LAB 1 - Scientific Method Questions PDF

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Biology 001 Laboratory Exercise 1 Question Package

Scientific Method, Observations & Measurements (Health and Safety; Metric Measurements; The Scientific Method; Compound Light Microscopes)

Jocelyn

Reyes Hernandez NAME Last: ____________________ First: ______________________

02/11/19 04 Date Submitted: __________________ Section # ___________________

Total time commitment: 2 hours 50 minutes 1) Heath & Safety = 10 minutes 2) The Scientific Method = 40 minutes 3) Measurements = 25 minutes 4) Microscope use = 1 hour 25 minutes

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SECTION I – Health and Safety NO QUESTIONS

SECTION II – The Scientific Method Exercise 1- Questions and Hypotheses Which of the following questions do you think can be answered scientifically? • • •

Does watching television before the age of one contribute to the development of autism in children? yes Do cactus spines reduce herbivory? yes Should human embryonic stem cells be used to treat Parkinson's disease? no

Q1) How did you decide which questions can be answered scientifically? Hypothesis needs to be testable. Q2) Take a few minutes to write down 3 scientific theories that you know about: a Big Bang theory Natural Law moral theory b. Evolutionary theory c. Q3) For each of the following questions, write an explanatory hypothesis. Recall that the hypothesis is a statement that explains the phenomenon you are interested in investigating. 1. Does cell phone usage reduce auditory function? 2. Do offspring of mothers who jog each day have a mental advantage over offspring of sedentary mothers? If the mother is jogging then the offspring will have mental advantage.

Exercise 2 - Designing experiments to test hypotheses The Dependent Variable Within the experiment, one variable will be measured or counted or observed in response to the experimental conditions. This variable is the dependent variable. For the soybeans, several dependent variables are measured, all of which provide information about reproduction. Q1) What are they? Dependent = Measurement Independent = Manipulated

Control = variables that won’t change Page 2 of 8

The Independent Variable The scientist will choose one variable, or experimental condition, to manipulate. This variable is considered the most important variable by which to test the investigators hypothesis and is called the independent variable. Q2) What was the independent variable in the investigation of the effect of sulfur dioxide on soybean reproduction? independent = sulfur dioxide

Q3) Can you suggest other variables that the investigator might have changed that would have had an effect on the dependent variables? water, soil Q4) Why might it be useful to have more than one dependent variable? It’s useful to have more than 1 variable because we have more variety. The Controlled (or Standardized) Variable Q5) What are the controlled variables in this experiment? amount of light, and amount of soil. Q6) What variables other than those you may have already listed can you now suggest? Q7) What was the level of treatment in the soybean experiment? Q8) Describe replication in the soybean experiment. Q9) In the case of the soybean experiment, what was the control treatment? the amount of soil and light the plant is receiving

Q10) What is the difference between the control and the controlled variables the difference between a controlled and control variables are discussed previously?

that control variables are useful because it allows to not change anything from the experiment. However, controlled variables may be factors that can affect the experiment results.

Q11) For the soybean experiment, the hypothesis was: "Exposure to sulfur dioxide reduces reproduction." What should the prediction be? State your prediction. my prediction is that as the soybean is being expose to the sulfur dioxide then the the reproduction will reduce

Q12) Do offspring of mothers who jog each day have a mental advantage over offspring of sedentary mothers? yes they do

Q13) Now consider an experiment you might design to test this hypothesis. How will you measure "mental advantage"? keeping in track how the kid is developing

Q14)

State a prediction for this hypothesis and experiment. Use the if/then format: If we continue to track the child progress and he continues growing the will be able to see how much of the mental advantage he has developed Page 3 of 8

SECTION III – Measurements Q1) How many millimeters are there in a centimeter? 10 millimeters per centimiters Q2) How many nanometers are there in a millimeter? 10^6 nanometers per centimeters ACTIVITY IIA Activity A.1 – Length Q3) Which object did you select? A piece of rope_____________________________ Q4 ) Estimate its length in centimeters. Estimate: 11 __________ cm Q5 ) Measure its length using a ruler. Measured length:___ 12.6____ cm Q6) How close were you to the actual length? 1.6____________ mm Complete Table A.1 below with respect to the length of the same piece of string that you measured above: Table A.1: Interconversion between units Measured length of string = 12.6 0.126 Length in meters = 126 Length in millimeters = 1.26e+8 Length in micrometers =

cm m mm μm

Activity A.2 – Weight is a measure of the mass of an object under gravitational pull. Q7) Which object(s) did you select? A paper clip _______________________________

Activity A.3 – Volume is a measure of the amount of material. Q8) What is the weight of the water?____ ~100 grams/millimiters ________________ Q9) Since one ml of water weighs one gram, what was the volume of water in your measuring cylinder?__________________ we didn’t had cylinders __________ ————— ———— Q10) How much did you select? ______________________________________________ ——— Q11) How accurate was the instrument? Within __________ μl

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SECTION IV – Compound Light Microscopy ACTIVITY IVA – Use of a microscope Activity IVA.1 Safe handling of the microscope. NO QUESTIONS Activity IVA.2 Examine your microscope and identify and label the following parts on Figure 1: Ocular lens (eyepiece)

Arm

Objectives

Nosepiece

Stage

Stageclips

Iris Condenser

Base

Fine & Coarse adjustment knobs

Light source

Stage controls

On/Off switch

Arm Ocular Lens Nose Piece Stage Controls Objectives Coarse adjusment

Stageclips

Fine Adjustment On/Off switch

Iris Condenser

Base Stage

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Activity IVA.3 Observations with the compound light microscope. Observation 1. Calculating total magnification. Q1) How is the total magnification calculated?

ocular lense x magnification = total magnification

Q2) What is the magnification of your microscope in its current configuration? 1) 4x10 = 40 2) 10x10 = 100 3) 100x10= 1,000 4) 40x10 = 400 Observation 2. Depth of Field Q3). Which of the cross fibers is on top and how do you know this? The fiber that was on the top and I was able to notice it was the blue, because when my partner and I used the fine adjustment I was able to see clearly that the blue fiber was on top. Observation 3. Specimen orientation Q4) Diagram what you see through the eyepiece at each of the following total magnifications: 40X

100X

400X

Observation 4. Physical properties of the microscope. As you increased the magnification in the step above, what happened with respect to the following properties? As the magification gets higher, it Q5) Diameter of the field of view: decreases how we see the image Q6) Brightness: When I added more brightness it allowed me to see the image more clearly.

Observation 5. Compare the orientation of the letter ‘e’ on the actual slide with its appearance under magnification. Q7) How is the viewed image orientated compared to the actual specimen? The image is upside down which makes the image viewed differently. Page 6 of 8

Observation 6. Use the stage controls to move the stage of the microscope. Q8) If you move the slide on the stage left, which direction does the image move as viewed through the ocular lens? if the slide is on the stage left, then the direction is moving to the right.

__________________________________ Activity IV A.4 Determining actual size using a microscope

Table A.4: Calibrating ocular micrometer. Total Magnification Size of one micrometer unit (mm/unit) 40x (use size calculated from grid slide) 100x 400x

0.025mm 0.01mm 0.0025mm

Activity IVA.5 Live Specimens – Wet Mounts elodea cell

Q9) Draw several cells in the space below, annotating the cell parts that you find.

Activity IV A.6 Measuring the length of several Elodea cells Having previously calibrated your ocular micrometer, you may now use it to measure the lengths of cells in your Elodea sample. Remember to note which objective you are using (10x and 40x objectives will work best). Measure the length of four different cells on your wet mount slide. Then, determine the average length of an Elodea cell by calculating the mean of the four cell lengths you measured. Q10) 14+10+11+8 = 43 8 __________ mm, __________ mm, __________ mm, __________ mm 14 10 11 Average = 10.75 _____ mm

43/4= 10.75 mm

Q11) Why is it necessary to take more than one measurement on the size of the Elodea cells? it’s important to take more than one solution because having more solutions helps to back up our hypothesis. In some cases we have experiment errors, lie moving the stageclips. so ____ by having more than 1 measurement it provide us with more than 1 specific result. Activity IV.7 – Enhancement by Staining Q12) Draw a typical cheek cell and label the visible structures. This is not perfect and accurate,but that’s how the cheek cell looked in the microscope. Page 7 of 8

Q13) Was the slide stained with methylene blue solution better for viewing and seeing structures than the unstained slide? Why? Having methylene blue solution helped us see the structure of the cheek cell better because it allowed us to see the specific structure and its details of the cell.

Homework questions based on paper “ Plant defenses limit herbivore population growth by changing predator -prey interactions”. 2. Plant resistance indirectly regulates herbivore populations by a. What is the hypothesis for this paper? changing the impact of In the paper there was 2 hypothesis stated predators on prey. 1. Plant resistance directly affects the herbivore population growth rate through resource limitation or plant defences . b. In your own words how was the hypothesis tested.

It is posted to your catcourse site. Then answer the following questions.

They used aphids genetic expressions to see if it would satisfy the significants amount of the population.

c. Were there any controls used? If so what were they? Environment, soil and the rain d. Identify the dependent variable. Aphid and the population e. Identify the independent variable.

f.

Was the hypothesis supported? How or why not? The hypothesis was actually supported , because they noticed that plants were eating less and less

g. What types of graphs were used? The graphs that were being used were scatter plot graphs, and bar graphs

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