The Science of Life: Projects and Principles for Beginning Biologists
144
The Science of Life: Projects and Principles for Beginning Biologists
144eBook
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Product Details
| ISBN-13: | 9781613742785 |
|---|---|
| Publisher: | Chicago Review Press, Incorporated |
| Publication date: | 07/01/2001 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 144 |
| File size: | 4 MB |
| Age Range: | 9 Years |
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The Science of Life
Projects and Principles for Beginning Biologists
By Frank G. Bottone Jr.
Chicago Review Press Incorporated
Copyright © 2001 Frank G. Bottone, Jr.All rights reserved.
ISBN: 978-1-61374-278-5
CHAPTER 1
Bacteria Are Everywhere
(Kingdom Prokaryotae)
Microbiology is the study of microscopic organisms, which are organisms that you cannot see with the unaided eye. Bacteria are the most common form of microscopic organisms. Bacteria are found in soil and water, on the surfaces of plants and animals, and even on you. Bacteria and the related blue-green algae (also known as cyanobacteria) belong to the kingdom Prokaryotae (formerly Monera). The word Prokaryotae comes from the Greek word prokaryon, which means "before a nucleus." (A nucleus is the structure within a cell that contains genetic material and is found in all creatures except those in this kingdom.) Since prokaryotes do not have a nucleus to contain genetic material, the material is located within the cell along with the rest of the cellular material.
Bacteria serve an integral role in nature and everyday life. Bacteria, along with other organisms, decompose (break down) dead material such as leaves and other tissues on the forest floor, in rivers and streams, and in your own backyard. For example, have you ever noticed that every autumn, leaves accumulate on the ground, and by the next spring they are almost gone? This is in part due to decomposition by bacteria. Without decomposition, nutrients called vitamins and minerals wouldn't become available when an organism dies. It is through decomposition of dead material, animal waste, and other tissue that nutrients are returned to the soil. These important compounds are then available for other living organisms such as plants.
Bacteria are also significant to our lives because they can cause diseases, produce food and medicine, and are used to research human diseases. Bacteria that cause disease are often referred to as "germs." Germs are what we call bacteria or viruses that make us sick. However, most bacteria do not make us sick. In fact, many bacteria are beneficial to us. Bacteria on the surface of our skin and mouth help to prevent germs from attaching and growing on these surfaces. The beneficial bacteria are able to do this by outnumbering the germs. Luckily, most bacteria do not cause disease. Beneficial bacteria are also used in the production of medicines, such as antibiotics, foods, such as sauerkraut and cottage cheese, and fuels, such as methane gas. Antibiotics are chemicals used to kill or inhibit the growth of unwanted microorganisms. Antibiotics are prescribed by doctors and are found in over-the-counter ointments. However, doctors and scientists were not the first ones to use antibiotics. Bacteria, yeast, and especially fungi have been producing antibiotics to kill one another long before we discovered uses for them.
Growing Bacteria
Even though bacteria are microscopic, you can grow them at home the way that scientists grow them in the laboratory in order to study them. Because bacteria can grow quickly and reach very high numbers in a short period of time, they are easy to study. Bacteria divide (split from one to two cells) about every 30 minutes. If just one cell were to continue to divide at this rate, there would be 1,048,576 cells in just 10 hours. That's a lot of bacteria. However, many factors such as nutrients, predation, and space limit this outrageous growth.
There are many different ways to grow microorganisms in the laboratory. When scientists grow microorganisms such as bacteria, they refer to the bacteria as a culture. The material used to grow the microorganisms is called culture medium. Culture medium contains all the essential nutrients needed to support bacterial growth, such as sugar, protein, vitamins, and minerals. A liquid culture is often called a broth, while a solid culture is called an agar dish. Agar, the most common form of culture medium, is a gelling agent used to grow bacteria on. Agar often contains agarose, which comes from certain seaweeds.
Objective
Make a culture medium using gelatin from Jell-O instead of agar. Use the culture medium to determine if your arm, a bathroom countertop, or soil contains more bacteria by growing bacteria from each on a solid form of growth medium.
Results
What did you find growing on your medium? Can you see bacteria growing in a Z pattern on the surface of the medium? Compare the three cups and then visually determine which one has the most bacteria growing on it. Did your arm, the soil, or the countertop have the most bacteria?
Did anything grow on your control medium? Was there a difference between the control medium and the medium you added the bacteria to?
Variations
Can you think of any other places where bacteria might grow? Keep in mind that bacteria thrive in warm and wet places. Compare the amount of bacteria on two different surfaces in your backyard that are of interest to you by growing them on bacterial growth medium, as you did in this experiment. Determine if there are more bacteria growing on dead leaves from the top or the bottom of a pile of leaves. The growth medium that results in the most bacterial growth likely had more bacteria on it. Where else would you expect to find a lot of bacteria?
