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Anton van Leeuwenhoek (1632-1723)   . . . my work, which I’ve done for a long time, was not pursued in order to gain the praise I now enjoy, but chiefly from a craving after knowledge, which I notice resides in me more than in most other men. And therewithal, whenever I found out anything remarkable, I have thought it my duty to put down my discovery on paper, so that all ingenious people might be informed thereof.

Anton van Leeuwenhoek. Letter of June 12, 1716

Anton van Leeuwenhoek was an unlikely scientist. A tradesman of Delft, Holland, he came from a family of tradesmen, had no fortune, received no higher education or university degrees, and knew no languages other than his native Dutch. This would have been enough to exclude him from the scientific community of his time completely. Yet with skill, diligence, an endless curiosity, and an open mind free of the scientific dogma of his day, Leeuwenhoek succeeded in making some of the most important discoveries in the history of biology. It was he who discovered bacteria, free-living and parasitic microscopic protists, sperm cells, blood cells, microscopic nematodes and rotifers, and much more. His researches, which were widely circulated, opened up an entire world of microscopic life to the awareness of scientists.

Leeuwenhoek was born in Delft on October 24, 1632. (His last name, incidentally, often is quite troublesome to non-Dutch speakers: “layu-wen-hook” is a passable English approximation.) His father was a basket-maker, while his mother’s family were brewers. Anton was educated as a child in a school in the town of Warmond, then lived with his uncle at Benthuizen; in 1648 he was apprenticed in a linen-draper’s shop. Around 1654 he returned to Delft, where he spent the rest of his life. He set himself up in business as a draper (a fabric merchant); he is also known to have worked as a surveyor, a wine assayer, and as a minor city official. In 1676 he served as the trustee of the estate of the deceased and bankrupt Jan Vermeer, the famous painter, who had had been born in the same year as Leeuwenhoek and is thought to have been a friend of his. And at some time before 1668, Anton van Leeuwenhoek learned to grind lenses, made simple microscopes, and began observing with them. He seems to have been inspired to take up microscopy by having seen a copy of Robert Hooke’s illustrated book Micrographia, which depicted Hooke’s own observations with the microscope and was very popular.

Leeuwenhoek is known to have made over 500 “microscopes,” of which fewer than ten have survived to the present day. In basic design, probably all of Leeuwenhoek’s instruments — certainly all the ones that are known — were simply powerful magnifying glasses, not compound microscopes of the type used today. A drawing of one of Leeuwenhoek’s “microscopes” is shown at the left. Compared to modern microscopes, it is an extremely simple device, using only one lens, mounted in a tiny hole in the brass plate that makes up the body of the instrument. The specimen was mounted on the sharp point that sticks up in front of the lens, and its position and focus could be adjusted by turning the two screws. The entire instrument was only 3-4 inches long, and had to be held up close to the eye; it required good lighting and great patience to use.

Compound microscopes (that is, microscopes using more than one lens) had been invented around 1595, nearly forty years before Leeuwenhoek was born. Several of Leeuwenhoek’s predecessors and contemporaries, notably Robert Hooke in England and Jan Swammerdam in the Netherlands, had built compound microscopes and were making important discoveries with them. These were much more similar to the microscopes in use today. Thus, although Leeuwenhoek is sometimes called “the inventor of the microscope,” he was no such thing.

However, because of various technical difficulties in building them, early compound microscopes were not practical for magnifying objects more than about twenty or thirty times natural size. Leeuwenhoek’s skill at grinding lenses, together with his naturally acute eyesight and great care in adjusting the lighting where he worked, enabled him to build microscopes that magnified over 200 times, with clearer and brighter images than any of his colleagues could achieve. What further distinguished him was his curiosity to observe almost anything that could be placed under his lenses, and his care in describing what he saw. Although he himself could not draw well, he hired an illustrator to prepare drawings of the things he saw, to accompany his written descriptions. Most of his descriptions of microorganisms are instantly recognizable.

