Biology For Dummies®, 3rd Edition
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Library of Congress Control Number: 2017930023
ISBN 978-1-119-34537-4 (pbk); ISBN 978-1-119-34538-1 (ebk); ISBN 978-1-119-34541-1 (ebk)
Life is all around you, from invisible microbes and green plants to the other animals with whom you share the Earth. What’s more, these other living things aren’t just around you — they’re intimately interconnected with your life. Plants make your food and provide you with oxygen, microbes break down dead matter and recycle materials that all living things need, and insects pollinate the plants you rely on for food. Ultimately, all living beings rely on other living beings for their survival.
What makes biology so great is that it allows you to explore the interconnectedness of the world’s organisms and really understand that living beings are works of art and machines rolled into one. Organisms can be as delicate as a mountain wildflower, as curious as a grasshopper, or as awe-inspiring as a majestic elephant. And regardless of whether they’re plants, animals, or microbes, all living things have numerous working parts that contribute to the function of the whole being. They move, obtain energy, use raw materials, and make waste, whether they’re as simple as a single-celled organism or as complex as a human being.
Biology is the key you need to unlock the mysteries of life. Through it, you discover that even single-celled organisms have their complexities, from their unique structures to their diverse metabolisms. Biology also helps you realize what a truly miraculous machine your body is, with its many different systems that work together to move materials, support your structure, send signals, defend you from invaders, and obtain the matter and energy you need for growth.
Biology For Dummies, 3rd Edition, takes a look at the characteristics all living things share. It also provides an overview of the concepts and processes that are fundamental to living things. We make sure to emphasize the most important ideas in biology while taking a look at the diversity of life on planet Earth and our place in it.
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Part 1
IN THIS PART …
Take a look at the big picture of life on Earth.
Go behind the scenes of scientific investigation.
Explore the connections between chemistry and biology.
Discover life at the level of a single cell.
Delve into the details of how cells get energy.
Chapter 1
IN THIS CHAPTER
Seeing how cells are part of all living things
Finding out the fundamentals of where babies come from and why you have the traits you do
Recognizing that all of Earth’s ecosystems are interconnected
Surveying animal anatomy and physiology
Exploring the similarities and differences between plants and people
Biology is the study of life, as in the life that covers the surface of the Earth like a living blanket, filling every nook and cranny from dark caves and dry deserts to blue oceans and lush rain forests. Living things interact with all of these environments and each other, forming complex, interconnected webs of life. For many people, a hike in the forest or a trip to the beach is a chance to reconnect with the natural world and enjoy the beauty of life.
In this chapter, we give you an overview of the big concepts of biology. Our goal is to show you how biology connects to your life and to give you a preview of the topics we explore in greater detail later in this book.
Quick. What’s the smallest living thing you can think of? (Here’s a hint: Try to recall the basic properties of life; if you can’t, head to Chapter 2 to discover what they are.) Your mind may automatically call up images of ants, amoebas, or bacteria, but that’s not quite the answer. The absolute smallest unit of life is a single cell.
Everything an organism’s body does happens because its cells make those actions happen, whether that organism is a single-celled E. coli bacteria or a human being made up of approximately 10 trillion cells.
Of course, the number of cells you have isn’t the only difference between you and E. coli. The structure of your cells is a little bit different — your cells have more specialized internal compartments, such as the nucleus that houses your DNA (we cover cell structure in Chapter 4). Yet you have some distinct similarities as well. Both you and E. coli are made up of the same raw materials (flip to Chapter 3 to find out what those are) and have DNA as your genetic material (more on DNA in Chapter 8). You also use food the same way (see Chapter 5), and you build your proteins in the same manner (see Chapter 8).
You began life as a single cell, when a sperm cell from your dad met an egg cell from your mom. Your parents made these reproductive cells through a special type of cell division called meiosis (we explain meiosis in detail in Chapter 6). When their reproductive cells combined, your dad and mom each donated half of your genetic information — 23 chromosomes from mom and 23 from dad — for a total of 46 chromosomes in each of your cells. The genes on those 46 chromosomes determined your characteristics, from your physical appearance to much of your behavior. The science of genetics tracks the inheritance of genes and studies how they determine traits (see Chapter 7). Through genetics, you can understand why your skin is a certain color or why some traits seem to run in your family.
Your genes are found in your DNA, which is in turn found in your chromosomes. Each chromosome consists of hundreds of different blueprints that contain the instructions for your cells’ worker molecules (which are mostly proteins). Each type of cell in your body uses the blueprints found in your genes to build the proteins it needs to do its particular job. So what exactly does all that mean? Here it is, plain and simple: DNA determines your traits because it contains the instructions for the worker molecules (proteins) that make your traits happen.
Scientists are discovering more and more about DNA; they’re also developing tools to read and alter the DNA in cells (see Chapter 9). Chances are you’re already experiencing the impacts of scientists’ work with DNA, even if you don’t know it. Why? Because scientists use recombinant DNA technology to alter organisms used in food and medicines. This technology allows them to take genes from one organism and place them into the cells of another, changing the characteristics of the receiving organism. For example, scientists alter the cells of bacteria with human genes, turning them into tiny living factories that produce human proteins needed to treat diseases.
