Biology Archive

  • Is Dog Saliva Antiseptic?

    Is animal saliva antiseptic?

    Stories about pioneers, travelers, or hunters who made it through their injuries because certain wild animals happened to lick their open wounds. Many cultures believe this. There is even a French saying, “Langue de chien, langue de médecin,” which translates to “A dog’s tongue is doctor’s tongue.”

    We’ve all heard that a dogs lick can be antiseptic but is it really or is it–like so many things–an old wives tale.

    Problem stated:

    Are there components in animal drool that can kill bacteria in wounds?
    What you need:
    • Fresh saliva from either your cat your dog (some dogs drool a lot; cats drool sometimes as well when they like the way you pet or massage them)
    • 5 petri dishes that have sterile agar medium
    • Non-pathogenic, freeze-dried Staphylococcus bacteria found on the epidermis
    • Sharpies for labeling the petri dishes
    *** There should be adults present to handle the bacterial cultures

    How you do it:
    a. Inoculate one petri dish with few grains of the Staphylococcus bacteria. Do not use too much. Label it as “Control 1”. Set the petri dish aside.
    b. Inoculate the second petri dish with ¼ teaspoon of your pet’s saliva. Label the petri dish as “Control 2”.
    c. Inoculate the third petri dish with the Staphylococcus bacteria and a little of your pet’s saliva. Label the petri dish as “Sample A”.
    d. With your bare hands, rub your hair, your pet, and then the grass in your garden. Just make your hands as saturated with germs as possible.
    e. Take another petri dish and press your hand lightly on the agar for a second or two. Label the petri dish as “Sample B”.
    f. Repeat step “d” and add a bit of your pet’s saliva on the areas where you pressed your hand. Label the petri dish as “Sample C”.
    g. Isolate the petri dishes and put them somewhere in the room where they cannot be disturbed.
    h. Check the petri dishes after 12 hours, 24 hours, 36 hours, and 48 hours.
    i. Compare the size of the bacterial colonies in every dish. See if the petri dishes that contain your pet’s saliva reduced the bacterial colonies.
    j. Learn about lysozyme, opiorphin, IgA (immunoglobulin A) and peroxidases, which are present in the saliva of animals. These components are known to heal wounds because of their antiseptic properties.

  • Does Peeling Fruit Make it Deteriorate Faster?

    When you have too many seasonal fruits in your kitchen, you often want to taste them all at the same time. There are times when you pick a bunch of them and peel them all at the same time for convenient eating. Yet, have you ever thought that peeling the fruit removes its first layer of protection?

    Like other organic substances, fruits need protection, even if they are still up in their trees. Once they are a picked, they start to deteriorate because they lose their living connection of nutrients. Their skin delays their deterioration.

    Before you start this experiment, consider the many factors that contribute to the deterioration of fruits:
    • Microorganisms
    • Excess moisture
    • Exposure to oxygen
    • Extreme temperatures

    When a fruit starts to rot, it breaks down into simpler substances. This is the process of decomposition. It is nature’s way of recycling, which is imperative to keep matter in biome. In the natural world, the faster something decomposes, the better. This is because all the raw materials are returned to the soil much quicker. Once in the soil, other organisms can start using them immediately.

    The Question stated:
    Does peeling a fruit make it rot more quickly?
    What you need:
    • Two each of the following
    o Oranges
    o Apples
    o Strawberries
    o Peaches
    • Pen and paper for your notes
    • Knife
    • Small plastic bags

    How you do it:
    *** Note that this experiment yields the best results during winter. There are usually no bugs during this time of year.
    1. Take one of each fruit and cut it in two. Place them in small plastic bags.
    2. Take each of the whole fruit and place them in separate plastic bags.
    3. Observe the process of decomposition that happens daily.
    4. Note which of the fruits starts to rot first.
    5. Make a record of your observations with the use of a chart.


  • Oil Producing Algae



    Grades 6, 7, and 8

    Category – Earth Science

    Main objective:

    This project focuses on the oil content that is produced in different types of algae. This is done by comparing the beading water droplets on the surface of the algae plants. The goal is for the student to test and hypothesize about the oil production in the specific algae plants used. Useful questions to answer can be, “Which algae produces the most oil?”, “How do algae store the oils?”, and “What conditions allow for better oil production?”.

    What you need to know:

    Found in most aquatic environments, algae can grow and thrive no matter the state of the water. Multicellular macroalgae grow in fresh water lakes and ponds as well as in the ocean. Unlike pond algae which can be measured in inches, algae that grow in the ocean can grow as long as 100 feet in length. The long algae that grow in the ocean are also known as giant kelp. There are also microalgae that grow in swamps, bogs, and marshes and are quite small. These algae plants are measured in micrometers.

    Like most plants, algae require sunlight in order to grow. You can refer to the books on photosynthesis to document how plants grow and add your findings to your presentation. Algae, under normal circumstances, do not produce very much oil unless the plant experiences growth stress. This means that something must happen to deprive the plant of their basic growth requirements. The downfall to starving the plant to produce more oil is that the plant will grow less in mass than under normal growing conditions. This means that for the purposes of oil production, more plants will need to be grown.

    When you dry algae in a microwave, the cell walls of the plant are broken down. This allows the oils that are trapped inside the plant to reach the surface. When you place a drop of water on the top of the algae plant, if the water does not sink down into the plant but instead sits on top of the plant in a bead droplet, you know that the oils have all moved up to the surface of the plant.

