Topic 13 - Learning Objectives

Question 1

1. Explain the evidence of shared ancestry between the fungi and nucleariids. #understand

Answer 1

• Both fungi and nucleariids share several molecular and morphological characteristics, suggesting a close evolutionary relationship.
• Molecular studies have revealed similarities in genetic sequences, such as ribosomal RNA, between fungi and nucleariids.
• Morphologically, both groups exhibit similar structures such as flagellated spores (zoospores) and a chitinous cell wall, indicating a common evolutionary origin.

Question 2

2. Describe the defining characteristics of the fungi. #understand

Answer 2

• Eukaryotic organisms with chitinous cell walls.
• Absorptive heterotrophs, obtaining nutrients through external digestion.
• Typically multicellular, although some are unicellular (yeasts).
• Reproduce sexually and/or asexually via spores.
• Exhibit diverse forms including molds, yeasts, and mushrooms.

Question 3

3. Illustrate the typical fungus life cycle. #understand

Answer 3

• The typical fungus life cycle involves both sexual and asexual reproduction.
• Asexual reproduction often involves the production of spores through processes like budding or fragmentation.
• Sexual reproduction involves the fusion of haploid nuclei from different mating types to form a diploid zygote, which undergoes meiosis to produce haploid spores.
• These spores disperse and germinate under suitable conditions to form new fungal individuals.

Question 4

3. a) Identify the major differences between the life cycles of the five major fungus phyla. #analyze

Answer 4

Different fungal phyla may exhibit variations in reproductive structures, modes of spore formation, and the complexity of life cycle stages.

Question 5

4. Construct a phylogenetic tree of the five fungus phyla discussed in this course. #understand

Answer 5

A phylogenetic tree can be constructed based on molecular and morphological data to illustrate the evolutionary relationships between the five major fungus phyla (Chytridiomycota, Zygomycota, Glomeromycota, Ascomycota, and Basidiomycota).

Question 6

4. a) Identify the best outgroup for this tree. #apply

Answer 6

The best outgroup for this tree would be a group of organisms that is evolutionarily close to fungi but diverged earlier, such as the nucleariids or choanoflagellates.

Question 7

5. Classify fungi into phyla based on specific characteristics provided in a photo or written description. #apply

Answer 7

Fungi can be classified into different phyla based on characteristics such as the presence or absence of septa in hyphae, types of spore formation, and reproductive structures.

Question 8

6. Illustrate the mutualistic relationship that is a lichen. #understand

Answer 8

• Lichens are a mutualistic association between a fungus (usually an ascomycete) and a photosynthetic partner (usually a green alga or cyanobacterium).
• The fungus provides a protected environment and absorbs water and minerals for the photosynthetic partner.
• The photosynthetic partner, in turn, provides organic carbon compounds through photosynthesis to the fungus.

Question 9

6. a) Identify what each member gives and gains from the relationship. #apply

Answer 9

• The fungus provides structure and protection for the photosynthetic partner and gains access to nutrients produced through photosynthesis.
• The photosynthetic partner gains protection and access to water and minerals from the fungus and gains a stable substrate for growth.

Question 10

Chitin

Answer 10

A tough, flexible substance found in the cell walls of fungi and the exoskeletons of arthropods like insects and crustaceans.

Question 11

Filamentous

Answer 11

Made up of long, thin threads or strands, like the structures found in many fungi.

Question 12

Hypha

Answer 12

A single thread-like filament that makes up the body (mycelium) of a fungus.

Question 13

Septate

Answer 13

Having cross-walls (septa) dividing the hyphae into compartments.

Question 14

Coenocytic

Answer 14

Not divided into separate cells by septa, instead consisting of a continuous, multinucleate mass of cytoplasm.

Question 15

Mycelium

Answer 15

The mass of intertwined hyphae that forms the body of a fungus, typically found underground or within the substrate it’s growing on.

Question 16

Fruiting body

Answer 16

The reproductive structure of a fungus, such as a mushroom or a mold’s spore-producing structure.

Question 17

Haplontic

Answer 17

A life cycle characteristic of many fungi, where the organism spends most of its life as a haploid individual.

Question 18

Plasmogamy

Answer 18

The fusion of cytoplasm from two parent fungal cells during sexual reproduction.

Question 19

Heterokaryon

Answer 19

A fungal cell containing genetically distinct nuclei from different individuals.

Question 20

Dikaryotic

Answer 20

Having two genetically distinct nuclei within a single cell, often observed in certain stages of fungal reproduction.

Question 21

Karyogamy

Answer 21

The fusion of nuclei from two parent fungal cells during sexual reproduction, resulting in the formation of a diploid nucleus.

Question 22

Mycorrhiza

Answer 22

A mutually beneficial association between the roots of plants and fungi, where the fungus helps the plant absorb nutrients from the soil, and the plant provides the fungus with sugars.

Question 23

Ascocarp

Answer 23

The fruiting body of an ascomycete fungus, such as the cup-shaped structure of a morel mushroom.

Question 24

Ascus

Answer 24

A specialized reproductive structure found in ascomycete fungi that contains and releases ascospores.

Question 25

Ascospores

Answer 25

Sexual spores produced within the asci of ascomycete fungi.

Question 26

Conidia

Answer 26

Asexual spores produced at the tips or along the sides of specialized hyphae called conidiophores in some fungi.

Question 27

Basidiocarp

Answer 27

The fruiting body of a basidiomycete fungus, such as the mushroom cap and stem.

Question 28

Basidiospore

Answer 28

Sexual spores produced externally on specialized cells called basidia in basidiomycete fungi.

Question 29

Mycobiont

Answer 29

The fungal partner in a symbiotic relationship, such as in a lichen where the fungus provides the structure and absorbs water and nutrients.

Question 30

Photobiont

Answer 30

The photosynthetic partner in a symbiotic relationship, such as in a lichen where algae or cyanobacteria provide carbohydrates through photosynthesis.