Sunday, December 9, 2007

Concept 31.5

Q1: What are some of the benefits that algae in lichens can derive from their relationship with fungi?

A1: A suitable environment for growth, retention of water and minerals, protection from sunlight, and protection form being eaten.

Q2: What characteristics of pathogenic fungi result in their being efficiently transmitted?

A2: A hardy spore stage enables dispersal to host organisms through a variety of mechanisms; their ability to grow rapidly in a favorable new environment enables them to capitalize on the host's resources.

Concept 31.4

Q1: What feature of chytrids supports the hypothesis that they represent the most primitive fungal lineage?

A1: Flagellated spores.

Q2: Why are glomeromycetes so ecologically significant?
Q3: Give different examples of how form fits function in zygomycetes, ascomycetes, and basidiomycetes.

A2: Most plants form arbuscular mycorrhizae with glomeromycetes; without the fungi, the plants would be poorly nourished.

Q3: Give different examples of how form fits function in zygomycetes, ascomycetes, and basidiomycetes.

A3: Zygomycetes - sturdy, thick-walled zygosporangium can withstand harsh conditions and then undergo karyogamy and meiosis when the environment is favorable for reproduction. Ascomycetes - the asexual spores (conidia) are produced in chains or clusters at the tips of conidiophores, where they are easily dispersed by wind. Basidiomycetes - basidiocarp supports and protects a large surface area of basidia, from which spores are dispersed.

Concept 31.3

Q1: Why are fungi classified as opisthokonts when most fungi lack flagella?

A1: The fungal lineage thought to be the most primitive, the chytrids, have posterior flagella, as do most other ophisthokonts. This suggests that other fungal lineages lost their flagella after diverging from the chytrid lineage.

Q2: Explain the evolutionary significance of the presence of mycorrhizae in the earliest vascular plants.

A2: This indicates that fungi had already established symbiotic relationships with plants by the time the first vascular plants evolved.

Concept 31.2

Q1: In terms of haploidy versus diploidy, how do the life cycles of humans and fungi differ?

A1: Majority of human life cycles are dominated by dipoid stages while in fungi, majority consists of haploid stages.

Q2: Suppose that you sample the DNA of two mushrooms on opposite sides of your yard and find that they are identical. What are two hypotheses that could reasonably account for this result?

A2: The 2 mushrooms might be reporoductive structures of the same mycelium. Or they might be parts of 2 separate organisms that have arised from a single organism through asexual reproduction and thus carry the same genetic information.

Concept 31.1

Q1: Compare and contrast the nutritional mode of a fungus with your own nutritional mode.

A1: Humans and fungus are heterotrophs. In humans, we ingest relatively large pieces of food and digest the food within our bodies. While in fungus, it digests its food externally and then absorbing the small molecules that result form digestion.

Q2: Describe how the structure of a fungus is adapted to its nutritional mode.

A2: The extensive network of hyphae puts a large surface area in contact with the food source, and rapid growth of the mycelium extends hyphae into new territory.