and independent variables

Design data charts appropriate for both group and class data

Draw histograms comparing the controls to the experimental group for pH,

temperature, and light preferences

Calculate Chi Square to determine if preferences were significant for each

treatment

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IV. Hypothesis

In this experiment you will brine shrimp a choice of different temperature, pH and

light environments and then count the number of brine shrimp found in each variation of

the environment. For instance, you will give them a choice of a cold environment, a

cool environment, and a hot environment.

State the null hypothesis and at least one alternative hypothesis for each set of

environmental conditions, temperature, pH and light.

Null Hypothesis: The temperature, pH levels, and lighting of the environment will not

affect brine shrimp in any way possible.

Alternate Hypothesis:

Since salt water (brine water) has a pH level that of a base, the more

acidic the pH level of the water, the more hostile the environment is for the

shrimp, which will result to death inevitably.

Although according to research that brine shrimp can survive in hospitable

temperatures, their constant temperature for the ideal environment is

around 80oF; therefore, a temperature too cold (50oF) or too hot (100oF)

will result in a dead brine shrimp.

Lighting of the environment will not affect the brine shrimp organism at all.

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V. Materials

This lab experiment will use the following materials:

4 Tygon tubes at least 100 cm in length

8 corks or stoppers

3 screw clamps

Brine shrimp in aquatic solution

50 mL syringe

Ice

Hot water

0.1 M HCL solution

0.1 M KOH solution

Screens

Cups

Petri dish

Eye dropper

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VI. Safety

There are several safety concerns that must be observed and rules that must be

enforced to prevent injury. First of all, the chemical solutions cannot be ingested or

recklessly played with. Goggles, gloves, and aprons are ideal for this experiment as

well. Being careful with the hot water would also be a good safety procedure to follow.

The brine shrimp cannot be eaten under any certain circumstances. Not only may the

eater be subjected to harmful chemicals, but food poisoning may follow.

If the acid HCL spills onto the skin, DO NOT rinse with water. Instead, a weak

base to counteract the acid should be used. In addition if water or any other aqueous

solutions spill into the eye, immediately run to the eyewash station and fully rinse the

eyes out. A good idea would be to take out contacts beforehand. As in any other

experiment, follow the teacher’s instruction and do not play around in the lab.

Glassware and other lab equipment should be handled carefully. After the experiment,

the equipment used should be safely put back after cleaning and the chemicals should

be disposed of properly, according to the teacher’s instructions. In general, if any

accidents were to occur, informing the teacher should be the first step taken.

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VII. Experimental Design

#1. We must design a controlled experiment to test the preference of brine shrimp to

each of the three environmental conditions, temperature, pH, and light levels. That

being true, why do you suppose you were given 4 tubes instead of just 3?

Another tube is used as a “control group”. The purpose of a control group is to

compare it to the altered environments. Therefore, the differences can be observed by

comparison.

#2. We are going to put the brine shrimp inside the tubes. How will this be done?

We must consider the safety of the shrimps; therefore we have to put them gently

into the tube without injuring the specimen. To do this, there are several ways. The

easiest way would probably to get a funnel that feeds into the Tygon tubes. Then we

can simply pour the shrimp into the funnel which will course into the Tygon tubes.

#3. How will we create the different ranges of environments inside the tubes such as

cold, cool, warm, and hot; highly acidic, slightly acidic, slightly basic, and highly basic;

full light, slightly dark, moderately dark, and dark?

To change the temperature of the water, one side of the tube has to be

containing ice water while the other side holding hot water. As they converge at the

center, the cool and warm temperatures are produced. As for the lighting, one end of

the tube will be covered with something to produce artificial darkness while the other

end is being shined upon by a certain light source. Finally, the pH level will be

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controlled by the chemicals placed in the water (KOH and HCL). These two chemicals

will change the water’s pH level according to their characteristic, as KOH is basic.

#4. How long will we give the shrimp to move to their preferred habitat?

According to the teacher’s instructions and everyday practicality, we should wait

around 30 minutes before observing the shrimp and counting the deceased.

#5. Once they have moved, how will we separate the sections so we can count the

shrimp in each section?

Judging from the Materials list, we will most likely be using screens to separate

the shrimp into different sections. The screens will function as barriers between the

different environments. Therefore, the brine shrimps will not be able to move.

#6. What method are we going to use for counting the shrimp in each section?

Once again according to the teacher, we are going to pour them out one section

at a time counting the number of deceased shrimp and also to observe where the

majority of the shrimp go to find their new habitat.