Hand Washing
Recently, a new group of hand soaps called waterless hand soaps have become available. They are unique because they do not require the use of running water. Therefore, they are a convenient way of killing microorganisms on your skin when a sink is not available. The active ingredient in most waterless hand sanitizers is 60–70 percent alcohol, which evaporates from your skin within a few minutes after use.
Objective
Compare the effectiveness of ordinary hand washing to hand washing with waterless hand soap. Determine how effectively your ordinary hand soap works at preventing bacteria from growing on growth medium after washing your hands.
Results
How well did you wash your hands? Did hand washing reduce the number of bacteria that were able to grow? Which hand soap was more effective at killing bacteria? The cup with the least amount of bacteria growing on it was the most effective.
Antiseptics and Disinfectants
Have you ever scraped your knee while running around in the yard? If so, you may have applied an antiseptic such as hydrogen peroxide, antibacterial hand soaps, or rubbing alcohol to the scrape. This kills the germs, thus preventing them from getting into the wound. Antiseptics are chemicals that destroy a wide variety of germs. The root word septic comes from the word sepsis meaning "infection." Antiseptics are a class of disinfectants that are safe and mild enough to use on your skin. As a result, they are only moderately effective at the removal and killing of microorganisms.
Antiseptics work in a variety of ways. Soap increases the effectiveness of hand washing by helping to dissolve and break up the natural oils that are found on your skin as well as removing and killing bacteria and some viruses. While the physical act of scrubbing is moderately effective at removing bacteria from your hands, without the aid of soap, literally millions of bacteria can survive in the tiny cracks of your hands. The physical act of scrubbing, the effectiveness of the soap, and how long you wash your hands are all very important factors in the removal of microorganisms from your skin. Hydrogen peroxide works by breaking down in the presence of heat from your skin into a form that is deadly to some bacteria. When hydrogen peroxide breaks down, it is converted into water and a special form of oxygen that bubbles.
Disinfectants are chemicals used to kill or inhibit the growth of microorganisms on objects such as countertops, floors, and sinks. They are too strong to use on your skin. Some common household disinfectants include Lysol, detergents, and bleach. Alcohol (ethanol) is the main ingredient (by weight) in Lysol. It works by disrupting the outer surface of the microorganism and thereby killing it. It also contains a complex compound used as a germicide, to kill germs such as bacteria, viruses, and molds on nonliving surfaces. You can test these products to see which one is more effective at killing or inhibiting the growth of bacteria.
Objective
Determine which household antiseptic is more effective at killing or inhibiting the growth of microorganisms from soil on medium, hydrogen peroxide or Lysol.
Results
Was the hydrogen peroxide or Lysol disinfectant more effective at inhibiting the growth of microorganisms? If the bacteria grew on the control side but was unable to grow on the treated side, it was effective. How well did the bacteria grow on the control sides? Was the growth partially or totally inhibited on the treated sides of the cups?
Variations
Determine how well some other common household antiseptics and disinfectants work. Choose two different types of antiseptics or disinfectants and grow bacteria from your bathroom sink using a moist cotton swab. Determine which one works best by comparing the amount of bacteria that grow on each medium cup. The one with the least growth worked best.
Bacteria and Antibiotics
Antibiotics were first discovered by Alexander Fleming when a fungus contaminated, then killed, several colonies of bacteria on an agar dish. You can grow microorganisms in the presence of various antibiotics to test their resistance or susceptibility to them. An organism is said to be resistant to an antibiotic if it is able to grow in its presence. If the organism cannot grow, it is said to be susceptible. Doctors and scientists have become increasingly concerned about antibiotic resistance among bacteria that cause illnesses. This means that antibiotics will be less effective in fighting illnesses. In order to slow this trend, prescription antibiotics should be taken as instructed by a physician, in the appropriate dose, and only when absolutely necessary. Unlike antiseptics, antibiotics take some time to work because they have to be absorbed by the bacteria. Once absorbed, they act in a variety of ways to interfere with the normal growth of the bacterium.
Objective
Determine if Neosporin or bacitracin is better at preventing the growth of microorganisms.
Results
Assuming you spread the same amount of bacteria on each of the surfaces, the antibiotic with the largest zone of inhibition is likely the most effective antibiotic on the strains of bacteria you grew. This is because bacteria are present in the zone, but they are not able to grow enough to form colonies that you can see with the unaided eye. Which antibiotic was most effective? How did they compare to the control?
