Question 1

In a protist,the portion of the cytoplasm that lies just beneath the plasma membrane is called the

Accepted Answer

The portion of the cytoplasm that lies just beneath the plasma membrane in a protist is called the ectoplasm. This is a more gel-like and supportive layer compared to the inner, more fluid endoplasm.

Question 2

Protists are believed to have arisen about __________ years ago.

Accepted Answer

Protists are believed to have arisen about 1.5 billion years ago. This is based on molecular and fossil evidence.

Question 3

Protists in this supergroup are amoeboid in morphology and have very fine pseudopodia called filopodia that are supported by axopodia.

Accepted Answer

Rhizaria includes protists that are amoeboid in morphology and have fine pseudopodia known as filopodia, which are supported by microtubules forming axopodia.

Question 4

The common means of sexual reproduction among ciliated protists is

Accepted Answer

Conjugation is the common means of sexual reproduction among ciliated protists. During conjugation, a temporary fusion of two cells occurs, and genetic material is exchanged between them, resulting in genetic recombination. Other options listed here are not typically associated with sexual reproduction in ciliated protists; budding, fragmentation, and multiple fission are typically associated with asexual reproduction, while schizogony is a type of multiple fission found in some parasitic protists but does not involve sexual reproduction.

Question 5

In protists,both gas exchange and excretion occur by __________ across the plasma membrane.

Accepted Answer

Gas exchange and excretion in protists occur through diffusion across the plasma membrane. Larger molecules are transported through endocytosis, exocytosis, or facilitated diffusion, but gases and waste products such as CO2 and ammonia diffuse readily across the membrane. Active transport requires the use of energy to move molecules against their concentration gradient, which is not necessary for gases and waste products in protists.

Question 6

Egestion vacuoles release their contents by

Accepted Answer

Egestion vacuoles are structures in unicellular organisms that collect waste materials and expel them through a process called exocytosis. Exocytosis involves the fusion of the egestion vacuole membrane with the plasma membrane, releasing the waste material outside the cell. Therefore, the correct answer is E, exocytosis.

Question 7

The protozoan Trypanosoma brucei is the causal organism of the disease

Accepted Answer

Trypanosoma brucei is the causal organism of African sleeping sickness, a disease that is transmitted by the tsetse fly and affects humans and animals in sub-Saharan Africa.

Question 8

In some protists,food may be ingested in a special region,the

Accepted Answer

The cytopharynx is a specialized region in some protists where food is ingested. It is a part of the cell membrane that extends inward, forming a funnel-shaped structure. This structure helps in engulfing the food and forming a food vacuole. The other options, such as oral hood, oral aperture, and cytosome, are not specific regions in protists for ingesting food. The cytopyge is a structure in some protists where waste is expelled from the cell.

Question 9

Toxoplasmosis is primarily carried to humans by

Accepted Answer

Toxoplasmosis is primarily carried to humans by cats, as they can be infected by Toxoplasma gondii and excrete the infectious oocysts in their feces, which can contaminate soil, water, and food. Other animals, such as chickens, can also carry the disease but are not the primary source of transmission to humans. The disease is not transmitted by the tsetse fly or mosquito. While consumption of contaminated water is a potential route of transmission, it is not the primary one.

Question 10

The vectors of Trypanosoma are

Accepted Answer

The vectors of Trypanosoma are tsetse flies, which are found in sub-Saharan Africa. This parasite causes African sleeping sickness in humans and Nagana in livestock. None of the other choices listed are known vectors of Trypanosoma.

Question 11

__________ is an organism that causes one of the opportunistic diseases affecting AIDS patients in the United States.

Accepted Answer

Toxoplasma is an opportunistic organism that causes Toxoplasmosis, which is a common opportunistic infection in AIDS patients in the United States.

Question 12

In heterotrophic protists,digestion and transport of food occurs in

Accepted Answer

In heterotrophic protists, digestion and transport of food occurs in food vacuoles. These vacuoles are formed by the ingestion of food particles by the cell and then merge with lysosomes where the food is broken down into smaller molecules that can be absorbed by the cell.

Question 13

The principal nitrogenous waste of protozoans is

Accepted Answer

Protozoans excrete ammonia as their principal nitrogenous waste. Ammonia is highly toxic and requires a large amount of water to be excreted out of the body. Protozoans, being aquatic animals, are able to excrete ammonia directly into the surrounding water without significant water loss.

Question 14

__________ occurs in protists when a large number of daughter cells are formed from a single parent cell.

Accepted Answer

Schizogony, also known as multiple fission or schizontogenesis, is a form of asexual reproduction in which a large number of daughter cells are formed from a single parent cell in protists. This process involves multiple rounds of DNA replication and cytokinesis, resulting in the formation of multiple nuclei within the parent cell before it finally divides into daughter cells.

Question 15

Because protist groups cannot be traced back to a single common ancestor the group is considered to be

Accepted Answer

Protist groups are considered polyphyletic because they do not have a single common ancestor. Instead, they come from multiple lineages, making their evolutionary relationships more complex than a monophyletic group.

Question 16

The most recent classification scheme put forth by the International Society of Protistologists places protists into six

Accepted Answer

The most recent classification scheme by the International Society of Protistologists groups protists into six supergroups: Excavata, SAR, Archaeplastida, Amoebozoa, Opisthokonta, and Rhizaria. This classification is based on molecular data and reflects the evolutionary relationships among protists. Therefore, option D is the correct answer.

Question 17

Pseudopodia that are broad and are used for locomotion and engulfing food are called

Accepted Answer

Lobopodia are broad pseudopodia that are used for locomotion and engulfing food. Filipodia are long, slender pseudopodia that are used for sensing the environment and capturing food. Reticulopodia are a network of pseudopodia used for capturing food. Axopodia are long, thin pseudopodia used for support and capturing food. Amphipodia are paired pseudopodia used for both crawling and swimming.

Question 18

Contractile vacuoles in freshwater protozoans function to

Accepted Answer

Contractile vacuoles are specialized organelles found in freshwater protozoans that function to remove excess water from the cell. Freshwater is hypotonic to the cytoplasm of the protozoan and water will tend to enter the cell by osmosis. The contractile vacuole collects water and then expels it from the cell, preventing it from bursting.

Question 19

Egestion vacuoles release their contents through the

Accepted Answer

Egestion vacuoles release their contents through the cytopyge, which is a specialized structure in some protozoans for expelling waste.

Question 20

"Red-tides" are caused by

Accepted Answer

Red-tides are caused by an overgrowth of dinoflagellates, a type of planktonic algae. These overgrowths can consume large amounts of oxygen, produce harmful toxins, and ultimately create a condition that is harmful to other marine life and even humans.

Quiz 8: Animal-Like Protists: the Protozoa