In 1673, Leeuwenhoek began writing letters to the newly-formed Royal Society of London, describing what he had seen with his microscopes — his first letter contained some observations on the stings of bees. For the next fifty years he corresponded with the Royal Society; his letters, written in Dutch, were translated into English or Latin and printed in the Philosophical Transactions of the Royal Society, and often reprinted separately. To give some of the flavor of his discoveries, we present extracts from his observations, together with modern pictures of the organisms that Leeuwenhoek saw.

In a letter of September 7, 1674, Leeuwenhoek described observations on lake water, including an excellent description of the green charophyte alga Spirogyra: “Passing just lately over this lake, . . . and examining this water next day, I found floating therein divers earthy particles, and some green streaks, spirally wound serpent-wise, and orderly arranged, after the manner of the copper or tin worms, which distillers use to cool their liquors as they distil over. The whole circumference of each of these streaks was about the thickness of a hair of one’s head. . . all consisted of very small green globules joined together: and there were very many small green globules as well.”

A letter dated December 25, 1702, gives descriptions of many protists, including this ciliate, Vorticella: “In structure these little animals were fashioned like a bell, and at the round opening they made such a stir, that the particles in the water thereabout were set in motion thereby. . . And though I must have seen quite 20 of these little animals on their long tails alongside one another very gently moving, with outstretched bodies and straightened-out tails; yet in an instant, as it were, they pulled their bodies and their tails together, and no sooner had they contracted their bodies and tails, than they began to stick their tails out again very leisurely, and stayed thus some time continuing their gentle motion: which sight I found mightily diverting.”

On September 17, 1683, Leeuwenhoek wrote to the Royal Society about his observations on the plaque between his own teeth, “a little white matter, which is as thick as if ‘it were batter.” He repeated these observations on two ladies (probably his own wife and daughter), and on two old men who had never cleaned their teeth in their lives. Looking at these samples with his microscope, Leeuwenhoek reported how in his own mouth: “I then most always saw, with great wonder, that in the said matter there were many very little living animalcules, very prettily a-moving. The biggest sort. . . had a very strong and swift motion, and shot through the water (or spittle) like a pike does through the water. The second sort. . . oft-times spun round like a top. . . and these were far more in number.” In the mouth of one of the old men, Leeuwenhoek found “an unbelievably great company of living animalcules, a-swimming more nimbly than any I had ever seen up to this time. The biggest sort. . . bent their body into curves in going forwards. . . Moreover, the other animalcules were in such enormous numbers, that all the water. . . seemed to be alive.” These were among the first observations on living bacteria ever recorded.

Leeuwenhoek looked at animal and plant tissues, at mineral crystals and at fossils. He was the first to see microscopic foraminifera, which he described as “little cockles. . . no bigger than a coarse sand-grain.” He discovered blood cells, and was the first to see living sperm cells of animals. He discovered microscopic animals such as nematodes and rotifers. The list of his discoveries goes on and on. Leeuwenhoek soon became famous as his letters were published and translated. In 1680 he was elected a full member of the Royal Society, joining Robert Hooke, Henry Oldenburg, Robert Boyle, Christopher Wren, and other scientific luminaries of his day — although he never attended a meeting. In 1698 he demonstrated circulation in the capillaries of an eel to Tsar Peter the Great of Russia, and he continued to receive visitors curious to see the strange things he was describing. He continued his observations until the last days of his life. After his death on August 30, 1723, the pastor of the New Church at Delft wrote to the Royal Society: . . . Anton van Leeuwenhoek considered that what is true in natural philosophy can be most fruitfully investigated by the experimental method, supported by the evidence of the senses; for which reason, by diligence and tireless labor he made with his own hand certain most excellent lenses, with the aid of which he discovered many secrets of Nature, now famous throughout the whole philosophical World.