    Materials needed:

    Algae – (marshes, ponds, swimming pools, swamps, fish tanks)

    Filter paper – (science outlets and the internet)

    Water dropper – (drug store)


    Collection jars



    For the first part of your project, you will want to review and learn why and how algae store their oils.

    Build a hypothesis that allows you to predict which types of algae contain the most oils.

    Collect samples of different algae using your specimen jars. Be sure to collect a little water from each of the sources that the algae are growing in so that your algae will continue to survive during your testing. Do not cross-contaminate your water or algae samples. This is very important. You also want to make certain that you collect both microalgae and macroalgae for your experiment.

    Be sure to document the data. Write down where and under what conditions you collected each algae specimen. Make sure that you note whether the conditions were nutrient starved or had an abundance of light.

    Choose one of your specimens and divide it into two separate samples.

    Using separate pieces of filter paper, place a sample of each specimen on their own piece.

    Let the two samples air dry.

    On low power, heat one of your samples in the microwave for a short period of time. Be careful that it doesn’t burn! What you are looking to do is to bring the oils in the algae to the surface by cracking the cell walls.

    Using your dropper, place one drop of water on the surface of the air dried algae and one drop of water on the surface of the microwave dried algae. Note any differences in what happens to the water droplet. Be sure to record all of your notes.

    Repeat this testing on all of your different samples, recording your observations.

    Take your findings and write your hypothesis. If needed, revise and retest as is necessary.



  • Discovering Blood Type Compatibility

    Basic Blood Types

    Discovering Blood Type Compatibility

    This is a great science project for younger kids, to introduce them to how blood types work. There are four different blood types, and this experiment shows kids that some types are compatible, while others aren’t.
    While supervision will be required in case things get messy, this is an inexpensive and easy project to do.
    Materials List:
    • 16 Cups to put water in
    • Pencil or pen & paper
    • Blue food coloring
    • Red food coloring


    Put an equal amount of water in each of the 16 cups. This doesn’t have to be a lot of water, but enough to pour some into other cups and still have some that you started with.
    Once all the cups have water, leave four of them with plain water. Add red coloring to four of the cups, blue coloring to four other cups, and add both red and blue coloring in the last four cups to make purple water.
    Make sure your child writes down that the red water represents Type A blood, and that the blue water represents Type B. The purple water will be used to represent Type AB, and the plain water represents Type O.
    Then you start adding some of the water to other cups. In order to keep things organized, it’s probably easiest to start with adding water from an “A” cup into another “A” cup. The color of the water will not change, which means that Type A blood is compatible with Type A for transfusions.
    You will get the same result adding “B” to “B”, “AB” to “AB”, and “O” to “O”. You can either do all of these at once, or stick with each blood type and add it to all the others before moving on to the next.
    Then add an “A” cup to a “B” cup and let your child witness what happens. Since the color of the water changed from blue to purple, they can know that Type A and Type B blood are not compatible for transfusions.
    Repeat these steps with all the different colors, and make sure that your child is making notes on the reactions of all the different “Types.”
    The experiment will end with these results: Type A and Type AB people are the only ones that can have Type A blood. Similarly, Type B and AB people are the only ones who can have Type B blood. Type AB people may have any blood but they can only give blood to other Type AB people. And finally, Type O people can give blood to anyone but they can’t take blood from anyone but another Type O.
    Interested in other things about your body? Did you know that we have a blind spot? Find out more about Blind Spots here.
  • Experimenting with Blind Spots

    Blind Spots are Fascinating

    The human eye has a “blind spot.” This is a fascinating topic, since it is one of those things that we don’t usually notice as we go about our day to day lives. But at the same time, when we do notice it, it can be a little startling.

    The reason we have this blind spot is because of the “optic disc.” This is where the optic nerve meets your retina. Photoreceptor cells are nonexistent here, which is why images vanish when they hit this spot.

    So if we have a small blind spot on each eye, why do we not have “holes” in our vision? This is because both our eyes work to cover the blind spot of the other, so generally we never even notice. The blind spot experiment shows us why our eyes work correctly..


    Finding the Blind Spot

    This is a fun experiment to do just to experience the blind spot experiment and see how it works – or doesn’t work, as the case may be. The easiest way to locate it is to take a piece of paper and draw a square, and then a few inches away, draw a circle. You could also use something like shapes made of construction paper, or stickers. Just be sure both shapes contrast against the paper nicely.




    Once you have your two points separated by three or four inches, hold the paper as far out as you can, and close your right eye. Keep your left eye on the circle, and bring the paper closer slowly. At some point, the square will vanish, and you will know you have found the blind spot in that eye. Now you can repeat this process with your other eye, looking at the other shape.

    When the shapes vanished, what you saw instead was the color of the paper. Our brains are marvelously wired to fill in our blind spots in this way. This will work on any color of background, and it will even work on shapes. For example, if you draw two long rectangles that have a break or circle in between them, and you try this experiment again, looking at a shape a for inches to the side, the circle will vanish, and the two rectangles will suddenly be linked.

    Your brain could not “see” the circle, so it just finished the shape it saw around the spot.

    Try this blindspot experiment with your original piece of paper, but this time surround one of the shapes with shapes in a different color. Your brain will fill in this new color!

    While our blind spot isn’t something that affects our daily lives, it is still a fascinating topic, and worth experimenting with. It really shows us how amazing our brains are!