CHAPTER 30: FUNGI
Kelsey and Kendra
What is a Fungus?
• Fungi have absorptive heterotrophy and chitin in their cell
walls. Fungi have various nutritional modes: Some are
saprobes, some are parasitic, and others are mutualistic.
• The body of a multicellular fungus is a Mycelium: a
meshwork of thing string-like structures called hypae. The
hyphae may be septate or coenocytic.
• Fungi are tolerant of hypertonic environments.
(Envirionments with high pressure) And many are tolerant
to very high or very low temperatures.
• Fungi reproduce both sexually and asexually.
How do Fungi Interact with Other
Organisms?
• Saprobic fungi, as decomposers, make crucial
contributions to the recycling of elements. Certain fungi
develop symbiotic and mutualistic relationships with other
organisms.
• Many fungi are parasitic to plants and harvest nutrients
through haustoria.
• Some fungi associate with green algae to form lichens
which live on many exposed surfaces of rocks, trees and
soil.
• Mycorrhizae are mutualistic associations of fungi with
plant roots. They improve a plant’s ability to take up
nutrients in water.
• Endophytic Fungi live within plants and can provide
protection to their hosts from herbivores.
What Variations Exist among Fungal Life
Cycles?
• Some Chytrids have a life cycle that includes alteration of
generations.
• In sexual reproduction of terrestrial fungi, Hyphae fuse,
allowing gamete nuclei to be transferred. Fusion of
cytoplasm precedes fusion of nuclei.
• Zygospore fungi have a resistant-spore stage with many
diploid nuclei.
• In sac fungi and club fungi, a dikaryon is formed. The
dikaryotic condition is unique to the fungi.
How have fungi Evolved and Diversified?
• The relationship of microspordia, chytrids, ans zygospore
fungi are not well resolved, but these groups diversified
early in fungal evolution.
• Microspordia are reduced. Intracellular parasitic species
that infect several animals, especially insects.
• The three distinct lineages on chytrids have flagellated
gametes.
• The for lineages of zygospore fungi have coenocytic
hyphae.
• Arbuscular mycorrhizal fungi form symbiotic associations
with plant roots. This helps the plant get nutrients from the
water.
• Sac fungi have septate hyphae. There sexual structures
are asci. Sac fungi are the fungal halves of lichen.
• Club fungi are plant pathogens, but also form mushrooms.
Their dikaryon stage may last several years.
Resources
• Sadava, Hillis, Heller, Berenbaum. Life The Science of Biology.
• http://travelblog.org
• http://magickcanoe.com/fungi/fungi-links.jpg
• http://www.scienceclarified.com/Ex-Ga/Fungi.html
• http://163.16.28.248/bio/activelearner/25/images/ch25c4.jpg
• http://163.16.28.248/bio/activelearner/25/ch25c3.html
• http://www.kimmerer.com/blogs/wp-
content/uploads/2008/11/photocolorizedelectronscope.jpg
• http://www.botany.hawaii.edu/faculty/wong/BOT135/Lecture03/
Rhizopus_Zygospore.gif
• http://bama.ua.edu/~chytrid/