Citation:

Ford, B. J. 1991. The Leeuwenhoek Legacy. Biopress, Bristol, and Farrand Press, London. <http://www.ucmp.berkeley.edu/history/leeuwenhoek.html>

 

Lab 8   Population Genetics Write Up

Introduction:

Read and summarize the lab introduction being sure to include both HW equations and what each variable stands for, explain what a population is and what type of population HW applies to, list and explain the 5 assumptions necessary for HW to be true, and be sure to give a brief description (not the procedures) for each of the 4 cases in the lab.

Hypothesis:

Use the objective (s) for the lab and write them into a single statement for your hypothesis.

Materials:

In sentence form list the materials you will need including paper, pencil, PTC paper, index cards, and calculator.

Procedure:

Type 4 paragraphs, one for each case study. Remember to write in paragraph form without numbering steps.

Data & Analysis:

·        Include the 4 case study sheets with all calculations completed

·        Write out and answer the questions from your lab sheet. Remember to underline the question, but not the answer.

·        Write out and answer the questions at the end of Lab 8 in your lab manual.  Remember to underline the question, but not the answer.

Conclusion:

·        Explain the effect each of the situations had on the allele frequencies and genotypic frequencies (include supporting data)

·        Explain why each condition could or could not actually occur in nature

·        Explain the effect natural selection has on recessive traits

·        Explain how the HW law helps determine whether evolution is occurring

Click Here For Case Study Sheets

 

 

 

Lab 10   Physiology of the Circulatory System

 

Introduction: The human circulatory system is a collection of structures thorough which oxygen and nutrient rich blood flows to all tissues of the body for metabolism and growth, and to remove metabolic wastes. The blood is pumped to these tissues by the heart through a circuit composed of arteries, arterioles, capillaries, venules, and veins. Oxygenated blood is pumped to the tissues from the left side of the heart, whereas deoxygenated blood is pumped to the lungs from the right side of the heart. This circuit where gas exchange takes place within the alveoli of the lung is very important and is known as the pulmonary circuit. When the body is exercised changes can take place in the circulatory system that allow more blood to pass to actively respiring muscle cells and less to nonmuscular tissue. Increased heart rate, arterial pressure, body temperature, and breathing rate also occur during exercise.

Arterial blood pressure is directly dependant on the amount of blood pumped by the heart per minute and the resistance to blood flow through the arterioles. This is an important measurable aspect of the circulatory system and it is measured using a sphygmomanometer. This device has an inflatable cuff that connects to a hand pump and a pressure gauge, graduated in millimeters of mercury, by rubber tubing. The cuff is wrapped around the upper arm and inflated, the person taking the pressure then listens for two sounds and observes the gauge to determine what the blood pressure is. The systolic number is determined by the first noise heard as the cuff is deflated, and the diastolic number is determined by the last distinct noise heard.

Hypothesis: From this experiment it is expected that a subject’s heart rate and blood pressure will change during rest and exercise based on how physically fit they are. If the subject is in good shape the heart rate will not increase significantly and the blood pressure will increase. The opposite is true of someone in poor shape.

Materials: The materials used in this experiment include a blood pressure kit, alcohol swabs, a stopwatch, two depression slides, a cotton ball, four rubber bands, a pipet, a petri dish, a Daphnia culture, a stereomicroscope, and some ice.

Methods:

A. Measuring Blood Pressure: To measure blood pressure, one member of the lab group sat down in a chair, rolled up his sleeve, and then the sphygmomanometer cuff was placed around his upper left arm at heart level. The cuff was then pumped to 200mm Hg, which is safely higher than the blood pressure of the subject. The stethoscope was then placed in the well of the subject’s elbow, where the brachial artery is located, and pressure was slowly released as the taker listened for a pulse. The pressure on the gauge was noted when first sound of Korotkoff was heard, which is the pressure that blood is first able to pass through the artery during systole, representing systolic pressure. The sounds of Korotkoff are heard between the systolic and diastolic blood pressures. The diastolic pressure is the reading of the gauge at the time the sounds of Korotkoff can no longer be heard. The subject’s blood pressure was taken two more times and an average was calculated and recorded in Table 1.