As you discover in Chapter 10, the amazing diversity of life on Earth helps ensure that life continues in the face of environmental change. Each type of organism plays a role in the environment, and each one is connected to the other. Green organisms such as plants combine energy and matter to make the food on which all life depends, herbivores eat plants, predators hunt prey, and decomposers such as bacteria and fungi recycle dead matter so it becomes available again to other living things. (For more on the interconnectedness of all living things on Earth, head to Chapter 11.)
Organisms such as plants form the foundation of every web of life (ecosystem) because they can combine energy and matter from the environment to make food. All organisms use food to get the energy they need to stay alive and the matter they need to grow. Ultimately, energy flows from the sun to plants, to organisms that eat other organisms, and then back out to the atmosphere (and ultimately outer space) as heat. At the same time, matter constantly cycles from the environment to the bodies of living things, then back out to the environment again. (For more on the flow of matter and energy, head to Chapter 11.)
Humans are part of the natural world, and like all living things, use resources from the environment and produce wastes. However, the human species is unusual in its ability to use technology to extend its reach, drawing heavily on the natural resources of the Earth and changing environments to suit its needs. The human population has expanded to cover most of the Earth, and the numbers just keep on growing.
Yet as humans draw more heavily upon the Earth’s resources, we’re putting stress on many other species and possibly driving them to extinction. The great lesson of biological evolution (a topic we cover in Chapter 12) is that not only do populations change over time but they’re also capable of going extinct. The challenge that humans face today is discovering ways to get what we need but still live in balance with the Earth’s various ecosystems.
All animals work hard to maintain homeostasis, or internal balance, as change occurs in the environment around them (see Chapter 13 for more on homeostasis). In a complex, multicellular animal like you, all of your organ systems must work together to maintain homeostasis.
Following is a rundown of all of your organ systems, including what they do and what they consist of:
At first glance, plants seem pretty different from people, but actually humans and plants occupy nearby branches on the tree of life. Both humans and plants engage in sexual reproduction, meaning they produce new offspring from the fusion of sperm and eggs that contain half the genetic material of the parents (see Chapter 20 for more information on how plants reproduce). Also like you, plants have systems for moving materials throughout their bodies (flip to Chapter 21 for the scoop on this), and they even control their functions with hormones.
Of course, plants also have major differences from humans. Most importantly, they make their own food using carbon dioxide, water, and energy from the Sun, whereas humans have to eat other organisms to survive. As a byproduct of their food production, plants give off oxygen as waste. Humans gladly breathe oxygen in and return the favor by breathing out carbon dioxide that the plants can use to make food (see Chapter 5 for more on photosynthesis and respiration and how they lead to this gas exchange between humans and plants).
Chapter 2
IN THIS CHAPTER
Studying life
Using observations to solve the world’s mysteries
Recognizing science as an ever-changing thing
Discovering where to find scientists’ research and conclusions
Biology wouldn’t have gotten very far as a science if biologists hadn’t used organized processes to conduct their research or if they hadn’t communicated their research results with others. This chapter explores the characteristics that distinguish living things from the nonliving materials in the natural world. It also introduces you to the methods scientists (whether they’re biologists, physicists, or chemists) use to investigate the world around them and the tools they use to communicate what they’ve discovered.
Biologists seek to understand everything they can about living things, including
An individual living thing is called an organism. Organisms are part of the natural world — they’re made of the same chemicals studied in chemistry and geology, and they follow the same laws of the universe as those studied in physics. What makes living things different from the nonliving things in the natural world is that they’re alive. Granted, life is a little hard to define, but biologists have found a way.
All organisms share eight specific characteristics that define the properties of life:
Different types of biologists study living things at different levels of organization, from the very tiny to the very large. Cell biologists might focus on individual cells, or even particular structures inside a cell. Physiologists study whole organisms or focus on a particular system within the body. Ecologists go big and study entire populations of organisms, or the interactions between populations and their environment. Each of these types of scientists chooses which area or system to focus on based on the questions he or she wants to answer.
A system is a group of related parts that work together. As an example, consider your own body. You are a system. You have a boundary (your skin) that keeps all of you separate from the outside world. Within your body, you have many smaller systems like your nervous system or your cardiovascular system that work together so that your whole body functions. To truly understand how one of your organ systems works to help keep you healthy, we need to look not just at that system, but also how it interacts with the other parts of your body.
Systems thinking is an approach that seeks to understand the whole system by looking at the connections between the parts of the system. Systems thinking is a very powerful approach for solving complex problems because it makes people widen their perspective and consider many different components that could contribute to the situation. By taking a wider view and considering the big picture, people are more likely to identify how they can change a system to solve a problem.
For example, let’s say you visit your doctor and find out that your blood pressure is high. Easy fix, right? Just start taking medication to lower your blood pressure. That seemingly quick solution doesn’t look at the causes of the problem, and might have some side effects. Instead, your doctor might start asking you questions to try to figure out how your cardiovascular system (where the blood pressure is detected) is interacting with your other systems, such as
By getting answers to questions like these, your doctor is taking a systems thinking approach to considering your high blood pressure. Based on your answers, your doctor may be able to identify the likely causes of the problem and help you identify the best solution, or combination of solutions (which may include medication), to correct the problem.
Scientists all over the world are using systems thinking as a new way to analyze problems, from understanding human development and aging, to understanding disease, to understanding complex global issues like climate change and public health.