Case Study: Our Invisible Inhabitants
Julia is suffering from a fever, body aches, and a painful sore throat that gets worse when she swallows. She visits her doctor who examines her and performs a throat culture. When the results come back, he tells her that she has strep throat, which is caused by the bacteria Streptococcus pyogenes. He prescribes an antibiotic to kill the bacteria, and advises her to take the full course of the treatment even if she is feeling better earlier, because stopping early can cause an increase in bacteria that are resistant to antibiotics.
Julia takes the antibiotic as prescribed. Towards the end of the course, her throat is feeling much better but she can’t say the same for other parts of her body! She has developed diarrhea and an itchy vaginal yeast infection. She calls her doctor, who suspects that the antibiotic treatment has caused both her digestive distress and her yeast infection. He explains that our bodies are home to many different kinds of microorganisms, some of which are actually beneficial to our bodies by helping us digest our food or keeping the population of harmful microorganisms down. When we take an antibiotic, many of these “good” bacteria are killed along with the “bad” disease-causing bacteria, which can result in diarrhea and yeast infections.
He prescribes an antifungal medication for Julia’s yeast infection. He also recommends that she eat yogurt with “live cultures” to try to help replace the beneficial bacteria in her gut. Clearly, our bodies contain a delicate balance of inhabitants that are invisible without a microscope, and changes in that balance can cause unpleasant health effects.
What Is Human Biology?
As you read the rest of this book, you'll learn more amazing facts about the human organism and how biology relates to your health. Human biology is the scientific study of the human species that includes the fascinating story of human evolution and a detailed accounting of our genetics, anatomy, physiology, and ecology. In short, human biology focuses on how we got here, how we function, and the role we play in the natural world. Importantly, this helps us to better understand human health – how to stay healthy and how diseases and injuries can be treated. This is probably of personal interest to you in terms of your own health and the health of your friends and family, and also has broader implications for society and the human species as a whole.
As you read this book, think about what you want to learn about your own human body. What questions or concerns do you have? Make a list of them and use it to guide your study of human biology. You can revisit the list throughout the course to see if your questions have been answered. If not, you'll have the tools to find the answers. You will have learned how to find sources of information about human biology and how to judge which sources are most reliable.
Chapter Overview: Introduction to Human Biology
In the rest of this chapter, you'll learn about the traits shared by all living things, the basic principles that underlie all of biology, the vast diversity of living organisms, what it means to be human, and our place in the animal kingdom. Specifically, you'll learn:
- The seven traits shared by all living things including: the maintenance of a more-or-less constant internal environment, called homeostasis; multiple levels of organization consisting of one or more cells; using energy and exhibiting metabolism; the ability to grow and develop; the ability to evolve adaptations to the environment; the ability to detect and respond to environmental stimuli; and the ability to reproduce.
- The diversity of life, including the different kinds of biodiversity, the definition of a species, the classification and naming systems for living organisms, and how evolutionary relationships can be represented through diagrams such as phylogenetic trees.
- How the human species is classified, our close relatives and ancestors, and some ways in which we evolved.
- The traits humans share with other primates including physical characteristics and social behaviors.
As you read this chapter, think about the following questions about Julia’s situation:
- What do single-celled organisms, such as the bacteria and yeast living in and on Julia, have in common with humans?
- How are bacteria, yeast (a fungus), and humans classified?
- How do the concepts of homeostasis and biodiversity apply to Julia’s situation?
- Why can stopping antibiotics early cause the development of antibiotic-resistant bacteria?
Credit: By U.S. Navy photo by Journalist 1st Class Jeremy L. Wood. [Public domain], via Wikimedia Commons;
License: CC BY-NC 3.0