 

Average Blood Pressure

 

 

	Systolic Pressure		Diastolic Pressure
Age in Years	Men	Women	Men	Women
10	103	103	69	70
11	104	104	70	71
12	106	106	71	72
13	108	108	72	73
14	110	110	73	74
15	112	112	75	76
16	118	116	73	72
17	121	116	74	72
18	120	116	74	72
19	122	115	75	71
20-24	123	116	76	72
25-29	125	117	78	74
30-34	126	120	79	75
35-39	127	124	80	78
40-44	129	127	81	80
45-49	130	131	82	82
50-54	135	137	83	84
55-59	138	139	84	84
60-64	142	144	85	85
65-69	143	154	83	85
70-74	145	159	82	85

 

B. Physical Fitness Test: The first numbers recorded from this section of the experiment were those of standing vs. resting blood pressure. To do this a member of the lab group had to lie down on a table for five minutes. After five minutes the subject’s blood pressure was taken while he was still lying down and the numbers were recorded in Table 2. The subject remained lying down for another two minutes, stood up, and their blood pressure was taken again. The standing systolic pressure was subtracted from the resting systolic pressure and recorded in Table 2. A chart was used to determine the number of points received by the subject and recorded in Table 3.

The next part of this section is where the subject’s standing heart rate was determined. Taken by the subject was the radial artery pulse by counting the number of beats for 30 seconds. That number was multiplied by 2 to obtain the number of beats per minute. That number was recorded in Table 3. Another chart was used to determine the amount of points the subject received for this section and that number was also recorded in Table 3.

Next the resting heart rate was determined by having the subject lie down on a table for five minutes. After five minutes the subject’s pulse was taken and recorded in Table 3. Once again a chart was used to determine the number of points the subject received for this section of the experiment and the number was recorded in Table 3.

Next the Baroreceptor reflex test was given to the subject. The subject had to lie down for five minutes, stand up quickly, and record the pulse. From this number the resting heart rate was subtracted and recorded in Table 3. A chart was then used to determine the number of points the subject received for this section and recorded in Table 3.

The endurance test was the last leg of this section of the experiment. To do this the subject stepped up with one foot onto an 18 inch high surface and then brought up the other foot onto the surface. This was continued for 15 seconds, and then his pulse was taken at several intervals. First the pulse was taken right after the exercise for 15 seconds and multiplied by four. This was repeated one more time after that as well. Then the pulse was taken every 30 seconds for 120 seconds after that. The data was recorded in Table 4. The amount of time it took for the subject’s heart rate to return to normal was figured and a chart was used to award points. These heart rates were then compared to the standing heart rate. Next, the standing heart rate was subtracted from the rate taken right after exercise, and yet another chart was used to award points.

 

C. Investigating Heart Rate in Daphnia: Two depression slides were obtained and a small piece of cotton was placed in the center of one of the slides. Several Daphnia were placed on the slide with a pipet and the other slide was placed on top of this slide and wrapped together with a rubber band on each end. A petri dish was filled with room-temperature water, 1cm deep and the slides were placed into it. The heart of the largest Daphnia was then located under the stereomicroscope and the number of beats in 15 seconds was determined, multiplied by four, and the results placed in Table 5. Into the dish was then added ice water and the same Daphnia’s heart rate was determined and recorded in Table 5. Gradually warm water was added and the heart rate was taken at five minute intervals until the normal heart rate is noted. These results were put in Table 5.

