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Life Science

Life Science

Lesson Objectives

In this lesson, we will review the basics of the life sciences. Specifically, we are going to cover how
we organize and categorize life. We will be able to identify all the major groups of living things, and
describe how they are related to each other.

Taxonomy: What’s in a Name?

Although it may not always seem clear, taxonomy is designed to facilitate understanding by organizing the
vast array of living things into meaningful, and hopefully manageable, groups. This is no small task and
the job is far from complete as many species remain unidentified.

As discoveries are made, different systems of classifications develop. Depending on the system used
there are five or more kingdoms of living organisms with seven levels of classification and often several
sublevels within each. At each level, organisms get more similar until an individual species is reached.
Here’s one way that will probably look familiar:

• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species

Using the five kingdom system, these classifications include Animal, Plant, Fungi, Protista, and Monera.
Additional kingdoms arise when some systems split the Monerans into the true bacteria and the blue-
green or cyanobacteria. Other systems split Protista into the photosynthetic and the mobile Protists.

Biologist Carl Woese proposed two new ways of organizing life—either by six kingdoms or three
domains.

The system of taxonomy and classification used today is based in part on the work of Carolus Linnaeus.
Linnaeus’s system uses the genus and species name of an organism as its scientific name. These names
are in Latin or are Latinized because that language is non-evolving and at the time was well known to
most scientists. The need for this naming system is to avoid confusion that can occur when using more
common names. For example, the common names puma, mountain lion, and cougar are all used to
describe Felis concolor, the large predator native to the United States.

Fitting It All Together

In taxonomy, living things are categorized at various levels and are classified by numerous physical and
genetic traits as well as fossil evidence. Biologists often disagree, however, about whether something is a
subspecies or a separate species. Classification is essential in determining where new species fit and
understanding evolutionary relationships among living organisms. These types of decisions are important
especially in areas such as conservation where endangered or threatened status may depend on whether
an organism represents a separate species.