#7. How will we set up the control tube? What conditions will represent the “normal”

situation for the control with regard to temperature, pH, and light?

After doing research on brine shrimp, the conditions of the control tube should

have a pH level of around 8-9, temperature around 80oF, and slightly dark.

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VIII. Data Charts

Control Group

Individual Data:

Section 1 Section 2 Section 3 Section 4

Number of Shrimp

pH Level of Solution

Individual Data:

Highly Acidic Slightly Acidic Slightly Basic Highly Basic

Number of Shrimp

Class Data:


Number of Shrimp

Temperature Variations

Individual Data:

Cold Cool Warm Hot

Number of Shrimp

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Class Data:

Cold Cool Warm Hot

Number of Shrimp

Light Variations

Individual Data:

Dark Mod. Dark Slightly Dark Full Light

Number of Shrimp

Class Data:


Number of Shrimp

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X. Sources of Error

What are some potential problem areas that could cause error in your results?

You need to think about these in advance and attempt to minimize their impact.

There are several different areas where error had happened in our experiment.

For example, when we were placing the shrimp into the proper Tygon tubes, the brine

shrimp specimen may have been damaged due to the concussive drop they

experienced from the pipette into the tube. For the Temperature variation test, it may

have been rather inaccurate because our heat pad may not have been as hot as it

should have been. Therefore, the hot temperature was still habitable by the brine

shrimp. Another source of error may have occurred in the pH level variation group. The

acid and base may not have been as spread apart as we would have wanted it.

Instead, the solutions of KOH and HCL were usually clumped around the ends of the

tubes, close to the corks, so only that part was actually concentrated of acid/base. The

light variation experimentation group also experienced error. Our group did not have a

good idea how dark the slightly dark and the moderately dark should have been. We

basically fudged the darkness of the tube for that particular test group. Other sources of

error may have occurred due to manhandling. A shrimp may have been counted twice

or not at all. In addition, some of the clamps were not fastened tight enough, so water

and shrimp from other sections were also poured into the section being observed. In

general, many sources of error occurred throughout this experiment.

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XI. Calculations: Chi Square Chart

pH Level:


# Observed 0 226 553 326

# Expected (average) 276 276 276 276

(#Observed-#Expected) -276 -50 277 50

(#Observed-#Expected)2 76,176 2,500 76,729 2,500

(#Observed-#Expected)2

#Expected 276.0 9.1 278.0 9.1

Chi Square (X2) = ∑ (¿Observed−¿Expected )¿Expected = the sum of the bottom line = 572.2 _

Temperature:

Cold Cool Warm Hot

# Observed 96 378 547 560


(#Observed-#Expected) -299 -17 152 165

(#Observed-#Expected)2 89,401 289 23,104 27,225


#Expected 226.3 0.7 58.5 68.9


2

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Light Variation:


# Observed 689 672 364 220


(#Observed-#Expected) 203 186 -122 -266

(#Observed-#Expected)2 41,209 34,596 14,884 70,756


#Expected 84.8 71.2 30.6 145.6


The number of Degrees of Freedom = (the number of categories you have -1).

How many Degrees of Freedom are there in this experiment? 3____

The Chi Square Chart has alpha level of 0.05, there is only a 95% chance it is correct.

What is the critical Chi Square Value for this experiment? 7.82____

If the Experimental Chi Square Value is less than or equal to the Critical Value, we must

accept the Null Hypothesis to be true (fail to reject the HO).

Do we accept or reject the (HO)? Reject__ Is there a difference? Yes__

If so, which are there statistically more of? For pH levels, most of the shrimp

go to the Slightly Basic section, for Temperature, the shrimp cluster around the

Hot portion, as for Light, the shrimp stay around the Dark section.

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XII. Conclusions

For each variable: temperature, pH and light; do we accept or reject the null

hypothesis?

We rejected the null hypothesis because the evidence and observations that

translated onto the Chi Square Calculation Charts proved that the Critical Value

of the Degrees of Freedom did not equal to or was less than that of the

Experimental Chi Square value. Simply put, the shrimp had a preferred section of

habitat for each of temperature, pH levels, and light variations.

If we rejected the null hypothesis, which habitat did the brine shrimp prefer for each

variable?

Since we rejected the null hypothesis, the habitats preferred for the variables:

pH Levels: The shrimp preferred the Slightly Basic section.

Temperature: The shrimp occupied mostly the Hot section of the tube.

Light: The shrimp had a preference of the Dark section in the tube.

brine shrimp lab

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