Results:

Table 1

 

 

Blood Pressure	Systolic	Diastolic
Trial 1	115	72
Trial 2	115	70
Trial 3	115	74
Average	115	72

 

Table 2

Standing vs. Resting Blood Pressure

 

Position	Systolic	Diastolic
Lying Down 5 min.	110	72
Lying to Standing	120	72
Change	10	0

 

 

Table 3

Fitness Points

 

Activity	Result	Fitness Points
Change in Blood Pressure	10	3
Standing Pulse Rate	78	3
Resting Pulse Rate	64	3
Baroreceptor Reflex	76	3
Heart Rate Recovery After Exercise	28	4
Heart Rate Increase After Exercise	18	2
Total Points	–	18

 

 

Table 4

Heart Rate After Exercise

 

Interval	No. of Beats		Heart Rate
0 to 15 sec.	24	X4=	96
16 to 30 sec.	19	X4=	76
31 to 60 sec.	35	X2=	70
61 to 90 sec.	35	X2=	70
91 to 120 sec.	35	X2=	70

 

 

 

Total Score	Cardiovascular Fitness
17 to 18	Excellent
14 to 16	Good
8 to 13	Fair
7 or less	Poor

 

 

 

Questions:

1. What changes occur in the circulatory system when a person stands up from a prone position? How do these changes affect the heart rate and blood pressure of the individual?

 

The circulatory system is not working very hard when a person is at rest so when that person stands up suddenly the blood pressure and heart rate of that person increase.

 

2. How does the circulatory system, and the heart in particular, of a conditioned athlete differ from that of a person in poor shape?

 

The heart of a conditioned athlete is stronger because it has been worked harder pumping more blood when that person exercises. The heart of a person in poor shape has not been worked as hard.

 

3. Why is high blood pressure dangerous? What health problems does it lead to?

 

High blood pressure is dangerous because the heart has to work to hard to push the blood through the various veins and arteries and a heart attack can occur.

 

4. What sort of behaviors encourage high blood pressure? Why?

 

Eating fatty foods and not exercising cause high blood pressure because the heart is not working hard to pump the blood, which makes it weak.

 

Table 5

 

 

Temperature (C)	Heartbeats per Minute
Room Temperature	200
0 to 5	84
10	160
15	152
20	204
25	200
30	212
35	216

 

 

Change in Metabolic Rate

 

 

Temperature Range	Rate of the reaction (change in heart rate)
0-10	Q10 =1.9
10-20	Q10 =1.275
20-30	Q10 =1.04

 

 

 

Questions:

1. Why does the rate of activity of ectothermic organisms increase with a rise in the temperature of its environment? How is this different from an endothermic organism?

 

Ectothermic organisms’ body heat is determined by the environment, so their metabolic rates also change with this. Endotherms have a constant body temperature and do not change their metabolic rate strictly based on environmental conditions.

 

2. If this experiment were performed on a human subject, what results would you expect? Explain.

 

A human’s heart would also be affected by the temperature changes, but not to the extent that the Daphnia heart did.

Error Analysis: The only possible source of error in this lab would have been the slight misreading of the gauge on the sphygmomanometer.

Conclusions: Cardiovascular fitness is very important to living a healthy life. If one doesn’t exercise and eat healthy foods they run a risk of being in poor shape and having a heart attack or other serious things. Heart rate and blood pressure readings can give a person a good idea about how healthy they are or how healthy they need to be. Blood pressure is so important to a person’s health it is checked at every visit to the doctor or hospital.

 

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Lab 11   Animal Behavior

Introduction:

 

Ethology is the study of animal behavior. An animal’s behavior is its response to sensory input. There are three types of behaviors: orientation, agonistic, and mating.

Orientation behaviors take the animal to its most favorable environment. Taxis is when an animal moves toward or away from a stimulus. Taxis is often characterized by light, heat, moisture, sound, or chemicals. Kinesis is another type of movement that involves orientation. Kinesis is a movement that is random and doesn’t involve a stimulus. So an animal would respond to light by moving everywhere in random directions.

Agonistic behavior is when animals respond to each other in aggressive or submissive movements. Like the hair on dogs backs when they get ready to fight. Another excellent example is the Betta fish, which is sometimes studied in labs.

