Living on Earth
Living on Earth

Living on Earth

Lead Author(s): Terry Gates

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A book designed for non-majors introductory biology, Living on Earth takes a largely nontechnical approach to teaching the biological world through a myriad of examples that students can find in their own backyard or experience in museums or aquaria. The point of this approach is to bring biology back to the basics. Simplify the concepts, succeed with the content.


As a discipline, Biology, like all other sciences, has traditionally been slotted into its own silo of inquiry and teaching. Why would anyone delve into physics, chemistry, math, or even engineering when studying panda bears, bacteria, or dinosaurs? Certainly you have seen through the straw man that I set up in that last sentence. It is perfectly reasonable, and often times heard in doctors offices for a person’s blood chemistry to be used as an identifier of good health. Maybe you have been exposed to controversies in the past two decades about genetically engineered foods. Engineering humans at the genetic level is a popular topic for science fiction and science reality alike. Indeed, many fields of classic science have influenced biology over the past century. In fact, Galileo Galilei in 1638, was one of the first scientists to use math and physics to demonstrate constraints on biological entities in his Discourses and Mathematical Demonstrations Relating to Two New Sciences.

What may not be as obvious, but is by no means less important than integrating classic scientific disciplines with biology, is the influence of all other academic fields on the biological sciences. And vice versa, there is a strong benefit of including biological understanding within marketing, education, computer science, or architecture.

Despite the obvious advantages of breaking down the scientific silos and having all academic disciplines cohabitating in an open farm yard where all entities take advantage of the metaphorical food, interactions, protection, conflict, by-products, and companionship of each other, crossing of disciplinary boundaries has only recently taken root and is still not wholly embraced. Given that this book is designed for people not majoring in biology, one of my main goals is to present to you ways in which apparently disparate fields relate to biology. At the end of the book, I hope that you will have a better sense of how complex networks of knowledge and practice criss-cross our world and that behind every ‘I’, ‘Me’, and ‘My’, there is a legacy of evolutionary history, human civilization, agriculture, and trillions of organisms you can’t even see.

Structure and Philosophy of Book

This book is structured in a format that I hope will elucidate to you the many connections in our world between all sorts of things that previously may have seemed unconnected, such as various careers, disciplines, all the organisms on this planet, and Earth’s physical attributes. Given our biological focus, "Life on Earth" connects our world through three scales, or sections, that are interlinked.

The first is the evolutionary scale. Within Evolution we will explore the concepts of deep time, the fossil record, and the evolutionary mechanisms that produced the amazing biodiversity over billions of years.

Next, in DNA to Bodies, all levels of organization from the invisible nanoscale molecules that make up your genetic code through to the bodies we see all around us will be discussed. A central theme of this section is how each level influences the others to structurally produce the amazing organisms all around.

Finally, the interactions between life and the physical world will be mapped out in Ecosystems and Human Society. As the title also implies, the human-created world has not escaped examination. Expect examples of ecosystems on human bodies, ecosystems created by humans through conservation efforts or accidentally during the building of cities. We will even delve into newly emerging scientific lines of inquiry that combine knowledge of evolution and ecosystems to better understand the nature and behavior of businesses.

Vocabulary in this book is structured differently than in other books. I have bold texted the definitions of words, not the vocabulary word itself. This will provide two things, first, it will easily show you the important part of the text, which is the definition and context of which we are talking. Second, it will cause you to read a bit closer to find the vocabulary word. My hope is that you will first focus on the definition, gain an understanding of the concept, then learn the word for that concept.

Also, throughout this book there will be links to other sections of the book or to online resources that will hopefully guide the reader through the complex, yet beautiful ways in which our world is interconnected. It is not necessary to follow these links in order to understand the topics being described within each section. However, it is important to remember that everyone learns differently and perhaps seeing how one topic is related to a different topic may spark associations or click the switch that makes the puzzle fall into place.

Finally, validation of claims is important within scientific literature. Whenever a piece of information extends beyond general biological knowledge I provide a reference that links straight to the paper for downloading by the reader or if not available, to the abstract on the publisher's webpage. No reference lists here. Just the evidence.

Science as a Quest for Knowledge

As mentioned above, it is impossible to exclude the science of Biology from those other realms of inquiry that typically come to mind when one says the word Science. Chemistry and physics are certainly essential if we are to understand what molecules make up our DNA, control energy production in our cells, and what creates the flavors in fruits and vegetables, among much more.

Let’s take two examples, that of a long jumper and that of conservation of an ecosystem, to illustrate how different disciplines and careers influence biology.

Multidisciplinary Nature of Biology

A long jumper stands at the beginning of a long, straight asphalt path ready to sprint. Sweat runs down her face and her mind fixes on the line of her jump. Now her legs shoot out, swinging back forth with tremendous force, increasing the runner’s velocity until suddenly Up! she is flying through the air waving arms and legs. Finally, her body lands in the sand, having just propelled her body 7.4 m (24 ft 3 in). This is the Olympic record set by Jackie Joyner in 1988.

Watch the jumper in the GIF on the following page (not Mrs. Joyner). You also can watch this clip from a long jump competition in 2015. From a physics perspective the runner is overcoming the force of Gravity through the muscles in her legs pushing up against the Earth. She is simultaneously propelling herself forward by leaning in front as well as pushing her legs backwards. During the jump she once again uses her muscles to push against the force of Gravity, but this time her acceleration is greater than the opposing acceleration of gravity causing her body to fly up. Swing her arms and legs in midair helps move her through the gaseous atmosphere surrounding everything living on the land. Finally, the jumper lands in the sand, satisfied with the aerial dance her biological body performed with physics.

This explanation in physics speak is important because this is the same conversation that is had when biologists and physicists collaborate to figure out how all animals run and jump, or fish swim, or birds fly. The biological stuff inside our bodies arose through evolutionary processes to overcome the physics that is universal to our Earth.

As another example, imagine a beautiful forest that is under the protection of the federal government for conservation by either the Bureau of Land Management or the National Park Service. The forest has a high diversity of plants and animals and fungus and other living organisms, many of which can be found only in the protected area. Federal entities such as the Bureau of Land Management and the National Park Service strive to maintain these protected natural resources for many reasons. One that we have discovered in the recent decades is that ecosystems containing many linkages across their food web can process a great deal more energy than ecosystems without as many connections (in essence they have a higher metabolism; Brown et al., 2004).

The Bureau of Land Management preserves ecosystems all over the United States, as well as heritage sites such as these dinosaur trackways shown above from the Moab Field Office. Paintings on left are by Brian Engh and line drawings on right are from Matt Celeskey. Photos courtesy of ReBecca Hunt-Foster.​

Two of the sciences that have helped us figure out this important fact about all ecosystems on the planet is Network Theory and Information Theory. The first helps us understand how entities are connected, be them animals, plants, people in a social network, or even interactions between companies. Information Theory, along with telling us how we communicate with each other, helps us understand how much biodiversity is in a given ecosystem and what passes between organisms versus what is lost (Ulanowicz, 2002).

Another reason is economic. In many cases conserving ecosystems can have net economic benefits versus exploiting those same ecosystems to traditional economic practices (see Naidoo and Ricketts, 2006; Tallis et al., 2008). 

Consider the case of ecotourism. In these businesses, conservation areas attract tourists because there are animals to see in protected areas that are not as abundant or even extinct outside the parks. Some ecotourists even help with conservation efforts while on vacation. In situations such as this the local people gain tourist money for their income and get to maintain the original habitat that surrounds them.

Multidisciplinary Biology Discussion 1

Describe another way in which economics and biology influence one another.

Being a scientist/Scientific Method

​To begin, let’s establish some definitions. Science is defined by Webster’s Dictionary as “A state of knowing”. A fact is defined by Webster’s Dictionary as “a piece of information presented as having objective reality”. Therefore, in science we establish facts to help us increase the ever growing body of knowledge. And sometimes we have ideas about things that cannot be directly observed to establish a fact, such as the expansion of the universe, so instead we create a hypothesis, and use facts to support or refute the hypothesis. That is, “a tentative assumption made in order to draw out and test its logical or empirical consequences”. 

This summarily describes the Scientific Method.

The scientific method can be broken down into a series of steps that in an ideal case will be taken in sequence from start to finish, but in many cases requires one to repeat steps in order to properly test a natural phenomenon.

​The heart of the Scientific Method, and more generally speaking towards developing a science mindset, is the Observation. Just looking and taking note of the things we see. Asking questions like, 'What happens if I do this?' We also consider Observations as establishing a list of facts about the subject matter at hand before preparing to explain Why. Just look, don't explain.

Background research is one of the most important steps because it tells you what has already been done, what's left to do, what methods worked, and what not to do. It may not seem glorious to sit around reading what other people have been done, but it will definitely make your scientific discovery better.

The next step is creating a hypothesis that is predictive and testable. If your coffee is too weak in the morning, you may say to yourself, "Tomorrow I need to add one more scoop." Implied in this statement is that 1) you have identified a problem; 2) you predict that adding one more scoop will make it the correct strength; 3) and it is in fact testable. A teacher once told made the comment when I explained this example, "That is not science, that is just common sense." 

The best response to that statement is Science can be common sense.

Finally, we get to what most people think of as Science, doing an experiment. From your hypothesis you should develop a series of steps that you will use to test if your predictive hypothesis is supported or not supported. If you're not careful the method you use will be incorrect and therefore, the answer you get will not be valid. This often requires controls, which are samples dedicated to show the effect of doing nothing. For instance, if someone wants to see if a gene causes cancer, that researcher should take the gene out of a group of mice (or other test organism) and leave the gene in a series of mice to see if the changes in cancer occurrence was the same or different between the two groups.

Sticking with hypothesis testing a moment longer, I wanted to discuss Data Collection. Not all experiments are mixing chemical together to see what happens. Although those that are based on mixing things together, or splicing genes, or crashing objects together are considered Experimental hypotheses. Others, such as Astrophysics, Archaeology, Paleontology, and others have Discovery hypotheses, whose data are based not on experimental results, but instead are contingent on the discovery of something. Importantly, humans cannot derive the discovery-based results, these must be found in Nature.

Shark tooth discovered in NC by the author. Paleontology is largely a Discovery-based science because we need to find our data instead of deriving it from experiments.​ Photo copyright The Author.

After data analysis and determining if your hypothesis was supported or not supported, it may be necessary to Revise your Hypothesis. 

​One of the most misunderstood aspects of the Scientific Method is that it is ok to be wrong. That is, to have your hypothesis unsupported. In these instances it is necessary to reexamine and recalibrate your study. Maybe the test you performed was not right for the hypothesis. Or the hypothesis itself is not one that can be tested, but instead should be reframed into a simpler question. Maybe your test and hypothesis were well matched, but something went wrong in the data collection phase. Any or all of these could be true, therefore it is extremely important to keep track of all details in scientific research. In the end, even though your idea maybe wrong the greater human knowledge bank is richer than before. With every mistake we learn more. Science is only bad science if the Scientific Method was not followed correctly.

Scientific Method 1

Put the steps of the scientific method into correct order.


Test the hypothesis


Create a hypothesis


Collect data


Communicate your results with scientists and the public


Background research


If necessary revise hypothesis


Make Observations

​Finally, rarely included in the Scientific Method is Communication. Nonetheless, I feel it is imperative for the Public to understand the newest body of knowledge. Scientists can communicate with the world through a variety of media such as blog sites, press releases, interviews, and public talks. When an opportunity arises to read or see a talk about the newest research, take it, because this is world we live in and the more we understand the more we appreciate the billions of years it took to evolve.

Scientific Method 2

Described below is a scenario in which a scientist did not appropriately follow the scientific method. Which of choices listed best describes what is wrong with the study?

Dr. A wants to study why the SKG gene causes arthritis in mice. He takes the gene out of five mice and found they did not get arthritis. Therefore, he published that the gene caused the joint disease.


Dr. A should have taken the gene out of humans not mice.


Dr. A used too many mice in his study.


Dr. A did not use proper controls, because he only tested the mice without the gene


Dr. A did not create a hypothesis before beginning the study

Thinking like a scientist

I want to return to our prior example of the long jumper to first answer a question, then second to illustrate an important point in how to think like a scientist. To the question: Are humans the best jumpers on the planet? No. We are good, well, at least some of us are good, but there are animals that have specifically adapted to jumping who make human long jumpers look puny.

Image of a flea and NBA player Michael Jordan. Jordan is demonstrating his jumping prowess in an image called "The Shot"​. Check it out if you don't know about it. Flea image courtesy of, under CC0 Public Domain. Jordan image courtesy of, By Manny Millan/SI [CC BY-SA 4.0 (], via Wikimedia Commons.

The best jumper relative to body size is the flea. And this is where the scientific mentality arises. A dog flea jumps approximately 25 cm (10 in) high (Cadiergues et al., 2000). Whereas, a human can clearly jump much higher (Michael Jordan has a vertical leap somewhere on the order of 121 cm [~48 in]).

However, these numbers do not take into consideration the different sizes of the animals. A flea is around 3 mm long, which differs quite a lot from the 1, 973 mm that is Jordan’s length. Once we take this difference into account we will come up with the relative jump height. Simply divide the height of the jump by height (or in this case the length) of the flea (253 mm / 3 mm) and you will see that the flea jumps an astounding 84 times its body height. Michael Jordan jumped a lousy 0.61 times his body height (1,210 mm / 1,973 mm).

This example shows how within a scientist mindset you will look not just at numbers but at an entire system. Look at all of the components to make sure that the experiment or the comparison makes sense. It’s about recognizing all of the wonderful connections and fluidly adapting to changing conditions in data to better understanding the world around you.

In Science nothing is certain. But many ideas are so well supported that they are virtually certain.

Concepts in science come in three flavors: Hypothesis, Theory, and Law.

Hypothesis - The first level of inference within the scientist mindset is the hypothesis. From a set of observations and knowledge of related phenomena one can conjecture the cause and effect of another event or phenomenon. "If a chicken comes an egg 7.5 cm long, then a giant dinosaur 100 times larger than a chicken must come from an egg 750 cm long". In this case you would be wrong, the largest dinosaur eggs are only about 30 cm in long. 

 With repeated testing a hypothesis can become a Law, and with broadening a hypothesis can lead to a Theory.

Theory - Theories, on the other hand, are amalgamations of supported hypotheses and facts that aim to explain larger phenomena in the universe. For instance, the Theory of Relativity aims to explain time and space, no small feat. But to do that it incorporates facts and previously supported hypotheses about the subject. Even though Theories can always be proven incorrect, in most cases there is such a substantial amount of evidence supporting them that the likelihood of them being proven incorrect is quite small.

 In short, Theories look to explain bigger picture aspects of the universe that encompass many hypotheses and Laws.

 In the next section of this book we will explore the Theory of Evolution. Remember that this means there is a tremendous amount of support for why and how evolution occurs, not that it is simply "just an idea".

Laws - The final classification of scientific principles is Law. Bear in mind that this is not a top level, it is a different way of looking at the universe compared to a Theory or an Hypothesis. Scientific Laws explain phenomena in the Universe so long as the phenomena are always under the same conditions. Laws of Motion work so long as the object is not going close to the speed of light (see Theory of Relativity for an understanding of this). 

Citizen Science

Most of the public has an inherent belief that the pursuit of scientific knowledge is restricted to those few people who achieve a career as a scientist. Certainly throughout our public school education we are reinforced with this idea that contributing to science is not for everyone. That doesn’t mean that many folks outside of scientific circles are indifferent to science. The publication of popular science books, some even reaching the New York Times Bestseller List, and the prevalence of science fiction movies during summer blockbuster season shows how much inherent interest the public has in science.

A quickly growing movement across all major scientific disciplines is taking advantage of the general public’s potential energy in science to accelerate the pace at which new discoveries are made. In fact, some of the most important studies being done today are on such large geographic scales that it is impossible for scientists to perform the work without assistance from local citizens.

Where do we go to do citizen science? The easiest place is to go to one of the above websites. SciStarter and Zooniverse both help scientists develop their projects for everyone to help solve scientific problems.

Projects that you can contribute to include monitoring local environmental conditions (such as water quality, seasonal changes to leaves or insects, and identifying birds), classifying astronomical objects like galaxies or stars, aligning DNA sequences or folding proteins to help cure disease, and finding and measuring fossil shark teeth (this is a project that I run called Shark Tooth Forensics). Generally speaking, we can break citizen science into projects that cross a spectrum of personal involvement from having the public gather data only, to members gathering data and processing that data, all the way at the far end of the spectrum to projects that allow citizens to identify a problem then proceed through the entire scientific method.

Citizen Science Discussion 1

Go to the citizen science project hub Find three projects that you would be interested in trying. Describe them.

There are many benefits to using citizen scientists in a research project. As just mentioned, you can get a great deal of data from across large areas without traveling to those areas regularly; thereby saving considerable cost of your research. Also, data can be collected faster than doing it alone. Finally, there is an education for those citizens involved both on the phenomena being studied and connections to the rest of the world.

Students at a school in a North Carolina middle school are participating in the citizen science project Shark Tooth Forensics, in which students find and collect data on fossil shark teeth. Photo copyright the author.​

Education about the scientific method and education about the world around us is a central tenet of Citizen Science as a discipline. Awareness of local environments and resources also has the benefit of eliciting a sense of social responsibility among participants. In other words, many citizen science participants feel that they are contributing to a better, more knowledgable world. Some would even say that it is a social imperative as important as voting, jury duty, or shoveling your sidewalks after a snowstorm. Nonetheless, this movement to get everyone involved in the scientific process is only getting stronger and the opportunities to participate being more interesting, so be on the lookout for a new perspective on scientific research in the coming years.

Student in North Carolina public school looks at the type of bacteria that grows on ants as part of an NSF grant called Students Discover.​

Citizen Science Discussion 2

What are some actions that you have taken or have seen others take that you would describe as a social responsibility?

Your Questions

Introduction Questions

After reading this chapter, do you have any lingering questions? If so, write them below so they can be discussed in class.