Bio Tutorial 27 Q/a

Front 1

Review eukaryotic organisms. What characteristics separate them from prokaryotes?

Back 1

The non-mitochondrial/chloroplast DNA in a eukaryotic cell is located within a nucleus, which is surrounded by a nuclear envelope. Eukaryotic cells also possess extensive systems of intracellular membranes that provide elaborate internal compartmentalization. Additionally, they generally have organelles (e.g., mitochondria and, in some cases, chloroplasts). In contrast, prokaryotic DNA is concentrated in the nucleoid region, which is analogous to the eukaryotic nucleus, but is not membrane-bound. Prokaryotes do not have mitochondria or chloroplasts and they generally possess internal membrane systems that are far less complex than those found in the eukaryotes.

Front 2

How are protists classified in this course (i.e. how are they taxonomically separated into groups?) Why are protists considered to be “simple” organisms?

Back 2

Protists are considered to be relatively simple organisms because most are unicellular. This course will present a taxonomic scheme that uses three domains and five kingdoms. These five kingdoms are Archaezoa, Euglenozoa, Alveolata, Stramenopila, and Chlorophyta.

Front 3

Explain how single-celled organisms like protists are still able to complete complicated functions. Discuss the protist Euglena and use it as a model to show how sophisticated a single-celled organism can be.

Back 3

All of the essential metabolic functions that occur in multicellular organisms (e.g., respiration, photosynthesis, digestion, and excretion) also occur in protists. Moreover, they can show sophisticated locomotion. The ubiquitous Euglena, found in most freshwater ponds, illustrates such protistan sophistication. Euglena possess, within a single cell: a flagellum for locomotion; an eyespot and light detector which, when used in concert, allows them to discern the direction of the most intense light; chloroplasts and mitochondria; granules of the polysaccharide paramylum for storage of surplus carbohydrates from photosynthesis; a contractile vacuole for osmoregulation; a nucleus; and an extensive endomembrane system.

Front 4

What characteristics of protists have contributed to the difficulty in protist classification?

Back 4

Because protists are a metabolically and ecologically diverse group, they are difficult to classify. Metabolically, they range from photosynthetic autotrophic species to heterotrophic species. They occupy diverse ecological habitats ranging from marine, to freshwater, to terrestrial. They have diverse relationships with other organisms and are found both free-living and as members of various symbioses.

Front 5

What does the term polyphyletic mean? How does it relate to protist and the attempt to classify them?

Back 5

A polyphyletic taxon is one which arose from several distinct ancestors. Protista is considered to be a polyphyletic taxon because several kingdoms of protists arose from different ancestors.

Front 6

In how many kingdoms are protists currently grouped? In the past, how many kingdoms did scientists use to group protists? What techniques are used currently to classify protists (and other organisms as well)?

Back 6

Currently, protists are grouped into five kingdoms, whereas in the past they were grouped into only one kingdom, “Protista.” It has relatively recently been determined using modern techniques such as genetic sequence analysis and investigation of cellular components that protists arose from several distinct ancestors; therefore, they should not be placed in a single kingdom.

Front 7

What are the major groups of organisms found in the kingdom Archaezoa? What are the major characteristics that link the groups into one kingdom?

Back 7

The kingdom Archaezoa consists of diplomonads, trichomonads, and microsporidians. All three groups form parasitic symbioses with a variety of other organisms (including humans). They retain primitive characteristics, and therefore, are considered to be the most primitive of protists. Additionally, they all lack mitochondria.

Front 8

What does it mean to be in parasitic symbiosis? How does it compare to other types of symbiosis?

Back 8

When organisms are in a parasitic symbiosis, one organism is feeding off the other. Oftentimes, the parasitic organism cannot survive without a host organism. Unlike other types of symbiosis (mutualism and commensalism), the host organism, as a result of the symbiosis, has reduced fitness.

Front 9

How can Archaezoa survive without mitochondria, which provide energy for the cell in almost all the other eukaryotic organisms?

Back 9

Most Archaezoa spend the active portion of their lives under anaerobic conditions, deep within the body cavities of other organisms; aerobic respiration may not always be possible under these circumstances, nor is it necessary, since parasites acquire ample energy directly from their hosts.

