1. Outline the classification and include living examples at all levels of classification.

Biologist classify protozoa into four phyla: Sarcodina, Ciliophora, Zoomastigina, and sporozoa. The main criterion for classification is mechanism of locomotion.

• members of the phylum Sarcordina move by using cytoplasmic projections called pseudopodia

• members of the phylum Ciliophora move by the use of cilia

• members of the phylum Zoomastigina move by use of flagella.

• members of the phylum Sporozoa are immobile and parasitic

Some biologists suggest that organisms called euglenoids should also be considered protozoa. Although Euglena and related organisms look and behave much like protozoa, they photosynthesize under certain circumstances. In other words, they can be autotrophic as well as heterotrophic. For this reason scientists often consider them more like algae then protozoa. 

2. Discuss the phylogeny and evolutionary status

The first cells that evolved were prokaryotic and originated over 3.5 billion years ago. The first eukaryotes found in the fossil record are 1.45 billion years old. Eukaryotes may have arrisen much earlier, but because their cells are generally soft, it is not likely that many were preserved in rocks. However, evidence from comparative anatomy and cell physiology strongly suggests that eukaryotes evolved from prokaryotes. According to the theory of endosymbiosis, prokaryotic parasites once lived inside other prokaryotic cells. Then the parasitic prokaryotes lost the ability to live independently of their host and evolved into various cell organelles. Structural and biochemical evidence suggests that mitochondria arose from parasitic bacteria and that chloroplasts arose from parasitic blue-green bacteria. The nucleus, however, propably did not arise from an endosymbiont. It probably came to exist as an organelle when DNA was enclosed within a double membrane.

Biologist classify protozoa into four phyla: Sarcodina, Ciliophora, Zoomastigina, and sporozoa. The main criterion for classification is mechanism of locomotion.

• members of the phylum Sarcordina move by using cytoplasmic projections called pseudopodia

• members of the phylum Ciliophora move by the use of cilia

• members of the phylum Zoomastigina move by use of flagella.

• members of the phylum Sporozoa are immobile and parasitic

Some biologists suggest that organisms called euglenoids should also be considered protozoa. Although Euglena and related organisms look and behave much like protozoa, they photosynthesize under certain circumstances. In other words, they can be autotrophic as well as heterotrophic. For this reason scientists often consider them more like algae then protozoa.

3. Describe the main characteristics displayed by the phyla. Show examples of how these characteristics are found among all the members of the phyla.

All protozoa's are heterotrophic; most are unicellular. All have cellular mechanisms that monitor the environment.

Biologists have identified about 40,000 species of the phylum Sarcodina. The most familiar Sarcodines are members of the freshwater genus Ameba. Amebas are bottom-dwelling scavangers; they feed on decaying organic matter in rivers, streams and lakes.

Most sarcodines have flexible cell membranes. Many do not have any added protective covering. However, some, such as the marine sarcodines of the genus Foraminifera, have calcium carbonate shells with spikelike protrusions. Others, such as the marine sarcodines of the genus Radiolaria, have supportive silicon dioxide inside their shells. Freshwater sarcodines called heliozoans have a shell with thin, extended projections.

Sarcodines move by the means of pseudopodia. Pseudopodia are cytoplasmic extensions that function in movement. The cytoplams of a sarcodine is made up of two regions - the ectoplasm and the endoplasm. The ectoplams is the thin, slippery colloidal sol directly inside the cell membrane. The endoplasm is the colloidal sol and gel found in the interior of the cell. When movement begins, the endoplasm pushes outward, facilitated by the slippery ectoplasm, and becomes distinguishable as a pseudopodium. At the same time, previously formed pseupodia are retracted. Hence the sarcordine moves forward by ameboid movement. Ameboid movement is a form of cytoplasmic streaming which is the internal flowing of a contents of a cell.

