Bio 2; Test 3

What genus of protists appears to contradict the statement that unicellularity restricts cell size?

Caulerpa -->Caulerpa is a marine algae. This algae is single celled. These cells are very large, that is, about several meters in size. This clearly contradicts the statement that cell size is restricted by unicellularity.

The fungi that do not reproduce sexually use to be classified as _______

Deuteromycota Deuteromycota are called fungi imperfecta because of lack of knowledge of their complete life cycle. Their sexual life cycle is either absent or unknown. Their mode of reproduction is by production of asexual spores spores by the process of sporogenesis.

Why can superficial mycoses in humans lead to bacterial infections?

The spreading of mycoses takes place if proper medication or cure is not available → examples include: athletes foot, ringworm, and candidiasis → the prevention of mycoses is mainly done by keeping the place where we stay hygienic along with the maintenance of body hygiene; antifungal drugs also help prevention such as oral medication, ointments, and or injections

Which of these locomotor organs would likely be the shortest?

a cilium -->Cilia are the slender structures that protrudes from the cell body, and functions in locomotion of the cell. They are shorter than flagella, and are the shortest locomotor organs among flagella, cilia, and pseudopodia.

What event is thought to have contributed to the evolution of eukaryotes?

oxygenation of the atmosphere -->Oxygen is an important component for eukaryotes to survive. Its members started to appear on earth only after the oxygenation of the atmosphere. The first organisms to oxygenate the atmosphere is the cyanobacteria.

A fungal infection that affects nails and skin is classified as ________.

superficial mycosis Such fungi are limited to outer surface or organism; very common in chest, back, arm, and legs of young adolescents; the fungal spores get attached to the skin or sometimes inhaled which can cause persistent infections to the lungs and skin

Yeast is a facultative anaerobe. This means that alcohol fermentation takes place only if:

the atmosphere does not contain oxygen -Facultative anaerobes can make ATP with or without the presence of oxygen -The temp for alcohol fermentation is 37 C or higher; higher temp = faster fermentation -Alcohol fermentation takes place under anaerobic conditions: the absence of oxygen The sugar molecule can only be broken down by yeast in the absence of oxygen to form alcohol; Yeast will not function if O2 is present

The advantage of yeast cells over bacterial cells to express human proteins is that:

yeast cells are eukaryotic and modify proteins similarly to human cells

Explain in your own words why sexual reproduction can be useful if a protist's environment changes.

It allows recombination of genes between both parents that enable them to produce offspring that are genetically unique. These organisms will have better chances of survival in a new environment, and thus, can adapt well. Genetic variation due to sexual reproduction allows organisms to co-evolve with other species, allowing species with a mechanisms to rapidly improve. On the other hand, asexual reproduction does not involve any fusion of genes, resulting in offspring that are clones of their parent without any genetic variation, thereby, reducing the chances of survival of the species in a new environment. Thus, sexual reproduction is useful for the protists during environmental changes.

Why does protection from light actually benefit the photosynthetic partner in lichens?

Lichens( which live among the filaments of fungus) are examples of mutualistic association between the fungus and the photosynthetic organisms it lives in close contact with: → the algae and cyanobacteria benefit the fungus by producing food through photosynthesis and acts a photosynthetic partners → algae and cyanobacteria are protected from the environment by the fungus filaments that gather moisture and nutrients; and also help in their anchorage; → also helps them from excess sunlight which may cause bleaching of their photosynthetic pigments; which lets the photosynthetic partners survive in environments which are unfavorable

Conjugation between two Paramecia produces ________ total daughter cells.

8 -->When two Paramecia come in contact with each other, they are joined by a conjugation bridge. On contact, micronucleus in each cell divides by meiosis producing four haploid micronuclei, three of which degenerate. The remaining micronucleus undergoes mitosis producing two haploid micronuclei in each cell. One of the micronuclei is exchanged between cells, and the cells then move apart.

What evidence is there that mitochondria were incorporated into the ancestral eukaryotic cell before chloroplasts?

All cells of eukaryotes consist of mitochondria that functions as the powerhouse for all the cells. This gives us evidence that mitochondria were the first cell to get incorporated into the eukaryotic cell. The chloroplast cell is absent in animal cells. It is a characteristic of plants which allows them to carry out the photosynthetic process. Thus, chloroplast cell was incorporated later in the eukaryotic cell.

Members of which phylum produce a club-shaped structure that contains spores?

