Biology » Introduction to Biology » Biology Orientation

Defining Biology

Earth and the Diversity of Life

Viewed from space, Earth (see image below) offers no clues about the diversity of life forms that reside there. We think the first forms of life on Earth were microorganisms that existed for billions of years in the ocean before plants and animals appeared. 


This NASA image is a composite of several satellite-based views of Earth. To make the whole-Earth image, NASA scientists combine observations of different parts of the planet. Image Attribution: Earth image by NASA/GSFC/NOAA/USGS

In fact, the mammals, birds, and flowers so familiar to us are all relatively recent. Basically, we think they originated 130 to 200 million years ago. Humans have inhabited this planet for only the last 2.5 million years. However, only in the last 200,000 years did humans start looking like we do today.

What is Biology?


Formerly called blue-green algae, these (A) cyanobacteria, shown here at 300x magnification under a light microscope, are some of Earth’s oldest life forms. These (B) stromatolites along the shores of Lake Thetis in Western Australia are ancient structures formed by the layering of cyanobacteria in shallow waters. Image Attribution: A: Modification of work by NASA; B: Modification of work by Ruth Ellison; scale-bar data from Matt Russell.

What is biology? In simple terms, biology is the study of living organisms and their interactions with one another and their environments. Actually, this is a very broad definition because the scope of biology is vast. In fact, biologists may study anything from the microscopic or submicroscopic view of a cell to ecosystems and the whole living planet (See image above).

Listening to the daily news, you will quickly realize how many aspects of biology we discuss every day. For example, recent news topics include Escherichia coli (see image below) outbreaks in spinach and Salmonella contamination in peanut butter. Other subjects include efforts toward finding a cure for AIDS, Alzheimer’s disease, and cancer.


Escherichia coli (E. coli) bacteria, seen in this scanning electron micrograph, are normal residents of our digestive tracts that aid in the absorption of vitamin K and other nutrients. However, virulent strains are sometimes responsible for disease outbreaks. Image Attribution: Eric Erbe, digital colorization by Christopher Pooley, both of USDA, ARS, EMU.

On a global scale, many researchers are committed to finding ways to protect the planet, solve environmental issues, and reduce the effects of climate change. In general, all of these diverse endeavors are related to different facets of the discipline of biology.

Biology and Life Sciences

Biology is the study of life. When you study biology you will learn about all of the different kinds of living things. You will learn where they live, what they are like, how they depend on each other, and how they behave.

One of the main ideas in biology is that living things depend on each other. They are part of what is called the balance of nature. All living things interact with other living things and with the world they live in. Without these relationships, nothing would survive.

Humans need plants and animals to supply us with food and raw materials, such as wood, oil, and cotton. Plants provide the oxygen in our air.

We have just tried to define biology, which is a life science. While biology remains the centerpiece of the life sciences, technological advances in molecular biology and biotechnology have led to many specializations and interdisciplinary fields. 

Living systems exhibit levels of organisation from molecules to biomes. In addition, all life on earth is dynamic, with various processes maintaining equilibrium at every level of organisation. The life forms we observe today are a result of billions of years of change.

While studying life sciences, you will learn how scientists gather evidence about life using the scientific method in order to form theories to explain what they observe. The scientific method requires scientists to constantly re-examine their understanding, by testing new evidence with current theories and making changes to those theories if the evidence does not meet the test. The scientific method therefore is the powerful tool you will use throughout the sciences.

What is Life Sciences?

Life Sciences is the scientific study of living things from molecular level to the ecosystem level, and involves a study of the interactions of organic molecules to the interactions of animals and plants with their environment. The list below contains some of the various branches of Life Sciences.

  • Anatomy (plant and animal)
  • Biochemistry
  • Biotechnology
  • Botany
  • Ecology
  • Entomology
  • Environmental Studies
  • Genetics
  • Medicine
  • Microbiology
  • Morphology
  • Physiology (plant and animal)
  • Sociobiology (animal behaviour)
  • Taxonomy
  • Zoology

[Attributions and Licenses]

This is a lesson from the tutorial, Introduction to Biology and you are encouraged to log in or register, so that you can track your progress.

Log In

Share Thoughts