Most freshwater sarcodines are internally similar to the ameba. Ameba has a contractile vacuole which is an organelle that excretes water. Freshwater organisms are usually hypertonic relative to their environment, and water diffuses into them. To maintain homeostasis , many freshwater unicelluar organisms have contractile vacuoles that excrete excess water.

Sarcodines absorb many nutrients by diffusion from surrounding water and ingest nutrients by phagocytosis, the engulfing of food. When a sarcodine contacts food, it surrounds the food with pseudopodia. A portion of the cell membrane then pinches together and surrounds the food in a food vacuolle. Enzymes from the cytoplasm enter the vacuole and digest food. Any undigested food leaves the cell in a reverse process that is known as exocytosis.

The 8,000 species of phylum Ciliophora move by means of cilia, which are short, hairlike projections that line the cell membrane and beat in synchronized strokes. Ciliates live in marine and freshwater habitats. Members of the freshwater genus Paramecium, are the most thoroughly studied ciliates.

A paramecium never changes shape like ameba because it surrounded by a rigid protein covering, the pellicle. The pellicle is covered with thousands of cilia arranged in rows. The cilia beat in waves. Each wave passes slantwise across the long axis of the body of the paramecium, causing it to rotate as it moves forward. Internally a distinctive trait of the ciliates is the presence of two kinds of nuclei - the macronucleus and the micronucleus. The large macronucleus controls such cell activities as respiration, protein synthesis, digestion, and asexual reproduction. The much smaller micronucleus is involved in sexual reproduction and heredity.

Ciliates have numerous cellular structures adapted for feeding on bacteria and other protists. A paramecium, for instance, has a funnellike oral groove lined with cilia. These beating cilia create water currents that sweep food down the groove to the mouth pore of the paramecium. The mouth pore opens onto a gullet, which forms food vacuoles that circulate throughout the cytoplasm. The contents of the vacuoles are then digested and absorbed. The indigestible matter remaining in the vacuole moves to the anal pore, an opening where waste is eliminated.

Most ciliates exhibit avoidance behavior, a reaction away from a potentially harmful situation. A paramecium will back up and move away when it encounters an obstacle in its environment.

4. Explain in detail the reproductive patterns found in the phyla. How do these patterns increase the ability of the organisms to survive natural selection.

This is how members of the Phylum Sarcodina reproduce:

Sarcordines reproduce by binary fission, an asexual, mitotic division that produces identical offspring. Under ideal conditions it takes less then an hour for an ameba to undergo binary fission. When conditions are unfavorable, most sarcodines form cysts, protective outer walls. When conditions improve the cell breaks out of the cyst and resumes normal activities.

This is how members of the Phylum Ciliophora reproduce:

Asexual reproduction in ciliates occurs primarily by binary fission. In this process only the micronucleus divides by mitosis. The macronucleus, which contains up to 500 more times DNA than the micronucleus, simply elongates and splits in two parts, each part going to a daughter cell.

Sexual reproduction occurs in many ciliates by a process known as conjugation. Conjugation involves individuals from two mating strains, such as two paramecia. The two paramecia lie next to each other. Then the macronucleus of each individual disintegrates. Each diploid micronucleus then undergoes meiosis, producing four haploid micronuclei. In each cell three of these disappear; the fourth moves to the oral groove. Here it undergoes mitosis, producing two haploid micronuclei of unequal size. The smaller micronucleus from one paramecium then exchanges places with the smaller micronucleus from the other paramecium. Each small micronucleus then fuses with each larger micronucleus, forming diploid micronuclei. The two paramecia separate, and macronuclei form again.

This is how members of the phylum Sporozoa reproduce:

Members of the genus Plasmodium cause malaria, a disease that kills about 1 million people a year and that is most prevalent in the tropics. Like most protozoa's plasmodium has a complex life cycle with more then one host. When a female Anopheles mosquito that is carrying Plasmodium spores bites a person, the spores enter the persons blood stream. They travel to the liver, where they reproduce asexually. The new spores infect erythrocytes and continue asexual reproduction. Every two or three days spores burst out of the erythrocytes and release toxins into the blood. Some of the spores develop into plus and minus cells.

