Exam 3: Study Guide Ch. 12 DONE

Question 1

Define Mycology.

Answer 1

Study of fungi

Question 2

Differentiate between yeasts and molds as to their morphology, cellular structures and reproduction.

Answer 2

• Molds: grow as long, tangled filaments of cells in visible colonies.
• Yeasts: are unicellular fungi.

Question 3

Explain what a dimorphic fungus is.

Answer 3

o Dimorphic: 2 shapes
o Changes based on the environment: at one temp it molds and at another it yeasts

Question 4

Differentiate between hypha and mycelium as well as between coenocytic hypha and pseudohypha and describe what a septum is.

Answer 4

o Hypha: multicellular organisms that consist of long filaments of cells joined together
o Mycelium: Hyphae grow and branch forming a tangled mass
o Coenocytic hypha: Aseptated hyphae containing many nuclei
o Pseudohypha hypha:
o Septum: Walls that cells within a hypha have, where one or two nuclei separated by a wall

Question 5

Describe the factors that affect fungal growth

Answer 5

o Most fungi are aerobic but some yeast can carry out important fermentation reactions.
o Most fungi grow best in humid environments at around room temperature.
 Psychrophilic fungi grow in the refrigerator.
 Pathogenic fungi tolerate body temperature.
o Many fungi thrive at slightly acidic pH (pH 5-6) but can tolerate a wide range of pH

Question 6

Describe the reproductive processes of budding and spore germination.

Answer 6

o Budding:
 Occurs in unicellular fungi
 A new cell forms as an outgrowth from the parent cell
 Sometimes they do not fully detach (pseudohyphae)

o Spore Germination:
 Begins when a spore lands in a favorable environment
 Spore sends out a projection called a germ tube (elongates to form hyphae)

Question 7

Differentiate between asexual and sexual spores, how they are produced and explain the medical importance of spores.

Answer 7

o Asexual Sporulation: occurs through mitosis producing genetically identical offspring
o Sexual Spores: Sexual sporulation occurs by meiosis in specialized structures called fruiting bodies
o Medial importance: Can act as infectious agents in immunocompromised individuals.

Question 8

List and describe the different asexual and sexual spores.

Answer 8

o Asexual Spores:
 Sporangiospores: Develop in sacs called sporangia
 Conidia:
* * Unprotected spores
 Arthrospores:
* Fragmentation of hyphae produce this
 Blastospore:
* Hyphae producing spores by budding; develops from the parent cell
 Chlamidospores:
* Thick wall single cells formed as segments within the hypha

o Sexual Spores:
 Ascospores:
* single cells in a sac called and ascus that resembles peas in a pod. Often there are 8 spores in an ascus
 Basidiospores:
* single cells borne on a club-shaped pedestal called a basidium. Often 4 per basidium
 Zygospores:
* large spore encased in a thick wall

Question 9

List the five classes of fungi

Answer 9

Chytridiomycota
Glomeromyocta
Zygomycota
Ascomycetes
Basidiomycetes

Question 10

List and describe the general characteristics of the fungi class Chytridiomycota, particularly with regards to their life cycle and the type of sexual and asexual spores that they have.

Answer 10

 Related to the oldest known fungi
 They are primarily aquatic and have flagellated reproductive cells
 Sexual Spores: Form flagellated gametes, which fuse in water to facilitate reproduction.

Question 11

List and describe the general characteristics of the fungi class Glomeromyocta, particularly with regards to their life cycle and the type of sexual and asexual spores that they have.

Answer 11

 Primarily form symbiotic relationships with plant roots, known as mycorrhizae.
 Life Cycle: Do not undergo sexual reproduction; only reproduce asexually.
 Spores:
* Asexual Spores: Produce large, multi-nucleated spores that facilitate their symbiotic relationship with plants.
* Sexual Spores: Not observed, as Glomeromycota are considered mitosporic fungi, lacking a sexual cycle.

Question 12

List and describe the general characteristics of the fungi class Zygomycota, particularly with regards to their life cycle and the type of sexual and asexual spores that they have.

Answer 12

 Terrestrial fungi that commonly grow as molds on food, such as bread.
 Life Cycle: Involves both sexual and asexual reproduction
 Spores:
* Asexual Spores: Primarily sporangiospores, produced in sacs called sporangia.
* Sexual Spores: Zygospores, which are thick-walled, diploid spores formed by the fusion of two different mating types.

Question 13

List and describe the general characteristics of the fungi class Ascomycetes, particularly with regards to their life cycle and the type of sexual and asexual spores that they have.

Answer 13

 includes many fungi with significant economic and medical importance, such as Baker’s yeast, Penicillium, and Candida albicans.
 Life Cycle: Can reproduce asexually and sexually.
 Spores:
* Asexual Spores: Conidia, produced on structures called conidiophores.
* Sexual Spores: Ascospores, formed in a sac-like structure called an ascus. Typically, eight ascospores form in each ascus.

