What's in a Name?
Shakespeare wrote in Romeo and Juliet, “What’s in a name? That which we call a rose by any other name
would smell as sweet.” He is saying that it doesn’t matter what we call something. While names may not
matter to fiction writers, they are very important to scientists who need a way to sort and classify groups of
life forms, or organisms. How scientists do that has changed over time. As scientists learn more about the
world around us, the classifications are updated.
The highest or broadest rank of classification is the domain. There are three domains: Eukarya, Bacteria,
and Archaea. Eukarya is the domain for all eukaryotes. The cells of these organisms have a membranebound nucleus and other membrane-bound organelles. Most of what we think of as animals are in this domain,
but it also includes plants, fungi, and protists. Prokaryotes are organisms whose cells do not have a nucleus
or other membrane-bound organelles. The prokaryotic domains are Bacteria and Archaea. Bacteria is the
domain made up of bacteria. Some bacteria cause disease, others can cure illness. Archaea is a domain made
up of prokaryotes that often live in extreme places. Some can be found in the boiling water of a hot spring.
Others live in places that are extremely salty. Every living thing on the planet falls into one of these three
domains. All eukaryotes are a part of the Eukarya domain. All bacteria are a part of the Bacteria domain. All
archaebacteria fall into the Archaea domain.
The second highest rank of organisms is Kingdom. The eukaryotic Kingdoms are: Animalia, Fungi,
Plantae, and Protista. Humans are members of Kingdom Animalia. Mushrooms are well-known members of
Kingdom Fungi. Kingdom Plantae is made up of trees and other plants. Kingdom Protista was created to
classify most of the unicellular eukaryotes. The prokaryotic Kingdoms are Eubacteria, which includes all of
the organisms from Domain Bacteria, and Archaebacteria, which includes all of the extremophiles in Domain
Archaea. Organisms are sorted into Kingdoms based on how complex their cells are and how they obtain
nutrients and reproduce.
Some organisms have only one cell. These are called unicellular. They include all bacteria, all archaebacteria,
most protists, and some fungi. With only one cell, these life forms are usually tiny. Very few are large enough
to be seen with the naked eye. These organisms must carry out all life processes in that one cell. In contrast,
multicellular organisms have more than one cell. In multicellular organisms, cells serve specialized purposes.
They must work together to take care of all the life processes of the organism.
There are two ways an organism can get food. Autotrophs make their own. Heterotrophs get what they
need to survive from other organisms. The members of the bacteria and archaebacteria kingdoms can be
autotrophic or heterotrophic. Plants and some bacteria, archaebacterial, and protists are photoautotrophic.
They use light from the sun to make the food they need to survive. People are heterotrophs. We must eat
other organisms to get the nutrients we need. We still need food even if we walk around all day with our arms
stretched out to the Sun.
There are two types of reproduction. In asexual reproduction, there is just one parent. Offspring only carry
the genes of that parent. There are many different ways for an organism to reproduce asexually. They can
even simply divide into two daughter cells. This is called binary fission. Many unicellular organisms reproduce
asexually. In sexual reproduction, offspring are made by joining genetic material from two parents. This
happens with most multicellular organisms.
Naming and classifying organisms is a tricky process. Scientists must make changes to keep up with new
discoveries and information. Knowing the basics can help you think like a scientist as you discover new
organisms.
Across
10. the kingdom that you are a member of
11. organisms whose cell or cells do have a nucleus
13. the kingdom created for most unicellular
eukaryotes
14. reproduction that requires two parents
15. organisms whose cell or cells do not have a
nucleus
17. organisms made up of more than one often
specialized cells
19. the prokaryotic kingdom with organisms that
live in extreme environments
20. organisms that make their own food
21. the domain for all eukaryotes
22. the second highest rank of organisms
Down
1. organisms made up of just one cell
2. a domain made up of prokaryotes that often live
in extreme environments
3. reproduction that requires only one parent
4. life forms
5. the kingdom that includes mushrooms
6. the kingdom that includes trees and other plants
7. the domain made up of all bacteria
8. organisms that depend on other organisms for
survival
9. organisms are this when they use light from the
Sun to make the food they need to survive
12. the highest or broadest rank of organisms
16. the kingdom that includes all bacteria
18. the categories that are used to sort life forms