Variations
Some bacteria are resistant to antibiotics. Compare the susceptibility of bacteria from different sources, such a bathroom counter, the keypad of an automated teller machine, to Neosporin, bacitracin, and another household antibiotic. If the bacteria are able to grow in and around the antibiotic, they may be resistant (or there may be too much bacteria or not enough antibiotic). Apply the same amount of bacteria to each cup so that you can compare them using the diameter of the zones of inhibition. You can also determine if the bacteria can grow in the presence of a triple antibiotic ointment (an antibiotic cream that contains three antibiotics) such as Triple Antibiotic Ointment or other brands sold over the counter at most drugstores.
CHAPTER 2Plants Grow, Move, and Respond to the Environment
(Kingdom Plantae)
We live in a world filled with plants. Plants are not able to walk or talk, but they definitely shape, modify, and interact with the world around us. Plants sense and respond to movement, touch, vibration, and light. They serve an integral role in the recycling of water through a process known as transpiration, and they contain medicines used to heal us when we're sick. Plants are directly or indirectly responsible for producing all of the food we eat. Humans benefit from plants in a variety of other ways. We harvest plants as crops, use their wood for shelter in our homes, and we make paper money out of plant fibers called flax.
Almost every plant undergoes photosynthesis. Photosynthesis is the process by which plants convert energy from the sun into chemical (or food) energy such as sugars. During this process, plants consume carbon dioxide. In turn, they add oxygen back to the air. Most plants contain a compound called chlorophyll. Plants with this compound use it to undergo the process of photosynthesis. In this process, chlorophyll absorbs light and converts solar energy into chemical energy in the form of simple sugars. In this way, plants can make sugar that can be converted into many of the nutrients their tissues require. Plants provide a great number of organisms such as animals, fungi, and microorganisms with food. The importance of plants to our environment and all of the living things in it cannot be understated.
Transpiration
Animals and plants can go a long time without food. However, the same is not true with water. In fact, every living thing needs water. If an animal goes several days without drinking water, it will get sick. If you do not water an indoor plant, it will wilt, turn brown, and then die. When animals are thirsty, they search for a water supply and drink from it. But how do plants find and drink water?
Plants use roots, buried within the soil, to locate and collect water. Once the roots reach a water supply, the water travels through the plant roots, stem, branches, and leaves, where it then evaporates. The loss of water vapor from a plant is called transpiration. It is the process that causes water to move through the plant. Because of this process, a plant actually requires more water than an animal of the same weight. This is largely because plants do not recycle their water. Animals such as humans do not need to transpire water because they have a circulatory system (a network through which nutrients and waste travel to all parts of the body). You can watch a flower transpire water containing a dye and measure how much water it transpires. Factors that affect transpiration in plants include humidity, wind, temperature, internal carbon dioxide concentrations, and the structure of each different type of plant.
Objective
Learn about a process known as transpiration and then determine how long it takes an ordinary flower to transpire its own weight in water.
Results
How long did it take for your flower to transpire its own weight in water? How much water do you think a large tree such as an oak or pine tree transpires? How long do you think it would take a pine tree to transpire its own weight in water?
Variations
How long do you think it would take you to drink your own weight in water? Remember, drinking is much different than transpiration. You can calculate how long it would take you to drink your own weight in water by recording the volume of everything you drink and adding it up until it reaches your own weight. Assume 1 gallon (4 liters) is equal to 9 pounds (2.2 kilograms) and keep in mind that this is only a rough approximation. Can you think of a better way to account for the water content of food as well?
Germinating Seeds
Do you have any tall trees such as an oak tree in your yard or in a nearby park? Even a huge oak tree with its enormous trunk, hundreds of branches, and thousands of wavy leaves began life as a tiny embryo that continued to grow and grow and grow.
All seed-bearing plants (such as the flowering plants, conifers, cycads, and others) begin life as a tiny embryo wrapped inside a seed that was deposited in the soil under the right conditions. An embryo in plants can be defined as the part of the seed that will develop into the seedling after germination of a fertilized seed. Some seeds are contained within fruits such as apples, tomatoes, and watermelons. Beans, peas, and cantaloupe seeds are all seeds that develop within a fruit. These are known as angiosperms and they are the most common group of plants. Other seeds such as those from the trees of cycads, ginkos, and conifers are not contained within a fruit. These are known as gymnosperms.
(Continues...)
Excerpted from The Science of Life by Frank G. Bottone Jr.. Copyright © 2001 Frank G. Bottone, Jr.. Excerpted by permission of Chicago Review Press Incorporated.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.
Table of Contents
Contents
Acknowledgments,Safety First,
Introduction,
1. Bacteria Are Everywhere (Kingdom Prokaryotae),
2. Plants Grow, Move, and Respond to the Environment (Kingdom Plantae),
3. Animals That Fly, Walk, and Wiggle (Kingdom Animalia),
4. There Is a Fungus Among Us (Kingdom Fungi),
5. Last but Not Least: The Protozoans (Kingdom Protoctista),
Conclusion,
Resources,
Glossary,
Bibliography,
Index,