Front 10

Discuss the species Giardia. What human disease is it associated with? Why does the organism cause these symptoms?

Back 10

Giardia, is an intestinal parasite responsible for the disease giardiasis, or "beaver fever," which is generally transmitted via contaminated drinking water. Giardia attaches to the intestinal epithelium, or lining, in humans and other mammals (e.g., dogs, cats, bears, and beavers), creating severe diarrhea and intestinal cramps. Unlike bacterial infections, in which a large number of organisms must be ingested to cause illness, a few Giardia individuals can cause a severe case of giardiasis. While it is a decidedly unpleasant disease to have, giardiasis is fairly easily treated with drugs.

Front 11

What are flagella? How are they used by microorgansisms?

Back 11

Flagella are tail-like structures that projects from the cell function in locomotion.

Front 12

What are the major sub-divisons of organisms found in the kingdom Euglenozoa? How are Euglenozoa different than Archaezoa?

Back 12

Kingdom Euglenozoa includes heterotrophs, such as Trypanosoma, and autotrophs, such as Euglena. This kingdom can be divided into two groups. The first consists of Euglena and its relatives, collectively called the euglenoids. The second group of euglenozoans is the kinetoplastids, which includes Trypanosoma and its relatives, all of whom have one large mitochondrion and an organelle called a kinetoplast.

Euglenozoa are different from Archaezoa because they have mitochondria and are a monophyletic group. Euglenozoa also contain organisms which are autotrophic and heterotrophic, unlike the kingdom Archaezoa (all of which are heterotrophic).

Front 13

The organisms in kingdom Euglenozoa are monophyletic. What does this mean? Does it make them similar?

Back 13

Because the kingdom Euglenozoa are monophyletic, it is hypothesized that all of the organisms Euglenozoa have arisen from a common ancestor. While all of the organisms in this kingdom may share some similar ancestral traits, they most likely have evolved and adapted to different environment which would make them appear very different in structure and function.

Front 14

How are kinetoplastid parasites different in structure from those in the kingdom Archaezoa? Give examples of species from each group.

Back 14

Kinetoplastid parasites are in the kingdom Euglenozoa, and have mitochondria and therefore can survive outside of their hosts without forming a cyst. They also contain a unique organelle called a kinetoplast, which stores extra-nuclear DNA. Archaezoa, on the other hand, do not have mitochondria, and cannot survive outside of their hosts without forming a cyst. An example of kinetoplastid parasites is the disease African sleeping sickness by euglenozoans from the genus Trypanosoma. Examples of archaezoan parasites are Giardia and Enterocytozoons.

Front 15

Is kingdom Alveolata monophyletic or polyphyletic? What does that mean in terms of ancestry? Currently, what groups comprise the kingdom Alveolata?

Back 15

The kingdom Alveolata is another diverse group. This group is monophyletic, which means that all the members in this group arose from the same common ancestor. There are three distinct groups of alveolates: dinoflagellates, apicomplexans, and ciliates.

Front 16

What is the common characteristic of all alveolates? Describe this characteristic.

Back 16

All alveolates are recognizable by their alveoli, which are small cavities enclosed in membranes that hug the internal cell surface.

Front 17

What separates dinoflagellates from the rest of the kingdom Alveolata? Describe the structures and the locomotion methods which make them unique.

Back 17

Dinoflagellates are characterized by their flagella, which makes them different from the other members of the kingdom Alveolata. Furthermore, dinoflagellates typically possess distinct shapes due to "frames" of cellulose within their cell walls. Their cell surface is generally ridged with perpendicular grooves that house a pair of flagella. These flagella beat within their grooves and cause dinoflagellates to rotate as they move forward.

Front 18

What is the source of energy for many dinoflagellates?

Back 18

Because many dinoflagellates are photosynthetic, they use light energy to build molecules from CO2.

Front 19

What is phytoplankton? What role does it have in the food chain?

