Question 1

To what extent are the cells of a colonial Volvox specialized?

Accepted Answer

The cells of Volvox are specialized to some extent. The somatic cells perform functions such as nutrition and locomotion while the few germ cells carry out reproduction. This division of labor indicates some degree of specialization among the cells. However, it is not as extensive as seen in metazoan organisms where there is a wide variety of specialized cells.

Question 2

Usually we expect fission to produce two cells from one,but in Sporozoea and some Sarcodina,multiple fission of the nucleus is followed by rapid division of cytoplasm,releasing many new individuals immediately in a process called

Accepted Answer

Sporogony is the process where multiple fission of the nucleus is followed by rapid division of the cytoplasm, resulting in the release of many new individuals immediately. This process is observed in Sporozoea and some Sarcodina.

Question 3

The strange case of organisms that undergo meiosis to produce gametes that fuse to form a zygote internally without leaving the organism is a process called

Accepted Answer

The process described in the question is autogamy. Autogamy is a type of self-fertilization where gametes are produced by meiosis within the same organism, which then fuse to form a zygote without leaving the organism. This is in contrast to other types of fertilization, such as syngamy (fusion of gametes from different individuals) and conjugation (exchange of genetic material between individuals). Zygotic meiosis and gametic meiosis are terms used to describe the types of meiosis that occur in different organisms during sexual reproduction, and are not relevant to the process described in the question.

Question 4

Some organisms undergo meiosis to produce gametes that fuse to form a zygote internally without leaving the organism.What is the effect of this process on genetic diversity of the offspring?

Accepted Answer

Meiosis involves the shuffling and recombination of genetic material during the formation of gametes. Therefore, even though the offspring may remain within the same organism, the combination of genetic material from the two gametes can still result in genetic variation. However, this process does not necessarily increase genetic diversity with each generation, as there is still the potential for inbreeding and the accumulation of deleterious mutations.

Question 5

Protective cysts are triggered by

Accepted Answer

Protective cysts can be triggered by various environmental stresses, such as food shortages, drying out, and decreased oxygen. Additionally, in some species, the formation of protective cysts is a part of their regular life cycle, regardless of environmental conditions. Therefore, all of the choices are correct.

Question 6

Haploid cells that are unequal in size,such as sperm and egg,are called

Accepted Answer

The term "anisogametes" refers to haploid cells that are unequal in size, with one being larger and usually considered the female or egg cell, and the other being smaller and usually considered the male or sperm cell. The other choices are not accurate descriptions of this type of cell.

Question 7

Cilia or flagella are resorbed and the Golgi apparatus secretes wall material during

Accepted Answer

The resorption of cilia or flagella and Golgi apparatus secretion of wall material are part of the process of encystment, which is the formation of a protective cyst around the cell. The other choices listed do not involve this specific cellular process.

Question 8

Which protozoan is used to test hypotheses of how multicellular organisms arose from their closest unicellular relatives?

Accepted Answer

Choanoflagellates are a group of unicellular eukaryotes that have several characteristics similar to the cells that make up the collar cells or choanocytes of sponges, which are the simplest multicellular animals. Therefore, studying choanoflagellates is beneficial in understanding the evolutionary pathway of multicellular organisms from their closest unicellular relatives.

Question 9

When the haploid cells or pronuclei are borne in equal-sized cells that look alike,they are called

Accepted Answer

Isogametes are gametes that are identical in size and appearance. They can be either male or female, and they fuse during sexual reproduction to form a zygote. Anisogametes are gametes that differ in size and appearance, with the smaller typically being male and the larger being female. Syngametes refer to the fusion of two gametes, regardless of whether they are isogametes or anisogametes. Autogametes are gametes that are capable of fertilizing themselves, while unigametes are a hypothetical type of haploid cell that does not exist in nature.

Question 10

The macronucleus of a ciliate elongates,constricts and divides without going through the mitotic stages in a process called

Accepted Answer

The process described in the question, where the macronucleus of a ciliate elongates, constricts, and divides without going through the mitotic stages, is characteristic of amitosis. Amitosis is a type of cell division that occurs without the involvement of spindle fibers or complex chromosome movements that are typical of mitosis. The resulting daughter cells may have unequal chromosome content or genetic material, which is different from the even distribution of genetic material seen in mitosis.

Question 11

Chagas disease in the Americas is carried by

Accepted Answer

Chagas disease in the Americas is primarily carried by triatomine "kissing" bugs, also known as reduviid bugs. These bugs can pass on the parasite Trypanosoma cruzi to humans through their feces, typically through biting people's faces while they sleep.

Question 12

"Red tides" are caused by massive blooms of

Accepted Answer

Red tides are caused by massive blooms of dinoflagellates, which are single-celled algae with two flagella. These blooms can discolor the water and release toxins that can harm marine life and humans who consume contaminated seafood.

Question 13

The early development of a globular colony (with flagella inward)that then turns inside-out (with flagella outward)is

Accepted Answer

The early development of a globular colony turning inside-out (with flagella outward) is called inversion, which is very rare among animals, only occurring in colonial flagellates and sponges. This process is not related to undulating membrane, pseudoplasmodium, or reverse gastrulation.

Question 14

The strange case of organisms that undergo meiosis after fertilization and live out their adult life in the haploid state is a case of

Accepted Answer

The phenomenon described is known as "zygotic meiosis", where meiosis occurs only after fertilization has taken place, leading to the production of haploid individuals that live out their adult life cycle in the haploid state. This is different from the typical life cycle in most sexually reproducing organisms, where meiosis occurs before fertilization and leads to the production of haploid gametes.

Question 15

Most of the time,although they usually have other options,protozoans reproduce by

Accepted Answer

Asexual cell division, also known as binary fission, is the most common method of reproduction in protozoans. This process involves the splitting of one cell into two identical daughter cells. While some protozoans may have other options, such as conjugation or fusion of gametes, asexual cell division is the primary method of reproduction for most species. Parthenogenesis and autogamy are less common forms of reproduction in protozoans.

Question 16

Members of Euglena have starch-like food storage material in the form of

Accepted Answer

Euglena have starch-like food storage material in the form of paramylon bodies.

Question 17

Protozoans in the genus Trypanosoma cause

Accepted Answer

Trypanosoma species cause African sleeping sickness (T. brucei) and Chagas disease (T. cruzi).

Question 18

What happens during conjugation in most ciliates?

Accepted Answer

During conjugation in most ciliates, haploid micronuclei are exchanged between two individuals to provide genetic diversity. This is a form of sexual reproduction in ciliates. Macronuclei are not formed during conjugation, and binary fission is a form of asexual reproduction. The micronuclei do not disappear, but they are exchanged between two individuals.

Question 19

When a protozoan alternates between haploid and diploid generations,as occurs in most plants,it is called

Accepted Answer

Intermediary meiosis, also known as sporic meiosis, is the process where organisms alternate between haploid and diploid generations, similar to the life cycle seen in most plants.

Question 20

A protozoan with both plant-like photosynthesis and animal-like motility is most likely a

Accepted Answer

Euglenoids are unicellular organisms that have chloroplasts for photosynthesis but also have a flagellum for motility. They are often considered to be transitional between plants and animals. The other options given do not fit the description of an organism with both plant-like photosynthesis and animal-like motility.

Quiz 11: Unicellular Eukaryotes