Mating behaviors are activities that involve finding, courting, and mating with a member of the same species. An example would be a peacock fluffing up its feathers to attract females.

 

Hypothesis:

 

Pill bugs will prefer the wet side to the dry side of the petri dishes because they are used to living in dark moist conditions, such as under rocks or in rotting trees.

 

Materials:

 

Materials used in this experiment involved: a double petri dish combination, 10 pillbugs, bedding material, scissors, pencils, 2 pieces of filter paper, a piece of black construction paper, and a watch.

 

Methods:

Place 10 pillbugs in the petri dishes along with a little bedding material in each container. Observe them for about 10 minutes noting any observations that are characteristic to the bugs. Once that is done, take a piece of filter paper and soak it in water, then put the wet piece in the bottom of one of the containers. Put the other dry paper in the bottom of the other container. Put 5 pillbugs on each side and count how many bugs there are on each side every 30 seconds for 10 minutes.

Our designed experiment involved the same methods except substituting filter paper with a piece of black construction paper. Cut out the circular paper from a sheet of black paper and put it in one of the containers along with some bedding material. Place 5 pillbugs on each side and count how many there are on each side every 30 seconds for 10 minutes.

 

Results:

Table 11.1

 

Table 11.2

 

 

1. What conclusion do you draw from your data? Explain physiological reasons for the behavior observed in this activity.

– The bugs preferred it in the wet conditions. They probably like it there because they live in place like that, under rocks or in trees or just in the soil. That is probably the only way they can keep cool and obtain moisture.

 

2. Obtain results from all lab groups in your class. With respect to humidity, light temperature, and other environmental conditions, which types of environment do isopods prefer? How do the data support these conclusions? Give specific examples.

– Our class didn’t exchange data with each other.

 

3. How do isopods locate appropriate environments?

– They use their antennae for a lot of their locating. One thing that I observed was they did use their antennae when they were walking around. They probably don’t have very good eyesight.

 

4. If you suddenly turned a rock over and found isopods under it, what would you expect them to be doing? If you watched the isopods for a few minutes, how would you expect to see their behavior change?

– I would expect them to scurry around, probably find and tunnel and go down it to keep out of the sunlight. If you found one that wasn’t already underground, I would probably see it walking out in the grass, looking for another object to go under.

 

5. Is the isopod’s response to moisture best classified as kinesis, or taxis? Explain your response.

– I think it’s best classified as kinesis because they moved around in random directions. Some of them just sat there while the others were moving around.

 

1. Select one of the variable factors above, and develop a hypothesis concerning the pillbug’s response to the factor.

– Background Color- I hypothesize that the pillbugs will prefer the dark background color over the light background color because they are used to living in dark places for most of their lives.

 

2. Use the material available in your classroom to design an experiment. Remember that heat is generated by lamps.

A) State the objective of your experiment.

– To see if background color has anything to do with behavioral responses in pillbugs to their environment.

 

B) List the materials you will use.

– Scissors, black construction paper, pillbugs, petri dish containers, and bedding material, as well as a watch.

 

C) Outline your procedure in detail.

– Our designed experiment involved the same methods as the real experiment except substituting filter paper with a piece of black construction paper. Cut out the circular paper from a sheet of black paper and put it in one of the containers along with some bedding material. Place 5 pillbugs on each side and count how many there are on each side every 30 seconds for 10 minutes.

 

 

Error Analysis:

 

Not many things could have drastically changed our results. All we had to do was to watch them and watch the time. If the bugs were forced into one of the chambers then that could have changed our results. Also if we hadn’t had kept a good time method then we could have been lost.

 

Conclusions:

 

The bugs like it in the wet environment because that is what it’s used to. It’s an easy way to get water and stay cool in their environment. They also liked the dark background because, again, that is what they are used to in their environment, under rocks or other things.