Category: Curriculum Map

Origin of life PPT Qs

Origin Of Life
ppt Questions

Early Thoughts on Life

1. What was Aristotle’s idea about how life arose called?

2. What is another name for spontaneous generation?

3. Explain spontaneous generation of life.

 

4. How long did the idea of abiogenesis or spontaneous generation last?

5. The idea of abiogenesis lasted so long because, instead of testing their ideas, people based their beliefs on what?

 

6. Were their observations tested?

7. Did they use the scientific method for their observations?

Examples of Spontaneous Generation

8. What observation about new life did Egyptians make when the Nile River flooded each year?

 

9. What observation about new life did Medieval farmers make when they stored their grain each year?

 

10. The English people centuries ago, threw their garbage and sewage out on the streets. What observation about new life did these people make?

 

 

11. This practice led to a plague that killed many Europeans. What was this plague called and what carried the disease organism?

 

 

 

12.Before refrigerators, large slabs of meat were hung after being purchased. What observation about new life was made from this practice?

 

 

13. People believed so strongly in abiogenesis that they had recipes for making living things. Name two organisms that had accepted recipes.

 

Disproving Spontaneous Generation

14. Francesco ____________ was an early scientists who conducted experiments to try and disprove spontaneous generation.

15. What was Redi’s hypothesis?

 

16. Explain how Redi tried to prove this.

 

 

 

17. What were the results Redi found in the closed jars & why?

 

18. What were the results in the open jars?

 

19. How did maggots appear in the open jars?

 

20. Complete this table summarizing Redi’s experiment:

 

Evidence Against Spontaneous Generation
Unsealed Jar
Sealed Jar
Gauze Covered jar

 

21. Redi’s experiment disproved spontaneous generation for _____________ organisms.

Use of the Scientific Method

22. Did Francesco Redi use the scientific method in his experiment?

23. What served as the control in Redi’s experiment?

 

24. What jars served as the experimental groups?

25. What was Redi’s conclusion?

 

Disproving Spontaneous Generation of Microbes

26. Anton Van _______________ made one of the first simple microscopes.

27. Leeuwenhoek called the living things he saw in pond water ______________.

28. By the end of the 19th century, these organisms were known as ______________.

29. John _____________ did experiments with microorganisms growing in broths.

30. Needham believed there was a __________ __________ present in nonliving substances like air.

31. Why were bacteria able to grow in Needham’s soups?

 

32. What could have been done to the broths to kill the bacteria already present?

33. What scientists repeated this experiment but with boiled broth?

34. After boiling, what did Spallanzani do to the tops of the bottles? how did this help?

 

35. Critics of Spallanzani’s experiment said there was not enough _______ for the bacteria to survive and that boiling had destroyed the _________ __________.

The Theory Changes

36. What did the Paris Academy of Science do in 1860 to solve the problem?

 

37.Who won the prize? 

38. What was Pasteur’s experimental hypothesis?

 

39. What was the shape of Pasteur’s flasks? Include a sketch.

 

 

40. What was the special S-shaped neck intended to do?

 

41. Did Pasteur boil the broth in his flasks? Why?

 

42. The flasks were left at ___________ locations.

43. Did the broth change cloudy because microbes were growing in it?

 

44. What was visible in the neck of the flask after collecting there?

45. Once the S-shaped stem was broken off the top of the flasks, what happened to the broth and why?

 

46. Pasteur’s S-shaped flasks kept ___________ out but let ______ inside.

47. Pasteur’s experiment proved that living things only come from other _________ ___________.

48. What is the name of Pasteur’s theory?

Review

49. Where did the maggots come from in Redi’s experiment?

50. What was the purpose of the sealed jars?

51. Redi was trying to disprove – spontaneous generation or biogenesis?

52. Where did the microbes come from in Needham’s broth?

53. Needham & Spallanzani were trying to disprove – spontaneous generation or biogenesis?

54.Who proved biogenesis?

 

 

 

Pasteur Experiment

Recreation of Pasteur’s Experiment

Introduction:

Today, we take many things in science for granted. Many experiments have been performed and much knowledge has been accumulated that people didn’t always know. For centuries, people based their beliefs on their interpretations of what they saw going on in the world around them without testing their ideas to determine the validity of these theories — in other words, they didn’t use the scientific method to arrive at answers to their questions. Rather, their conclusions were based on untested observations.