Basidiomycota Basidiomycota are club shaped fungus comprising of mushroom, puffballs among other members. This group is distinguished by the presence of basidium, a reproductive organ. They are believed to have evolved from Ascomycota. The group of basidiomycota, which reproduces sexually, forms a specialized structure called basidia, which is club shaped in structure. The basidium gives rise to basidiospores.

What are the evolutionary advantages for an organism to reproduce both asexually and sexually?

Both have their own benefits: -Asexual reproduction does not involve finding a mate in order to undergo fusion, this process is rapid and allows an increase in number at a much faster rate ; it also allows for exponential growth during favorable conditions due to production of many offspring → ensures large growth rate of the organism -The same organism could undergo sexual reproduction when the environmental condition is unfavorable; sexual reproduction allows exchange of genetic info to take place thus increasing genetic variation of organisms → allowing organisms to adapt to changing environment conditions and ensure population fitness; process also acts as parasite defense mechanism and protects organisms from any harmful attacks from predators or the environment

Which of the following statements about Paramecium sexual reproduction is false?

Both mitosis and meiosis occur during sexual reproduction -->During conjugation, each parent cell will produce four micronuclei each by meiosis. Out of four micronuclei, 3 degenerates and 1 micronucleus will persist. The remaining one micronucleus will undergo mitosis in of both the parent cells to produce two micronuclei each.

Alternation of generations describes which of the following?

Both the haploid and diploid forms can be multicellular. -->Alternation of generations describes the fluctuation strategy used by protists, in which the haploid (gametophyte) stage alternates with the diploid (sporophyte) stage. Here, both the haploid and diploid forms are multicellular.

The most primitive phylum of fungi is the ________.

Chytridiomycota The most primitive fungus and are called the true fungi. They appeared during the pre-cambrian period, which is about 500 million years ago. They are mostly unicellular, and do not possess septum between cells. Their cell walls are composed of cellulose and chitin, in some of the members. Its zoospores swim by the help of flagellum.

For each of the four groups of perfect fungi (Chytridiomycota, Zygomycota, Ascomycota, and Basidiomycota), compare the body structure and features, and provide an example.

Chytridiomycota -unicellular or multicellular -aquatic w/ motile spores which has flagella - ex) allomyces Zygomycota -multicellular -present in soil and includes zygospores -ex) bread and fruit molds Ascomycota -unicellular or multicellular -presence of sexual spores in sacs -ex) yeast used in bread and wine production Basidiomycota -multicellular -presence of sexual spores in the basidiocarp (mushrooms) and act as decomposers -ex) mushroom producing fungi

A fungus that climbs up a tree reaching higher elevation to release its spores in the wind and does not receive any nutrients from the tree or contribute to the tree's welfare is described as a ________.

Commensal Commensalism is the interaction between two organisms

Which characteristic is shared by prokaryotes and eukaryotes?

DNA-based genome -->According to the endosymbiotic theory, eukaryotes have developed by engulfment of one cell by another. Overtime, the engulfed cell undergoes evolution. This process has occurred by deriving heat from the volcanic activity.

Members of which phylum establish a successful symbiotic relationship with the roots of trees?

Glomeromycota Glomeromycota is a new phylum comprising of about 230 species, and live in close association with tree roots. THey share a long evolutionary history with the roots of higher plants. THey cannot reproduce sexually, and cannot survive without the roots of plant. They form an obligate symbiotic relationship with roots of trees. The tip of the hypha produce spores called glomerospores.

What is the advantage for a basidiomycete to produce a showy and fleshy fruiting body?

Is to attract agents which will help them in dispersing its spores; the dispersal rate of the spores is increased by producing the showy/fruiting body

The chlorophyte (green algae) genera Ulva and Caulerpa both have macroscopic leaf-like and stem-like structures, but only Ulva species are considered truly multicellular. Explain why.

Only Ulva organisms are considered multicellular organisms. Protists belonging to the genus Caulerpa are very large cells that are multinucleate and single-celled. These organisms undergo cell division through mitosis, but cytokinesis does not occur, Unlike Ulva, they lack cytoplasmic divisions, and hence, cannot be considered completely multicellular. In Ulva, the sporangial and gametangial thalli are similar morphologically. They undergo meiosis, where diploid adult plant produces zoospores that are haploid. These zoospores then, grow into male and female plants. Later, these haploid plants release gametes, and form a zygote that germinates and grows into a diploid plant.

Compare plants, animals, and fungi, considering these components: cell wall, chloroplasts, plasma membrane, food source, and polysaccharide storage. Be sure to indicate fungi's similarities and differences to plants and animals.

