2 Kingdom Protista: the most diverse of all eukaryotes Ch 17.1
3 Protists Protists: eukaryotes that are not animals, plants, or fungi Most protists are unicellular and free-living (not parasitic)Protists have the typical eukaryotic cell structure, including internal membranes, a nucleus surrounded by a nuclear envelope, and organelles such as mitochondria and chloroplasts (in some species)
4 Protist ComplexityBeing mostly unicellular, protists are considered the simplest form of eukaryotic organismMost human cells are highly specialized, carrying out only certain tasksThe protist's one cell must consume and process food, respond to stimuli, excrete wastes, and reproduceProtists can justifiably be considered the most complex of eukaryotic cells, since each cell must carry out all of an organism's life functions.
5 Protist nutrition used for classifying Scientists group protists by lifestyle: animal-like, fungus-like, and plant-like protistsProtozoans: Animal-like; heterotrophs that ingest (eat) foodAlgae: Plant-like; autotrophic making food through photosynthesis
7 Structure & Function of Fungi Hypha: a thread of cytoplasm; many hyphae together make up the body of a fungusMycelium: interwoven mat of hyphae that functions as the feeding structure of a fungusfunctions as the feeding structure of a fungusfungal mycelium can grow as much as a kilometer of hyphae each day as it branches within its food
8 What’s the world’s largest organism? Scientists have discovered one enormous mycelium in Oregon that measures 5.5 kilometers across and spreads through almost 9 square kilometers of forest (larger than 1,600 football fields)Scientists also estimate that this fungus is at least 2,400 years oldQualifies as one of Earth's oldest and largest living organisms
9 MyceliumThe branching mycelium enables the fungus to obtain food by absorptive nutritionAbsorptive nutrition: method by which fungi absorb small organic molecules from their surroundingsFirst, the fungus digests food outside its mycelium by secreting powerful enzymes into its surroundingsThese enzymes break down complex molecules into smaller molecules the mycelium can absorb
10 Fungi’s role Many fungi play an important role as decomposers Fungi recycle nutrients such as nitrogen and carbon by breaking down organic materialCommon food sources for fungi are fallen logs, bodies of dead animals, or the wastes of living organismsParasitic fungi absorb nutrients from the cells or body fluids of living hostsParasitic fungi cause about 80 percent of all plant diseases
11 Reproduction of FungiFungi reproduce by releasing large numbers of microscopic sporesSpores: haploid single cell with a thick wall that functions in the dispersal stage in fungal reproductionspread by the wind and can withstand unfavorable conditions for long periods of timeMost fungi produce spores asexually by mitosis at the tips of specialized hyphaeMany fungi also produce spores sexuallyHaploid hyphae from different mycelia fuse together and combine their genetic material
12 Fungi have a major impact on other life Ch 18.3
13 Lichens Lichens: mutualistic pairing of a fungus and an alga The photosynthetic algae feed the fungusThe fungal mycelium provides a suitable habitat for the algae, helping to absorb and retain water and mineralsLichen actually consists of millions of tiny algal cells within a mesh of fungal hyphae
14 LichensOne benefit of symbiosis is that lichens are able to live in environments where neither fungi nor algae could live aloneLichens are important pioneer organisms on newly cleared rock and soil surfaces, such as burned forests and volcanic flowsIn the arctic tundra, caribou graze on lichens at times of the year when other foods are unavailableAs tough as lichens are, however, many do not tolerate air pollutionTheir absorption of minerals from rain and moist air makes them particularly sensitive to chemicals such as sulfur dioxideThe death of sensitive lichens in an area can be an early warning of poor air quality.
15 MicorrhizaeMicorrhizae: symbiotic relationships between fungal hyphae and plant rootsThe fungi absorb water and essential minerals from the soil and provide these materials to the plantThe fungal mycelium greatly increases the surface area of the root in contact with the soil, which increases the plant's absorption of water and mineralsThe sugars produced by the plant nourish the fungi
16 Disease causing fungiOf the 100,000 known species of fungi about 30 percent are parasites, mostly on or in plantsDutch elm disease- has eliminated most elm trees in North AmericaThe fungus was accidentally introduced into the United States on logs sent from Europe after World War IOnly about 50 species of fungus are known to be parasitic in humans and other animalsAmong these are yeast infections of the lungs, some of which can be fatalOther fungal parasites produce a skin disease called ringworm, so named because it appears as circular red areas on the skinSome fungi attack the feet and cause intense itching and sometimes blisters- known as athlete's foot, is highly contagious, but it can be treated with various fungicides
19 Commercial use of fungi The distinctive flavors of certain kinds of cheeses come from the fungi used to "ripen" themYeasts are particularly important in baking, brewing, and winemakingUsed in making of antibioticsIn addition to edible mushrooms, other edible fungi include trufflesIn nature, truffles release strong odors that attract mammals and insects that dig up the fungi and disperse their spores
20 Role of fungi in chemical cycling Fungi and bacteria are the principal decomposers that supply ecosystems with the nutrients essential for plant growthThe air is so loaded with fungal spores that as soon as a leaf falls or an insect dies, it is covered with spores that quickly grow into fungal hyphaeWithout decomposers, elements such as carbon and nitrogen would accumulate in organic matterPlants and the animals they feed would starve because elements taken from the soil would not be returned
21 Questions? Which of the following is a symbiotic relationship? PenicelliumBread moldYeastlichenWhat do fungi produce that allows them to break down dead organisms?How do humans use fungi?To flavor certain foodsAs a source of antibioticsAs ingredients in baking and brewingAll of the above
22 Questions? What is an important role of fungi in an ecosystem? What is the cause of the human disease ring worm?