1.3: Kingdoms and Domains
pg. 24 – 30
Introduction
There are over a million of species of organisms on Earth. They all
share certain fundamental similarities, such as; being made of cells
and having DNA. Although they have similarities they also have
differences, in Structural Diversity., both internally and externally.
To study the species, their similarities and differences, it would be
easier to start at a higher Taxonomic ranking, such as kingdom
towards species.
The Six Kingdoms:
- during the 1800’s there were only two kingdoms; plant and
animal.
- Late 1800’s a new kingdom, protista, a single celled
organism was added.
- 1900’s a single celled organism without a nucleus was
discovered, creating anew kingdom, bacteria.
- During the 1960’s, the kingdom of fungi was established.
- In the 1990’s, using new genetic information, the kingdom of
bacteria was divided into two kingdoms; bacteria and archaea.
Three important ideas to remember:
1. there are two main cell types that are significant for classification at the upper
ranks, such as kingdoms.
2. the study of cell types and genes has led scientists to add a rank higher than
kingdom, call Domain.
3. it is important to understand how biologists think the domains and kingdoms are
connected in their evolutionary history.
Table 1.3: Changes in classification Systems for Life’s Kingdoms
Two Major Cell Types
An organism made up of only one cell is called unicellular.
An organism made up of more than one cell is called multicellular.
There are two major types of cells, Prokaryotic and Eukaryotic.
Prokaryotic cells, e.g. bacteria, are the most ancient of cells. They
do not contain membrane bound organelles or a membrane bound
nucleus. Prokaryotic indicates that the cells existed before the
nucleus.
Eukaryotic cells, e.g. animal, are more complex, containing
membrane bound organelles and have a true nucleus. These cells
are 1000 times large then prokaryotic cells.
figure 1.14 Two kinds of cells, pg. 25
The Three Domains
Scientists studied the kingdoms of Bacteria and Archaea at a
genetic and cellular level, it was determined that they were very
much different. These were elevated to domain status, higher then
kingdom. All other kingdoms were placed in a third domain called
Eukarya.
In the domain of Eukarya, the organisms found in each of the four
kingdoms are made up of the same complex eukaryotic cells.
The cells found in the domains of Bacteria and Archaea are
unicellular, while cells in the domain of Eukarya are either
unicellular or multi-cellular.
Dichotomous Keys
- an identification tool consisting of a series of two-part
choices that lead the users to a correct identification.
When a new species is discovered, it is very difficult to place it in
the appropriate rank; kingdom, and giving it a scientific name.
Taxonomists use another tool to identify individuals or species,
such as a dichotomous key.
This system will narrow down the identification of the specimen,
one step at a time. For each question in the dichotomous key there
are only two choices. Each question leads to another question or
answer, which narrows down the possible solution.
Using the Dichotomous Key
The ultimate goal of many taxonomists is to make an
identification at the species level.
Table 1.4: Dichotomous Key – Frogs and Toads of
Algonquin Park
Pg. 27
Main Characteristics of Kingdoms
Autotroph: an organism that captures energy from sunlight (or
sometimes non-living substances) to produce its own energyyielding food.
Heterotroph: an organism that cannot make its own food and gets
its nutrients ad energy from consuming other organisms.
First distinction to determine is whether the organism is made up
of prokaryotic or eukaryotic cells.
Second distinction would be to determine whether the cell has a
cell wall or not.
Third would be to determine whether the cell get its nutrition by
producing its own food or having to consume food, such as: an
autotroph or a heterotroph.
The fourth distinction would be its reproduction method. All
Kingdoms have organisms that reproduce asexually, but sexual
reproduction, exchange of genetic information, only occurs in
Eukarya.
Table 1.5: Characteristics that Differentiate the Six
Kingdoms,
pg. 29
Learning Check: questions 13 – 17, pg. 26
Section 1.3 Review: 1 – 10, pg. 30
CHAPTER 1
Dichotomous Key Graphic Organizer
Procedure
Use the dichotomous key graphic organizer below to assist you with Activity 1.2
Create a Dichotomous Key.
BLM 1-5