Among these ideas, for centuries, since at least the time of Aristotle (4th Century BC), people (including scientists) believed that simple living organisms could come into being by spontaneous generation. This was the idea that non-living objects can give rise to living organisms. It was common “knowledge” that simple organisms like worms, beetles, frogs, and salamanders could come from dust, mud, etc., and food left out, quickly “swarmed” with life. For example:

Observation: Every year in the spring, the Nile River flooded areas of Egypt along the river, leaving behind nutrient-rich mud that enabled the people to grow that year’s crop of food. However, along with the muddy soil, large numbers of frogs appeared that weren’t around in drier times. Conclusion: It was perfectly obvious to people back then that muddy soil gave rise to the frogs.

Objective:

In this experiment, you will conduct an experiment similar to the one done by Pasteur whenever he disproved spontaneous generation.

 

Materials Needed:Experiment Set-Up

  • Low-salt broth (chicken or beef, home-made or purchased)
  • 2  250-mL Erlenmeyer flasks
  • 2  1-hole rubber stoppers with bent glass tubing inserted (see diagram)
  • Glycerine
  • Hot plate & pot holders
  • 50-ml Graduated Cylinder
  • Marker

Procedure:

  1. Students should work in teams of 2 to 3 people. Each team should perform the following steps.
  2. Use glycerine and a twisting motion to insert glass tubing into the stoppers. be sure to rinse off excess glycerine with water.
  3. Mark Erlenmeyer flasks accordingly:
    1. Flask 1 with stopper and glass tube going straight up
    2. Flask 2 with stopper and glass tube bent in S-curve
  4. Using a graduated cylinder, place about 50-mL of broth in each Erlenmeyer flask.
  5. Place appropriate lids on flasks.
  6. Use a hot plate to boil broth in flasks with appropriate lids on them for 30 min., then let cool.
  7. For the next ten days, observe the flasks and record any changes in color, turbidity, smell, etc. (Be careful to NOT remove the stoppers from the flasks.)

Data:

Microbial Growth Record
Record the appearance of the flask contents.
Day Flask 1 with Straight Tubing Day Flask 2 with S-shaped Tubing
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
10 10

Conclusion:

  1. What was the appearance on the broth in each flask on Day 1?
  2. Was their an observed appearance change in flask 1 over the 10 days? Describe the change, if any.
  3. Was their an observed appearance change in flask 2 over the 10 days? Describe the change, if any.
  4. Explain why there was or was not a change in the appearance of the broth in each flask.
  5. Why do you think the idea of spontaneous generation was believed to be true for so long (1000+ years)?
  6. Did your experiment support spontaneous generation of organisms? Explain why or why not?

Mitosis Activity

 

Stages of Mitosis

Introduction

Mitosis, also called karyokinesis, is division of the nucleus and its chromosomes.  It is followed by division of the cytoplasm known as cytokinesis.  Both mitosis and cytokinesis are parts of the life of a cell called the Cell Cycle.  Most of the life of a cell is spent in a non-dividing phase called Interphase.  Interphase includes G1 stage in which the newly divided cells grow in size, S stage in which the number of chromosomes is doubled and appear as chromatin, and G2 stage where the cell makes the enzymes & other cellular materials needed for mitosis.

Mitosis has 4 major stages — Prophase, Metaphase, Anaphase, and Telophase. When a living organism needs new cells to repair damage, grow, or just maintain its condition, cells undergo mitosis.

During Prophase, the DNA and proteins start to condense. The two centrioles move toward the opposite end of the cell in animals or microtubules are assembled in plants to form a spindle. The nuclear envelope and nucleolus also start to break up.


Prophase

During Metaphase, the spindle apparatus attaches to sister chromatids of each chromosome. All the chromosomes are line up at the equator of the spindle. They are now in their most tightly condensed form.


Metaphase

During Anaphase, the spindle fibers attached to the two sister chromatids of each chromosome contract and separate chromosomes which move to opposite poles of the cell.


Anaphase

In Telophase, as the 2 new cells pinch in half (animal cells) or a cell plate forms (plant cells), the chromosomes become less condensed again and reappear as chromatin. New membrane forms nuclear envelopes and the nucleolus is reformed.