PLANTS -cell wall; composed of cellulose -chloroplast; carries out photosynthesis -plasma membrane; stabilized w/ phytosterol -food: obtain N from N fixing bacteria or environment/ carbon comes from photosynthesis -storage of polysac: in form of starch ANIMALS -no cell wall or chloroplast - food sources via internal digestion -plasma mem stablized w/ cholesterol -polysach in form of glycogen FUNGI -cell wall; made up of chitin -no chloroplast -plasma mem stabalized w/ ergosterol -food source: external digestion -polysach in form of glycogen

Which protist group exhibits mitochondrial remnants with reduced functionality?

Parabasalids -->Parabasalids belong to the subgroup, Excavata of the kingdom Protista. They exhibit mitochondria with reduced functionality, that is, semi-functional mitochondria, which are known as hydrogenosomes. They are called so because they function anaerobically during which hydrogen gas is produced as a product.

If symbiotic fungi are absent from the soil, what impact do you think this would have on plant growth?

Plants won't be able to gain essential nutrients from the soil because of their complexity nature. The absorption of minerals and water will decrease and the overall metabolism of the plant will be affected. There are some plants and fungi which depend completely on each other for their survival, and if any of their counterparts is missing, it will result in death of the other member

Why might a light-sensing eyespot be ineffective for an obligate saprobe? Suggest an alternative organ for a saprobic protist.

Since an obligate saprobe does not have the ability to perform photosynthesis, it cannot make its own food; thus it cannot obtain nutrition directly by the presence of any light sensing eyespot; making the light sensing eyespot ineffective for an obligate saprobe → an alternative would be the use of chemotaxis; which could be utilized by obligate saprobes to search for food (organism responds to chemical stimulus allowing them to sense odors being released from decaying organisms)

Giardia lamblia is a cyst-forming protist parasite that causes diarrhea if ingested. Given this information, against what type(s) of environments might G. lamblia cysts be particularly resistant?

Since it is an intestinal parasite, the infection occurs through ingestion of microbial cysts via contaminated food or water. The dominant cysts of Giardia are exposed to the acidic conditions due to the stomach acids that are present in the body of the host. The acidic condition is created due to low pH in the stomach, which is a result of production of HCl. HCl is stimulated by the hormone gastrin. In order to survive in this environment and reach the intestine where it reproduces, the cysts need to be resistant to the low pH, that is, to these acidic conditions.

A basidiocarp is the fruiting body of a mushroom-producing fungus. True or false?

TRUE A basidiocarp is the fruiting body of basidiomycetes. Inside the gill like structure of basidiocarp, there are numerous basidia which produce haploid spores by meiosis called basidiospores. The basidiospores when germinated will give rise to mycelium and the cycle continues.

A dikaryotic ascus that forms in the ascocarp undergoes karyogamy, meiosis, and mitosis to form eight ascospores. True or false?

TRUE A dikaryotic ascus if formed when two different cell types fuses its cytoplasm by plasmogamy. The nuclei will not fuse at this point, rather it will cohabit in one cell. When the fertilization process is triggered, the nuclei will fuse by karyogamy process, and give rise to a zygote. The zygote in the ascus of ascocarp will undergo meiosis to form four haploid cells. These four haploids will undergo mitosis to form eight ascospores.

Historically, artisanal breads were produced by capturing wild yeasts from the air. Prior to the development of modern yeast strains, the production of artisanal breads was long and laborious because many batches of dough ended up being discarded. Can you explain this fact?

The discarding of dough was mainly due to the contamination of the dough by toxic spores that float in the air, making it uneatable This contamination was later removed by purification with reliable baker's yeast (saccharmoyces cerevisiae) strain developed by Louis Pasteur→ this allowed production of toxin free bread and maintained a consistent freshness

Which of the following statements about the Laminaria life cycle is false?

The gametophyte is diploid. -->The asexual spores, which are haploid in nature, will undergo mitosis to form a multicellular structure called a gametophyte. The ploidy level of the gametophyte will be the same as the sexual spores which is haploid.

How does killing Anopheles mosquitoes affect the Plasmodium protists?

The immune system of the host body is lost in the developing inflammatory response as result of waste product released from the parasites in the RBC's The Anopheles is required for the complete cycle of asexual reproduction of Plasmodium protists By killing anophele mosquitos, the production of plasmodium protists is halted; and thus there is a reduction in human infections

Without treatment, why does African sleeping sickness invariably lead to death

The initial symptoms are headache, fever, and vomiting When the parasite reaches the central nervous system it will mainly damage the brain cells Disturbance in the sleep cycle, partial paralysis, frequent seizures, coma, and organ failure are what invariably lead to death

Why are fungi important decomposers?