Question 14

List and describe the general characteristics of the fungi class Basidiomycetes, particularly with regards to their life cycle and the type of sexual and asexual spores that they have.

Answer 14

 Known as club fungi; includes mushrooms, puffballs, and some plant pathogens.
 Life Cycle: Sexual reproduction is predominant, with basidia as the primary structure for spore production.
 Spores:
o Asexual Spores: Rarely produced; conidia may form in some species.
o Sexual Spores: Basidiospores, formed on club-shaped structures called basidia, usually located on the gills of mushrooms

Question 15

Define parasitism and differentiate between intermediate host and definitive host as well as between infective stage and transmission stage.

Answer 15

o Intermediate host: Shelters the juvenile or immature stage of the parasite
o Definitive host: Harbors adult stage
o Infective stage: corm of the parasite coming in contact with a possible final host and is able to invade it
o Transmission stage: the form of the parasite that comes out of the host

Question 16

Describe the role of a host and of a vector in the life cycle of a parasite.

Answer 16

o Vector: living carrier, often an insect that actively transports a pathogen from the sick to the well
o Host: the organism serving as shelter to a parasite

Question 17

To know the general characteristics of protozoans in terms of cellular structure, composition, mode of reproduction and type of infective forms.

Answer 17

o Do not possess a cell wall
o Reproduce by binary fission, budding or schizogony
o Sexual reproduction by conjugation or gamete formation occurs in some species
o Infective form: trophozoite, others a cyst

Question 18

List the three groups in which they are classified according to their means of locomotion and describe their specific characteristics as well as examples for each class.

Answer 18

o Excavata: move by means of flagella
o Amoebozoa: move by means of pseudopodia (false foot)
o Chromalveolata: include the ciliates (move by means of cilia) the apicomplexans which move by means of flexing produce flagellated gametes

Question 19

Describe the general characteristics of Platyhelminthes (flatworms), particularly those of the classes Trematoda (flukes) and Cestoda (tapeworms).

Answer 19

o Flukes:
 All parasitic and are characterized by having 1 or more suckers, the most anterior one is connected with the digestive system
 They are hermaphrodites except the blood fluke
 Have complex life cycles, often involving 2+ hosts
o Cestoda:
 All parasitic
 Have a head region called a scolex and their bodies divided into short segments (proglottids)

Question 20

Differentiate between monoeciuous (hermaphroditic) and dioecious trematodes as well as between egg and miracidia

Answer 20

o Hermaphroditic: both male and female in one organism
o Dioecious: male and female are different genders and not in one organism
o Egg: 1st stage in the life cycle of trematodes
o Miracidium: next stage after egg hatches, typically in water

Question 21

Describe the body structure of a cestode.

Answer 21

o Head: scolex
o Body is divided into short segments (proglottids)
o Size ranges from 20mm to 2+meters
o Epithelial covering is called cuticle

Question 22

Know the general characteristics of Aschelminthes in particular those of the class Nematoda (roundworms).

Answer 22

o Characterized by cylindrical bodies with tapered ends
o Roundworms have a complete digestive system with mouth, digestive tract and anus.
o Most are dioecious
o Parasites of humans are all members of the class Nematoda
 Do not have the succession of larval stages exhibited by the flatworms
 Some pass their entire lifecycle, from egg to mature adult, in one host
 Damage to the host often occurs by large worm burdens in vessels of intestines

Question 23

List the two categories in which roundworms are classified according to their infective stage.

Answer 23

o 1- Egg is the infective stage
o 2- Larva is the infective stage

Question 24

Describe the general characteristics of fungi with regards to cellular structure and composition, mode of obtaining energy, their physiology and metabolism and optimal environmental growth conditions

Answer 24

Cell Structure and Composition:
- eukaryotic organisms
- Have cell walls
- Can be multicellular (molds) or unicellular (yeasts)
- Molds can grow filamentous structures called hyphae then those form mycelium
Mode of obtaining energy:
- Heterotrophic (don’t produce own food)
- Secrete enzymes into their surroundings to break down matter and absorb the nutrients Physiology and metabolism:
- Aerobic
- Yeasts can carry out fermentation (can survive in low O2 environments)
Optimal growth conditions:
- Fungi thrive in humid environments and grow best at room temp
- Slightly acidic pH (5-6) but can tolerate a range of pH levels

Question 25

Differentiate between Platyhelminthes and Aschelminthes.

Answer 25

o Platyhelminthes:
 Flatworms; have bilateral symmetry
 Digestive system: Have one opening for ingestion and waste disposal
 Gas exchange occurs directly through their body surface
 Classes of medical importance: Trematoda (flukes) and Cestoda (Tapeworms)
 Have a life cycle with multiple hosts
o Aschelminthes:
 Roundworms; have bilateral symmetry
 Digestive system: Have distinct mouth, digestive tract and anus
 Reproductive: Dioecious (either male or female)
 Can complete life cycle in a single host