Telophase

Objective: 

In this lab, you will determine the approximate time it takes for a cell to pass through each of the four stages of mitosis. You may use your textbook and class notes to help you identify the stages of mitosis as seen under the microscope. 

Materials:

Microscope, prepared slide onion root tip or whitefish blastula, textbook, lab worksheet, pencil

Procedure:

  1. Set up a compound light microscope and turn on the light.
  2. Place a slide containing a stained preparation of the Allium (onion root tip) or Whitefish blastula.
  3. Locate the meristematic or growth zone, which is just above the root cap at the very end of the tip or
  4. Focus in on low power, and then switch to medium or high power. Below find micrographs of the four stages of mitosis. Use them to help you identify the stages on the microscope slide.


Prophase (onion)

 


Metaphase (onion)

 


Anaphase (onion)

 


Telophase (whitefish)

 

  1. Now count the number of cells found in each stage of mitosis and place the data in the chart below.
  2. Determine the percentage of time each cell will spend in each stage of mitosis. Divide the number of each cell by the total number of cells and multiply by 100 to determine the percentage. Place these values in the chart below.

 

Stage of Mitosis Number of Cells Percent of time in each stage =

# of cells in stage     X  100%
Total # of Cell
Prophase %
Metaphase %
Anaphase %
Telophase %
Interphase
(Not a Mitotic Stage)		 %
Total # cells 100%

 

  1. Line graph the data you have just collected.  Be sure to label the X and Y axis & include the units of measurement.

Title: __________________________________________________

Graph Legend:

 

Questions:

1. Of the four stages of mitosis, which one takes the most time to complete? 

 

2. Which is the shortest stage in duration?

 

3. What would happen if the process of mitosis skipped metaphase?  telophase?

Further Study:

Normal Cell Division may be observed in onion root tips. Many of the processes are similar to those in animal cells. However, in plant cells, the cell plate between daughter cells forms from the Golgi.

Find all of the stages of mitosis and  interphase in the above picture. Make a sketch of each stage and briefly describe what is occurring. Count and record the number of cells you see in each stage.

Projects
Notes

 

Metric System

Metric System (SI)
Scientist use a single, standard system of measurement.  The official name of the measurement system is SYSTEME INTERNATIONAL d’UNITES (International System of Measurements) or SI.

The metric system is based on the number 10.

Main Units of Measurement
Length Volume Mass
meter (m) liter (l) gram (g)

Using the above values (meter, liter, & gram) as the base, their value can be increased or decreased by moving the decimal point to the right (lowers the value) or left (raises the value).

Metric Conversion Table
Kilo-
(k)		 Base Unit
(m, l, g)		 Centi-
(c)		 Milli-
(m)		 Micro-
(µ)		 nano-
(n)
x 1000 meter, gram, liter 100 1000 1000 1000
1000 1 .01 .001 .000001 .000000001

Convert the following values by moving the decimal point the correct number of spaces and in the right direction .

1. 69.8 meters (m) =  ________________ centimeters (cm)

2. 152.97 milliliters (ml)  =  ________________ liters (l)

3. 42.67 liters (l) = _____________ milliliters (ml)

4. 299.32 kilometers (km) = ____________ nanometers (nm)

5. 26 grams (g) = _____________ kilograms (kg)

6. 123.43 centigrams (cg) = ______________ grams (g)

7. 75.2 liters (l)  = __________________milliliters (ml)

8. 456.3 grams (g) = ________________ micrograms µg

9. 4507.22 kilometers (km) = _______________millimeters (mm)

10. 0.00297456 kilograms (kg) = ___________ nanograms (ng)

BACK

Mitosis and Meiosis

 

Mitosis and Meiosis

Introduction
All new cells come from previously existing cells. New cells are formed by the process of cell division which involves both replication of the cell’s nucleus (karyokinesis) and division of the cytoplasm( cytokinesis).