Back 19

Phytoplankton is a collection of various organisms which float near the surface of the ocean. Dinoflagellates are one type of organism which contribute to the mass of phytoplankton in the ocean which is used as the “base” of the food web. Phytoplankton is an essential food resource for many other organisms, ranging from heterotrophic protists to baleen whales and many other organisms in between (most of whom serve as food themselves for creatures at higher trophic levels).

Front 20

What are examples of non-photosynthetic dinoflagellates? Describe the methods they use to acquire their energy.

Back 20

Some dinoflagellates are heterotrophic. Some of these heterotrophs exploit chloroplasts from photosynthetic protists, becoming autotrophic themselves for a time. Some dinoflagellates live in symbiosis with different species, as parasites in some cases and as mutualists in others.

Front 21

Describe the mutualistic symbiosis is seen between zooxanthellae and coral. Why is this relationship advantageous for both organisms?

Back 21

Corals engulf dinoflagellates called zooxanthellae, but do not digest them. These zooxanthellae live out their lives within the tissues of corals. Corals provide dinoflagellates with a relatively safe refuge from predators and fluctuating environmental conditions. In return, photosynthetic dinoflagellates provide the chief source of food (photosynthate or fixed carbon) for coral-building cnidarians.

Front 22

Discuss the phenomenon of “red tides.” What causes “red tides” and what affects do they have on marine life and, subsequently, humans?

Back 22

Dinoflagellates are responsible for red tide events, or "harmful algal blooms.” Blooms (population explosions) of dinoflagellates are sometimes called "red tides" because dinoflagellates can reach such high densities that they actually change the color of the water in which they reside. Depending on the pigments present in these dinoflagellates, these tides actually appear brown, red, orange, or yellow. A number of dinoflagellate species release toxins into the water, killing many aquatic animals during major algal blooms and poisoning others with sub-lethal doses of toxins. filter feeders (e.g., shellfish) are particularly vulnerable to these compounds because they actively ingest plankton. In turn, heterotrophs (e.g., humans) that eat poisoned animals are often themselves unintended victims of dinoflagellate's defensive chemicals, contracting such conditions as paralytic shellfish poisoning.

Front 23

Discuss the protists Apicomplexans. What is unique about them, and what adaptations have they developed to assist in infection?

Back 23

Apicomplexans are parasites, specialized for living and reproducing within the tissues of animals. The apical complex is a cluster of microtubules and organelles located in the apex of cells that are in the sporozoite (infectious stage). This structure's function is to facilitate penetration of host cells.

Front 24

Name one disease that is caused by an Apicomplexan.

Back 24

Plasmodium, which causes malaria, is an apicomplexan transmitted by mosquitoes.

Front 25

Use Plasmodium as an example of the complex life cycles seen in some Apicomplexans. Draw how the parasitic organism changes as it moves from host to host.

Back 25

Use Plasmodium as an example of the complex life cycles seen in some Apicomplexans. Draw how the parasitic organism changes as it moves from host to host.

Front 26

Review heterozygote advantage. Discuss how malaria may explain the sickle-cell allele in humans.

Back 26

Heterozygote advantage refers to the phenomenon in which a heterozygote may have an increased fitness than either homozygote. The allele for sickle-cell anemia confers a heterozygote advantage in individuals exposed to malaria, so for this reason the sickle-cell allele may have persisted in the population where it otherwise may have not.

Front 27

List the major characteristics of slime molds. Describe how the characteristics are fungus-like and protist-like.

Back 27

Slime molds used to be classified with the fungi, due to their heterotrophic feeding habits and appearance. However, they are more closely related to amoeboid protists. They are quite enormous and have given many a hapless gardener a good scare when found growing on a damp pile of bark mulch. Despite their size, plasmodial slime molds are unicellular; basically, they are large bags of cytoplasm. However, within each "cell" are many nuclei.

Front 28

What unique abilities do the single-celled Acrasiomycetes have? What advantages do they gain?

Back 28

Acrasiomycetes spend most of their lives as amoeba-like single cells, but when resources are scarce they converge, joining with other cells to form units that function as multicellular organisms. Unlike plasmodial slime molds, the cells within the acrasiomycetes retain their cell membranes and their ability to live independently.