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 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/