There are two types of nuclear division: mitosis and meiosis. Mitosis typically results in new somatic (body ) cells. Formation of an adult organism from a fertilized egg, asexual reproduction, regeneration, and maintenance or repair of body parts are accomplished through mitotic cell division. Meiosis results in the formation of either gametes (in animals) or spores ( in plants). These cells have half the chromosome number of the parent cell. You will study meiosis in Exercise 3B. Where does one find cells undergoing meiosis? Plants and animals differ in this respect. In higher plants the process of forming new cells is restricted to special growing regions called meristems. These regions usually occur at the tips of stems or roots. In animals, cell division occurs anywhere new cells are formed or as new cells replace old ones. However, some tissues in both plant and animals rarely divide once the organism is mature.

Exercise 3A.1: Observing Mitosis in Plant and Animal Cells Using Prepared Slides of the Onion Root Tip and Whitefish Blastula

Figure 3.1 Close up view of different stages of mitosis in an onion root tip:

 

 

Figure 3.2 Whitefish Blastula

 

Procedure:
Examine prepared slides of either onion root tips or whitefish blastula. Locate the meristematic region of the onion, or locate the blastula with 10X objective, and then use the 40X objective to study individual cells. Identify one cell which clearly represents each phase of mitosis. Sketch and label the cell in the box provided.

1. The non dividing cell is in a stage called interphase. The nucleus may have one or more dark-stained nucleoli and is filled with a fine network of threads, the chromatin. During interphase, DNA replication occurs.

Interphase

 

2. The first signs of cell division occurs in prophase. There is a thickening of the chromatin threads, which will continue until it is evident that the chromatin has condensed into chromosomes. With somewhat higher magnification you may be able to see the two chromatids held together by the centromere. As prophase continues , the chromatids continue to thicken and shorten. The nuclear envelope disappears and the beginnings of the spindle apparatus begin to appear.

 

Prophase

3. At metaphase, the chromosome pairs have moved to the center of the spindle. One particular part of each chromosome, the centromere, attaches to the spindle. The centromeres of all the chromosomes lie about the same level of the spindle called the metaphase plate.

 

r

Metaphase

4. At the beginning of anaphase, the centromere regions of each pair of chromatids separate and are moved by the spindle fibers toward opposite poles of the spindle, dragging the rest of the chromatid behind them. Once each chromatid is separate it is called a chromosome.

 

r

Anaphase

5. Telophase, the last stage of division, is marked by a pronounced condensation of the chromosomes, followed by the formation of a new nuclear envelope around each group of chromosomes. The chromosomes gradually uncoil into the fine threads of chromatin, and the nucleoli reappears. Cytokinesis may occur. This is the division of the cytoplasm into two new cells. In plants, a new cell wall is laid down between the daughter cells. In animal cells, the old cells will pinch off in the middle along a cleavage furrow to form two new daughter cells.

 

Telophase

 

Analysis Questions:
1. Why is it more accurate to call mitosis “nuclear replication” rather than “cellular division”?

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2. Explain why the whitefish blastula and onion root tip are selected for study of mitosis.

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Exercise 3A.2: Time for Cell Replication
Procedure:
It is hard to imagine that you can estimate how much time a cell spends in each phase of cell replication from a slide of dead cells. Yet this is precisely what you are going to do in this part of the lab. Since you are working with a prepared slide, you cannot get any information about how long it takes a cell to divide. What you can determine is how many cells are in each phase. From this, you can infer the percent of time each cell spends in each phase.

1. Observe every cell in one high power field of view and determine which phase of the cell cycle it is in. This is best done in pairs. The partner observing the slide calls out the phase of each cell while the other partner records. Then switch so the recorder becomes the observer and visa versa. Count at least two full fields of view. If you have not counted 200 cells, then count a third field of view.

2. Record your data in Table 3.1.

Table 3.1

Number of Cells

 Percent of Total Cells Counted Time in Each Stage
Field 1 Field 2 Field 3 Total
Interphase
Prophase
Metaphase
Anaphase
Telophase
Total Cells Counted

3. Calculate the percentage of cells in each phase.

Consider it takes, on average, 24 hours (or 1,440 minutes) for onion root-tip cells to complete the cell cycle. You can calculate the amount of time spent in each phase of the cell cycle from the percent of cells in that stage.

Percent of cells in stage X 1,440 minutes = ___________ minutes of cell cycle spent in stage.

Questions:
1. If your observations had not been restricted to the area of the root tip that is actively dividing, how would your results have been different?

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2. Based on the data in Table 3.1, what can you infer about the relative length of time an onion root-tip cell spends in each stage of cell division?

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