Slide 1
Kingdom Alveolata is a monophyletic kingdom comprised of three
main groups of organisms - the ciliates, dinoflagellates, and apicomplexans.
We will see that these three groups of organisms are quite different from each other but this is still considered to be a monophyletic kingdom because all three share a common diagnostic characteristic - the presence of structures known as alveoli.
Alveoli are small cavities enclosed in membranes that hug the internal cell surface.
Slide 2
The Ciliates are a group of free-living organisms that are covered
with cilia which are small hair-like structures.
A common representative of this group that you may have seen in a previous biology class are the paramercia - common inhabitants of pond water.
The ciliates are heterotrophic and they eat bacteria and other protists.
They make up an important part of the food chain in freshwater systems but they are not known to cause significant problems for humans.
Slide 3
The dinoflagellates are a large and ecologically and economically
significant group of organisms.
They have two flagella that they use for locomotion and they can have very complex life cycles.
Some are free-living and photosynthetic and some are parasites of other organisms.
The most obviously distinguishing characteristic of this group are the presence of cellulose plates that give the organisms an armored appearance.
Slide 4
You can see some of these complex cell structures here.
Slide 5
Dinoflagellates are an ecologically important group that are found
in both marine and freshwater systems.
Many are photosynthetic and thus form the base of aquatic food webs.
Some photosynthetic forms live within other organisms such as the zooxanthellae dinoflagellates that live in coral reefs.
Some are parasitic within marine animals and cause significant economic damage.
Some dinoflagellates are bioluminescent and luminesce when disturbed as seen in this picture here.
Slide 6
The term plankton refers to organisms living on the surface of
bodies of water. This plankton can be comprised of bacteria, protists
and small animals such as this small species of shrimp known as krill.
Plankton is hugely important for forming the base of the food chain in aquatic systems. To give you an idea of the amount of calories that are found in this plankton we can look at the example of the basking shark.
Basking sharks are huge animals - up to 33 feet long. They are not the scary carnivores we tend to think of when we think of sharks. They eat only plankton - and they feed by filtering the plankton through their large mouths with special filtering structures.
Slide 7
The plant-like component of plankton is known as
phytoplankton. This is the photosynthetic component of plankton.
Ecologically phytoplankton is important for not only playing a role in food chains but also for its role in global carbon dioxide levels.
Carbon dioxide is an important so called "greenhouse gas" and it plays role in heat retention in the earth's atmosphere.
Some photosynthetic dinoflagellates can experience population "blooms" and produce potent neurotoxins that can poison food webs.
Slide 8
Red tides occur when dinoflagellate populations expand rapidly or
"bloom".
When this happens the dinoflagellates can produce neurotoxins that can get taken up into the food chain.
For example, shellfish (bivalves) feed (by filtration) on these dinoflagellates and the shellfish concentrate the toxins their tissues. If a person eats these contaminated shellfish it results in a condition known as paralytic shellfish poisoning.
These neurotoxins can also accumulate in fish and result in a similar paralytic condition known as Ciguatera.
Slide 9
As an example of the complexity of the life cycles of some of
these organisms we can look at a suggested life cycle for an organism know as
Pfiesteria.
This is a controversial organism that has been blamed for massive fish dies offs off the coast of North Carolina. There is a video posted on ANGEL that explains the controversy around this organism and is a nice case study on the nature of science.
Slide 10
Our final group of alveolates are the apicomplexans. This
is a group of heterotrophic parasites.
They have no known means of locomotion and are spread from one host to another as the result of the movement of other organisms.
The distinguishing characteristic of this group is a structure known as an apical complex - which is a dense structure that helps the organism gain entry into a host cell during infection.
Most of the organisms in this group are parasites on invertebrates and we even use some of them to help control insect populations in agriculture.
There is one member of this group, however, that is of huge importance to humans and this is an organism known as plasmodium that causes the disease malaria.
Slide 11
Malaria is spread through mosquito bites and plasmodium is an
example of an organism with a complex life cycle.
Slide 12
Not all species of mosquitos spread malaria - the Anopheles
mosquito that is now found mainly in equatorial Africa is the vector.
In 2008, an estimated 190 - 311 million cases of malaria occurred worldwide and 708,000 - 1,003,000 people died, most of them young children in sub-Saharan Africa.
Control efforts have focused on mosquito control but mosquitoes have evolved resistance to many pesticides
Efforts to develop a vaccine have had limited success to date but there is still hope that a vaccine will be developed.
In the meantime, there are low tech and relatively inexpensive means to control the spread of the mosquitoes and thus the disease. Bed nets are an example of this.
Slide 13
Nothing But Nets is an effort which brings together multimedia
organizations, professional sports leagues, faith-based and civil society
organizations, corporations, and foundations to raise funds to send bed nets
to sub-Saharan Africa.
Bed nets can be an effective low tech tool