They recycle carbon and inorganic minerals by the process of decomposition. When fungi colonize a dead organic matter, it spreads its mycelium and hyphae by branching and invades the organic matter. On invasion, it breaks down the organic matter and converts inorganic matter to organic form, Thus, it recycles back the carbon and organic matter back into the soil. This is called decomposition.

Which parasitic protist evades the host immune system by altering its surface proteins with each generation?

Trypanosoma brucei Trypanosoma brucei is the parasite responsible for sleeping sickness which attacks the immune system of humans. This parasite has the ability to change its surface protein (glycoprotein) after every cycle that makes our immune system hard to combat with the virus. Whenever an attack of the parasite is encountered, our immune system develops antibodies to fight against this antigen but because of its ability to change its surface protein, it has the ability to infect the invaded organism multiple times. So far, there is no cure for this disease.

What term describes the close association of a fungus with the root of a tree?

a mycorrhiza The symbiotic relation between a fungus and roots of higher plants forms a mycorrhiza. The fungus in association can interact with the roots internally or externally. Through this association, the fungus will get a direct access to carbohydrates while the hyphae of the fungus will help the plants with better access to water and better absorption of minerals. 95% of the plant families show this symbiotic association with fungi.

During sexual reproduction, a homothallic mycelium contains

both mating types Homothallic mycelium is a condition when both the mating types are present on the same mycelium. The cytoplasm will fuse by plasmogamy and the nuclei by karyogamy. A zygote is formed after plasmogamy and karyogamy which, by meiosis will produce haploid spores. The spores of germination will give rise to mycelium.

Which polysaccharide is usually found in the cell wall of fungi?

chitin Chitin is a polymer of N-acetylglucosamine, which is a derivative of glucose. They form the primary component of the cell wall of fungi. The chitin has the ability to position itself on a specific site, which helps in maintaining the overall strength of the wall throughout its life cycle. They form a very thick wall around the cell of a fungus.

Which of these protists is believed to have evolved following a secondary endosymbiosis?

chlorarachniophytes

Which of these organelles is not found in a fungal cell?

chloroplast Fungi are heterotrophic organisms, like many higher organisms. They cannot synthesize its own food as they lack chloroplast. Chloroplast present in plants allows them to synthesize its own food. The fungus obtained its energy by invading other organisms both, dead and alive. The fungi are decomposers of an ecosystem.

Mitochondria most likely evolved by _____________.

endosymbiosis -->According to endosymbiotic theory, eukaryotes have developed by engulfment of one cell by another. Overtime, the engulfed cell undergoes evolution. It is believed that mitochondria and chloroplasts have evolved in eukaryotes through the process of endosymbiosis.

What is the function of the raphe in diatoms?

locomotion -->Raphe is a slit which is exhibited by diatoms in their silica shell. From the raphe, a stream of mucopolysaccharides is expelled by the diatoms. This stream helps them in locomotion (propelling in one direction) or attachment to surfaces.

An example of carbon fixation is _____________.

photosynthesis Carbon fixation is also called as assimilation of carbon. It is the process of conversion of carbon dioxide (inorganic carbon) into organic carbon compounds such as glucose. This process is carried out by living organisms. For example, photosynthesis is an example of carbon fixation in which carbon dioxide and water are converted into carbohydrates, in the presence of sunlight and chlorophyll.

Protists that have a pellicle are surrounded by ______________.

proteins -->Certain protists are surrounded by a thin outer layer called pellicle that provides protection to the cell. Pellicle is a flexible coat of armor that covers the cell membrane. This pellicle is surrounded by interlocking protein strips.

Protists with the capabilities to perform photosynthesis and to absorb nutrients from dead organisms are called ______________

saprobes -->Saprobes of protists consist of fungi that act as decomposers by feeding on dead organisms and organic material. Saprobes play a very important role in the ecosystem as they help in breaking down the dead organic material and releasing in back into the soil. Saprobes members comprises of minute microorganisms invisible to the naked eye. However, members like mushroom are large in size and can be cultivated for other purposes such as consumption.

The wall dividing individual cells in a fungal filament is called a _____________.

septum Hyphae are the vegetative part of fungus, which is formed by many dividing cells. The walls between these dividing cells are formed by septum, which has perforations to allow the flow of nutrients and cell organelles into the newly formed cells. Mitochondria, ribosomes and nucleus can travel through this perforated septum.