A Closer Look

This week we’re using microscopes to observe microorganisms in pond water.

Day 1:

 Today, we worked on getting affiliated with the microscopes, and practiced preparing wet mounts using newspaper clippings. 

  

 
First, we set the microscope to it’s lowest objective (4x) for a total magnification of 40x including the eyepiece. We viewed a ruler under the microscope, and found the field of view to have a diameter of 5 mm (or 5000 μm). Next, we practiced making wet mounts. We cut out a tiny c from a newspaper, and set it on a glass slide. Then, we added a drop of water, and allowed it to soak the paper. We then covered this all with a plastic cover. Our overall result?

   
As you can see, the opposite side of the paper was a colored picture. Because our slide was backlit, we were able to see the ink on both sides. We noticed CYMK dots used to print different colors but too small to see normally. Here are the rest of our observations

  Tomorrow we can examine and identify various microorganisms in pond water with microscopes, and put the skills we learned today to use.

Day 2:

Today we viewed pond water in wet mounts to search for microorganisms. Although we were not able to confirm with our teacher if there really were any specimens in our sample, we found some interesting observations.  
  

Here we found what may have either been air bubbles trapped within the mount, or else a colony of algae (chlorophyceae, although we doubted this due to a lack of visible chlorophyll).

  

Next, we examined two brown strands of our own hair.  Though it was difficult to snap a picture of it, we noticed that each strand was actually semitransparent, and was dotted by darker pigments along the very center.

 

Finally, we moved on to the analysis of our experiment. We noticed that as we increased the zoom, our field of view shrunk in an inverse relationship. We also noticed that because the objects we viewed were three dimensional, we could only focus on one layers of them at a time using a high-power objective. Hopefully, we will be able to continue to use the processes with the microscopes to observe more organisms throughout the year.

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Leafed Behind Lab

Last Thursday, our lab group attempted to measure a plant’s production of CO2 and oxygen in photosynthesis and cellular respiration. In particular, we wanted to compare leaves with a light source to leaves in the dark. We hypothesized that leaves in the light would begin to float as they converted CO2 into less dense oxygen, while leaves in the dark would sink due formation of CO2 through cellular respiration. To quantify these reactions, we first took ivy leaves, and cut out 20 small, uniformly sized discs.   
 Next, we created a solution of baking soda (to provide CO2) and detergent (to break down the waxy surfaces of the leaves) in water. We filled a syringe with 3 mL of the solution, and added the discs. We sealed the syringe, and created a vacuum to suck out any remaining air from the leaves.

  
Then, we divided these leaves into two groups, each of which were placed in a cup of the solution. The half in our control group were covered in tin foil, while the other half were exposed to sunlight. 

  
Next, we measured the amount of discs that rose to the top of the cup each two minutes. Unfortunately, however, during out experiment, none of our leaves rose.

 
Multiple other groups observed that their leaves in sunlight rose after a few minutes. Though plants in the dark could only perform cellular respiration with their limited supply of oxygen and lack of light, the sunlit leaves were able to photosynthesize, thus creating oxygen gas and floating to the top of the cup. Nonetheless, after 20 minutes, still none of our group’s discs had risen. Looking back at our experiment, our group noticed a few times when our procedure might have varied. Firstly, we suspect that we might have use too little baking soda in our solution. This would have lowered the available amount of CO2 for photosynthesis, thus preventing the leaves from rising. Otherwise, we may have accidentally crushed our discs when we first put them in the syringe. Thankfully, however, many other groups were able observe their sunlit leaves rising, meaning that photosynthesis really was occurring. This experiment showed all of us the importance of running an experiment multiple times. By comparing our results with others, we were able to spot potential flaws in our procedure, instead of using most likely inaccurate results. 

Catalase/Hydrogen Peroxide Lab

Last week we had lab examining how the enzyme catalase affects the decomposition of hydrogen peroxide into water and oxygen. Catalase naturally occurs in animals to avoid a buildup of toxic hydrogen peroxide. We used beef liver as our source of the enzyme, which was ground and mixed with water to form out ‘catalase solution.’ We soaked paper dots in the solution before sticking them to the walls of our reaction chamber. After adding hydrogen peroxide, we submerged the entire chamber. 

   
 
We used a graduated cylinder to catch the oxygen bubbles produced by the resulting reaction. We repeated this entire process, using one, two, three and four dots. Each 30 seconds for 7 minutes, we measured the amount of oxygen produced. As we expected, we found that the more catalase we used, the faster the reaction occurred.

