In this lesson, we will cover:
Kinetoplastids, which are related to Euglenida, are made up of two major groups of small protists with flagellates. Bodonids, which are common in freshwater enviroments, and also the trypanosomes. The most well known trypanosomes are those that belong to the genus Trypanosoma. They cause diseases in humans such as sleeping sickness and Chagas' disease. Trypanosomes, a serious public health problem, are transmitted by biting flies. Studies have shown that kinetoplastids are probably related to the euglenids as well as amoeboflagellates.
Euglenids are elongated cells that use one or two flagella for movement.
There are nearly one thousand species of euglenids. Some are photosynthetic and
have chloroplasts, while others
do not have chloroplasts and are colorless. Euglenid cells are covered with a flexible coat,
called the pellicle, which allows it to change it's shape. Most
euglenids live in shallow freshwater enviroments that have been enriched by decaying organic matter, but some euglenids live
in marine waters, and a few others are parasitic.
Amoeboflagellates, also known as Schizopyrenida, are small,
colorless protists. Most amoeboflagellates are able to transform between amoeboid forms and
flagellate forms. An amoeba that meets water can grow two flagella and swim,
reverting back to the amoeba stage again when it encounters food. Amoeboflagellates can also
form into cysts that are resistant to extreme conditions. These
can lie dormant years and still come back to life. Therefore, they can live in
changing enviroments. A few species of amoeboflagellates are adapted
to live at human body temperature and can cause serious
brain infections if introduced into the body. This, however is very rare. The comparisons of
rRNA sequences have shown that amoeboflagellates are related to euglenids and
to kinetoplastids.
That's it! You have made it through lesson 4, cell profiles. If you want to proceed to the next
lesson, first take the lesson 4 quiz.