Brooks Biodiversity Unit 2 Exam Study Guide 2024 with complete solution.

Brooks Biodiversity Unit 2 Exam Study Guide 2024 with complete solution. The Primary role of Fungi Decomposers- they break things down Modes of Nutrition in Fungi Heterotrophs with extracellular digestion Exoenzymes Fungi Release these enzymes outside of the cell wall. Break down complex molecules into smaller organic molecules which can be absorbed. Extracellular Digestion The release of exoenzymes out side of the cell wall, followed by the absorption of nutrients.. Saprobes Fungi that feed on non-living/dead organisms Symbionts Fungus that lives with another living organism (form a symbiotic relationship) Mutualism in Fungi both organisms benefit, neither is harmed. Ex: Lichens - fungi and algae (cyanobacteria) Ex: Mycorrhizae - fungi and plant roots Commensalism One organism benefits, the other is unharmed Parasitism One organism benefits, the other is harmed Examples of Parasitism in Fungi Ex: Fungus as a human parasite (Athelete's Foot) Ex: Fungus as a plant parasite 1. black stem rust on wheat 2. ergots on rye 3. strawberries with botrytis mold 4. pink ear rot of corn Black Stem Rust Parasitic relationship with fungus and plant. Occurs on wheat Ergots Parasitic relationship with fungus and plant that occurs on rye and gives hallucinogenic sensations Botrytis Mold Parasitic relationship with fungus and plants that occurs on strawberries Fungi Characteristics 1. Heterotrophic 2. Extracellular Digestion 3. Chitin-Based Cell wall 4. Most fungi are made up of filaments called Hyphae Hyphae filaments (long and branching) that make up the structure of a fungus In most fungi, hyphae are the main mode of vegetative growth Hyphae are Septate or Coenocytic Yeast Yeast is a unicellular fungi and do not have/grow hyphae MOST FUNGI ARE MULTICELLULAR, BUT YEAST IS UNICELLULAR Septate You can see the cell separation because the nuclei are confined in and separated by cell walls Think "separate" Coenocytic You cant see the cell separation. It is multinucleated meaning that there are multiple nuclei not separated by a cell wall Thallus/Mycelium collectively refers to a bunch of hyphae that together make up the body of the fungus Hyphae (smallest unit) make up the mycelium (entire fungus body) Haustoria The hyphal tip of a parasitic fungus that penetrates the cell of other organisms (the host) After penetration these specialized hyphae release enzymes that break down the cell wall, thus allowing greater potential movement of organic carbon from host to fungus. What is Fungi Most closely related to? Fungi have cell walls and fruiting bodies, so were originally thought to be plants. However, they are most closely related to animals Fungi Nuclei Most fungi cells have 2 nuclei Mitosis Has NO prerequisite for cell division, all it needs is a nucleus. What you start with is what you end with (identical nuclei and identical DNA) Meiosis Cell must be a diploid (2n) Process of nuclear division which the ploidy of the parent cell is halved 3 Types of Meiosis Zygotic - Phylum Zygomycota Gametic - Usually in animals Sporic - Usually in plants Ploidy Number of sets of chromosomes present in a nucleus Haploid - 1 set Diploid - 2 sets (Humans have 23 different kinds of chromosomes in each cell and 46 chromosomes in total) Syngamy synthesis of the games Composed of 2 parts: 1. Plasmogamy 2. Karygamy There are morphological differences between the two individuals (gametes) that engage in syngamy. How do fungi reproduce? Both sexually through meiosis and asexually through mitosis Asexual Reproduction Haploid spores produced (n) Spores produced are the same as original fungus because they are produced through mitosis. Generally occurs when conditions are good because fungus is well adapted to environment so it can just reproduce itself without needing modifications to survive. Sexual Reproduction Haploid spores produced (n), however spores are different from the original fungus because they are produced by meiosis. Generally happens with an extreme change in the environment, which makes sense because it would require genetic variation to adapt to these new conditions. What is the benefit of asexual reproduction? To remove bad genes What is the benefit of sexual reproduction To create genetic variation which reduces the possibility of extinction Are there males and females in fungi? No. They are known as "+" or "-" Sexual Dimporhism Fungi are characterized by Sexual Dimorphisim. Basically, there are morphological differences between the cells of sexes (males and females) of the same species. Examples include differences in morphology, size, ornamentation, and behavior. Heterokaryon Heterokaryon hyphae produced - have 2 OR MORE nuclei resulting from fusion of hyphae (n + n) Dikaryon Dikaryon hyphae - possess 2 genetically different nuclei in each cell (n + n) What is the difference between heterokaryon and dikaryon? The number of nuclei. Heterokaryon can have more than two nuclei, however dikaryon is precisely two. Plasmogamy fusion of the cytoplasm Plasma membrane of the hyphae fuse Comes first before dikaryotic stage and karyogamy Two different n's come together to form n + n First Part of Syngamy Dikaryotic Stage Stage between Plasmogamy and Karyogamy Plasma membrane and cytoplasm have fused, but nuclei have not joined yet (n + n) Karyogamy