  
Multiple factors, such as temperature and pH, affect the behavior of enzymes. This experiment demonstrated that an enzyme’s concentration also plays a role in its effectiveness.

Strawberry DNA

Today my lab group extracted the DNA from two delicious strawberries. Unfortunately, the strawberries didn’t remain delicious for long, but we’ll get to that in a moment. We started with two regular, washed, and dyed strawberries. 

First, we created a solution of water, detergent, and salt to mix with the strawberries. We then pipetted 10 mL of this into two plastic bags, each of which was also given a strawberry. We then closed the bags, and pounded them to a mush. The water helped the strawberries form a liquid with a few extra ingredients. The detergent dissolved the cell membranes, and the salt ions help separate out the DNA strands. The result:
 

As I mentioned, not quite as delicious anymore (we must make certain sacrifices for science). We slowly filtered this mixture through cheesecloth and a funnel, and were given 4 test tubes filled 1/4 with red strawberry goo. 
   

Next up was the alcohol. We pipetted an equal amount of ice cold alcohol  into the test tubes. Then, we watched as a gooey substance (DNA) rose into the alcohol (without being dissolved).  

Though we weren’t able to catch much of it with our wooden stick, we were able to observe the DNA in the rubbing alcohol. We even managed to pull a bit of it out on our pipette. And that’s how we extracted some strawberry DNA! 

 

pH Indicator Lab Report

Last Thursday, during Biology class and the first half of lunch, I used red cabbage to create a veritable rainbow of colors. No, I did not use photoshop. Instead, I used acids and bases. My lab group used boiled, blended, filtered cabbage-water to help demonstrate levels of pH. First, we would add a dilute Acid or base drop by drop until our pH meter told us a change of one whole number had occurred. Then, we put 5 mL of the solution into a test tube to compare to the other steps. We ended up with a whole spectrum of colors, as seen below.  

This lab taught me a lot of things, both about acids and bases as well as the scientific method.

Firstly, I learned how to calculate the number of ions or molecules in a given substance. Firstly, you need to know the molar concentration of the substance (the number of ions present in 1 liter), and then you multiply his by the volume of your sample.

I also learned that a scientist is only as great as his or her measurements. Our pH meter did not give us consistent measurement of our samples, and  would often jump around by as much as .5 when reading the pH. 

   

Therefore, I’m not sure how accurate our data was, and I hope to see some of the data from the other groups. I was, however, able to use our data to make graphs of our findings. Here they are:

Effect of Sodium Hydroxide on pH of Indicator Solution  Effect of Hydrochloric Acid on pH of Indicator Solution

 Finally, I learned that doing homework earlier makes things easier for everyone. For the group portion of this project, I sent out a file with the lab group’s measurements last night. Or so I thought. Thankfully, I was able to resend the email today and it actually went through. I’m quite glad, though, that I didn’t save that piece of work for tonight. On the other hand, I saved the blog lab report for last, and it’s due tomorrow. So now I’m blogging

 

(you’ll never guess) Why I want to study biology

Summer is leaving, and despite my best efforts (begging, weeping, holding my breath, puppy eyes, the usual) I can’t make it stay. I don’t especially like the weather or the season itself, but I do enjoy the freedom it grants from school. However, here I am, reliably back in school. Before starting classes, I needed to choose a science class, and you can probably see how that went assuming you can read the title (if you can’t read… Why am I typing this?). Here’s why I chose biology: 

(Presented in proper, list style. Blogs are basically buzzfeed, right? I should really add something to the title…)

1. I tested into it. Hopefully this class will be challenging enough without killing me.

2. Labs are fun. I’m really looking forward to learning from something other than a lecture or textbook.

3. This will help me decide which AP class to take down the road. In junior or senior year, I can look back at biology and either say “That was a disaster! There’s no way I’m taking AP Bio,” or else “I’ll take AP Biology. It probably won’t kill me” (Or perhaps “After that, I’m never taking a science class again.” Let’s hope that doesn’t happen).

Incidentally, after choosing to take Biology, I was given an assignment to write a blog post about my reasoning. So now I’m blogging.

P.S. I was also supposed to add some picture or videos, but wasn’t sure how to naturally slip them into the post. Instead, here’s a visual summary: