Science as a way of knowing

The science of biology

It’s now time to shift from a discussion of science in general to the specific scientific discipline that you will be learning about, biology. Biology is the study of life. that naturally leads to the question – What is life? Suprisingly, that has proven to be a difficult question to answer in just a few words! Most textbook-level definitions of life are merely a list of characteristics; anything that exhibits all of those characteristics is said to be alive. Here’s a typical list.

Living things:

• Respond to the environment.
• Assimilate and use energy from their environment.
• Maintain a relatively constant internal environment, even as the external environment changes ( homeostasis ).
• Reproduce (at the level of organisms) and can evolve (at the level of populations).
• Are highly organized, relative to their environment.

These are general characteristics, and might describe all organisms, even those which have not yet been discovered yet (e.g., those on other planets or solar systems). Until those organisms are discovered and studied, however, that statement is provisional. In addition, scientists have discovered that all living things discovered to date (i.e., the ones on this planet).are composed of one or more cells, and have DNA as their hereditary/genetic material. Some textbooks include these characteristics in their definition of life as well. More importantly, the commonality of DNA as the genetic molecule in all known life forms is strong evidence that all living things on this planet are related, i.e., they have a common ancestor. A putative common ancestor was a prediction made by Charles Darwin when he elucidated his theories about evolution and natural selection. The fact that his prediction proved to be correct is one (of many) pieces of evidence that support that theory. You’ll learn about some of the other evidence later in this course.

One productive way to study and understand living things is to recognize that there is a biological hierarchy , which is basically an organizational concept map that allows us to focus on various levels of life.

This hierarchy ( [link] )extends from atoms and molecules, through cells, tissues, organs, organ systems, organisms, populations, communities, and ecosystems all the way to the biosphere (Planet Earth and the living organisms populating it). Biologists often focus on one or another of these levels, simply because it is far easier to study one level than to try to understand the entire spectrum, and the interactions between those levels. But all biologists recognize that there ARE many interactions between these levels, and those interactions lead to some very interesting and important processes as well.

Consideration of this hierarchy, coupled with the difficulty in coming up with a simple definition of life, leads some scientists to another perspective as well. These scientists argue that it is pointless to try to define life. If life arose from self-replicating chemical systems, which is the working hypothesis in the field of science known as abiogenesis, and if there is a continuum running from atoms to molecules to cells, etc., then it is not possible to point to some arbitrary place on the continuum and define it as “living”. Nobel Prize-winning abiogenesis researcher Jack Szostak writes” None of this matters, however, in terms of the fundamental scientific questions concerning the transitions leading from chemistry to biology.” Indeed, as you come to learn more about viruses in this course or elsewhere, you will probably have some sympathy for this perspective. Are viruses alive? Or would it be better to say that they are somewhere along this continuum, and bypass that question altogether?

As you proceed to learn biology in the studio classroom this semester, you will expand your understanding of the details underlying those characteristics of living things. For example, in regard to organisms responding to the environment, you will learn some of the ways that bacteria, plants and animals sense and respond to environmental conditions. You will learn how bacteria, plants and animals reproduce, and how that process of reproduction is integral to the process of evolution. You will learn about cells and tissues and organs, all of which are highly structured and organized arrangements, and how energy is obtained and expended so that these organized structures can be produced and maintained. Hopefully you will come to the realization that life, in all of its diverse incarnations, is amazing. Which is why biologists continue to study it!