Bio lecture 5/21/26chpt 28 Advanced Eukaryotic Diversity: Alveolates, Rhizarians, Archaeplastida, and Unikonta
Dinoflagellates and Red Tide Phenomena
These organisms are complex in their design and utilize two flagella to facilitate swimming and movement.
Under a microscope, their movement is comparable to a person in a single rowboat with two oars: if the oars are not coordinated correctly, the boat does not move forward but instead spins in circles. This spinning motion is characteristic of these organisms as they attempt to coordinate their flagella.
These organisms are responsible for the geographic phenomenon known as "red tide," particularly prevalent in coastal areas like Florida and the Gulf of Mexico.
Observations of red tide include:
Water appearing deep red in color near the shore.
The phenomenon is caused by life forms blooming into massive population numbers simultaneously.
Biological impacts of red tide toxins:
The organisms produce a toxin within their cells.
Humans swimming in affected water may experience intensely itchy skin due to toxin contact.
The toxin causes large-scale fish die-offs, where dead fish wash up on beaches, leading to aesthetic issues and foul odors that negatively impact tourism.
Bioaccumulation and health risks:
Shellfish such as clams and oysters consume these organisms.
While the toxin does not kill the shellfish, it accumulates in their tissues.
Human consumption of contaminated shellfish leads to food poisoning.
It is critical to be aware of where shellfish are sourced during red tide events.
Current research trends:
Wildlife researchers and conservationists have noted that red tide events have become more common and more disastrous over the past years.
The exact reason for this increase in frequency and severity remains unknown.
Apicomplexans: Structure and Parasitic Life Cycles
Apicomplexans are single-celled life forms that function as parasites of animals, primarily focusing on vertebrate hosts.
Etymology and Naming:
They are named for a specific structure called the apical complex.
This structure is located at the top or "apex" of the cell during one point of its life cycle.
The complex is used specifically to penetrate host cells.
Malaria and Plasmodium:
Apicomplexans are responsible for causing malaria in humans.
Many parasites in this group have complex life cycles requiring more than one host to complete.
The life cycle of the Plasmodium parasite:
The parasite enters the human and spends time in the liver cells.
It morphs into a form called the merozoite.
The merozoite form invades red blood cells.
Inside the blood, it creates gamete-type structures.
A mosquito bites the individual, picking up the gamete structures.
The life cycle finishes within the mosquito, producing sporozoites.
When the mosquito bites another human, it transmits the sporozoites back into the human host.
Global impact of Malaria:
Millions of people suffer from malaria annually worldwide.
There is currently no cure available.
While it is less frequently mentioned in the news today, it remains a threat, particularly if it spreads into densely populated tropical areas like Florida.
Ciliophora (Ciliates) and Rhizarians
Ciliophora (Cilians):
These are single-celled life forms covered in numerous cilia used for movement.
They often possess multiple nuclei: typically one large nucleus and several smaller nuclei called micronuclei.
Micronuclei can be traded between individuals to increase genetic variety, a process known as conjugation.
Rhizarians:
Historically described as "amoeba-like" because they move using extensions of the cell membrane.
Unlike "true" amoebas, which have very thick pseudopodia, Rhizarians possess thread-like, thin pseudopodia.
These thread-like structures wrap around food particles to bring them into the cell via phagocytosis.
Most are chemoheterotrophs, though a few species are capable of photosynthesis.
Subgroups of Rhizarians:
Foraminiferans (Forams): They create a protective shell, or "test," made of calcium carbonate (). The shell is covered in tiny pores through which the thread-like pseudopodia extend. They are highly abundant in marine systems. Population explosions can turn ocean surfaces white, making them visible in satellite imagery.
Radiolarians: They possess thread-like pseudopodia and produce a glass-like shell made of silica (), similar to diatoms. They are highly abundant in freshwater systems.
Archaeplastida: Plastids and Classification Debates
The supergroup Archaeplastida is named for the presence of organelles called plastids.
Types of Plastids:
Chloroplasts: Contain large amounts of chlorophyll.
Leukoplasts: Colorless plastids used for storage.
Amyloplasts: Used for starch storage.
Chromoplasts: Contain pigments other than chlorophyll.
Evolution of Plastids:
It is believed that plastids were once free-living prokaryotes that were absorbed by larger cells via endosymbiosis.
The Classification Debate:
Taxonomy is a hypothesis that is constantly being tested and revised.
Lumpers: Taxonomists who prefer to keep groupings simple by lumping organisms into as few groups as possible.
Splitters: Taxonomists who are more precise/detailed and prefer to split organisms into many specific categories.
The Argument: Some researchers want to group green algae and terrestrial plants together due to the shared use of chlorophyll. Others want distinct groups: Green Algae (Chlorophyta) and Terrestrial Plants. There is a specific group of green algae (Charophyceans) thought to be the direct ancestor of terrestrial plants.
Course Decision: For this class, a moderate route is taken: we define two separate kingdoms, one for True Plants and one for Green Algae.
Red Algae and Green Algae
Red Algae (Rhodophyta):
The color name refers to the primary photosynthetic pigment used, not necessarily the visual appearance.
They contain the pigment phycoerythrin.
In paper chromatography, this pigment separates as a red color.
Many are large, multicellular organisms.
Example: Porphyra is a type of red algae farmed and used as sushi wraps (nori).
Green Algae (Chlorophyta):
Chlorophyll is the major photosynthetic pigment, giving most of them a green appearance.
Forms include single-celled, colonial (e.g., spheres of single cells), and large seaweed-type multicellular forms.
Key distinction: All true plants are multicellular, whereas green algae can be single-celled.
Pigment Ecology and Aquatic Survival
Light penetration in water dictates where different algae can survive:
Sunlight consists of various wavelengths.
As light penetrates water, wavelengths are filtered out at different depths.
Red wavelengths are filtered out in very shallow water.
Blue wavelengths penetrate the deepest into the aquatic system.
Survival Strategies:
Chlorophyll primarily captures red wavelengths, meaning organisms relying solely on chlorophyll must live in the shallowest parts of the water.
Phycoerythrin (in red algae) is highly efficient at capturing blue wavelengths.
Consequently, red algae can survive at much greater depths than green algae because they utilize the light that reaches those depths.
Unikonta and the True Amoebas
Unikonta is the final supergroup, containing kingdoms such as Amoebozoans, Fungi, and Animals.
Amoebozoans (Amoebas):
Characterized by very large, thick pseudopodia.
Movement involves extending the pseudopod in one direction, followed by the rest of the cell flowing into it.
They are abundant in freshwater systems and are single-celled creatures.
Health Risks in Florida:
Some freshwater amoebas are dangerous; they can enter the body through nasal passages while swimming.
Once inside, they can travel to the brain and consume brain cells.
Cultural Reference:
The "B-level" black and white sci-fi movie The Blob starring Steve McQueen features a giant amoeba that eats a town.
Questions & Discussion
Question from the instructor: "Anybody know what the deal is with this [red tide]? Experience this? Anybody? Who's from the South Florida, you can see this, especially in The Gulf."
Response/Context: The instructor notes that those living in Florida or near beaches are likely familiar with the announcements of red tide events and the localized red color of the water.