Mystery worms
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Mystery worms

Mystery Worms

A teacher collected some beetles from a rotting log and placed them in a container of dry oatmeal in her classroom. She kept the box covered with a light cloth so that the beetles could not escape. She also asked one of her students to add potato and apple pieces once a week to provide food and moisture for the beetles. After several weeks, the student reported that there were some strange-looking, wormlike organisms in the container.


Mystery worms1

Mystery Worms

  • 1. Formulate a hypothesis that might explain the presence of the “worms” in the container.

  • 2. How could you test your hypothesis?

  • 3. Identify the variables in your proposed experiment. Identify the control in your proposed experiment.


Mystery worms

1 – 2 How Scientists Work


Mystery worms

The Scientific Method

The Steps of the Scientific Method

Designing an Experiment

State the Problem

Analyze Results

Form a Hypothesis

Draw a Conclusion

Set Up a Controlled Experiment

Publish Results

Record Results


How is science done

How is Science Done?

  • Scientists use the scientific method. When scientists have a question about something in the world they use this method to find an answer:

    • State the Problem or Question

    • Research

    • State a hypothesis

    • Design an experiment with a control

      group, constants and variables

    • Analyze data/ results

    • Conclusion or Summary


1 state the problem or question

1. State the Problem or Question

What have I observed?

What do I want to know?


2 research

2. Research

Has anyone asked this before?

Did they discover an answer?

How did they go about looking for an answer?

What other things do I need to understand to answer my question?


3 form a hypothesis

3. Form a Hypothesis

Based on the research you have done, write a possible answer or solution – your best educated guess – to your question.


4 design an experiment

4. Design an Experiment

  • Control Group: Part of your experiment that is not varied in anyway. You can compare your test groups to this set standard group.

  • Independent variable- The change/difference you make in the experiment (the thing you are testing). Also called manipulated variable

  • Dependent variable- The differences that result from the experiment, the resulting effect. Also called responding variable.

  • Constants- Things in the experiment that do not change, kept exactly the same for each test group so they do not affect the results.


5 data results

5. Data/Results

  • It is easier to understand the data if it is put into a table and/or graphed.

  • Make sure all data is clearly labeled. Charts and graph should always include units and titles.

  • When graphing the independent variable should be on the x axis and the dependent variable should be on the y axis.

Dependent variable

Independent variable


6 analysis

6. Analysis

What happened?

What was expected? What was unexpected?

What trends did you notice in the data?


7 conclusion or summary

7. Conclusion or Summary

Indicate whether or not the data supports the hypothesis and explain why or why not.

Suggest possible improvements to the experiment.

Suggest further avenues of research or uses for the information discovered.


Learning checkpoint

Learning Checkpoint

  • What are the steps of the scientific method?

  • In which step would you find charts and graphs?

  • What is the difference between an independent variable and a dependent variable?

  • What is the purpose of a control group?

  • What does it mean to have a controlled experiment?


An example of science at work 1 2

An Example of Science at Work (1-2)

  • Observed: sometimes organisms just “arose” from nonliving things: ex. maggots came from meat.

  • The Question: How do new living things come into being?

  • Hypothesis: In some cases, nonliving objects can spontaneously generate living organisms.

    1st Experiment- 1668, Francesco Redi:

  • Meat in covered and uncovered jars

  • Proposed a new hypothesis: The maggots came from eggs left by flies on the meat that were too small to see.

  • Concluded: Maggots came from flies.


Mystery worms

Figure 1-8 Redi’s Experiment on Spontaneous Generation

OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat.

HYPOTHESIS: Flies produce maggots.

PROCEDURE

Uncovered jars

Covered jars

Controlled Variables:

jars, type of meat,

location, temperature,

time

Several

days pass

Manipulated Variables:

gauze covering that

keeps flies away from

meat

Responding Variable:

whether maggots

appear

Maggots appear

No maggots appear

CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur.


Science continues new ideas with new discoveries

Science continues...New Ideas with new discoveries

  • New discovery!- tiny microorganisms (discovered by Anton van Leeuwenhoek)

    2nd Experiment- Mid 1700s, John Needham:

  • Repeats Redi’s experiment.

  • His hypothesis: Spontaneous generation can occur

    under the right conditions.

  • Result: microorganisms appear in sealed flask of boiled gravy.


Science experiments are always repeated

Science Experiments are always repeated:

3rd Experiment- Lazzaro Spallanzani:

  • Thinks Needham did not boil gravy long enough to kill existing microorganisms.

  • Results: When left exposed to air, microorganisms will appear in boiled gravy.

  • He concluded that microorganisms could not come from gravy but appeared instead from microorganisms existing in the air.


Mystery worms

Figure 1-10 Spallanzani’s Experiment

Section 1-2

Flask is

open.

Gravy is teeming

with microorganisms.

Gravy is boiled.

Needham tried first but didn’t bring gravy to hot enough temperature.

Flask is

sealed.

Gravy is free of

microorganisms.

Gravy is boiled.


New question is air the life force

New Question: Is air the “life force”?

4th Experiment- 1864, Louis Pasteur:

  • Set out to dismiss the notion that the “life force”, air was needed to generate life.

  • Used curved neck on flask so air could get in but organisms would not.

  • Concluded that all living things

    can only come from living things.

  • This has been tested over and over

    and is now considered a theory

    called biogenesis.


Mystery worms

Figure 1-11 Pasteur’s Experiment

Broth is boiled.

Broth is free of

microorganisms

for a year.

Curved neck

is removed.

Broth is

teeming with microorganisms.


Learning checkpoint1

Learning Checkpoint

  • Did all 4 scientists use good scientific thinking and a controlled experiment?

  • What is spontaneous generation?

  • What was the point of the “swan neck” Pasteur added to his flask?

  • What is biogenesis?


Example tomatoes

Example: Tomatoes

  • Plant 20 seedlings = 50-60 tomatoes harvested

  • Plant 20 seedlings w/ fertilizer = >100 tomatoes harvested

    What can you conclude?

    What other factors may affect the growth?

    • weather better that year, different type of tomato seed, fewer pests than last year

  • Hypothesis

    • If I use fertilizer then the tomato crop will increases in production


Experiment

Experiment

Field 1

  • Brand A tomato seed

  • Water three times a day for 15 minutes

  • Similar type of soil

  • Try to control pests

  • Doesn’t receive fertilizer

Field 2

  • Brand A tomato seed

  • Water three times a day for 15 minutes

  • Similar type of soil

  • Try to control pests

  • Receives fertilizer


Mystery worms

  • Control

    • Unfertilized tomato plants

  • Independent variable

    • Fertilizer

  • Dependent variable

    • # of tomatoes yielded

  • Results

    • Unfertilized = 55

    • Fertilized = 82

  • Conclusion

    • The fertilizer caused an increase in the tomato crop


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