When a female Anopheles bites the infected person , it ingests these cells. In the digestive system of the mosquito the cells develop into gametes that combine to form a zygote. The nucleus of the zygote divides internally many times and forms internal spores. When the zygote membrane bursts, the spores migrate to the salivary glands of the mosquito. If the mosquito then bites another person, the cycle begins again.

The destruction of red corpuscles and the release of toxins into the blood cause the fewer, anemia, and other symptoms of malaria. The disease causes the liver and spleen to become enlarged, and in the most acute cases the kidneys fail.

5. Describe the relationship of these phyla with humans both positive and negative. Do they effect our survival.

The 2,500 species of phylum Zoomastigina, also called Mastigophora, are characterized by the presence of one or more long flagella. The undulations of whiplike flagella push or pull the protozoan throughout the water. Many zoomastiginoids are freeliving, moving throughout lakes or ponds and feeding on small organisms. Some zoomastiginoids are parasites. Among these are members of the genera Trypanosoma, Leishmania, and Giardia.

Several members of the genus Trypanosoma are powerful agents of disease. Trypanosomes are slender, elongate, flattened protozoa with one posterior flagellum. They live in the blood of their hosts, which include humans and other animals, and are carried from host to host by bloodsucking invertabrates such as flies.

African trypanosomiasis, or sleeping sickness, is a trypanosome disease that occurs in two forms - Gambian, caused by T. gambiense, and Rhodesian, caused by T. rhodesiense. Both are transmitted by the tsetse fly, which lives only in Africa. Trypanosomiasis is characterized by fewer and swollen lymph nodes. In later stages the parasites invade the brain, causing uncontrolled sleepiness. T. gambiense may take several years to invade the brain. T. rhodesiense effects the host more quickly, and Rhodesian trypanosomiasis is usually fetal.

Zoomastiginoids of the genera Leishmania and Giiardia cause serious diseases in humans. Leishmania, carried by sand flies, cause leishmaniasis, which afflicts millions of people in Africa, Asia, and Latin America The disease is characterized by disfiguring skin sores and may be fetal.

giardia, carried by muskrats and beavers, cause giardiasis, a disease characterized by fatigue, diarrhea, cramps, and weight loss. Drinking water that is contaminated with giardia will not effect muskrats and beavers, but it will harm humans.

All 6,000 species in the phylum Sporozoa have adults with no means of locomotion and all are parasitic. They are carried in the blood and other bodily fluids of their hosts, absorbing nutrients from the fluid in which they float. Several sporozoans, including Toxoplasma and Plasmodium, cause diseases in humans.

The sporozoan toxoplasma is a parasite found in animals. In humans it causes toxoplasmosis, a disease that has few or no symptoms in adults with healthy immune systems but that is often fetal to newborns. One species of Toxoplasma causes coccidiosis, a deadly disease effecting birds and young cattle.

Members of the genus Plasmodium cause malaria, a disease that kills about 1 million people a year and that is most prevalent in the tropics. Like most protozoa's plasmodium has a complex life cycle with more then one host. When a female Anopheles mosquito that is carrying Plasmodium spores bites a person, the spores enter the persons blood stream. They travel to the liver, where they reproduce asexually. The new spores infect erythrocytes and continue asexual reproduction. Every two or three days spores burst out of the erythrocytes and release toxins into the blood. Some of the spores develop into plus and minus cells.

When a female Anopheles bites the infected person , it ingests these cells. In the digestive system of the mosquito the cells develop into gametes that combine to form a zygote. The nucleus of the zygote divides internally many times and forms internal spores. When the zygote membrane bursts, the spores migrate to the salivary glands of the mosquito. If the mosquito then bites another person, the cycle begins again.

The destruction of red corpuscles and the release of toxins into the blood cause the fewer, anemia, and other symptoms of malaria. The disease causes the liver and spleen to become enlarged, and in the most acute cases the kidneys fail.